Fiberglass former?

[Steve Sampson]

I want to make a couple of fairings from scratch in fiberglass. In particular a wing root fairing for my -4.

I know how to lay the cloth and stipple it if I have something to lay it on.

What I would like to know is what best to use to create the wing/fuselage interface shape to lay the f'glass cloth onto. I have searched, but been unable to find a guide as to what sort of material to use. I have tried to fill the wing /fuse gap with insulating sheet foam, and then cut some away, but because of the irregular shape of the gap, and the nature of this particular foam, it does not work (perhaps just for me).

Because it is a double curve around the front of the wing it does not lend itself to using flat sheet material. I have thought about using clay but if one is to fill the whole void it is a huge volume.

Can someone steer me in the right direction? Thanks.

[DanH]

Steve,
There was a recent thread where I was looking for alternatives to clay, the conventional method. The alternate was mix-and-pour urethane foam. Urethane wouldn't be easy since the airplane is upright, so I think it is clay for you.

[rv72004]

Why dont you put the original fairing on and then build up on that. Once you have the fairing formed, remove the aluminium fairing and fit the fibreglass fairing taking care to fill any gaps with some mill fibre. EJ

[Steve Sampson]

Dan - I think I will investigate the urathane. I could perhaps build some sort of containement on the upper surface where gravity is helping. On the lower surface, perhaps clay.

EJ - the reason I am trying to think how to do this, is 'cos the VANS fairing is so 'clunky'. I would like to make a fairing of the same quality as the rest.

Thanks for the thoughts. More welcome!

[pierre smith]

Have you considered just doing a simple, flat fairing like the -6's and 7's do? This way you have a one piece fairing that's clean and light and wraps around the leading edge to the belly skin. A friend has this on his very fast -4.

One poster removed a radiused fairing from his bought RV6 and replaced it with the flat aluminum skin and picked up 7 MPH.

Regards,

[gmcjetpilot]

One of his first two or three classic plane building books talked about how to do this. He used wire screen. It will definitely take compound curvature.

However may I suggest YOU DON'T put a fillet root faring. People find it does NOT increase speed and its way harder to make and install, not to mention holes in the side of the body.

You would think a big root faring would reduce drag, but for one I think the installation adds more drag. You are going to end up with thicker edges of fiberglass along both lap joints on the wing and body. Also the dihedral is so low and the wings are almost coming in a right angles, "form" or intersection drag is low.

People like the looks. James Aircraft sells wing root fairings; if a root fairing is what you want, buy them. The work and effort are going to be more work.



I don't have a report on how they fit. Some times off the self formed fairings may not fit perfectly from RV to RV because RV's vary slightly; there's probably more variation on the pre pre-punched RV's. Any way James Aircraft does nice work.

Van's stock flat factory aluminum sheet with rubber strip is light, simple and low drag. You don't need holes in the fuselage either. My advice is save yourself the grief and countless hours of work. However if done well a wing root fillet fairing can be pretty, but don't expect to gain anything but a little more empty weight, build time and cost. That is the word on the street. You millage may vary. I got this info from Tracy Saylor who has one of the fastest RV-6's around. He went to the root fairing and gained no speed, so he took them off.

[szicree]

It's pretty amazing what can be built up out of black plumbers tape. I made my front canopy fairing out of tape and then glassed right over it. I started with small strips running fore and aft, and then went over this with long pieces of tape running perpendicular to the smaller strips. I know it sounds hokey, but you can actually produce a nice clean shape this way.

[RV7Guy]

Strike me dead but I'm kind of agreeing with George on this one. I'm not sure the weight and additional drag created will be an advantage. The rubber gasket forms a minature fairing and eliminates the dreaded "right angle" speed brake.

If you insist, I'd block up the wing/fuse joint with blue foam. Put the stock fairing on first. Use a hot glue gun to attach the foam.

Now find a model airplane guy with experience at cutting foam wings utilizing a hot wire method. You can make a template with the radius you want. The modeler dude will make a hot wire cutter to cut the radius. If done correctly you can glass with very little additional work. I could probably do these in a weekend. However I'd probably just call Bob at Fairings etc and order a set.

BS factor eliminated!!!

[tin man]

The fastest RV4 in the world has a very simple wing/fuselage fairing. No special fiberglass/modelers clay/foam/chickenwire/ area 51 super secret stuff. Airplane featured in Sport Aviation and Cafe reports. KISS.
Tom

[Robert M]

I've never done this to take it for what it's worth.......

This process is what I seen another guy do in the Radio Control world of airplanes.

Use the original to make/form a thick (very thick) mold of fiberglass. then use the fiberglass mold to form the new piece.

This, however, sounds like a bunch of work.