Laminated fins - edges?

[SolarYellow]

I see a lot of how-tos by various rocketeers on laminating fins. I can't think of one, from paper to carbon fiber, that didn't leave an open layer cross section at the edge. By that, I mean the skins on each side aren't securely joined to each other. There is generally a layer of epoxy coating the edge of the core, but at the end of the day, there is an exposed section of laminate-core-laminate. This means that the strength of the core is all that's keeping the laminate from separating at the edges where dings, aero loads, etc. occur. It seems logical to me that it would have greater structural integrity if the/a laminate wrapped around the edge, or if the core was brought down to zero thickness in such a way that the laminates on either side could be joined directly. If you're doing tip to tip on a G10 or c.f. plate core, this is a non-issue, but if you're laminating over balsa, plywood, or foam, it seems like it could matter quite a bit.

Is anyone in our little community wrapping the laminate (or maybe a final strip of tape) over at least the LE to lock the skins together and eliminate any gap between their edges?

 

[David_Stack]

The name that came immediately to mind is Gerald Taylor (G_T) here... He's been heavily involved in composites work for aeromodelling (primarily R/C sailplanes) as well as rocketry.

Had to go back several years, but found this thread/post where he talks about using kevlar to apply over the leading edge as part of his layup.

https://www.rocketryforum.com/threads/sprite-6-and-a-baby-o.37382/page-2#post-435909

 

[SolarYellow]

Thanks for that link! I love the LE reinforcement and the fins coming out of the bag with the paint already on them.

BTW, I'm currently OCDing around Nike-style fins for a 4-inch tube.

Major other how-tos I've seen are Harshberger's and John Coker's YT vid, plus a lot of little posts along the way.

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There are a ton of vids and how-tos out there on how to make DLG sailplanes. I'll be down that rabbit hole for awhile.

 

[Troy3003]

I vacuum sealed mine in a food saver. Both sides at one time I believe. I did not add any additional edge pieces and they turned out pretty good. If you zoom in you can see the gaps sealed up. Might not hold for high Mach flights though?

 

[neil_w]

Wrapping tape over the leading edge is recommended practice for the two-piece PS2 fins for exactly that reason.

 

[Art Upton]

Wrapping tape over the leading edge is recommended practice for the two-piece PS2 fins for exactly that reason.

What kind of tape would you use on the PS2 fins and how to attach it?

 

[neil_w]

What kind of tape would you use on the PS2 fins and how to attach it?

Scotch tape. Just fold it over.

 

[Art Upton]

Scotch tape. Just fold it over.

Not lookin' good to me. I use Zap-A-Gap CA on all PSII Plastic Fin Edges after they are glued together. My Method of CA gluing the halves does it automatically, but in case there is any gap, a Bit of Zap-A-Gap fills it in.

 

[SolarYellow]

By tape, I meant cloth tape as part of the layup, as seen in the link posted by David_Stack. Not just self-adhesive tape over the finished fin.

For my WIP PSII build, I will be using either mylar or aluminum tape over the LEs.