Scratch building a mid-wing plane. After making a fillet where the wing meets the fuselage, how do I cover it. I will be using pearl white monokote. 2nd question, what is the best way to make a fillet that monokote will stick to? Thanks

When I covered the wing fillet on my Mustang, I started in the rear and ironed down strips of chrome Monocote length-wise along the fillet. I started with longer/wider strips in the rear of the fillet, and shorter/narrower strips as I went around the curve in the front of the wing. It created a shingle effect, and the borders between the strips weren't too prominent. You're trying to cover a concave section combined with a convex curve, and the longer/wider the piece of covering, the less it will tolerate a more pronounced compount curve. You have to judge the length of the strip by the amount of "bend" you're dealing with. Make the strips on the outside edge about 1/2" wider than is needed, then pull them around the bottow of the fillet and iron them down.

One thing that helped was that I was able to borrow a friends trim sealing iron. It's got a rounded bottom on the shoe, which really helps glue the Monocote to the fillet. Then I used a heat gun and an OveGlove to really press down the covering. I think it might actually be easier to cover a compound curve with Ultracote because I think it shrinks better, but adhesion to the curve might suffer because I think Monocote sticks better. But that's just me, and I don't want to ignite that whole Monocote/Ultracot argument again.

I built the fillets from balsa strips, then rough sanded them to contour and used BalsaRite to smooth out the curves. If I had it to do over, I think I'd rough in the large areas with balsa, then use some sort of epoxy/microballon mixture to smooth it out, going heavy on the microballoons so it's easier to sand. The problem with the BalsaRite was that it would melt under the heat from the trim iron if I pressed too hard.

Good luck with it.

Fred

Thanks for the reply Fred. Never thought about using balsa to make the fillet. I know that monokote doesn't like to stick to epoxy. I use hairspray instead of balsarite.

Have you got the fillets built yet?

When I did the Mustang, I wedged some pieces of triangular balsa between the fuse side and the fillet base, then used them to glue shaped pieces of 3/32 balsa to form the surface of the fillet. Then I thinned out some balsarite with a little water, troweled it into the corners and smooth things out with a spoon.

Another way to do it (at the expense of more wood and a little extra weight) is to glue a length of 1/32 plywood under the wing saddle as a base for the fillet, then countour it to the fore/aft shape desired. Then build up the entire fillet structure using pieces of 1/16 balsa soaked with some water/alcohol so they bend to the necessary shape. After the whole thing dries, go in with sandpaper wrapped around a dowel (or if you're really brave, a Dremel with a sanding drum!) and sand the concave shape into the fillet. Then you'd have a smooth wood surface for the Monocote.

The adhesive of monokote likes to stick to well sanded balsa and it will stick to glass just fine if the surface wax is cleaned off after the resin cures. If the fillets have spackle on them, the spackle will need to be sealed. Bondo works better for adhesion.
I use as low a heat as possible and it would be nice to have a special shaped iron, but I just struggle with the standard $20 special.
Shingling in strips of covering lengthwise with the fillet is the safe bet. If you encounter lifting, it's time to try again, or slit the spot that lifted and splice in a patch. The monokote video makes it look easy, but it's the hardest part of the plane to do.

I don't know if this will work with Monokote because Monokote is a HIGH HEAT film. I know it works with low heat films and Ultracote.

First, cut your covering into strips that are about 1/4 the width of the filet and a couple of inches longer than the filet.

Next, apply a coat of SIG's "StixIT" to the filets and let dry.

Now, USING A TRIM IRON WITH A ROUNDED SHOE, iron your strips on going from the back of the filet to the front. You want to start with the strip on the outermost part of the filet and work your way towards the fuselage. I recommend using a high heat on the film even though it is a medium of low temp film. You will need the heat to get the film to stretch into the assorted concave areas. Overlap your strips about 3/8".

The StixIT WILL HOLD the covering inplace and the covering will not come loose without applying heat to it.

Depending on the degree of detail you want to go to, you can get some latex paint color matched to the film and paint the filets, then after the latex has cured, clear coat the paint to fuel proof it. If you decide to go this route, cover the plane, then mask off the filet area prior to painting and clear coating so that the heat from the iron/gun does not damage the paint.

For filet material, I make a base/frame from 1/16" sheet balsa, then mix up some auto body filler (Bondo) with microballoons (mix the micro balloons in before adding the hardener) and apply the bondo to the balsa frame. The micro balloons make sanding a breeze. Have a dowel or piece of tubing as well as some rubbing alcohol available. Dip the dowel/tube in the alcohol so it is litteraly dripping wet, then use this to smooth the filet and contour it.

Hope this helps.

No not yet I don't. Just getting ready to slide the wing into the opening. Maybe the triangle stock may be my best bet. I can soak in amonia and H2O. Should be able to make the bend. The wing fits in the slot pretty good, not much of a gap.

Thanks Campy

It won't take much of a fillet as the gap is really quite small. Just want something to blend the fueslage to the wing. It is a scratch built Not-for-sale plane size 91 4 stoke. I fly the 40 size and it is a great flyer. This is a picture of the 40 size.