How to shape the form for fiberglass ?

[Larry DeCamp]

Forgive me if this has been covered in the past. Tube and rag antique projects gave me the idea of a simple way to get consistent shapes between empennage and canopy skirt components for fiberglass laminations. Polyester fabric ( stits peel ply), cemented to parts ( poly tac) and heat shrunk generate a uniform shape between components. Results are excellent.

http://s1300.photobucket.com/user/LarryDeCamp/library/Empennage Fairing

 

[Ron B.]

How difficult was it to remove the polytac polyfiber from the alum?

 

[Ironflight]

When I think about how much clay and shaping I did to make our fairing, I can't help but call your solution Brilliant Larry! I want to see the finished result.

Paul

 

[rocketbob]

A friend of mine who has passed on used this method to layup engine baffle plenum covers.

 

[jarvis]

I don't know anything about anything, but danged if this doesn't look like a GREAT idea/method.

 

[Larry DeCamp]

Polytac removal

Ron B,

On my preliminary test, the polytac peeled clean and easy with an "orthogonal" peel. Yet in shear, when shrinking and tensioning the polyester, it was amazingly stabil. IF you have a corner such as the intersection of VS and HS's, you lift as much as possible and squirt some MEK in the crack. Surface tension wicks it in and VOILA, the part pops off. Good luck...Larry

 

[DanH]

Cross section:

 

[az_gila]

Cross section:

Dan, doesn't the curve of the front bulkhead make the rest of the fabric have a similar curve? Essentially ending up with a vertical slice of a "dunces hat".

It seems that way in the pictures.

The edges along the fin and stab. will have sharper corners though.

 

[Bob Kuykendall]

Cross section...

Dan, I think that this is one of those things were 2D analysis does not do the topic justice, especially when non-orthogonal (bias) fiber orientations are at play.

A good example of the technique is when Dick Johnson used bias Ceconite to smooth out the pod-to-boom transition on the PIK-20 sailplane when he was doing performance testing. It didn't add any performance, but it looked great, especially considering the minimal effort expended.

 

[DanH]

Don't read too much into the observation. The technique is interesting and useful, but won't allow a tangent intersection with the tail skins. That's all.

Heck, I've been known to flesh out shapes with tape...whatever works.