pixelator

After successfully flying my plane (Hobbico Avistar) yesterday, I did a post-flight inspection and noticed that my firewall is coming loose!!! I've also noticed that some of the balsa in the fuselage, right where the wings sit, the layers are starting to split. I would imagine that the loose firewall is from some of the rather "rough" landings I've had over the course of my flying career, seeing how the front gear is mounted into the metal engine bracket, attached to the firewall. And in the past, I have stalled on approach and busted off the front gear.

Any suggestions on how to fix this? I figured the split balsa layers could just use a bit of CA to fix, it's not that severe of a split, that I can tell.

As for affixing the firewall, the only way I can really get to it is behind the engine, unless I break open the front portion of the fuselage, and epoxy it from the inside.

Would I be safe if I just run a solid bead of CA on the outside of the seam? Or would it be worth my time to cut open the fuselage and CA it on the inside? To me, that seems like it might invite more problems than it might be worth... I dunno.

Thanks

I Got Hit

It would be nice if you could remove the tank and use some epoxy to fix the firewall.

"Would I be safe if I just run a solid bead of CA on the outside of the seam? "
I wouldn't think.

pixelator

Only problem with removing the tank... I still won't be able to get at the backside of the firewall.

My only option to epoxy the inside would be to cut open the top of the fuselage, and peel it back, thus requiring even more damage/repairs!?!

WCB

I cracked the firewall on my trainer during a rough nose gear first landing. I removed the bracket from the firewall and cut a piece of plywood and epoxied it over the bottom half of the firewall. Then I redrilled the holes and reattached the nose gear bracket. Now it is stronger than new.

Montague

I'd look at this as an opertunity to install a tank access hatch in the top of the fuse.

Or, if you want to keep things looking prettier, cut the sheeting off the bottom of the fuse and get to the back of the firewall that way. Then, instead of replacing the sheeting with balsa, use some aircraft ply the same thickness of the balsa. If the firewall sits in front of the bottom sheeting, the plywood will add a lot of strength to take landing loads. If the sheeting sits on top of the firewall it will still help, but you should add some triangle stock along the bottom as well.

Failing that, see if you can work some slow setting epoxy in between the firewall and the sides of the fuse. If the fuse sides extend past the firewall, put some triangle stock there, if not, the epoxy is about as good as it's going to get, and you should keep an eye on it going forward.

jucava

You have to get epoxy somehow there, my trainer is 1/2 balsa and 1/2 epoxy and still flying and looks good also, so keep a cloth with rubbing alcohol handy.

Combat Addict

I had a hobbico superstar select same deal. What I did was put an epoxy coat on the outside corners. That will hold it. When the fire wall comes out later(after a crash), you will need to make a newone. Not that big of a deal. Try to get epoxy on the back, but don't kill your self going after it. Also, the wood on top of the fuel tank area is balsa. So it would be easy to remove however I wouldn't bother. You might try using triangle stock. I would not use CA for firewalls, epoxy all the way!

Just to let you know, I learned on my superstar and now my dad is flying it. It is over 3 years old. Oh yeah, the (new)fire wall has a Tower 46 on it.

pixelator

Haha, so CA isn't epoxy?

Guess that's just another case of a newbie trying to latch on to terms used in the boards, and doing it all wrong!

I'll head to the hobbystore tonight and pick up some 'epoxy'.

Thanks for the advice, I knew I'd get some great answers here.

MinnFlyer

My Feedback: (4)

Here's a suggestion.

Use 30 minute Epoxy. Mix it up, and put it in place, then hit it with a heat gun (A Hair dryer will do if you don't have a heat gun). The heat will thin the epoxy temporarily, and it will seep into all of the crevises. The heat will also make it harden quicker, so don't waste too much time.

pixelator

Roger that, MinnFlyer.

Thanks for the advice. I'll break out my heat gun tonight, and see if I can't get that thing back in operation.

longobardia

Do you have any more information as to how to do this? Maybe a picture or 2 or maybe some diagrams. For us newbies trying to picture it is a little hard.

jester_s1

This is a 17 year old thread, longobardia.
But to help you out, all he did was add another layer of plywood to the front bottom of the firewall. Honestly, it's not the best way to handle the repair, IMO. If a firewall is glued well and reinforced with hardwood tri stock, it'll be very near indestructible. If a 1/4 inch firewall does get ripped out (assuming it's not fuel soaked) it's a good indicator that the nose gear is too strong.