hybrid rear skirt?

[prkaye]

I've been considering doing a fiberglass rear slider canopy skirt. I know others have done this. One warning I've heard is that this might be prone to cracking.

Another idea I've been toying with is a hybrid skirt, made with alum and fiberglass. The idea is I would make vans alum skirts a little shorter than normal, get them to fit reasonably close, and then glass over top of thes and extend the glass back beyond the edge of the metal skirts to get a good close seal. My idea is that the metal substrate under most of the glass might provide additional strength and help prevent cracking.

Does this seem like a silly idea? Has anyond tried something like this?

[rv9builder]

Phil,

I like your idea and thought about doing something similar. What gave me the idea was an old story in the RVator about a guy who made each rear skirt out of two pieces of metal. By making each rear skirt in two pieces, he was able to get a better fit. On the other hand, by the time you make half the skirt out of fiberglass, perhaps it's just as easy to make the whole thing out of fiberglass.

[prkaye]

perhaps it's just as easy to make the whole thing out of fiberglass

Probably, but my main motivation here was added strength, particularly for the relatively large gap between the aft canopy edge and the skin. I thought bridging this gap with the alum skirt and having this alum provide somethign for the glass to grab onto might prevent future cracking? The other thing is that the glass could start aft of the screws, so there would be no screws going through the glass, preventing cracking there. The only thing is this would mean the glass would have to be tapered down to blend into the metal part of the skirt seamlessly (is a super thin layer of glass bonded to metal crack-prone?)
I don't know anything about the crack-proneness of fiberglass, so hoping somebody will chime-in.

The following diagram roughly shows what I'm thinking. Green is Vans skirt (shortened), brown is fiberlgass.

[alpinelakespilot2000]

Why would your fiberglass crack? The cowl doesn't crack. The wing tips don't crack. The emp. fairing doesn't crack. Get my point?

If you try to lay up fiberglass over the metal skirt you're going to have some really thick (read heavy) skirts.

Good luck.

[hgerhardt]

Fiberglass only. Metal expands at a different rate and the joint will forever cause problems with paint. Besides, fiberglass is plenty strong by itself, if you do it right. By that, I mean at least 5 plies and alternate the ply direction each layer. Use glass that's about .012 thick so that the final thickness is about .060-.070". Use epoxy resin.

I did my -6 that way and after 5 years, the skirt still fits perfectly with absolutely no gaps and doesn't lift from aerodynamic pressure. Another nice benefit is the perfect fit to the slider rail, and it's all one piece.

The way you make it is to bridge mylar packing tape between the rear edge of the plexiglas and turtledeck. Wax everything so that the cured laminate will peel off. Lay up the glass on the tape "tool". Then trim it and treat it as if it were metal, as far as riveting it on to the canopy frame. I used Proseal to glue/seal the skirt on before riveting.

Heinrich Gerhardt
RV-6, flying

[prkaye]

thanks guys... both good points, the weight issue and the thermal expansion of metal. I'll go with an all-glass skirt.
So proseal and/or other ahdesives will not harm plexi?

[cytoxin]

military windows of plexi are installed with proseal.

[petehowell]

Hi Paul,

My skirts have been flown 350 hrs from 0degF to over 100deg F and I have no cracking. I used the tape method mentioned in a post above. You can see my writeup here.

Good Luck!

[prkaye]

Great writeup Pete!!
I've already countersunk the plexi, assuming I was doing the metal skirt. Obviously the fiberglass can't be dimpled to match.
I guess the proseal will fill the countersink in the plexi. The fiberglass skirt will be pretty thin... OK to countersink this?