I’m hoping to start on the journey of building my first compsand stlye board. I was initially thinking of going HWS route, but then I found out about compsand and want to follow that route instead. I have lots of experience with vac bagging and resin infusion already through skateboards and snowboards.
I read Berts thread, and a few others here but there’s still some gaps I hope some people can help fill in. My plan is to do a full balsa comp, so balsa deck skin, bottom skin, and rails and use 1 lb eps core with 4 oz on either side of the sandwhich.
Questions:
Lets say I use a hotwire to shape the blank, then I should have the correct rocker/thickness from the get go. Do I still need to use a rocker table to keep that true?
What about foiling the top? Hotwire that part after the rocker/thickness is wired?
Bottom contours: can I shape in the bottom contours on 1 lb eps foam by hand and then skin the bottom to conform? I’ve heard 1 lb is hard to work with. I’ve heard of contour mats and wouldn’t be super opposed, I have decent cad knowledge and could 3d print an exact bottom contour mold.
Now the rails: I’ve heard of people bending the rails over using the vacuum, kind of like a seam between the top and bottom skin. And I’ve also seen most people wrapping the rails in multiple layers/building it up to say 1/2 thick and then shaping after. Any thoughts?
My idea of a plan so far would be this:
Hotwire rocker in
Hotwire outline 1/2 inch thinner than the finished board would be to account for rails.
Hotwire foil (or hand shape foil?)
Hand shape bottom contours (or use contour mat)
Vac laminate bottom skin (no rocker table if already hotwired?)
Vac laminate top skin
Build up rails and shape them
Glass top and bottom.
Thanks a bunch. Many of the old threads have a lot of technical lingo and missing links and compsand.com is no longer around.
Yes, they are great videos but still leave some information out.
Seems like these are a typical EPS construction with skins added and maybe xps some other density rails. I’m looking to a 1 lb foam with thicker balsa or paulownia skins and rail wraps.
I’m mostly concerned about how to get the blank properly shaped ahead of time using a hotwire/shaping by hand and then vacuuming. The rails are also up to interpretation.
I made only one board that style , I skipped the bottom contours and stayed with a flat bottom, so I cant give you tried and proven advice.
1)My ( limited)experience is that not using a rocker bed is sketchy at least. If you can just use the eps offcut with a support as your rocker table that should be sufficient. I put 2mm HDF over the offcut and taped some thin PE sheet over that for release.
Don’t try to use a lot of vacuum, just enough to keep the wood in place. I punctured my vacuum hose with several holes and taped them later to control the pressure.
2) I did it the way you suggested, bagged the balsa together with the inside glass with the help of the rocker table, trued the outline, then foiled the deck and put on the primary rail band . I don’t think hotwire alone will work. If you want to get a decent result you have to shape by numbers here. I was hesitant to cut the band as small as my numbers were telling me and ended up with a thicker rail than i wanted.
i can’t help you here because I left that out , but the way with the contour mat you suggested sounds promising to me. If you can print TPU for example that would be my choice.
How well the wood will conform depends on the chosen thickness obviously…my bottom balsa was 1 mm
I used cork, 5 layers of 3 mm , and made one rail at a time , shaping the overlaps at nose and tail in between.
On the first try I crushed my build by using too much vacuum…so again , go light, low pressure.
Again, no real experience here, so stick to your plan .
My biggest mistakes were :
Too much vacuum
Choosing the visual path were I should have chased numbers.
Good luck!
What will you be using for skins? I’ve been using wood veneer, like Greg Loehr’s video. If you are using high density foam like Bert I cannot help you as I’ve nevef done that.
I stopped using 1lb foam because I felt you had you make a stronger skin and in the end it felt stiffer than a 1.5 or 2.0lb blank with lighter skin. The 1.5 or 2.0 boards are still really light and plenty strong. I think Greg Leohr in those videos was using a multi density blank wih wood perimeter rails? I’ve made stringerless 1.5 and 2.0 boards and never had any failures (knock on wood skins).
If you can get paulownia get it. I did peel tests and glass stuck much better to paulownia than to balsa. It’s a little bit heavier, although balsa can vary a lot. If I was doing paulownia I 'd go with 1.5lb eps.
I use veneer which is roughly 1/40. Greg Loehr says it’s equivalent to a layer of 6oz but lighter and, depending on the wood species, more springy. I like poplar (cheap too) and hickory (super tough).
I fyou can get paulownia get it as thin as you can. I’ve even seen it, rearely as veneer. If you can’t get it thin you can always sand it down but be careful not to sand through.
I used to do banded balsa. It was a lot of extra work and turned out to be over kill. Just made the board stiffer. I go stringerless now. There are 3 layers of 4 oz over the rails. I paint the rails with tempera. Loehr would leave the rails unpainted but at the time I didn’t like the look. Now I think I’m OK with leaving them white. Although one thing about wood and colored boards is , if the epoxy yellows over time you don’t even notice it. If you leave the rails white eventually they will yellow. I’ve toyed with using basalt. I think the brown color would compliment the wood, but I’ve not found a local supplier (California).
I haven’t done a full compsand for a while, but when my brother and I did them with soft EPS we used a rocker bed and bent the rocker in instead of hot wiring the rocker. We used flat sheets that were 1" and 2" thickness then glued them together with the 1" piece on the bottom at the same time that we did the bottom skin. If you have a contour mat you can make your contour at the same time. We often used boards we already had as the rocker bed and they would end up transferring the bottom contours of that board. We used either 4 oz or 2 oz glass under the skin (usually 1/8" balsa for model airplanes), sometimes my brother added a piece of 1/8" thick wood about 3 or 4 inches wide between the layers of foam where a stringer would be as a “springer”. That also helped to keep the center box solid.
Once the bottom skins were glued on with the vac bag, we added the first rail band, usually 1/8" balsa or plywood keeping the rocker bed in place. That would hold the rocker in and I could then shape the deck. After shaping the deck, we added the deck skin, then added the rest of the rail bands. We started with just balsa or layers of balsa and cork, but sometime later we switched to XPS rail bands because it is water proof and lighter than cork. Then we shape the rails and glass the board.
My brother started having issues that looked like he was sensitized to epoxy so he stopped doing boards after about 5 years. It was time consuming to do some work at my house then go to his to do the vac bagging. I started cutting out stringer bands from heavier foam and gluing them up to get the width I wanted using 3", 4" or 6" thick slabs of foam. I found that I had a lot less wasted foam. Once the boards were shaped, I would glass them with one layer of glass and only add a deck skin for extra strength. Sometimes, I glass the bottom then add the deck skin, then finish glassing the deck. That’s the way I make EPS or XPS boards now, I make rocker slices, glue them up, shape the board, glass the bottom, then add the deck skin and glass the deck. The only difference is I recycle foam and I glue up lots of small pieces of foam to make a blank.
I always add wood or HD foam where a box will be for extra strength. I have torn out boxes from boards that didn’t have extra support. I prefer Probox fin boxes, so I place a piece of wood 1/2" x 1/2" x 4" long perpendicular to the box, usually 2 pieces about where the screws are. I route out the area where they go on the bottom of the board before glassing. Sometimes I use FCS Fusion boxes and I don’t add the wood.
Grant Newby has some good methods.
Plenty of documentation on his site.
He uses expanding foam glue to glue the skins to the foam.
Scroll down and notice how far the expanding foam glue is able to penetrate into the foam (9 -10mm) or 3/8’', this effect creates another barrier against water penetration. SurfboardsByGrantNewby
I don’t know what kind of glue he is using but I remember a few people experimenting with gorilla glue year ago, but the glue becomes brittle and led to failures and was quickly abandoned.
It’s not Gorilla glue, it’s Fixtech Fix it mate glue FMP 200 suitable for marine bonding, 100% waterproof.
I have not heard of any bad feedback from anyone who has tried it.
I have tried it once gluing cork to EPS foam and had no issue.
Grant Newby has built lots of boards over a fairly long period of time (he documents most of his builds) and there is no mention of glue failure.
Having said that imagine if a resin chemist could come up with an epoxy resin with the characteristic of expanding foam glue, where it could penetrate say 12mm (1/2’') into an EPS foam blank, it could be a win for surfboard durability.
Super interesting. I’ve seen another guy that uses XPS/Paulownia, fly screen and cork rails with the foaming PU glue and makes entire boards with no resin at all.
