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Potentially dumb question about glassing elevator tips

N546RV

Well Known Member
Disclaimer: I am a fiberglass neophyte, like many here, so I've been drinking from the information firehose the last couple months. Still need to get some practical experience at some point.

Anyway, on to the real question. I've seen where some builders glass over the transition between the fiberglass tips and the aluminum of the actual control surface itself. From the couple of build logs I've looked at describing the process, it seems like people are laying up a single layer of light cloth across the transition and then doing the normal micro/pinhole/etc dance.

What I'm wondering is - why bother with the cloth? Before reading those build logs, I'd imagined in my mind just roughing up the tip and aluminum as needed and adding just enough micro to get a smooth surface.

The main thing that comes to mind is potential adhesion issues between the micro and aluminum, but offhand it seems like these issues would exist for the cloth as well. The other is having something more substantial than micro to bridge the intersection. But I don't have enough practical knowledge to do more than sort of guess here.

What it really comes down to is: do I need to place an order for some light cloth to get this done?

As always, appreciate any insight.
 
flox

I don't use single layer cloth on mine.

I fill the void with epoxy and flox (not microballoon). This will give you a much stronger result. Of course the typical course sand paper and cleaning before.

Once you sand that down you can smooth it out with microballoon. I've never had one crack.

One thing I do to make it really strong is install the fiberglass tips with epoxy flox (and pop rivets) and then fill the void with more flox. That way you have a stronger bond that carries into the joint.
 
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I have micro/epoxy mix to fill out the void and also smooth out any deeps and valley (for painting purpose) as well as body filler then I run a 3oz glass over it to make sure no cracks show up later. Both of my planes went thru this process and never had a crack.
 
Embrace your rivets

My plan was to embrace the transition, and the rivets. Mainly because I tried to fix the transition and it looked horrible. However, my painter had a different idea, and made it look perfect. Not sure how, probably some kind secret handshake painter stuff.

In general, where rivets can be seen under the paint I think it looks cool. Shows the structure - it's not a glass aircraft, it's aluminum.

What I didn't do is cap the ends - you can see in there, I think it's good for inspections, and again, it shows how it's made. Probably going to lose a couple of tenths of a knot, but I'm not racing.
 
Philip, I used a 1/2" strip of thin glass tape over the joint with epoxy everywhere except on the top of the rudder. The only place I had a crack is on the rudder. Any flexing could cause finish cracks. I know on boats you glass all corners and transitions and that is where I learned glass work so I went with what I had done before.
 
I read this post with interest since I had the same question, but hadn't decided to tackle the fiberglass-to-alum transition yet. I'm not surprised from this group that there isn't one approach! I'm curious what you decided to do. I'm thinking of just filling any void with flox and sand smooth since I like the idea of seeing the rivets through the paint. I'm guessing there's not enough stress at the tips, and sufficient rivets, to result in any future cracking in the absence of tape.
 
Top tip from Synergy Air: To help stabilize the tip attachment through heat/cold cycles and the different expansion coefficients of fiberglass and aluminum, adhere the tips to the aluminum with Pro Seal before riveting. This should help eliminate paint cracks along the filled seam later.
 
I did it

All my fiberglass tips and canopy are installed with Proseal for the joint. Sure, a "glassed in" tip looks smooth and pretty, but often will later crack or if need to replace the tip for some reason..good luck. Proseal is super easy to make a smooth, good looking joint that will be paintable, and flexible. Its on every single joint on virtually all airliners, my true historical testbed for conditions.
 
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