I've decided to put together a desktop version of BoardOff design tool with the goal of making more intuitive to use than the Excel workbook version. It will have the same main section (outline, rocker, flex) but I'm going to try to improve each of these over time but adding visual design tools, improved flex modelling and improved easy of comparing different designs.
I'm going to use C#.NET because its the only language I don't have a really step learning curve with so it means that it will run on windows machines and because its not a WPF application it means that for folks using other operating systems you should be able to run it if you install MONO ( the open source .NET libraries).
So, it anyone has any suggestions on functions and features to add then please send them my way so I really make it useful and powerful.
Sunday, February 26, 2012
Saturday, February 25, 2012
Pre-cured sheet
I just finished my first attempt at pre-curing a topsheet and it turned out okay.
I bought 1oz surface tissue which is 1oz CSM matting. It has a small amount of binder in it but as it turns you out can't wet it out with a squeegee or roller without it coming apart. So I had to do some remedial work real time.
firstly , I masking taped some plastic film to a sheet of Perspex. Then, I painted a good layer of resin on the plastic to help avoid air bubbles on the underside of the first layer of glass. I figured the surface tissue would be thin enough to not need wetting out first. I've seen in a video RoadToRoad sent me that the key to a mirror finish is to put resin on the surface first, wet out the glass on a separate table before placing over the wet surface.
So I placed the surface tissue over the wet plastic film and poured 80gm of resin which should have been plenty but it seemed like it was only half as much as needed. I suspect the resin ratio for CSM is much higher. Anyhow, I placed the surface tissue down and poured the resin on. that's when I realised I couldn't spread the resin out. it pulled the surface tissue apart and the fibres balled up like fairy floss. So to fix it I decided to push ahead with the whole layup and hope the vacuum would be enough to push it through, which it mostly did.
So here's the pile from bottom up:
Vac bagging seemed to be the right move because only after sometime under the vacuum did it vanish. I'm wondering if this is because of the spray adhesive I used to stick it to paper to print on creating a barrier for the resin to soak through.
After it was all cured, the finish on the surface was good but it was milky in places which is from the fine air bubbles. Happy to say that the surface was void free so coating the surface with resin seems to have helped.
I then mixed up resin with white pigment (5%) and painted over the back with a foam brush and let it self settle.
I bought 1oz surface tissue which is 1oz CSM matting. It has a small amount of binder in it but as it turns you out can't wet it out with a squeegee or roller without it coming apart. So I had to do some remedial work real time.
firstly , I masking taped some plastic film to a sheet of Perspex. Then, I painted a good layer of resin on the plastic to help avoid air bubbles on the underside of the first layer of glass. I figured the surface tissue would be thin enough to not need wetting out first. I've seen in a video RoadToRoad sent me that the key to a mirror finish is to put resin on the surface first, wet out the glass on a separate table before placing over the wet surface.
So I placed the surface tissue over the wet plastic film and poured 80gm of resin which should have been plenty but it seemed like it was only half as much as needed. I suspect the resin ratio for CSM is much higher. Anyhow, I placed the surface tissue down and poured the resin on. that's when I realised I couldn't spread the resin out. it pulled the surface tissue apart and the fibres balled up like fairy floss. So to fix it I decided to push ahead with the whole layup and hope the vacuum would be enough to push it through, which it mostly did.
So here's the pile from bottom up:
- plastic film stretched and taped on flat surface
- liberaly coat of resin on the plastic to reduce bubbles trapped under the subsequent layer of cloth
- surface tissue (I'll try to get some scrim next time which apparently is like fibre glass gauge and wets out easier.)
- graphics printed on tissue paper
- 4oz e-glass (next time I try wetting this out seperately)
- Peel ply
- let it cure under vac.
- painted white fill over the back. I used resin with pigment but I was wondering if painting it with epoxy spray paint might also work?
Vac bagging seemed to be the right move because only after sometime under the vacuum did it vanish. I'm wondering if this is because of the spray adhesive I used to stick it to paper to print on creating a barrier for the resin to soak through.
After it was all cured, the finish on the surface was good but it was milky in places which is from the fine air bubbles. Happy to say that the surface was void free so coating the surface with resin seems to have helped.
I then mixed up resin with white pigment (5%) and painted over the back with a foam brush and let it self settle.
Turned out well. Really flexible, check out the picture of it draped over the table. No concerns now about whether it will conform well with a 3D surface. There were some streaks for uneven thickness of the fill coat I painted over it to get the white background. This probably means that the resin was going off before it had a chance to self level out. It was a hot day so this was probably the cause. Next time I'll try a sponge roller and see if I can get a better result or maybe use gelcoat.
Thursday, February 23, 2012
Thinning on top
For the next board I'm going to make it a bit thicker because I'll be using it in higher wind conditions and in the surf so I want to make sure its up to the task. It's still only going to be 8mm thick but the 33% increase will increase the stiffness of the unlaminated core by around 60% which means around 30% stiffer overall.
My dilemma has been that I've previously tried thinning the 6mm planks that I have using 40 grit sandpaper on a random sander and also using an electric plane and with my emerging woodworking skills the result has been uneven or excruciating long.
To get the 8mm I've decide to thin all the 6mm planks to 4mm because this will mean they are the same thickness as the rail material I'm using so no problems of having to sand it down to avoid bridging and 2mm veneer of paulownia seemed too flimsy to work with and I imaged it would be easy to break. Also, 2 layers of 4mm will be relatively easy to bend while they are not glued together.
So, I took the idea that Fibre n Foam showed in his video of making a jig for using the router and clamped it to the table saw table I made for the HandyCut saw. I used the rail material to set the depth of the router and whao hoo, homemade thicknesser.
The first piece I did was a bit uneven. Only a fraction of a mm but enough to see the obvious furrows. The 4 tips I picked up which lead to the last 2 planks looking almost perfect where
i) make sure you clear the saw dust and shavings off the surface the plank passes over. This is enough to cause the furrows as it makes the surface uneven
ii) make sure the wood plank is pressed flush against the sliding surface by bending the the end of the plank up and so forcing the section near the router bit hard against the surface. A better solution would be to have guides either side of the router to force the plank hard against surface. I'm thinking HDPE strip held down by a compressed spring would be perfect.
iii) If you stop or take pressure of the plank around the router area the bit can easily lift up slightly and the router will put a crop circle on the wood. Feed it through continuously and at a constant rate.
iv) The largest router bit I could find was only 20mm diameter and so I had to keep repositioning it. It only dawned on me half way through that each time I repositioned it I could turn the board around and thin out same section on the other half of the plank. This sped things up.
The final plank was near perfect. The surface was roughed up a bit but I left some extra thickness on there to let me sand it down later.
My dilemma has been that I've previously tried thinning the 6mm planks that I have using 40 grit sandpaper on a random sander and also using an electric plane and with my emerging woodworking skills the result has been uneven or excruciating long.
To get the 8mm I've decide to thin all the 6mm planks to 4mm because this will mean they are the same thickness as the rail material I'm using so no problems of having to sand it down to avoid bridging and 2mm veneer of paulownia seemed too flimsy to work with and I imaged it would be easy to break. Also, 2 layers of 4mm will be relatively easy to bend while they are not glued together.
So, I took the idea that Fibre n Foam showed in his video of making a jig for using the router and clamped it to the table saw table I made for the HandyCut saw. I used the rail material to set the depth of the router and whao hoo, homemade thicknesser.
The first piece I did was a bit uneven. Only a fraction of a mm but enough to see the obvious furrows. The 4 tips I picked up which lead to the last 2 planks looking almost perfect where
i) make sure you clear the saw dust and shavings off the surface the plank passes over. This is enough to cause the furrows as it makes the surface uneven
ii) make sure the wood plank is pressed flush against the sliding surface by bending the the end of the plank up and so forcing the section near the router bit hard against the surface. A better solution would be to have guides either side of the router to force the plank hard against surface. I'm thinking HDPE strip held down by a compressed spring would be perfect.
iii) If you stop or take pressure of the plank around the router area the bit can easily lift up slightly and the router will put a crop circle on the wood. Feed it through continuously and at a constant rate.
iv) The largest router bit I could find was only 20mm diameter and so I had to keep repositioning it. It only dawned on me half way through that each time I repositioned it I could turn the board around and thin out same section on the other half of the plank. This sped things up.
The final plank was near perfect. The surface was roughed up a bit but I left some extra thickness on there to let me sand it down later.
Sunday, February 19, 2012
Video Guides to BoardOff (WIP)
BoardOff has been downloaded over 1000 times now but there is relatively little in the way of user guides so I've finally got around to starting some tutorials on how to use it. I've done a few screen movies and will keep building the library of videos until all the basics are covered.
I hope you find them useful!
BoardOff Video Tutorials
I hope you find them useful!
BoardOff Video Tutorials
Saturday, February 11, 2012
B6 Design - Mini-Me
For the next board I was going to try the light wind board again but this time getting the process right. I still will do this but I'm quite keen to try a scaled down version. Here's a mockup of the design for the next board. Its 130x41cm and othersiwe exactly the same parameters as the light wind board.
I compared this to the Lunacy and its turns out to be very similar. However, the lunacy has very little rocker and is around 11-12mm thick. My version of it will have the same rocker /concave as the lightwind board (now that I have the jigs all set ) and will be be thinner. Hopefully this will help it in the surf and the chop an bit more.
Am going to try to get the production process running a bit smoother this time and hope to pre-cure the topsheet.
I compared this to the Lunacy and its turns out to be very similar. However, the lunacy has very little rocker and is around 11-12mm thick. My version of it will have the same rocker /concave as the lightwind board (now that I have the jigs all set ) and will be be thinner. Hopefully this will help it in the surf and the chop an bit more.
Am going to try to get the production process running a bit smoother this time and hope to pre-cure the topsheet.
Light wind maiden voyage
Hey, I got to test the light wind board in around 15 knots on choppy water. Didn't break!!
Here's a few observations. I can't connect all of them to a feature so all input is welcomed.
i) Very smooth ride, zero spray in the face. I put this down to thin board (6mm) and 30mm rocker which is more than any board I've had before.
ii) Amazing upwind. Tracked up wind better than people on same size kite on surfboards. Strange thing about it. It didn't feel like it was trucking up wind. Normally a lot of force and edging hard is associated with tacking hard upwind but this didn't. I put it down to the very straight rails.
iii) Skatey feel. The extra width (44cm) made it difficult to hold the rails down because of this. The extra distance from my heal to the rail is too much to be able to edge hard. Although its the width that is the driver of this I think the real variable at work here is the distance from heal to edge which depends on your foot size.
Because the board flattened out it slide out easily. Landing jumps was tricky because it was hard to get the edge it and so the only way to land was to land with the board pointing down wind. I watched another couple of people ride it and the same thing with them. I'm going to increase the fin size ( its got 1.75" fins but am going to put 2" fins which are proportionately larger than the size increase). Other then move the footstraps to one side in the next version and maybe channels I don't know what else could be done.
iv) Light wind coasting - it planed with almost no forward momentum at all. Great light windness
v) It rode over chop without any spray at all but wasn't exactly comfortable. I felt every bump. Each piece of chop was like a ramp and board jumped over each one. The board didn't cut through the chop with a sense of stability like the flatter boards I've ridden. This could be for a few different reasons:
i) The rocker is curved in middle then straight. The straight section would be hitting the chop at a steeper angle than my other flatter board. Maybe this pushes the board up more.
ii) The concave profile is set up so that the concave is largely gone by the time it reaches the footpads. This means that the tips are flat which I believe doesn't spill water as well as concave surfaces.
iii) The thinner board being more flexible than the others means that the tips bend up then recover with bigger amplitudes so you have the chop plus the vibration of the board together.
Not really sure. Could just be as good as it gets. Don't know...
Overall, I'm very happy with it. Landed a few big jumps and it felt tough enough. I'm still tentative about taking it into the big surf. The plan for the next board is to reuse the outline but shrink it to 130x41 and add an extra 2 mm thickness in the middle to stiffen it a bit. Will be interesting to see the impact of reducing the size.
vi) You're definitely aware that its a bigger board. Its takes more to turn it in the air and it feels heavier even though it 3.5 kg (with accessories) which is very similar to my other board. The dimensions must just give it more inertia.
Here's a few observations. I can't connect all of them to a feature so all input is welcomed.
i) Very smooth ride, zero spray in the face. I put this down to thin board (6mm) and 30mm rocker which is more than any board I've had before.
ii) Amazing upwind. Tracked up wind better than people on same size kite on surfboards. Strange thing about it. It didn't feel like it was trucking up wind. Normally a lot of force and edging hard is associated with tacking hard upwind but this didn't. I put it down to the very straight rails.
iii) Skatey feel. The extra width (44cm) made it difficult to hold the rails down because of this. The extra distance from my heal to the rail is too much to be able to edge hard. Although its the width that is the driver of this I think the real variable at work here is the distance from heal to edge which depends on your foot size.
Because the board flattened out it slide out easily. Landing jumps was tricky because it was hard to get the edge it and so the only way to land was to land with the board pointing down wind. I watched another couple of people ride it and the same thing with them. I'm going to increase the fin size ( its got 1.75" fins but am going to put 2" fins which are proportionately larger than the size increase). Other then move the footstraps to one side in the next version and maybe channels I don't know what else could be done.
iv) Light wind coasting - it planed with almost no forward momentum at all. Great light windness
v) It rode over chop without any spray at all but wasn't exactly comfortable. I felt every bump. Each piece of chop was like a ramp and board jumped over each one. The board didn't cut through the chop with a sense of stability like the flatter boards I've ridden. This could be for a few different reasons:
i) The rocker is curved in middle then straight. The straight section would be hitting the chop at a steeper angle than my other flatter board. Maybe this pushes the board up more.
ii) The concave profile is set up so that the concave is largely gone by the time it reaches the footpads. This means that the tips are flat which I believe doesn't spill water as well as concave surfaces.
iii) The thinner board being more flexible than the others means that the tips bend up then recover with bigger amplitudes so you have the chop plus the vibration of the board together.
Not really sure. Could just be as good as it gets. Don't know...
Overall, I'm very happy with it. Landed a few big jumps and it felt tough enough. I'm still tentative about taking it into the big surf. The plan for the next board is to reuse the outline but shrink it to 130x41 and add an extra 2 mm thickness in the middle to stiffen it a bit. Will be interesting to see the impact of reducing the size.
vi) You're definitely aware that its a bigger board. Its takes more to turn it in the air and it feels heavier even though it 3.5 kg (with accessories) which is very similar to my other board. The dimensions must just give it more inertia.
Wednesday, February 8, 2012
QR Codes
These QR codes are great. Discovered that the free scanner I have on the iPhone has a creator as well. The QR codes themselves look cool so thought it would be fun to create some and use them as graphics on the board. The QR codes can containn text or direct you to a website and an number of other things. I though it would be cool to have link to the construction photos of the board and also a write up on the board details.
Here's is the text for the board description. It seems that the more text you add it just adds more QR codes nested in the overall image. Not sure the limit.
Just scan it with you QR scanner
Some more
Just scan it with you QR scanner
Some more
Monday, February 6, 2012
The board that should never have been pt.2
So there I was, staring down at my precision designed, poorly executed, slick looking wobble board. To coffee table it or not?
Nah!
Attempts to repair it
Things left out were footpad reinforcement patches and the unidirectional carbon cross straps (65mm). Easy enough to add on and it had been less that 24 hours since the last layer wet down very little surface prep needed. All good.
So why not add the graphics too. Hey, sure. They needed a white background to cover over the carbon so I'll give it a white back ground too. Hey sure.
The plan was to wet out a layer of 4oz glass with clear resin and place graphics down, let that cure a bit and then put a coating of resin with white pigment. So I wet out a layer cloth for the bottom, lay down the carbon cross straps and placed the board on top of it. With the carbon straps being about 0.25 mm thick, this was about 0.5mm where the crossed. With the board laid on top and the perspex underneath, this left the board standing off the surface of the rocker table in a large area around where they crossed. As a result the resin pooled and the vacuum was of no use in removing any air bubbles in the vicinity of the carbon.
Here's the result which gets uglier the closer you get.
You can see the white resin that's pooled around the edges of the carbon giving it the halo effect. This resin has lots of voids in it.
So then I wet out the top layer of glass on a piece of release film and laid the graphics down. This went well and the tissue paper around the graphics vanished and there was no visible diffusion of the ink (standard ink jet printer ink from Coles supermarket). I had visions of letting it mostly cure and then putting a coat of white resin over the back but I realised I had already put the bottom skin down so I didn't have long enough to wait for it to go off and so I gave it about 1/2 an hour before I added the white resin. This wasn't nearly long enough and as soon as this piece got transferred over and laid down on the top surface of the board, the white resin started to diffuse into the graphics, almost completely obscuring them.
The the final screw up was to use felt carpet underlay as the breather material once I had put everything under the vacuum. Turns out the felt underlays density varies a lot and as a result the denser parts pushed the white resin away and it pooled under the leas dense areas. As a result the board came out with what looks like leprosy with the carbon plainly visible through the blotchy white resin.
You can see in the above photo the behaviour of the colored resin. It gathered in the foodpad support areas but was squeezed out of the layer between the partially cured topsheet and the previous top surface of the board.
A closer inspection also shows lots of voids on the top surface. While I worked on the topsheet to get air bubbles out it seems that the lack of bleeder material on top of the glass gave it zero tolerance. The bumpy breather material then seemed to force all the air bubbles into larger voids areas from which the air could escape.
The Don'ts
Nah!
Attempts to repair it
Here's the result which gets uglier the closer you get.
 |
| Close up of blotchy resin showing the diffusion of white resin into the graphics. |
A closer inspection also shows lots of voids on the top surface. While I worked on the topsheet to get air bubbles out it seems that the lack of bleeder material on top of the glass gave it zero tolerance. The bumpy breather material then seemed to force all the air bubbles into larger voids areas from which the air could escape.
- Don't skimp on your planning. Might be worth listing all the steps and checking everything is ready prior to pouring the resin. Once the clock starts ticking its easy to get distracted and forget a step or two. This is especially true when there is more than just putting the laminate on.
- Don't rely on non-cured resin to make carbon invisible
- When creating a top sheet on a smooth surface (and especially if vac'ing it) then there seems needs to be breather /bleeder material on one side to give the air bubbles an way to exit. My only concern here in creating pre-cured topsheets is that the breather material may wick too much resin out and leave the top sheet dry. This will need a bit of experimenting.
- Given the time and pressure in these process, colored resin will diffuse into resin that is not fully cured so don't apply a fill color over your graphics until the resin they are encapsulated in is fully cured.
- Where the thickness of reinforcement materials is not uniform across the entire surface of the board then you need to make sure the table surface or the vac bag can conform to the shape so that resin doesn't pool. On the underside of the board there will need to be something that can, in my case, accommodate a 1/2 mm bump. Maybe some dense rubber matting.
- Don't use breather material that is not uniform in density, it will give the board leprosy.
Wednesday, February 1, 2012
The board that should have never been Pt. 1
It all started out fine. The goal, to be able to assemble and glass the board in one pass. I pre-made the inserts, rails cut to size and flame treated, stitched 450gm glass so only one pass was necessary, moulds to hold it all together.
And was I focused, oh yeah. The steps were almost choreographed. So focused and impatient that I ended up forgetting to insert the carbon tape and the footpad reinforcements and the white pigment!!!!!! So I ended up with an efficient, good looking wobble board
....But lots of good things came out of this . One of them was not the board (it's a real pig) but I tried a lot of new things with this one. Some worked brilliantly, some limped over the line but have potential and some ... na.
So the score is:
Do's - 50%
Dont's - 30%
Do know's - 20%
First things first
I started the clock ticking and poured the resin. R180 from FGI with slow hardener because I wasn't sure how long it would take. Pot life is about 40 mins but this extends to a couple of hours workable time once its spread out and the heat generated by curing can easily dissipate.
First I applied just a single layer of mould release onto all the mould pieces.
Then the glass and mould over the top.
Note the Velco (top and bottom) used to hold the mould pieces together. Reusable and strong and can be easily adjusted.
Then it was time to put all the pieces together. This took about 40 mins. I used a paint brush and fingers to get resin into all the joins including the inserts and rails etc. One of the snags was that because I was thinking that the wood grain would just show through, I could not mark the planks in order to make sure they went into the right place. The board is not completely symmetrical so it mattered where every piece, including each insert, was placed. I spent a lot of time working out where bits when. I think next time I need to stick something on each piece to remind me were it all goes. How to do this without contaminating the surface?? Don't know yet. Possibly using Super 77 spray adhesive which Dave tells me works a treat and doesn't interfere with the epoxy bond to the core. Brokites also use this stuff to stick the carbon cloth in place. I could stick tags on and pull them off once its laid down. Doing this would have saved about 15 mins and some angst.
I spent some time preparing the rails. Abraded them and flamed them with a propane torch. 2- 3 close quick passes with some time for them to cool a little in between passes as the plastic will distort. The surface of the plastic at the end felt cindered almost a little chalky. I was careful not to scorch it as I had seen in previous experiments that as soon as you see brown scorch marks on the outside then bubbles will have already formed inside and the plastic will be brittle.
No photos for this stage cause I was focusing (too) hard.
After all assembled on a flat surface I put the next layer of glass, peel ply, paper towels (bleeder material stand in) shade cloth ( a tip from Dave that this stuff makes for great breather material and it did.
Into to full vinyl bag, sealed with packing tape and evacuated it to 80% of vac . At this stage , still on the flat table.
Then I moved the whole lot onto the rocker table jigs which I had covered with felt carpet underlay to reduce the chance of puncturing the bag. Then clamped it down using ratchet straps.
From the first resin mixing to now was 1 hour 33 mins.
With the core not being pre-glued flat, the concave profile across the board was exactly as designed and virtually no spring back given there was not stresses locked into the board width-wise.
24 hours later...
Because the mould pieces around the heal and toe side where the same thickness as the rails it was very little resin caked on the outside of the rail and this also meant that the excess fibreglass could just be trimmed with scissors. The pictures about are of the board straight off the table after trimming off the excess.
The trick I picked up was to put the excess glass away from the mould pieces first so that there is only a little bit of glass overlapping from the rails to the mould. Do this all the way around because when you do this you can then very easily just snap the mould pieces away from the board with the risk of delaminating the rails which is always a risk given that even under the best preparation the glass plastic bond is still not great.
With a core thickness of only 6mm and 450gm/m2 cloth top and bottom the board was very flimsy; very little stiffness lengthwise and in torsion. The unidirectional carbon straps in an X layout were the key to locking it all into place but without these nada.
So decision time. My wife suggested turning it in to a sign. I suggested that was inappropriate and asked her to please leave the room:)
With just a single layer of wood and the more economical glass it is the cheapest effort so far but I decided to go ahead and try to fix it. Nothing ventured nothing gained. In hindsight a nice sign might have been the way to go...
Wrap up of the good 50%
Full bag - yep. Reusable, no wasted tacky tape or vac film which saves about $15-$20 given the small quantities I buy, reliable. If the board has more curves on the top it might have been necessary to add some pleats to the bag to have some excess to conform to the curves as it doesn't stretch very well. With the table surface fully enclosed in the bag the chance of the table being distorted is greatly reduced as the forces top and bottom are balanced. In my previous attempt the force was just down on the board which meant that the table could bend up to meet it and concave disappeared
Mould pieces - yep. Allowed the held everything together very tightly, reduced drastically the amount of effort needed to clean the board up after coming of the table. This is especially true compared to puring the rails and then having to cut the excess wood and glass off. Also allowed the whole 'kit' of core pieces to be really squeezed in together tightly ( and even more so when you bend it into the rocker table as there is some compression even with the slight curves baked into the board) which helped get a good bond but also helped make up for the inevitable gaps due to the slight mismatches between rail and core.
Laying it up flat first - a very solid base to work from and so was just easier to work. Certainly made it easier to work the resin in with the resin roller. Gave much easier access to the work space. Generally just more convenient. Clamping it into the jigs after laying it up flat was easy and again very convenient.
Shade cloth for breather material - yep. Worked great.
Using a fibreglass roller to work out the air bubbles - yep, again worked well. I have since found out that it might also help greatly to put resin down on the rocker table surface first and wet out the glass on a separate table before laying it over the resin'd surface. This was there are no air bubbles to start with so no change of ending up with the voids on the underside. The top side is a different story and in the absence of plastic topsheet material, pre-curing seems to hold the greatest hope for a shinny finish with graphics and an opaque background.
Assemble in one pass - hmmm. It added more work and time pressure to the layup but it was very efficient to do it all in one pass. For larger volume production runs I think that pre making a kit is probably critical as it will allow processes to be run in parallel rather than in series which is the time killer. However, for 'micro' quantities of production I think there is a middle ground needed if the board shapes are more complex ( surface profiles etc). While it did eliminate the waiting periods for letting inserts cure and then rails stick an then the core planks to glue, I think it would be a bit more difficult to shape all the pieces if the board had several layers. I need to think this through some more because each example against I come up with makes me think of a solution to. Here are some of the issues and resolutions that come to mind
i) Difficulty managing multi-deck shaping because of the large number of unsecured planks of wood - solution use wood the thickness of the board and cut it into narrower strips ( 25 mm). Make them longer than the board and tack glue them or clamp them at the very ends only. Then you could shape the surface, then route out using the template and clamp the pieces in place with the mould to continue working it around the rail areas.
ii) Fine tuning of inserts needed when they are not poured into the core. Just get the sizes more accurate when making the inserts outside the board. Either make the holes in the template a little oversized as the bearing on the router necessarily makes the cutting surface stand off from the template a small amount , enough to required hand working of the inserts to get them to fit. Could use round ABS plastic rod for the inserts as per The mighty might brokites.
iii) Mismatch of the core with the mould - don't screw the mould up in the first place. Make sure the rail widths are exactly the size of the router bit. I feel another home made tool coming on here.
The pro's for this process is that its possible to stockpile many of the pieces needed and then produce a board quickly as needed. Where there is a desire to make a number of the same or similar boards, this hands down necessary. For one and two off's, its a great deal more convenient and fits better with the pieces of time I have available to work on it and a desire not to have the long series of wait times. Both both cases the lack of lateral stresses baked into the board means your concave with survive the test of time.
Con's are that you need to be much more accurate in making the various components otherwise the efficiency gains are lost through having to tweak every bit to make it fit properly. It also potentially makes the shaping process a bit more difficult unless you can find a was to hold all the bits together when shaping it.
I think I am talking myself into persevering with the approach another couple of times.
Next post will be the on the Don'ts....
And was I focused, oh yeah. The steps were almost choreographed. So focused and impatient that I ended up forgetting to insert the carbon tape and the footpad reinforcements and the white pigment!!!!!! So I ended up with an efficient, good looking wobble board
....But lots of good things came out of this . One of them was not the board (it's a real pig) but I tried a lot of new things with this one. Some worked brilliantly, some limped over the line but have potential and some ... na.
So the score is:
Do's - 50%
Dont's - 30%
Do know's - 20%
First things first
I started the clock ticking and poured the resin. R180 from FGI with slow hardener because I wasn't sure how long it would take. Pot life is about 40 mins but this extends to a couple of hours workable time once its spread out and the heat generated by curing can easily dissipate.
First I applied just a single layer of mould release onto all the mould pieces.
Then the glass and mould over the top.
Then it was time to put all the pieces together. This took about 40 mins. I used a paint brush and fingers to get resin into all the joins including the inserts and rails etc. One of the snags was that because I was thinking that the wood grain would just show through, I could not mark the planks in order to make sure they went into the right place. The board is not completely symmetrical so it mattered where every piece, including each insert, was placed. I spent a lot of time working out where bits when. I think next time I need to stick something on each piece to remind me were it all goes. How to do this without contaminating the surface?? Don't know yet. Possibly using Super 77 spray adhesive which Dave tells me works a treat and doesn't interfere with the epoxy bond to the core. Brokites also use this stuff to stick the carbon cloth in place. I could stick tags on and pull them off once its laid down. Doing this would have saved about 15 mins and some angst.
I spent some time preparing the rails. Abraded them and flamed them with a propane torch. 2- 3 close quick passes with some time for them to cool a little in between passes as the plastic will distort. The surface of the plastic at the end felt cindered almost a little chalky. I was careful not to scorch it as I had seen in previous experiments that as soon as you see brown scorch marks on the outside then bubbles will have already formed inside and the plastic will be brittle.
No photos for this stage cause I was focusing (too) hard.
After all assembled on a flat surface I put the next layer of glass, peel ply, paper towels (bleeder material stand in) shade cloth ( a tip from Dave that this stuff makes for great breather material and it did.
Into to full vinyl bag, sealed with packing tape and evacuated it to 80% of vac . At this stage , still on the flat table.
Then I moved the whole lot onto the rocker table jigs which I had covered with felt carpet underlay to reduce the chance of puncturing the bag. Then clamped it down using ratchet straps.
From the first resin mixing to now was 1 hour 33 mins.
With the core not being pre-glued flat, the concave profile across the board was exactly as designed and virtually no spring back given there was not stresses locked into the board width-wise.
24 hours later...
Because the mould pieces around the heal and toe side where the same thickness as the rails it was very little resin caked on the outside of the rail and this also meant that the excess fibreglass could just be trimmed with scissors. The pictures about are of the board straight off the table after trimming off the excess.
The trick I picked up was to put the excess glass away from the mould pieces first so that there is only a little bit of glass overlapping from the rails to the mould. Do this all the way around because when you do this you can then very easily just snap the mould pieces away from the board with the risk of delaminating the rails which is always a risk given that even under the best preparation the glass plastic bond is still not great.
With a core thickness of only 6mm and 450gm/m2 cloth top and bottom the board was very flimsy; very little stiffness lengthwise and in torsion. The unidirectional carbon straps in an X layout were the key to locking it all into place but without these nada.
So decision time. My wife suggested turning it in to a sign. I suggested that was inappropriate and asked her to please leave the room:)
With just a single layer of wood and the more economical glass it is the cheapest effort so far but I decided to go ahead and try to fix it. Nothing ventured nothing gained. In hindsight a nice sign might have been the way to go...
Wrap up of the good 50%
Full bag - yep. Reusable, no wasted tacky tape or vac film which saves about $15-$20 given the small quantities I buy, reliable. If the board has more curves on the top it might have been necessary to add some pleats to the bag to have some excess to conform to the curves as it doesn't stretch very well. With the table surface fully enclosed in the bag the chance of the table being distorted is greatly reduced as the forces top and bottom are balanced. In my previous attempt the force was just down on the board which meant that the table could bend up to meet it and concave disappeared
Mould pieces - yep. Allowed the held everything together very tightly, reduced drastically the amount of effort needed to clean the board up after coming of the table. This is especially true compared to puring the rails and then having to cut the excess wood and glass off. Also allowed the whole 'kit' of core pieces to be really squeezed in together tightly ( and even more so when you bend it into the rocker table as there is some compression even with the slight curves baked into the board) which helped get a good bond but also helped make up for the inevitable gaps due to the slight mismatches between rail and core.
Laying it up flat first - a very solid base to work from and so was just easier to work. Certainly made it easier to work the resin in with the resin roller. Gave much easier access to the work space. Generally just more convenient. Clamping it into the jigs after laying it up flat was easy and again very convenient.
Shade cloth for breather material - yep. Worked great.
Using a fibreglass roller to work out the air bubbles - yep, again worked well. I have since found out that it might also help greatly to put resin down on the rocker table surface first and wet out the glass on a separate table before laying it over the resin'd surface. This was there are no air bubbles to start with so no change of ending up with the voids on the underside. The top side is a different story and in the absence of plastic topsheet material, pre-curing seems to hold the greatest hope for a shinny finish with graphics and an opaque background.
Assemble in one pass - hmmm. It added more work and time pressure to the layup but it was very efficient to do it all in one pass. For larger volume production runs I think that pre making a kit is probably critical as it will allow processes to be run in parallel rather than in series which is the time killer. However, for 'micro' quantities of production I think there is a middle ground needed if the board shapes are more complex ( surface profiles etc). While it did eliminate the waiting periods for letting inserts cure and then rails stick an then the core planks to glue, I think it would be a bit more difficult to shape all the pieces if the board had several layers. I need to think this through some more because each example against I come up with makes me think of a solution to. Here are some of the issues and resolutions that come to mind
i) Difficulty managing multi-deck shaping because of the large number of unsecured planks of wood - solution use wood the thickness of the board and cut it into narrower strips ( 25 mm). Make them longer than the board and tack glue them or clamp them at the very ends only. Then you could shape the surface, then route out using the template and clamp the pieces in place with the mould to continue working it around the rail areas.
ii) Fine tuning of inserts needed when they are not poured into the core. Just get the sizes more accurate when making the inserts outside the board. Either make the holes in the template a little oversized as the bearing on the router necessarily makes the cutting surface stand off from the template a small amount , enough to required hand working of the inserts to get them to fit. Could use round ABS plastic rod for the inserts as per The mighty might brokites.
iii) Mismatch of the core with the mould - don't screw the mould up in the first place. Make sure the rail widths are exactly the size of the router bit. I feel another home made tool coming on here.
The pro's for this process is that its possible to stockpile many of the pieces needed and then produce a board quickly as needed. Where there is a desire to make a number of the same or similar boards, this hands down necessary. For one and two off's, its a great deal more convenient and fits better with the pieces of time I have available to work on it and a desire not to have the long series of wait times. Both both cases the lack of lateral stresses baked into the board means your concave with survive the test of time.
Con's are that you need to be much more accurate in making the various components otherwise the efficiency gains are lost through having to tweak every bit to make it fit properly. It also potentially makes the shaping process a bit more difficult unless you can find a was to hold all the bits together when shaping it.
I think I am talking myself into persevering with the approach another couple of times.
Next post will be the on the Don'ts....
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