making glass panels for fins

I recently made my first pair of fins out of a fiberglass panel I’d made (all previous fins had been made from wood). I realized that before I do this again, I need help on how to make the fiberglass panel to cut the fins out of.

Thinking I was very clever, I decided to lay up the fiberglass on a HDPE cutting board, because does not stick to HDPE. Because I thought there was a small chance I could be wrong, I thought I was being extra clever by putting a piece of waxed paper over the HDPE. I was not nearly as clever as I thought I was. When the panel was done, I realized that the cutting board was not flat, and my panel had a bow in it. Then I realized that the wax paper had not laid flat on the (curved) cutting board, and there were areas where it had lifted off the cutting board. So this first panel was far from ideal. For the next one, I’m going to make sure the base is very flat, and I will use wax or something else to prevent the resin to sticking to it. I’m thinking of making a frame to support a melamine panel.

I used solar cure resin, would lay up about four layers of 6oz glass, and would then go hold it in the sun for a few minutes, and repeat. Perhaps I’m impatient, but this seemed to take a long time. I am wondering if I used either epoxy or regular resin (instead of solar cure), then I could do all the layers at once (say 35 or 40 layers), instead of 4 at a time. The panel I made was about 12” by 12”, and I wonder if it would have been easier to make a larger panel (and use it for another set of fins).

So I’d appreciate any advice on how people make panels for fins. What do you lay the fiberglass on, how many layers can you do at a time, do you use solar cure, and does a certain size panel make things easier?

(I did find out that my cnc router needs to cut fiberglass a lot slower than wood, and I got a few gouges in the fin. For those interested, here is a photo of the fins I made (my friend’s design))

I’m no expert but from what I’ve read on here people use glass, plexiglass, granite slabs, etc to lay up on. Wouldn’t try doing 40 layers at once, most I’ve read of is 6. I used a piece of shower pan liner with some PVA mold release on my first panel. I used clamps to stretch the liner out to make sure it wasn’t warped. It worked great. I do three layers at a time and kick t slow so that it doesn’t go off while I’m still laying up, then let it sit overnight.

Edit: When I mean don’t try doing 40 at once I mean don’t try wetting out 40 layers at once, I definately lam the whole panel in one go

Those fins look like the fins Halcyon showed.
For solid panels, I use a piece of thick chip board or plywood, lay wax paper over it and tape it down. I can only make the panel as wide as the wax paper, but I can make a long panel if I want.
I’ve done 30+ layers at one time, but I do it in increments of 2 or 3. I’ll get the wax paper wet first then add some glass and more resin, squeegee or roll it out, then add more and do the same. I try to keep it fairly dry while building it up, not too wet. Then once I get to the end of the glass layers I’ve cut or if I run out of resin, I place more wax paper on the glass and lay another sheet of thick wood and put bricks on top of that. With this method, I usually don’t get a panel thick enough for single boxes the first time, so I have to do more. I clean the panel with acetone if it is poly resin and denatured alcohol if it is epoxy, then add more layers of glass until I get the thickness I want. Make sure you change the wax paper. I also like to make the poly resin a slow cure mix. You could add a little catalyst to the UV resin and not flash it between layers.
Can’t mess with epoxy cure times, but you can get slow cure epoxy. I haven’t done may of those as full panels, but I use epoxy on foam core fins.
I’ve found G10 panels on ebay at very good prices. You can get a 1/4" panel for FCS, Probox or Futures style fins at reasonable costs. I also have bought 3/8" and 1/2" G10 panels and made fins with that. I like the way the G10 sands, and the finished fins look really nice with the tight pattern. They are made with heat and pressure, so I got the idea of putting the panel under pressure from that.
Another thing I’ve done is buy cheaper fins off ebay and refoil them. Buy a older big fin and cut it down to the shape I want. Sometimes I can get a good deal, and the fin is half way done.
I think the solid glass panel tends to end up with a lot of waste, so I’ve done foam and wood cores, then have maybe 10 to 20 layers of glass depending on how strong you want it. I’m also trying to do a core section from glass then just add more glass where I know it needs to be. I draw the outline on the wax paper, so I know how much glass I need to have. Kind of foiling in reverse, I build up the fin where the foil is going to be thickest. Then when I foil it, I’m not cutting through so much excess glass. Just takes more planning and time to lay it up right.

(first, I didn’t mean to imply my friend designed the fins–he had some fins with this shape he broke, and I simply copied that design)

Thanks very much for this detailed description of what you do; I learned a lot from it. I will certainly try some of your techniques next time. I was worried about adding more layers later if I ran out of resin, which is one reason I went with solar cure–glad to know there is another way.

I had looked at G10 on eBay, and some of it was reasonable. One reason I’m still considering making panels is for different colors.

I also was a bit saddened by the amount of waste in the panel I made, and for next time I was thinking of making the panel an inch or so larger than the finished fin, all around. I’m a bit concerned that laying up the glass in that shape may be messy and uneven, since I found the edges were less consistent in thickness on the panel I made. At some point I’d like to be able to do cores of different materials, and foam sounds interesting. I’ve often wondered what the honeycomb material I see in many fins is, and where to get it.

Thanks again–this helps a lot.

I use an old storm window. Generally I lay up 12 layers of cloth at a time and use a resin roller to make absolutely sure there is no air hiding.

Colors or fabric inlays always look nice.

Never made a fin.
How many layers of cloth do you typically use for a panel?
6-oz? E glass?

Depends what fin system,40 layers 6oz for a single fin box. I hear that one layer of 6oz is about 0.01 inches. So for fcs (1/4") I did 30 layers to make sure it wasn’t too thin.

Hi - I have a pane or two of window glass I use for fin lay-ups. After cutting 36-40 adequately sized layers of cloth, I smear a couple of coats of Johnson’s paste wax on the window pane, buff and start pouring resin. After each pour, I add several layers of cloth. I’ve found that I can make good use of scraps if I trace the fin outline on the bottom of the glass and make sure that all my cloth pieces ‘fit’ the fin outline. What typically happens to me is the top side that is squeegeed ends up tapering a bit around the edges while the side against the glass is perfectly flat. One way to avoid this is to use 2 panes of glass - one on the bottom and once all the layers are saturated, lay the second pane on top and place a cinder block or something to weight it all down. Spacers along the edges between the panes of glass keep everything from ‘tilting’ while it cures. Once cured, carefully pry the window glass apart and with any luck, you’ll have a nice sheet of laminate to work with. With a clear lay-up you can usually peek through the window glass and look for bubbles. Careful squeegee work, adequate resin and pressure helps avoid those. I’ve never used a CNC device for foiling… just a disc sander.

What type and weight of cloth do you use?

I lay up my solid glass fins on clear glass. benefit is can be lit up from below to see air.
Wax paper or surf wax works well.
My wood fins I lay up cloth on top and sandwich.
Have had some success laying up panels on white melamine wood.
Glass just pops of fine.

Lighting up the panel is brilliant! Never thought of that one. Any smooth surfaced will do with a wax release or wax paper. The fin blank doesn’t have to be perfectly flat just bubble free which makes the backlighting genius. Thanks Barry for that tip.

Another trick is to use 4 nuts that are the same thickness as your desired panel thickness as spacers. Lay them on your sheet of glass and then place a second sheet of glass on top making a sandwich with your wetted out cloth in between. You will wind up with a smooth finished surface on both sides of the panel and a means to control the panel thickness.

Very cool trick Mako.
Barry too.
Simple technical pearls like these are Sways’ greatest assets.

Appreciate the input.
I should have thought of using cloth thickness to calculate/estimate the number of layers.
Your post reminded me about thickness values (below) given to me by 2 Sways members.
(Also found some tables I forgot I had – attached .)

Wildy wrote:
“One layer of 6oz is about 0.3mm…
Glass and carbon are about the same, and that’s measured with a vernier, dry. If your lamination is good it should end up the same thickness when saturated.
That’s hand lay-up.”

Zfennell wrote:
“Budget for approx .008 -.010” for a single layer of 6oz glass.
Theoretically if the carbon was the same weight, weave and thread count it would be slightly thicker due to its lower density.”

Hi stoneburner… I generally just grab scraps of whatever I’ve been glassing boards with. I cut the pieces big enough to cover the traced fin outline. I have a box of scraps from years of glassing so it’s hard to tell what’s in there at any given time. Most of my home made fins have a sandwich core so I don’t really count layers - I lay up a ‘spine’, add core material, foil and cap. The fin tab(s) often take a bit of extra work.

John Mellor wrote:
“Most of my home made fins have a sandwich core so I don’t really count layers - I lay up a ‘spine’, add core material, foil and cap. The fin tab(s) often take a bit of extra work.”

Curious. What materials do you use for spine and core. I assume you are capping with FG.
Do you do anything to re-inforce a Bahne box tab?

Buying cheaper and re-foiling works great. I bought two of these:
and re-foiled them for my Thrailkill twinzer. The fins work great and were a great price.