Duane-RCU

My Feedback: (5)

I hit a little hard on the wheels the other day landing, and the firewall broke loose on my Viper. What do they use on the glass? When I took all the old stuff off, it felt like it had nothing in the cloth. It was fuzzy when I tore it, and inside the tank area, it seemed like all the glue was stuck to the balsa, none in the cloth. Are they using CA, or epoxy? And it didn't seem like they worked the cloth into the corners very good. What weight cloth should I use to fix it?

Bill Vargas

My Feedback: (5)

Hi Duane, what I have done in the past for my firewalls is to use strips of 1 or 2 oz cloth going around the sides, across the firewall and from the top to the bottom. 2 or 3 layers is all I use followed up with an extra layer or 2 in the corners. I know some guys like to use a chopped fiberglass mixture in some epoxy for the corners and that works good too. As for the engine mount bolt holes, put a drop of some lite oil on the screws and screw them in all the way. When the epoxy has cured they will pop loose when you remove them.

Other options would be to glass on the outside of the nose and to use round tooth picks to pin the firewall to the sides of the fuselage.


BV

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hi, never had one come loose, but I have in the past used servo screws in preference to pegging with matchsticks or alike. Use two servo screws per side, screw in the s/screw to cut the thread, remove, then put some slow set cyano into the hole then reinsert the screws. regard trevor h.

Duane-RCU

My Feedback: (5)

I was thinking about using 3/4 glass on the outside, back to where the wing saddle is (like original), only over-lap each side on the front firewall, and then bring the bottom up, and fold it inside the tank area. The firewall itself would have three layers of glass on the front, then glass the tank area too. Is this ok, or should I go ahead and use heavier cloth, and just do the inside like Bill suggested? I'm going to pin it too, I just didn't want to add too much weight glassing it the way I'm thinking of doing it, inside and out....I just think the factory didn't get the cloth saturated with whatever they use on it, and that's why it failed. Thanks for all the help, you guys are great!

HighPlains

My Feedback: (1)

Is the firewall glued directly to the balsa sides internally? If so, it would be very weak regardless of being pinned or glassed with light weight cloth. I don't have any problems with the firewall breaking loose on my designs, but I have the firewall glued to 1/64 or 1/32 plywood that doubles all balsa sides on the inside of the nose.

On the top, it extends to the leading edge of the wing, on the bottom it extends to the back landing gear mounting plate. The sides go back to also pick-up the front bulkhead, landing gear plate, and front wing holddown plate, as well as the rear bulkhead and servo tray. In other words, a plywood box.

I don't glass the insides, or pin anything. I do fill the corners all the way around with hard 1/4" triangle stock, and glass the outside with 2 or 3 oz. cloth. The rest of the fuselage is only 1/8" balsa glassed with 3/4 oz. cloth.

This may not help much with an ARF, but if you build your own it gives an idea of what works and what is strong and light. A completely finished fuselage weighs about 6 to 7 oz. depending on balsa density.

Duane-RCU

My Feedback: (5)

It is plywood on the inside, but the nose is notched, and the firewall is notched, where they glue together, so it's not a complete, plywood-plywood joint. Plus, I think this thing is glued together with hot glue, not epoxy, the old stuff was stretchy and rubbery. And it does have triangle stock inside too, but they were only about one inch long, not the entire length of the firewall.

colesifer3d314

My Feedback: (9)

i highly recomend pinning that firewall...it will make it a ton better and alot stronger...i would also suggest putting come carbon in there to keep it stiff.

Cole

DMyer

My Feedback: (2)

I do just like Highplains when I build except I have a 1/8" ply plate glued onto the front of firewall that glues to the front edges of fuse... about 50% more ply to ply glue area there. I actually make up my firewalls with the front plate added with all holes drilled and rough sanded to shape. I then glue on firewall and install motor mount and sand all edges to the motor mount for that perfect front end fit. I also pin the firewall with 3 tooth picks per side. Even in the hardest crashes... the firewall will not separate from the fuse front.

Good luck fixing that fish head Viper!


Dan