What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Intersection fairing layup issues

Cam7nut

Member
Hi,
I'm making my wheelpant to gear leg fairings and have been having trouble getting the fibreglass cloth layups to conform around the sharp radius of the trailing edge and aft part of the fairing.
I tried a dry run with 1 piece of cloth for the front and one for the rear. The front conformed ok but the rear, once wetted would not follow the tight radius.
Any suggestions?
I'm thinking maybe an inch width strip along the sharp radius and cut the main part of the layup to conform to the profile of the curve.
Any suggestions from builders who have successfully made their fairings would be much appreciated.
Cheers,
Cam
4hqdqu.jpg

331eii1.jpg

wwawbb.jpg
 
Be sure to cut your fiberglas at a 45 degree angle (on the bias,). It will then form around the curves easily. You can lay up in several pieces as well. Be sure to use a stiff separator such as a thin piece of aluminum, at the aft end so you can remove the fairing easily after it hardens. Good luck.
 
Glass

Try laying the glass at a 45 degree bias to the edge, this will help it lay down better. Or you can make it a split line to help removal. Lay a thin piece of aluminim along the edge lay over it, once cured remove the aluminim. Make sure you wax or add release to it. You can also glass this split line from the inside built up with glass or flox, then it's just and easy bondo and fill job.
It's a sharp edge so maybe a pain.
 
Thanks.
I was intending to make the fairing in one piece and then Dremel cut it along the wheel pant split line.
I'd like to permanently attach the fairing halves to their respective wheel pant halves.
 
Placing the weave at a 45 to the edge won't help much with an edge that sharp.

I'd try a flox corner.
 
Yep, no way it will turn that corner. I would cut the corner back about 1/8", lay your first piece down and trim it 1/2" past the trailing edge. The lay in some flox to back fill the void, the lay up the other side. It will be a 1 pc fairing.
 
Thanks Dan and Scott.
I decided to do as you say and use a flox trailing edge.
Also thought it might be easier to lay the top half then trim the trailing edge once the epoxy starts to harden. The top trailing edge will need to be pretty much flush as the lower layup will tend to push away because of the intersecting angle.
I cut a pattern for my 2 layers and also added an inch wide strip along the trailing edge, also overhanging a bit.
I'll fibreglass the bottom tomorrow.
nf4cuf.jpg

25s0eae.jpg

2hcfbjp.jpg

2irx1dw.jpg
 
Pretty work Cam.

Classic flox corner procedure below, illustration from Rutan's "Moldless Composite...."

Looks like you've elected to install the flox after laying up both sides, which is fine. That's the nice thing about FRP; understand the fundamentals, and you can use whatever procedure fits the situation.



Suggestion; After bonding the fairing to the wheel pant, cut away the unused wheel pant skin inside the fairing, clean out the form material, sand well, and lay another two or three plies overlapping the inside of the pant skin. It will ensure that the bonded-on fairing doesn't delaminate from the pant, given lots of grass field abuse.

 
Last edited:
Thanks very much Dan.
I thought with the flox trailing edge that I would tape the T.E. together and apply a small flox fillet from the inside. Maybe even see if I can put a strip of light fibreglass over the flox.
I didn't think of doing it the way of digging the foam and floxing before the second 'glass layup.
Cutting away the inside of the wheelpant to match the fairing then fibreglassing the inside was something I had been considering, but was not sure whether it would be worthwhile. Thanks for removing any doubt and confirming that idea.
While I'm getting the other side wheelpant fairing up to the same stage, I thought people following this might like to see what I did for the outboard wheelpant attach fitting.
I laid some carbon cloth on foil, then wet it out before applying a second layer of carbon. I then covered the wet carbon with 0.4mm clear plastic and squeegeed out excess epoxy. I marked 4 squares to be cut from the carbon sandwich.

11ghzba.jpg


After cutting I removed the plastic and applied the carbon square to my wheelpant. (Foil still on at this stage). Then pushed the carbon to conform to the wheelpant. Removed the foil and covered the carbon with peel ply.

a32srp.jpg


zmk11l.jpg


Removed peel ply, drilled rivet holes and countersunk, then riveted on bracket

14e5o5g.jpg


5tz8g6.jpg
 
After separating the left fairing from the wheel pant and rough trimming, I thought I'd try fibreglassing the trailing edge.
Before doing this I added a few layers of masking tape with a cover of packing tape to the gear leg fairing to allow for Mylar wear tape strip that will eventually be applied after paint. Probably would have been a good idea to do this earlier on, but the split in the trailing edge of my intersection fairings allows this.

i3dldh.jpg


I used 2.5oz cloth cut on 45 deg and was able to get it to conform to the sharp corner. Used 4 layers and held the whole thing together with peel ply.

33krs52.jpg


4kcvvq.jpg


After drying, with peel ply removed, I'm pretty happy with the result. The rest of the trailing edge will be floxed and glassed as per Dan H's suggestion.

1zqyr.jpg


I got a bit carried away trimming the rh fairing and got a bit of a gap

21mdufo.jpg


Still, I don't think this is a big problem, the top part took the 2.5oz fibreglass ok and I think the trailing edge will be ok with the flox method to finish it off.

2ngc03m.jpg


2hz64pk.jpg
 
Fairings trimmed and wheelpant cut to follow inside of fairing as per Dan H suggestion.

sfkxap.jpg


Then I glued fairings to wheelpant with epoxy/flox.

im545l.jpg


Flox fills inside lip joint so future layup will sit nicely.

33mppna.jpg
 
Fairing joint sanded to prepare for fibreglassing.

vmrwus.jpg


An inch wide strip of 6oz cloth on the joint and 2 full layers of 6oz over the whole surface of the lower aft fairing. Before peelply.

1zbgqww.jpg


Before trimming the lower fibreglass I ran a bead of flox along the trailing edge.
This will be sanded down to match the upper surface profile and (hopefully) leave me with a nice strong trailing edge to lay the upper surface fibreglass across. Another great Dan H suggestion. Thanks!

2agje37.jpg
 
Removed peel ply, drilled rivet holes and countersunk, then riveted on bracket

5tz8g6.jpg

Can't do that Cam. Carbon in direct contact with aluminum is a no-no. It's a corrosion issue. That includes the rivets.

Not much reason to use carbon there anyway.
 
Thanks again Dan. At this stage it's no problem to remove the brackets and replace the carbon with fibreglass... or maybe drill the holes bigger and fill them with flox, then drill the #30 holes for the bracket through the flox? What do you think?
 
For reinforcement, on my 25 yr old RV-4's pants I epoxied patches of aluminum sheet at the screw insertion areas, using the same technique used to attach the hinge stock to the cowl. Fairly quick; no corrosion issues.

Charlie
 
Thanks again Dan. At this stage it's no problem to remove the brackets and replace the carbon with fibreglass... or maybe drill the holes bigger and fill them with flox, then drill the #30 holes for the bracket through the flox? What do you think?

Anything to isolate from direct contact will work. When the concern is simple surface contact, the usual prophylactic is a layer of glass between the carbon and the aluminum. However, that doesn't help with fasteners through the carbon.

Me? I'd remove the carbon, and patch 3 plies of glass because I'd want thickness under the rivet head. When cured, butter a little bit of epoxy/flox under the bracket tab and set the rivets while it is wet. Let the wet flox mix squeeze out to form a filet around the edge of the aluminum
 
Last edited:
Back
Top