Hello all,
In the instructions manual it states to have the engine so you have the dimensions of the motor mounts to install the blind nuts. I have a friend who would like me to build him the kit while I'm building mine. He wants the mods he wouldn't get in an ARF. But he has no intention to fly it soon and doesn't know what engine he would like in it yet. Could this be done without the engine purchased. The only thing I see in the way is that the 3/4" angle stock with is glued vertically behind the firewall in the tank compartment where I think the blind nuts would be behind. Any suggestions on how to get around that problem, and how are ARFs sold, do they have engine mounts in them or does the buyer have to deal with mounting the engine mounts into the 3/4" angle stock, or are the ARFs built different. Any advise would be great. Thanks in advance.

Regards,

Pat

Pat:

Two ways to go.

1) If he can get to the back of the firewall after the plane is built, no further attention is needed at this time. Build it, wait until he gets the engine, and then mount it.

2) If the back of the firewall will not be accessible, decide on the engine, buy the appropriate mount without the engine, bolt the mount on and finish the plane.

Actually, there's a third way - set the kit aside until he gets the engine.

But if he wants to build now he has the two options.

HTH.

Bill.

The back of the firewall is accessable enough to get the blind nuts in (barely). You'll have an easier time if you don't glue in the back half of the tank floor. Set it up so that you can flex the tank floor down after assembly. The tank compartment is kinda tight - you can barely squeeze in a 14oz tank IF you can flex the tank floor.

You could use a Great Planes adjustable engine mount which has the same mounting holes for all widths. I like them a lot better than the Sig T mounts, anyway.

As for blind nuts, use threaded brass inserts instead. They easily install from the front. I have used them for many planes without a hitch. Most hobby shops and Tower carry them.

Great idea with the GP mount. Question: Won't the blind nuts be considerably stronger with that huge plate behind the firewall to squeeze against?

I have used the brass inserts for ST 3000's and Quadra 42's without any problem. If the firewall is made from reasonably good plywood, you won't have any problem.

After I install the threaded brass inserts, I go around them with thin CA to harden the area and fix them in place.

My problem has always been getting them in, not having them come out. Here's the way I have found the most effective.

Take a bolt that fits the insert, 6-32, for example and screw a nut on it. Then screw the insert on and jam it with the nut. Screw the insert into the firewall. Hold the bolt and lossen the nut. Now you can remove the bolt without it sticking to the brass insert.

I just mounted an OS .61SF on a Kangke SK/50 this way. The plane was made for a .46, but tends to come out tail heavy, so I opted for the .61 I had available. The included motor mount was too narrow even for grinding out so I went with the Great Planes. Rather than try to install blind nuts, I put in 6-32 brass inserts. Couldn't have been easier.

BTW, the plane balances well and has great vertical with the .61.

Hi Ed,
I like the idea of the Great Planes adjustable engine mount. When mounting the engine mount could I assume that all engine manufacturers and engine sizes thrust lines would be lined up parallel with the top of the engine mount rails ? Thanks again.

Regards,

Pat