Friday, December 23, 2011

Open Office version of BoardOff

I've had a few emails from people asking if BoardOff will run on any of the free spreadsheet programs. I've had a bit of time on OpenOffice Calc but never for macro creation and so I did not realise that it actually implements a version visual basic for apps (VBA) called OpenOffice Basic which is very close to MS VBA.

I did a trial conversion over to openoffice and found that 2 key objects are implemented differently. The Range Object and the Application Object. The range object does have the row count property used in the SPLINE function in BoardOff but its a simple matter to fix that. Once that is done all the calculations work!!!!

There are a few things to iron out (charting on multiple axis screws up and the load,save, merge dialog boxes need to be convert to the Oo equivalents and the macro buttons need to be re-added).

I don't think this is a big job and so I will have a crack at it over the next week or so and see if I can't get an Oo version out there. This should make it possible to use BoardOff on Mac's and Linux machines as well.

I'm also toying with the idea of making a web-based version of board off to get a community of ideas and designs going online so we can compare and share designs. It would also create a change to make BoardOff more user friendly


Thursday, December 22, 2011

Musing on concave

I had a chance to try out the new board at a great flat water spot about 4 hours north of Sydney called Old Bar. We had great wind there and so got to try the new board out on the flat water as well as in the surf.

Overall very happy despite the rocker table mess up the board feels great despite being different.

One thing I noticed is that the narrower tips seemed to compensate for the lack of rocker when it came to handling the chop. I working theory on tips is that because when your edging the hard the board is more vertical than is it horizontal, the curve of the rails toward the tip is works like the rockerline in the case the board is being ridden fairly horizontally. The net result is the the board rode over the chop nicely didn't through up much spray.

The other plus of the narrow tips is that it carved really well on the waves. Because there is more pressure on the wider mid section of the board its easy to balance your weight and pivot the board about the mid point rather than drive the carve from the back fins. This meant it turned on a dime!

I rode this board and my other board back to back and I could not really detect any difference as a result of the absence of concave. This has got me thinking about whether concave is worth it when working with stiffer core material.

My understanding is that concave does 2 , maybe 3, things:

i) It adds stiffness 'artifical thickness' which the BE equation analysis shows a doubling of stiffness when the concave is equal to the thickness of the board although the maximum stresses on the top and bottom layer as a result of the concave are very different (the top experiencing greater stresses - not good when it comes to compression). The stiffness is important for foam cores where the core itself contributes nothing other than to keep the laminate separated and locked relative to each other. The stiffness of the core means this is not so critical.
ii) It flattens the rocker line down the center of the board relative to the rails. This means earlier planning.
iii) Concave also means that the angle of attack of the rail is greater than that at the middle and so the rails bite into the water better and there is the possibility that can reduce the losses associated with cross flow on the underside of the board resulting in more lift on the toeside edge (helping dig the healside in) and possibly more forward momentum if the water flow is redirected towards the tail. However, I don't have any sense of how large these effects are.

On the negative side:

i) Concave adds drag because of the increased angle of attack.
ii) The increased angle of attack means your more likely to catch the toeside edge when you land and have the board too flat. This is the reason that some boards end up having slight bevel on the rails or take then edges from concave to convex as they approach the edge.
iii) Although there is a weight penalty, the stiffness issue can be addressed with additional reinforcement over portions of the board (say the middle)

So what's the so what of this?

i) For wood cores concave may be less effective of desirable than foam cores boards that use it as artificial stiffness.
ii) In wood cores, maybe the edge holding benefit of concave might be replaced with simpler carved channels close to the rails.
iii) The early planning advantage may be partially addresses by the rockerline design. The current rockerline I'm trying is like the NHP where most of the curvature is in the middle 25% and from there to the tips is quite flat. This gives a good planning surface towards the tips rather than the middle so may require a different stance to get started but should benefit early planning potential.

Sunday, December 11, 2011

Board #3 Debrief - Do's, Don'ts and Don't Knows

Time to capture some learnings from the project what worked and what didn't and what I'll do differently next time. Here's the  key

 + are what worked
 - what didn't
* neutral feeling about it
!! idea for next time.


I used Paulownia wood planks 1400x100x6 mm. The deck was built up from 2 layers.

++ cutting a template first so that the core shape could be routed out was perfect. Very quick and efficient. Its important to get the hole spacing for your fin bolts exact because when the screws are off center even the smallest amount its screamingly obvious when you don't have an opaque surface.
+ the wood is stiff. The elastic modulus of the wood is quoted at around 5-7 GPa compared to Klegecel which is effectively zero. e-glass in epoxy comes in at around 15 GPa (typical) but the core is 40 times thicker than the layer of laminate to its contribution to stiffness is huge. This means less layers. I used x 200 g each side but have heard of someone using 2x 160g.
+ using double sided tape to hold the core in place while the shape is routed out.
* exposed wood looks great but the 2 distinct decks don't look so good together - this is obviously a personal preference.
* I left the planks at 100mm wide rather than trimming to 50mm and reassembling them. !!Thin planks look better and apparently help break up weakness in the wood.
- I really needed to thin it down to less that 10 mm as this stuff is really stiff. Using an electric plane and 40 and 60 grit sand paper was time consuming and left an uneven surface as the electric planer leaves tracks on large areas like this and they need to be sanded out. !! Use a router and jigs to do the bulk of the shaping on the core and then an orbital sander to take unwanted sharp edges off.
- Sealing the core before glassing. I think sealing is the right thing to do but I did not let it cure long enough and so it has not sufficiently gelled by the time I placed it on the table. The result was that the white pigment in the underside sealing coat diffused into the graphic inlay and obscured parts of the image. !! Let it cure for at least a few hours so that it is tacky but notquite set yet.
- I left the tips at 6mm and I think that this is too thick to get enough flex. Will have to wait and see.
- building the core up from 2 layers, while straight forwarded, added lots of time to the process. (gluing the planks, routing, sanding and then gluing the layers together. A single piece carved into shape is much easier if you can carve it efficiently.
--- the stiffness of the wood when glued into the 400mm width was too much for the perspex (plastic) sheet used on the rocker table surface and it deformed. This resulting in concave vanishing and rocker reducing significantly. !! Either change to using Formica for the rocker surface of brokite style 2 layer mould to encase the core pieces while they set.


I poured the rails with the same epoxy I used for laminating. I didn't add any thickener to it because I wanted to keep them transparent so the graphics showed through and didn't want to run the risk of reducing the strength. Given they were being poured into a channel I didn't see any reason to use q-cell etc to improve adhesion. It used around 250 g of resin which is actually slightly more expensive than using ABS plastic strips (hence the reason to use q-cell in them). Alternative pouring materials I've heard of are liquid polyurethane (can't remember the exact name) but think that is had a shore hardness rating of 70D

++ clear rails look great. Graphics shine through when sun is behind it.
++ using the router to create the channel gave a good uniform width rail and allowed the laminate to be laid past the rail so no steps that might have accumulated resin or resulted in the glass bridging.
++ mixing the resin very slowly and pouring the resin in really slowly into the channel meant that I had no air bubbles trapped in the resin. I used a plastic tomato sauce squeeze bottle with a pointy nozzle to direct the resin.
+ cutting the slot for the rail all the way through the material and using tape on the underside to create the channel work OK. Only hiccup was that the tape had a couple of wrinkles which of course meant wrinkles on the surface. This can be overcome with better technique, I'm sure. Maybe put tape down first with adhesive side up and then place the core pieces on top.
* I'm still be be convinced that pouring the rails is the best approach. It was critical to get the table level and the core an even thickness to ensure that resin didn't pool and overflow while draining away from another place. I didn't manage to do this and so a lot of work was needed to sand it back and refill.
- There is no way around the waiting time for curing. And because I had to top it up I had to wait again. This puts a lot of delay in the process.


+++ Inlays printed on 'silk' ( I haven't heard from the supplier about the actual material. It feels like a very thin peel ply). Looks brilliant, super easy to work with and cheap.
-- no scratch protection or UV protection and requires you to do all the surface finishing that wouldn't be necessary if protective bottom and top sheets were used. 
!! would still like to get PBT bottom sheet to avoid have to do all the surface finishing that was royally screwed up.

Laminate and vac bagging

++ as much as I hate working with it and its expensive (cause it has to be thrown away) tacky tape seals like a champion. The only viable alternative I can see is to put the entire table/mould inside a the bag so that tape is not necessary. I'm keen to have a go at this for next time. !!Maybe creating a fibreglass mould for next time.
++ doing the laminating in one go rather than top then bottom as I did previously. Saved an entire curing cycle.
+ using paper towels as breather/bleeder material seems to work fine. Despite the surface coming out a bit dry (and I think that this may be due to the wood absorbing resin) the finish was nice and uniform.
* Peel ply is very effecting in letting excess resin flow through it. However, I think that may too much as able to flow out and so !! next time I'd like to try using perforated release film instead of peel ply. The release film lets less resin flow across it and so holds more in the laminate. Because of the wood soaking up lots of resin, holding it in there might be a better idea. It also means less is required to finish the surface as its already quite shinny.
* 27 mmHg may have been too much pressure and resulting in the dry laminate on top. Not sure, I need to explore more. It took about 20 mmHg to get the board to conform. If the planks are being glued together (along the length of the board) at the same time as laminating then the problem would go away.
? Resin. The top layer of laminate appeared too dry after it came off the table and there are a few different theories going around in my head. One being that the resin soaked into the wood core because of the long cure time ( I used slow hardener which has a 45 min pot life and multiples of that when its spread out). Maybe this gives too much time and allows the resin to be absorbed into the core. Although, this was not the case on the underside which had a good quantity retained in it. Maybe I need to use a more viscous rather than less viscous resin to prevent too much flowing out when its under vacuum. I followed up the lead from a discussion about the viscosities of FGI and west system 'entry level' resins but the data sheets for the FGI resin quote a huge range for the viscosity 110 -1500 CPS. The West System'2 105/205 is quoted at 580 CPS. I don't understand why the range is so big. A question for FGI.

Rocker table

+++ The matching metal frames, the jig setup, working height very low, the ratchet straps to apply lots of clamping pressure to the jigs.
--- The rocker table surface for wood cores was a disaster and changed the rocker and concave to flat and flat.
!! add 400w workshop lights ($14.95 each at bunnings hardware) to be able elevate the temperature for post curing. Needs a temperature controller for switching on and off.
!! change the surface to either Formica laminated to the ply or use a brokite style construction where a bottom and an upper layer of perspex is laid over the core and the whole thing placed inside a vac bag. The 2 layers together and the symmetrical pressure on the mould should be enough to prevent the distortion. It also works to hold all the pieces together and so makes it possible to do just one gluing and laminating pass instead of the 4 needed to do the rails, 2x cores + 2 cores together, laminating and finishing.

Surface finishing

Really not sure how to turn this around an would like to avoid it as much as possible by using PBT bottom sheets top and bottom ideally. Reality is that probably will only use it on the bottom if I can get hold of it (due to cost).

++ Perspex sheet on the bottom results is a great finish on the board straight off the table.
--the sanding I did made the surface murky. !! do another sanding pass with greater than 600 grit paper and maybe buff it.
-- using epoxy to do a final coat left the surface uneven, 'wavey' as it did not self level very well. !! Maybe try thinning the epoxy of finding good advice on UV stabilised varnish.


+2.3 kg without accessories. 0.4 kg heavier than foam core board. Can't complain about that.


+++ Antig99 footpads and fins. Hard to be on price and work fine. I've give the fins a good flogging in the sand and hit a few rocks and they handle as well as the fibreglass fins do maybe even better without the screen printed logos to show wear.

Saturday, December 10, 2011

Wrap-up - bill of materials

I just did a bit of a round up of the total cost of the board.

Other than the cores, the other material was bought in one-off quantities so no volume discounts.
Due to the transport costs there would be some economies of scale by buying 2x the quantity. Also, buying the cores in 100x1400x6 planks was expensive. I think that buying the kiteboard blanks or larger planks an milling it myself would save a lot.

Also, buying larger quantities of resin reduces (4 kg vs 1 kg) saves around 30% and buying 4 sets of pads and fins reduces the cost buy around $20 per set.

There is also scope to reduce the volume of resin used.

I don't believe there is any discounts on other materials until you start to buy industrial quantities.

So with the discounts I can access I reckon $250 for a complete board with accessories might be possible.

I'd be very interested know how this stacks up with other peoples costs.


Finally finished!

Very happy with the graphics. Other stuff............

I pfaffed around with the final surface finish quite a bit and I have to say that it let the whole project down. But, at least now I have something concrete to get help with.

The bottom side came off the rocker table very slick with a great shine on it. There were a few small voids in it but not enough that I was worried about it letting water get in. The top side came out fairly dry of resin (at least that's how it looked). So, I thought that I do some final work on the surface finish on both sides to see if I could get a high quality finish.

I sanded the top side with 400 then 600 grit wet and dry and sanded the underside with just the 600 grit (to see if that roughness would have any impact of the lustre of the finish). It certainly did. The top looked milky. The bottom not nearly as much but the shine was definitely taken out of it.

I went bought some Gold Spa yacht varnish from Witworth Marine but the weekend staff were not particularly knowledgeable on the varnish but the convinced me to try alternative one that was a polyurethane varnish and is supposed to have better UV protection. Seemed to make sense. Problem was that the varnish was too viscous to get into the small voids and all it did is make them more pronounced. I tried it on a test piece first so it was no dramas but it meant that I decided to just put down a thin coat of epoxy.

I thought about thinning it out and in hindsight should have. Although it did give a very nice clear, shinny finish it did not self level very well (maybe because the FGI resin is relatively high viscosity?) and so it left an uneven surface that I am none the wiser about how to fix. In the picture of the underside at the bottom of the photo you can just make out some of the brush marks. A close inspection of the board shows a lot of these and it looks pretty ordinary. Chalk this up to experience.  

So, I'll do a little googling around to find out more but I am officially calling this board finished and started to think about the changes I'll make next time round.

The biggest success out of all of this was the graphic inlay. Easy to apply, looks great and cheap ($25 per side)

Wednesday, December 7, 2011

Board #3 comes off the table

After leaving it on the table for 36 hours (its been wet here so I left it in the evacuated environment of the vac table, safely away for the moisture - go the vac pump which run reliably for 36 hours!!!).

Overall I'm pretty happy. Other than the rocker/concave disaster, lots of things I tried worked well.

Sorry about the weird orientation of the images, they got rotated in transit and not sure how to change it.

Peel ply peeled back

Off the table - the footpad reinforcements are visible due to the different density weave of the 4oz s-glass

Eureka!!!!! Look at that shine right of the damn perspex - what a love/hate feeling I've got right now.
The bottom and the graphics looks awesome. There's a lot to be said for getting the amount of resin right and not letting too much get squeezed out.

The top surface was another story. I'm going to need to ask around about this one cause I'm not really sure why it came out with what appears to be too much resin extracted. In the image below you can see the white weave of the fibreglass that is not fully saturated with resin.

Slightly too dry top surface. What the?
Not quite sure what the culprit is here. Some possibilities that come to mind are:

i) The clamping pressure was too high? 27 inHg = c. 90% of a vacuum.
ii) The wood drank up the resin from below and left the voids
iii) The bleeder material is too effective? The paper towels are very absorbent material and so maybe there was excessive 'wicking' up of the resin.
iv) Too little resin in the first place. This didn't seem to be the case when I wet it out but perhaps when the resin got absorbed it was a different story.....

To fill the voids I literally did a 'hot coat' of resin and pushed it into the weave by dabbing it vigorously with a end of a paint brush.

Hot coat, I believe, refers to a polyester resin mix that has a bit of extra catalyst in it so that it goes off quickly. That doesn't work with epoxies but heating the epoxy up sure as hell does. When I was pouring the inserts the other day I put 70 gms of epoxy in the microwave for 15 seconds. It thinned out brilliantly but it went off in about 5 minutes. So I used the same idea here. I heated up 70 gms of resin, put it in the microwave for 10seconds. As soon as it hits the board and the surface area of the resin expands it looses a lot of the heat to the atmosphere so I figured it would be ok to leave it in the pot for 1 minute before I poured it as this would let the reaction that is speeding along due to the elevated temperate progress. It seemed to work ok and after I poured it by about the 15 minute mark it was already very tacky. Given it was slow hardener with a pot life of 35 mins it certainly was a faster process.

I have read, and this is in the category of Trev reckons, that for each 10 degrees you reduce the temperature of the epoxy below the design ambient temperature you slow the curing by a factor of 2. It would seem that raising the temperature by 10 degrees has a more dramatic effect.

Rocker Table Disaster

Despite the workflow running smoothly, albeit slowly, the major failure that occurred was the deformation of the rocker table surface under the stiffness off the wood.

The table surface I've been using is 4mm ply with 4mm perspex over the top. The ply gives the stiffness required to get the nice parabolic concave profile that the perspex can't do on its own and in addition the perspex gives a brilliant finish on the surface right off the table.

For a foam core that has effectively zero stiffness the perspex was strong enough that the force required to bend the foam core was not enough to bend the clamped perspex. For a wood core with no rocker its also strong enough but as soon as you add rocker the lateral stiffness of the core cores through the roof even though the grain runs perpendicular to it. The net result is that the perspex lifted off the ply and through the clamping pressure of the jigs and so about 1 cm of rocker vanished in an instant!!!!!

Board at the lower side of image. Shadow shows the extent to which the perspex lifted off the surface

Rocker reduced. This gap should represent around 1/2 the rocker. which puts it in the 2.5 cm vicinity

Concave all but vanished!!!
 So not the board that I was aiming for but there are a number of great outcomes from this.

i) I've been very curious about how concave affects the performance (other than stiffness) so now I have an unexpected chance to see first hand. The board is quite similar to board #1 but without the concave. Rocker is about the same. So it will be possible to test by riding them back to back.
ii) Its increased my commitment to being able to put the entire table (or surface) is a vac bag so that I don't have the asymmetrical forces on the surface doing exactly what it did hear ( again another tick for their Royalty Highness's at Brokite)
iii) Lots of other things worked spectacularly well: The workflow setup, all other aspects of the rocker table, laying up both sides at once.

Not the outcome I was designing for but some great real experience !!!!!


Tuesday, December 6, 2011

Under the pump

We had an unexpected break in the weather and so yesterday I took an early mark and got board #3 onto the rocker table. Overall things when smoothly with the exception of the rocker table surface which deformed under the pressure required to get the concave into the board once the rocker had applied.

Getting everything ready to avoid wasting time once the curing starts

First thing was to assemble the rocker table and clamp it tight with the ratchet straps.

Note the rocker table surface is 4 mm perspex over 4 mm ply wood. The perspex in this clamp style rocker table bends sharply over the middle jig and so the smooth 'beam' bending on which the rocker calculations don't work and you end up with a 'triangular' concave rather than the (almost) parabolic profile.

Ratchet straps worked well, The metal pole over the top was just to assist applying clamping pressure to the jigs in the middle where the greatest force is needed. It didn't get in the way too much because there was a lot of clearance under it.

Next I sealed the core with resin. Couple of reasons for this. Firstly, I want a white background for the graphics on the underside and secondly the wood drinks in quite a bit of resin and I have read that this can also lead to air bubbles in the laminate (though with temperatures falling its more likely to be drawing air and resin into the core rather then expelling it). It took around 100gms of resin to do both sides.
The as the pigmented resin did soak into the core the coloration became a translucent white with wood grain showing through. I was wanting opaque white but it was not to be.

Then to the layup. I'm using 200gm e-glass 0/90 degrees. Two layers both sides. The resin/fibre ratio for this is around 50% so given the board size I figured that the ideal would be around 200gms resin per side + 10% for excess required to saturate the glass. This turned out to be spot on even with the decal insert.

On the bottom, I put the graphics in between the 2 layers. The material the graphics is printed on is like thin peel ply and so as soon as it touched the resin it started to wick it up and it saturated with almost no pressure being applied. I did pour some extra resin on it to make sure. Any excess here will be drawn into the next layer of glass and excess beyond that will be sucked out under vacuum.

Graphics ( blurry)
 Then the core and top 2 layers plus the footpad reinforcements.

top 2 layers pre-bagging
I am not very quick with the resin work and so but this stage it had been over 50 mins since the first layer of cloth was wetted out. Fortunately I was using slow hardener ( 35 min pot life but much longer once you spread it out and the heat generated by the curing does not speed the curing process up) and it was a cool night so it was still very workable. I was worried that it may have gone too viscous to effective squeeze out the excess resin but it did seem to be an issue based on the amount of resin that came out.

I used loads of paper towels as the breather/bleeder material and it works fine. In addition I used carpet felt underlay cut into strips and placed around the perimeter of the board to keep the air channel open so that the vacuum would be applied evenly around the board. This stuff works great.

Vac bag on and starting to evacuate it.....

..... evacuated and holding...

..... 27 inHg vacuum pressure.

Initially the vac pump engaged every 1-2 mins once it reached 27 inHg. I thin part of this is the lines in the pneumatic circuit distorting ( I'm only using fairly soft plastic hoses) and part was small leaks due to glass fibred draped across the tacky tap. I went around a pressed the film into the tape and also run a line of packing tape around the edges of the film. Because of the short duration of the starts the relay on the pump did not have time to reset properly and so the pump was not reengaging when the micro switch on my regulator closed but rather only when the relay on the pump reset. I was a bit worried about this but fortunately the seal got better and the restarts reduced to every 15-20 mins.

.... Next up a fuller debrief of what worked and what didn't....

Monday, December 5, 2011

Cores ready to laminate for board #3

Finally the cores are ready to laminate.
Life cycle of the core design...

The Paulownia cores are finally ready to rock.

The inserts and rails are cured and I've thinned the cores down from 12mm to about 10mm in the middle tapering to 8 at the end of the top deck and then 6mm constant thickness of the lower layer. I've also filled the insert holes with wax to prevent resin getting in (which is v. painful to remove afterwards).

I've got all the glass and graphics cut to size and now its just waiting on the rain to ease so I can start glassing.
The board 'kit' ready to roll.

Lay up schedule is going to be pretty basic:

+2 x 200 gm ( 6 oz) e-glass cloth top and bottom
+graphics encapsulated between 2 layers on bottom
+4 oz s-glass reinforcement under the foot pads
+R180 resin with slow hardener (to allow longer for excess resin to flow away)
+ White pigment in resin to seal the wood and provide the white background for the images on the underside
+ Seal the top with clear resin and let it yellow in the UV (for the antique wood finish)
+peel ply, paper towels (lots) for bleeder, breather material, proper 200 u vac bag. 25 mmHg vac.
+room temperature cure ( apparently R180 is designed for room temperate cure and doesn't benefit much from post curing. FGI's R300 series on the other hand requires it).
++ (new) glass both sides in the same session instead of one at a time.

Now just need the sun to come out and the rain to stop cause I'm working outside in the open car port and apparently moisture in the air weakens the resin. Although if its going to be under the vacuum film after 30 mins of wetting out then I am not sure how much opportunity there will be for it to absorb moisture.........

Thursday, December 1, 2011

Thinned the core and set inserts

I glued the core together but with the 11mm thick it was already very stiff so I shaved it down with an electric plane and 40 grit sandpaper on an orbital sander to get it to around 9-10mm. Cause the flexural rigidity is proportional to thickness cubed, a 10% reduction in the thickness leads to a 33% reduction in stiffness.
Next step was to add the inserts. I'm using just plain M6 stainless flange nuts. Last time I used these and pressed them into ABS plastic washers. The idea of the washer to spread the load around to reduce the stress at anyone point. However, after looking at the Decay boards, they used much small diameter holes to place the inserts into and so this time I going to use just the nut and rely on the smaller radius holes for the inserts to reduce the stress on the epoxy and hope that the 9-10mm core thickness gives enough area for it to stay put.
I had drilled the insert holes (20mm diameter) all the way through the board. I put a small amount of 5 min epoxy in the bottom of each insert hole to form the protective barrier to prevent too long screws pushing through the bottom of the board and delaminating it. The alternative is to cover the end of the nuts with metal ( this is how it is in most production boards I believe) so that the screw can't go through. This is obviously a more robust build but the unevenness of my core thickness was likely to make it necessary to chose a different screw length for each.
Tip: put masking tape over insert holes and then cut the hole out. This will stop the resin flowing onto the wood which takes time to sand back. I've also put some pigment in the resin and getting it on the wood stains it quite deeply.
To fix the inserts I place double sided tape on a piece balsa wood and pressed the head of the bolts ( the the nuts screwed on so that a couple of threads extended out the bottom) into the balsa. This made for a very simple support for the screws that could then be masking taped in place to keep them vertical and centered.
Next step is to actual start glassing. Got all the supplies I need from FGI. I also got a bit of a tour where then keep all the reinforcement they sell to walk-ins! After too'ing and fro'ing about s-glass and e-glass it ultimately came down to the availability of the right weights. So I've ended just going with 200gm woven e-glass, R180 resin and standard hardener ( 25 min working time).
Forecast for the next week is for rain so it looks like I may not get to finish the board in time for my trip to Old bar later this month. Shit!

Wednesday, November 30, 2011

Explanation of Composite Materials

I just stumbled across this useful information sheet on loads of different composite materials and tools. It seems to be aimed at aircraft (full and model) builders but included carbon,e-glass, s-glass and various resins.  It has good laymans explanations of the features of the product ( e.g the weave pattern, vac bagging, different reinforcements) and great info on when and why to use some of the things!

New Brokite Video

Its been a while since I checked out Brokites site so have just caught up on the fact that they have added 2 more tech videos to their web-site. One on how they work with ABS plastic and the other is how they make their inserts.

These guys have simplicity and sophistication down pat!

Monday, November 28, 2011

Cut core and poured rails

Today was my first attempt at using a router to cut the cores and I was very very happy with the way it turned out. A small victory but a victory none the less.

Routed around the top and bottom templates using with the templates on top. I used Deans tip of putting double sided tape down (under the template and under the board) and no clamping was needed. I used a inverted flush trim bit which has the bearing at the top and cut all the way through.

Instead of routing a channel for the rails I cut all the way through the core. My top deck extends out on to the rails and so it need the poured rails to be flush with the top surface. To create the channel for pouring the rails I put packing tape on the underside of the board to create the channel.

I poured the rails as well and fell into a trap for young players - forgot to level the table properly and because I didn't mix and q-cell in the resin ( going for clear rails) it very quickly flowed to one corner at the expense of the others.  This was quick to remedy and so its curing away as we speak.

The rail channel is 9.5mm x 6mm x 3.16m and used about 240gm of resin (c. 120 mls)

Sunday, November 27, 2011

Paper graphics

When I was gluing the woodplanks together I used some of the left over resin to see whether it would cause the inkjet printed graphics to run. I'm happy to say it did not.

I took a few picture but you can't see much from them because the font I used (old type-writter) already looks smudged and the camera had trouble focusing properly so the blurred images make it look like is has run. But, I assure you it did not. The pixelation that was visible right off the printer was still there, there was no obvious running of spreading of the inks.

I was using standard inkjet ink (bought from Coles in fact) on 80 gms printer paper. The paper became translucent but no were near transparet. Thin stock (tissue paper or rice paper), I've read, is the way to go.

I am going to try on thinner stock to see if it makes any difference but I am quietly confident it won't.

Just for completeness here's a few of the snaps ( I promise in real life its not running)
The logo in the free font 'Old Typewriter'
Close up of the underside - although the font has rough edges the edges remain well defined.  
The red dot - the red halo around it is due to light and poor focus of camera.

Thursday, November 24, 2011

Starting on the core at last!!!!

After many distractions, a couple of other projects and a fair bit of time sourcing materials for the boards I finally started on my first wood core. Only a baby step but it feels good to be  moving forward.

I decided to build the core up our of 6mmx100mm Paulownina planks instead of starting with a thicker core and cutting and routing it into shape. I don't have particularly good tools to work with so for this board at least I'm trying to minimise the work.

Tonight I stuck the planks together (told you it was a small step!). I had intended to slice them into 50mm widths and mix them up to average out the weakness in the wood by shuffling the planks but the strip cutter that I used for balsa previously wasn't up to the job of cutting the much denser Paulownia. So instead I decided just to work with what I've got until I can put together a small table saw to make sure I mill the planks perfectly.

So, the first thing I did was to squeeze the planks together and put masking tape on one side of the board. The idea is to use the tape as a hinge to make it easier to get the epoxy into the join and stop the resin flowing away.

Tape hinges to retain glue and apply some initial pressure to the join.

Tape hinge made it easy to 'wipe' glue along the vertical surface and have it run into the join before closing the join to squeeze the resin around.

Found an extra use for the angle iron of the rocker table. With the angle iron piece used to support the center jig I squeezed the planks tightly together. I put the tool box on top so that when I tightened the ratchet strap it put pressure down on the MDF board templates its sitting on at the same time as the strap squeezes the planks together and so that the freshly glued joints where nice and tight.

Next step is to cut out the layers using the router. First time using one so should be interesting!!!

Saturday, November 19, 2011

Check out Dean's progress on his new board

Dean in WA has got a great set up that is well worth checking out. He's a perpetual innovator!

I love the rocker table idea. He basically took a plaster mould of an existing board and tada!!! Instant rocker table which can be placed completely inside a sturdy vacuum bag - no clamping, no jigs. Brilliant!!!! He' used 1mm vinyl for the vac bag.

I've been thinking that it would be a lot easier with my set up to lay the board up with the acrylic part of the rocker table surface flat. Put the whole thing in a vac bag rather than fuck around with tacky tape and then clamp it down. I'm thinking that the vinyl would be strong enough to take the pressure of the jigs clamping down on it. Provided that there was plenty of bleeder material to soak up the excess resin then the bag would be reusable.

In the video by Fibre and Foam ( search youtube for it) her used vinyl for the vac bag too and it worked fine. However, he put the vinyl directly onto the board surface without breather/bleeder material and it left a ripple effect on the surface of the board because without the breather material, once it comes in contact with the resin, the resin is sticky enough that its nearly impossible to apply enough force to stretch the surface tight.

Friday, November 18, 2011

Rocker table upgrade

First things first, I had to get my rocker table sorted because parts of the last one I used were cut up in the course of the camper van fit out I was working. So this was a good chance to customise the table a bit to make it easier to use and stronger.

I stuck with the original Brokite style design because it just has so many benefits and that the setup that BoardOff's jigs are designed around.

The setup is two matching steel frames one each for the top and the bottom and made out of 40x40x3 mm angle iron. Then use middle and out rocker / concave jigs straight out of BoardOff and clamp easily to the angle iron frames. The top and bottom jigs then come together to bend the rocker table surface over the center jig to get the right compound curves into the table surface (which going to be the same 4mm ply and 4mm acrylic as I used previously. I checked with the plastic supplier I bought it from and they said that the plastic won't deform until it reaches 100 degrees so 50 degrees is no problem. Even if it was a problem, the plastic is supported on the 4mm ply.

Although the table's not tweakable like tables with individual slats that adjust, changing the set up is just a mater of cutting out the new jigs from scrap wood (MDF) and it seems there are no shortage of old cupboard doors thrown out on the pavement that suit the purpose nicely.

So here's the revised table with all the jigs clamped in place with a single G-clamp for each.

I was lucky enough to find a single bed frame at our local St. Vincent de Paul op shop. It has casters and the fold out legs you can see on the bottom section. Its handy for a number of reasons including being at a better working height and will make it easy to place heat lamps close to the work so that I can post cure it at 50 degrees.

The bed slats are pretty solid and I think that they should solid enough to support the load of the center jig without bending.

For the top frame I bought 40x40x3 mm angle iron from Edcon steel which cost about $17 for all c. 6 m of it (compared to $25 for 2m from bunnings). I welded it together and also welded some long bolts in each corner top and bottom to be used to pull the frames together.

My idea is to use ratchet straps around the bolts to clamp it together. The ratchets for both sides can be done simultaneously to help make the clamping action uniform so that it doesn't spill the rocker table surface out one side like it did last time.

The snap below shows the center jig. You can see it in the shadow but the center jig is clamped to a piece of angle iron. This will help keep it straight when its loaded up and also distributes the load across all the bed base slats which should limit bending further.

Next step is to work out how to turn it into an oven. Dean in WA cure his board using standard 100W bulbs. He said that its important to have a fan circulating the hot air and also to make sure you're measuring the temperature at the board surface and not in the top of the oven where the hot air will collect. I also spoke to Dave who runs the engineering show at maxi yacht building facility and he said they put temperature sensors right inside the work so they get exact temp measurements. I'm still working through some ideas for this one.

After that its on to doing the actual board!! Yeah fucking ha!!!

Thursday, November 17, 2011

Board graphics just arrived

I've just received the graphics that I'm going to encapsulate in the board and it looks awesome!
Printed on 135 x 41 cm SILK (although it feels like a synthetic material so maybe SILK is a working name for it. Have asked for some details).

StykerMedia ( on the Gold Coast in Queensland Australia supply prints like these for surfboard graphics so they've got experience with these being encapsulated in epoxy. $25 per print (cheaper for larger quantities) + delivery makes it about half the prince of dye sublimated PBT and has the advantage that you can actual find a supplier of it!!!!

The image is a photoshoped version of The Great Wave off Kanagawa which is one of the series 36 Views of Mount Fuji by Japanese artist Hosukai. I found it on google images (using the 'large' search option) and added the sky because the original is a grey and dull.

Colours came out brilliantly, 300dpi resolution, no pixelation (which was a concern as I pulled the image from the web and put it into a pdf). Website says that wets out completely clear. My plan is to use 2 layers of glass and encapsulate it in between. Will most likely use 4 oz s-glass as the last layer as its apparently much better for impact resistance due to the 30% greater strength and 3 times the strain to breaking (3.5% compared to 1% for e-glass)

Close up of the SILK material.

Flysurfer board making video

After a friend of mine broke the news to me that he had just bought a Flysurfer Speed 3 15m kite I checked out their website and came across an arty video of the board making facilities.

Note the appearance of that damn pneumatic press.. How do they do it without getting dry spots??

Couple of interesting things:

i) 90 psi pneumatic press
ii) wet layup and not pre-preg like I thought might have been used for the high pressure clamping
iii) screen printing the topsheet and not dye-sublimation printing like the other production board companies info that I've come across
iv) plastic tips covering most of the end of the boards - according to the commentary its to give the tip loads of flex 'for rider comfort and control'..
v) appear to be using superglue to stick the rails on. I remember using a gel type super glue one when making a model aeroplane. It helped prevent the glue being sucked into the wood and away from the join and also helped it bridge any gaps which the normal superglue (cyano-acrylics) would drip through.
vi) use a heat gun to heat treat the rails or maybe it is to accelerate the curing of the glue they are using.

Check out the video on the light wind board. Asymmetrical outline and negative heal-side rail. In the video they say that the negative rail helps take some of the pressure of the rail and allows you to put it over the tip and tail. Presumable to allow you to get the fins deeper in the water. 'Help you ride the fins more than the rails'... Why is this a good thing?

Sunday, November 13, 2011

Very, very cheap source for fins

I came across this vendor on e-Bay who sell fins v. cheaply. Their website is good and the video of the fin strength test is impressive. They are polycarbonate reinforced with fibreglass.

I'm going to order a few of the 2" fins and see how they go. They are listed on ebay at $22+$4 shipping for 4 - about 1/3 of the price of the cheapest fins I can get in Oz.

They also mention that the top and bottom sheet material they use is Dupont's Crastin® PBT. At least this is one lead to locate an AU distributor. Unforetunately they won't sell you printed sheets of PBT for DIY'ing

UPDATE: Fins on their way

Update 2: These guys also sell foot pads, strap and grab handles plus for a small setup fee will print your own logo on any of these accessories. No minimum order. Will keep you updated when I get hold of them. The ones below were $57 USD + postage ( $17 to Australia). Dimensions for the pads are on the website.

Update 3: All arrive very swiftly - 1 week ( express and 1.5 week regular post from taiwan!)

Logo for boards

I've been having a bit of fun trying to come up with a brand name for the boards and have settled on Dart Boards. Here's the logo.

The idea is to change the tag line in the middle each time to add something unique or funny and to include good quality artistic graphics each time (hence the 'art' part).

Board 3 Templates

It's a happy coincidence that each time I start a new board council clean day comes along and provides all the wood I need for the rocker table jigs and this time for the board templates.

Despite thinking about different ways to make the table adjustable, using fixed rocker and concave jigs that are cut from mdf and building a Brokite style clamp just proves to be so easy. It's easy to get the material, easy to make sure you have a symmetrical setup and is reusable. Also, because the plan is to post-cure the epoxy at 50 C (the recommended temp for the R180 epoxy from FGI that I'm using) then you have 2 of the sides of the 'oven' in place provided by the outer jigs.

So first step after finalizing the design in BoardOff is to trace and cut the jigs and outline templates.

Rocker table jigs cut from 15mm MDF using BoardOff Rocker/Concave profiles
Upper and lower deck templates. Also 15 mm MDF (black paint is just to seal it from the elements)

Thursday, November 3, 2011

Board Graphics Options

Well been out of action for a while doing a fit out our van ( which came out sweet). Now that project is behind me I'm getting the board building happening again.

I've been looking around at different options for graphics and thought I'd share the few things I've found out.

The most common production board approach is to use a high density, abrasion resist plastic film with the graphics printed on the underside using dye sublimation printing. The typical film material its printed on to is PBT or UHMWPE (ulta high molecular weight polyethylene) which has product names like Durasurf or PTex and is commonly used as a bottom sheet for snow boards. Problem is it seems to be near impossible to source in Australia. in the US sell it and will print your graphics for $50 but the shipping cost is about $150!!

Dye sublimation printing can be used to print onto othe synthetic fabrics and is used to print promotional material ( flags, banners etc) on polyesther fabrics. This might be an option if the polyesther is light weight with a big enough weave for the resin permiate. A local printer I spoke to suggested giving Trilobal Polyesther, commonly used in printing flags, a go. He said the weave is open and it holds a print well. Some further googling on polyesther fabric and epoxy turned up some info from a boat builder forum that suggests that certain polyester fabrics with epoxy are used for abrasion resistance in wooden boats. The one issue they point out it holds about 1.5 -3 times the resin that equivalent weight fibre glass does so it will add weight to the board. However, lots of other benefits if it works - drapes across 3-d surfaces, abrasion resistant, printable with photo images. Definitely worth an experiment. Pricewise, it going to cost $50 setup fee and $80 per meter but the width is up to 1850mm so you can get 2 full sides per  meter or 5 on 2 meters of material so the price is in the territory of PBT etc.

Because plastic inherently has average to poor bonding with resins some of the PBT material comes with a 'fur' called remay on the back which hold extra resin and assists with bonding. However, its not see through so if you want to show off you wood core it won't be ideal and it also holds extra resin which means extra weight. I believe that the film without remay on it requires a good amount of heat to get a good bond. On this topic I was speaking to a sales rep at Dotmar plastics and he was telling me you can get one side laser etched and this helps dramatically with bonding the film.

Anyhow I can't get hold of the material cheaply so this is all academic.

The other approaches I've read about are to use stickers on the finished board and paint over with Clear Coat to protect them. However, this relies on the strength of the sticker adhesion which I suspect will not be good for long and especially if it takes a beating now and then.

The other, more viable option, is to print the designs on porous, translucent material and put it under the glass during the layup. Turns out its as easy as using an inkjet printer and printing on cotton, rice paper or, I suspect, any light weight paper. This would be ideal if your graphics are less than A4 size, for example, like a series of differ geometrical shapes or photos.

I recently spoke with a guy at our local beach who had just been over for a tour through the Decay Boards factory in NZ and bought a couple of great looking wood grain finished boards. He said that they printed on silk and then encapsulated them in the layup. Looked great.They graphics were translucent so you could see the core. Silk also is pretty strong in its own right so may contribute to the strength of the board.

I looked around our local area for printers who could print onto silk but again no luck. A google search turned up some inkjet printable silk sheets that have a backing paper on them that helps them run through the printer. I could only find a US source for these as well. However, it turns out that Quilters have been successfully creating their own paper backed fabrics (silk, cotton etc) to inkjet printing. They use 'Freezer Paper' which is paper used to wrap things to put in the freezer (clever name hey!) It is normal paper on one side and has a thin plastic coating on the other. If you lay your material on it and iron over the top of it the plastic melts a bit a sticks to the fabric. Apparently you can then run it through the inject printer and then just peel the freezer paper off.

This seems like a great option for decals A4 or smaller.

There are 2 drawbacks.Firstly, the PBT/ UHMWPE provides a scratch resistant surface whereas encapsulating the graphics doesn't add anything. If you're going to encapsulate graphics it might be a good idea to have s-glass as your last layer on the board as the extra strength improves impact and abrasion resistance. Secondly, your limited to images less than A4 size unless you have more luck in converting your injet printer into a continuous feed printer (I am sure there is a way to supress page breaks. Anyone, anyone???)

Googling around I came across an obvious and exciting option (obvious once it presented itself ,not obvious because it was obvious before). 'Glass on Surfboard decals' . These are digitally printed and are designed to be encapsulated in the fibreglass. Turns out there are a few suppliers not too far from where I live. Check this out:


These guys print on high tensile strength cotton so it will work great.

These guys, based in Burleigh Heads near where I grew up, print on silk and have have done some SUPs as well as boards.

I've emailed off to get a price and expect that it will probably come in around $60 per side based on the prices on their website for a full surfboard size decal  This is a big chunk of the price of the board but the results are amazing. If you google surfboard graphics it turns up loads of producers. Obviosuly it would be half the price per board if you did not cover the entire surfcae area of the board.....

(UPDATE - the decals printed on silk from StrykerMedia came in at about hald what I expected!!!!).

This is the image that I'm keen to get on the underside of the board. It joins it self as well so can be extended to the full length of the board although stretching it out looks good too.

The great wave off kanagawa by Hokusai 

Wednesday, October 5, 2011

Board 3 - Making life easier

Easy Printing of BoardOff Plans 

I decided to make life easy and get the plans for Board 3 printed. The tiling and taping works perfectly but it is time consuming.

I was walking past a local print shop (hole in the wall type) and they were advertising plan printing. They print on continuous rolls of paper with a width of 1000mm (B1 landscape and B0 portrait). Not having used a printer before I didn't know you could get plans this size printed. Anyhow, for just $8 the printed off the 1:1 scale plans for each deck.

I made a change to BoardOff last night so that you can put the plans for the decks and the rocker jigs into the one pdf file for printing. They fit neatly on 24"x60" paper size in CutePDF but with 40" width ( c 1000mm) you could put multiple decks and the same plan.

Below is the printed plans. I used tape around the edges and across where the inserts go to protect the edge when transferring it to the wood templates.

Something that came up during the tweaking of this design was the need to be able to see where the footpads will fit on the decks. I want to use a router on this board to add a uniform taper around the edges and so I needed to know if this was going to result in the footpads hanging over the edge. So I've updated Board Off to be able to draw the footpad outlines in the .dxf files and added some footpad corner markers onto the draft outline design to help with working out how much taper can be put on. This will come out in v1.3.11

Monday, September 26, 2011

Finally settle design for board 3

I've just recieved a shipment of 100x1400x6 mm paulownia wood planks. Enough to make 10 cores.
I've been working up my ideas for 6mm cores Borkite style but need to rebuild my rocker table and trial-and-error a few things before I invest in the carbon to make this single decks.

So I'm going to stick to more convention design -
  1. 2 x 6mm decks 1 wood, 1 klegecel.  
  2. R180 Slow Epoxy from FGI
  3. poured rails
  4. 2 x 7oz e-glass top and bottom (less that usual 3 x 6 oz due to use of wood in core)
  5. vac bagged

New things I'm going to try
  1. Post cure at 50 C
  2. use router to but chamfer of 60 degrees from vertical and 85 degres from vertical aroundupper deck tip and middle like the new North designs
  3. Footstrap inserts all the way through the board to avoid any risk of delamination due to epoxy or sand in the inserts holes
  4. re-instate the use of 0.75mm holes right through board to allow excess epoxy from underside to squeeze through to the upper deck and be wicked away through the bleeder material.

 Heres the compositied design.

Sunday, September 25, 2011

Press used in North factory

I came across this picture of the press used by North. Presssure  = 170,000 pounds of pressure ( pressumable over the entire surface of the board).

Link to North site Which looks almost identical to the pnuematic presses used to make snowboards.
GrafSnowboards DIY site that used 6 bar (c. 90 psi)

However, I was under the impression that snowboards don't have concave so what does North kites do differently to their press that accomodates concave without the top part of mold causing dry spots in the middle of the board where the top surface bends over it?? Anyone know?

Cheers Matt

Wednesday, September 7, 2011

Humble beginnings

Tonight I printed of the 1:1 scale template for board #3 using the the grid overlay feature recently added to Board-off and it worked like a charm. The diamond shapes give you more than enough points of reference to position the A4 pages exactly right without the need for a straight edge to guide. Its only a minor success but a success none the less.
The pdf file contained the board template scaled up 125% and when I printed it I scaled it down to 81% so that the cut marks placed in the pdf by adobe acrobat reader x were visible inside the printable area and not in the margins where they are not printed. 125%*81% gave me the right amount of net scaling I needed. The need for greater than 100% net scaling may be due to my setup (printer etc) so check this for yourselves.

A4 pages stuck together into the 1:1 template from Board-off.

The annotations on the board with the 50mm diamond grid overlay showing.
I'm still waiting to hear back from Paulownia Paradise about transport costs for the wood core. As a back up I'll go with the light weight gaboon marine ply. Even though it comes in at 2x the weight, it is also substantially stronger. the strength to weight ratio is not as good as Paulownia but it is net stronger.

Tuesday, September 6, 2011

Lateral profiles of rocker table & Mega Clamp!

I've just uploaded another version of Board-Off that includes a new tab there the lateral profiles of the rocker table are generated. Previously the Rocker Jigs in Board-Off where for a rocker table design where the surface material is bent over a central and 2 side jigs that bend the right rocker and concave into the surface. The lateral jigs would be used perpendicular to these jigs to provide additional support to the surface to eliminate the chance of the surface being distorted.

Rocker Ribs plot

Why is this useful? A few different scenarios: i) You are trying to bend a core material that is stiffer than the surface material e.g a plywood core over a thinner ply surface or plexiglass/ perspex surface with just about anything. ii) If you are applying positive pressure to the surface of the board in addition to or in place of the vacuum. e.g. you a clamping the core onto the rocker table under a sheet of ply wood like when trying to clamp stiff core material or adding additional pressure to the surface to get greater than 1 atmosphere clamping pressure to squeeze out more excess resin; or (iii)Rather than deal wit #%@ing tackytape/table surface issues, you want to place the entire rocker table inside a bag and evacuate it. This would make the vacuum bag reusable and avoid the need to search endlessly for leaks every time you make a board.


Part of the motivation for drawing these up is an idea I have been thinking about for working at greater than 1 atmosphere without having access to a pressure vessel.

The idea is use a deep layer of sand over the top of the vacuum bag set up and then use a layer of thick plywood over the sand that can then be clamped down to achieve much higher pressures. The idea of the sand is to allow the pressure applied by the plywood cover to be distributed evenly over the surface of the board ( and so avoid dry spots).

Practically, the sand could be placed inside a large bag to make handling easier and to prevent sand flowing away (indeed removes the need to have a retaining barrier around the top of the table to keep the sand in.

This idea is a variation on the 'Quickstep' process for creating high performance composites for aerospace industry. Here, they use a plastics 'bladder' over the top of the part and fill it with hot water. This provides both the heat and the pressure they need to do away with the need for an Autoclave.

The questions I haven't yet found answers for is how much pressure will lead to dry spots in the reinforcement and what resin/fibre ratio might be able to be achieved.

.... to be continued.

Sunday, September 4, 2011

Board-Off Printing

I tried printing and sticking the tiled 1:1 plan together using the method described in the previous post. While it did work,  it was very tedious and getting the pages to align properly on both axes was very difficult. I ended up with quite an uneven surface and the final plan was not dead straight.

So, to make things a bit easier I've just added a switch to the OutlineParameters that lets you print a diagonal grid over the top of the baord plan so that you have multiple points and lines to get the pages aligned when you print off a tiled version of the 1:1 plans. The output looks like this and shoulb be much easier to sticky-tape together.

Board plan showing grid overlay to assist with physical compositing.
 This will be included in 1.3.10 that I'll post in the next few days.

Friday, September 2, 2011

Printing Board-off plans on standard printer

I've finally got a process down for printing Board-Off plans on a standard A4 laser printer at home. Its taken a while since trying rescale the charts to print from excel but now its a bit more stable. Its a 3 step process and uses 4 bits of software (freeware). Sounds a bit involved but the process is quick even if getting all the software is a bit tedious.


i) Board-Off design tool - get the latest version from this blog.
ii) A9CAD - free cad software that allows you to import the dxf files created by Board-Off
iii) CutePDF - a free tool that creates a virtual printer whose output is a pdf file. Use it just like a normal printer only it saves pdfs.
iii) Abode Acrobate Reader X (free version) - for splitting the 1:1 scale plan into A4 pages.


i) Export you design and rocker/concave jigs as .dxf file from Board-Off.
ii) Open the file in A9CAD
iii) In A9CAD select print and configure the options highlighted below to the settings shown.

A9CAD print configuration for exporting 1:1 scale pdfs of board plans
 iv) save the pdf to a new folder for this board.
v) Open the pdf doc in Abode Acroba Reader X.
vi) Click on file->print and again select 'cutepdf' as the printer.
vii) Configure it as follows:
  a) select 'tile all pages'
  b) scale tile = 125% (the reason for this will be obvious soon)
  c) check 'cut marks' and 'labels' and be sure to say yes when it asks if you want the comments printed.
  d) click on page setup and make sure A4 is selected ( or letter if in US)
 viii) click print to save it as a pdf with the 1:1 scale pdf split into A4 pages.

So, at this point you have a pdf file that contains the 1:1 scale plan split into around 28 A4 pages (many of which are blank) but the plan has been scaled up to 125% of the original size because of item (b) in the previous steps. The reason for doing this is that the pages produced by tiling the oversized image include crop marks that show you where to cu tthe pages so that you can stick them together to get your full size plan. However, these crop marks appear in the margins of the page and so will not normally be printed. To ensure that crop marks are visible you must reduce the page size so that what would be in the margins will appear in the printable area of the page. This invovles scaling the page before you print it out.

As we scaled it up by 125% you need to reduce it to 80% when you print it out (80% = 1/125%). You many need to look in the advance settings for 'free scaling' if the page scaling option in the basic settings doesn't have an 80% option. Below is an example of the 'free scaling' option in the Brother 2040 that we have at home.

Free scaling printing option. USed becasue the page scaling on the basics tab only has 100% and 75% scaling option.
 The printed document should then be the right size. I found that I needed use 81% reduction because of the scaling 'rounding' that I mentioned in my previous post.