So I have some plywood fins I want to put a few layers of glass on and I also want to bevel them. Do you typically glass first and then bevel or bevel first and then glass?
Thanks!
Thanks!
So when you glass a beveled fin, do you go completely tip-to-tip, or do you stop the glass at the beginning of the bevel? I suspect that you run the glass clear to the edge, but it seems that the glass would blunt sharp leading and trailing edges.
Hope this helps.
It sort of depends. Depends on how many plies you lay down (more than one) and if your plies are going to get larger or smaller. Meaning if the first ply is smaller than the next plies you lay, then really the top ply should fall at the edge of the bevel to create a "smoother" transition from ply(s) into the transition. This sort of lay up has a little more involvement with tow load transfers, but to be completely honest i'm not 100% sure of how much it effects the forces acted on the fin(s)
The other way would be to lay the largest ply first (assuming you are laying more than one) then to lay smaller subsequent plies. In this fashion the edge of each ply will be exposed all the way around covered by a smaller ply on top. For me I like this method more only because I can sand out a smoother transition from bevel, ply-ply. Doing so this way, for me, I would run the ply all the way to the edge and continue with the theme of sanding a transition.
Both have their advantages/disadvantages
The first description is probably the easiest, but you aren't able to sand any of the possible steps you may get from subsequent plies underneath the largest top ply. Why? You will end up burning through the tow in all of the ply to do so. If you aren't pulling vacuum you run the risk of little voids all the way each ply laying underneath the bigger ply above it. Just hope you stipple all the air pockets out, and none form after you are "done" (in my opinion if doing a contact layup without vacuum, you should check your lay up regularly for voids forming and stipple accordingly.) Under vacuum you shouldn't have any problem with voids, but will create more definite steps in each ply.
The second description for me, I can get a smoother transition. BUT you may want/need to seal the sanded edges with a quick finger swipe of resin just to be sure any possible fray edges don't lift.
Creating clean, EVEN, step backs/step ups in plies really helps in terms of looks and a smooth even transition. I.E. a lay up schedule.
Weave direction/Step Back
Ply 1 - 45 degree FULL COVERAGE
Ply 2 - 90 degree .25 "STEP BACK
Ply 3 - 45 degree .25" STEP BACK
Ply 4 - 90 degree . 25" STEP BACK
Ply 5 - 45 degree .25" STEP BACK
This lay up schedule would be an example of the second description. Reverse "STEP BACK" and "FULL COVERAGE" to "STEP UP" and "LAY FIN TEMPLATE PLY 1 inch FROM ALL EDGES", respectively.
My thinking comes from protoype aerospace. I may be completely off, but this is my thinking how to and why to do a lay up in this fashion.
Pull vacuum to reduce resin weight as needed. Pleat all fillets and outer edges of lay up to ensure a wrinkle free, tight bag.
Hope this helps.
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