How to Laminate Large Fins?

[RocketFeller]

I have spent a lot of time trying to figure out exactly how to build the fins for our 4.9x upscale Dragonfly.

In the end we have decided to go with 1/2" end-grain balsa ("Balsasud" brand) core material. The fin laminate is cut from 1.3mm carbon fiber sheet. The laminate is glossy on one side, while the other side has a matte textured finish designed to readily accept adhesives. The edges will be finished with strips of aluminum.

The balsa sheet will be cut to shape on a CNC, as you can see the CF sheet is already cut.

What I am currently pondering is how to laminate the skins to the core material. I am thinking about using melamine covered particle board and plywood to build a press of sorts. Using bolts around the edges and a few large c-clamps I would then compress the sandwich panel while it cures. We will be using Aeropoxy laminating resin to bond the CF to the balsa.

A couple of issues I can imagine running into:

How to keep everything lined up perfectly while it cures? It would be a major bummer if the layers were to slide around and get out of alignment. I am thinking about putting a couple of rods (or bolts) through the fin tab (so the holes will be hidden beneath the body-tube wall).

How to avoid getting resin on the glossy (finished) side of the CF sheet? I imagine a fair bit of resin is going to squish out from around the edges of the fins. We will be cleaning/squaring up the edges on a belt sander after it cures, but I am afraid that the resin could weep under the CF. Would covering the gloss side with a masking film of some sort (vinyl?) be smart? We could even use blue painter's tape, perhaps?

 

[JohnCoker]

What I've used is vacuum in these cases (I have a veneer press that I use for making larger flat lay-ups). For example, Nike-Asp sustainer fins.

I think your idea of covering the surface before handling is good. Maybe you could use shelf paper or something else with a light adhesive. Of course, masking tape would work, but that would take a long time to cover a large surface.

As far as materials, I usually don't use sheets for the surface but for cores. For example, my Comanche 3 upscale.

 

[RocketFeller]

What I've used is vacuum in these cases (I have a veneer press that I use for making larger flat lay-ups). For example, Nike-Asp sustainer fins.

I think your idea of covering the surface before handling is good. Maybe you could use shelf paper or something else with a light adhesive. Of course, masking tape would work, but that would take a long time to cover a large surface.

As far as materials, I usually don't use sheets for the surface but for cores. For example, my Comanche 3 upscale.

Thanks for the links - those are some seriously inspirational builds!

I have thought about vacuum bagging, but I have very limited experience and I don't believe that food-saver bags are wide enough.

That is a good idea to use shelf paper. I was looking into vinyl masking (sold at art supply places) but for the amount I need it was going to be a bit expensive - I don't mind spending money when I need to, but I hate to waste it on something that is going to get peeled off and trashed after one use.

 

[amarillo_rocket]

I use clear packing tape when I vacuum bag CF or FG fins to keep the side away from the epoxy clean. Alignment rods will work just be sure to coat them with a mold release and spray your press with a mold release. My first thought was drill 3 holes in the fin tab and a matching 3 holes in the press. Use 3 wooden dowels glued into the bottom of the press keeping the top of th dowel slightly below the height of the composite to allow from compression. I like spray release agents but since this is a one off project you could use bees wax, carnuba car wax in a pinch I even used Pam cooking spray.

 

[RocketFeller]

I use clear packing tape when I vacuum bag CF or FG fins to keep the side away from the epoxy clean. Alignment rods will work just be sure to coat them with a mold release and spray your press with a mold release. My first thought was drill 3 holes in the fin tab and a matching 3 holes in the press. Use 3 wooden dowels glued into the bottom of the press keeping the top of th dowel slightly below the height of the composite to allow from compression. I like spray release agents but since this is a one off project you could use bees wax, carnuba car wax in a pinch I even used Pam cooking spray.

I was thinking just that - three rods through the fin tab and press. I've thought about drilling holes through both halves of the press and using bolts (if they are unthreaded on the part that passes through the fin it would be good). If I wax them up well it shouldn't be any problem to drive them out once the epoxy sets. I will look into getting some mold release, I am sure I can use it on other projects in the future.

 

[pythonrock]

To prevent the epoxy from adhering to the shiny side, it should be waxed and then sprayed with mold release. Look at smooth-on.com or polytek.com for examples.
If any epoxy gets on that side, it should just peel right off.
If you get wax on the area that needs to be bonded later, it can be removed with ammonia cleaner, then solvent and sand as usual before bonding.

sorry amarillo_rocket, didn't notice you already said that