suggestions please

Supertigres are notorious for shedding mufflers. Make sure that the propeller is balanced, and you will lessen the vibration significantly. But there really isn't a lot you can do about it other than using lockwashers and thread lock.

From my rc car experience, i can recommend the evil 'stud locker' type loctite for this. Its available at the local auto store - right next to the blue stuff. Its so strong that you really need to heat it up (blowdryer, torch) to disassemble. When the blue stuff heats up, its almost worthless.

I had wondered if heat would hurt the thread locker I had used. It was the blue stuff that is supposed to hold but not be unable to disassemble. Anybody else have an opinion on this?

Get a good small drill and some safety wire (from an aviation mechanic or motorcycle race shop). Drill a hole through the head of each screw and wire them together after tightening them. You can also get screws with safety wire holes already in them from most machine supply houses.

The blue Thread locker is temporary and will loosen in heat. The red thread locker is permanant and will tolerate heat better.

That's funny. I'm a licensed aircraft mechanic and I didn't even think about safety wire. That's a great idea, if you can get the hole through the head of the screw without destroying it. If I remember correctly, those screws have round heads, don't they? It would probably be easier to drill hex head bolts.

Another thing you might try is a bolt keeper made of sheet metal. You find those sometimes on automobiles. Get a small piece of thin brass stock and drill a hole through it. Make sure it is against the muffler stack and cannot turn, and then bend one side up so that it will not allow the bolt to turn. This will work only with hex bolts.

I run a ST 45 and 51. The 51 is particularly bad for shedding gaskets and stacks after 1 1/2 flights,..or was. Here's how to make them behave.

Clean the bolts, engine and stack and lap the stack on a flat surface with fine emery cloth. Don't use a ST gasket(worthless), or red or blue loctite(yet). Instead, use some RTV Silicone (red high temp) and run a small bead on the mating surface as well as on the bolt threads. Assemble the damn thing, and tighten up.

If the bolts are through bolts and nuts like the 45, apply a little blue loctite to the nuts. Warm the puppy up and retighten the bolts.

The RTV is doing the main job now, and the loctite is just protecting your nuts. ;-)

Cheers,

Use nyloc nuts.

Thanks for all of the input. The good thing is most of it is the same so I don't have to decide which idea is best. A new twist is when I received the new exhaust stack the screws that were supplied were actually metric bolts designed to go thru the engine and tighten nuts on the opposite side. The problem is my engine is not drilled thru. It is tapped for shorter screws. I went ot my local hobby shop for advice. He gave much the same advice I have received here. But I was wondering should I drill the engine out for the bolts and nuts supplied?

Thanks again for all of the advice.

Ray

The muffler bolts on my ST bull ring .46 pass through the engine and use lock washers with regular nuts on the back. I've been flying all summer and they have never loosened one bit.

Kat3595 wrote:

I believe that if you attempt to drill through you may go into the transfer ports. Safety wire is the only secure method.

I agree. Unless you have a warped muffler manifold or a SERIOUS vibration problem, lockwashers should hold your muffler on securely. I've never lost a muffler in 20 years. Quality socket-head cap screws and lock washers should do it. Dr.1 Driver "There's a Hun in the sun!"