Dieselman1220

My Feedback: (25)

After 11 years and 600 plus flights my old hawk (who is now owned by a friend) has developed a leak in one of the air tech retract cylinders.
I’ve seen some folks on here (Marty) have replaced O rings. I had the retracts apart last night. However I cannot figure out how to remove the piston. There seems to be a cap with no way to unscrew it. Any tips or info on how to take it apart? Thanks.

Dave Wilshere

Large or small cylinder?

They unscrew from the block. Lightly warm the aluminium with an air gun.

Dieselman1220

My Feedback: (25)

Not sure Dave, it’s one of the mains. I’ll attempt to post some photos.

awanx

Hello

awanx

Dear Builders.

I have started a build of my comp arf hawk a couple of years after I bought that kit. This is an awesome thread, however, I am not very clear about a few things . I hope some of your experts can help me.

1- The thrust tube is passing very close to the elevator servo plate. Is it recommended to use some kind of insulator to protect the servos ?. I am using the CARF thrust tube.
2- The thrust tube cone does not fit centered in between the engine mounting rails. Bigger portion of the diameter stays under the rails. Is this OK?
3. With plane upright, should I mount the engine on underside of the rails? ( seems there is no other option if the engine exhaust cone has to center in the thrust tube cone)
4-There is no wooden former to hold the thrust tube in place on tail end. The tube is held in place by the fuselage. Is there a fire risk there due to hot thrust tube ?

thanks in advance

Dave Wilshere

The pipe is twin walled, so the air being draw down the gap keeps the outer wall relatively cool. The thread starter Hawk is still flying 15 years later, same servos as built with and I’ve never had the pipe out. My pipe is hard against the elevator servo plate because I raised the plate on production kits after finding a thrust line change necessary. You could either paint the bottom of the plate with BVM heat shield, or use some Alloy tape as a reflector shield, but it is not critical.

Thrust pipe cone position at the front could do with being centred on the top (sitting on wheels) of the turbine rails as it’s always needed a little down thrust for perfect trim. Then depending on your turbine mounting strap, mount the turbine central on the cone.

Again because the outer wall is cool it just slides into the rear hole.

Dave

awanx

Hi dave thanks alot for your quick reply . Very much appreciated . Is it possible to post a picture of your turbine install and the thrust tube carbon cone install ? I am little bit confused on the point of these two items. I see the point you are trying to make but really the thrust tube is literally pressing agains the wooden former in the tail of the kit and there is no way it could be centered on a turbine installed on top of the rails . It would be very interesting for me to see how you have done it.