[DarthAnal]

Is it just embedded in a slot, or is there ply/basswood embedded on either side for extra rigidity and surface area for glue?

[DarthAnal]

Also came across a sailplane site that had lots of styles and methods of sailplane tow hooks. My personal preference is the old basic bent threaded rod that wound up being used in most of my sailplanes. Would use a 1/4-inch 5-layer ply square to spread the loads.

[j-c terrettaz]

problem with above sometime the hook turn ..good for Gentle Lady
embedded with plywood or epoxy board, glued with West system or CA

[DarthAnal]

Using locking nuts and lots of compression will reduce it happening, plus checking the hook every time. When I was flying standard-class sailplanes, and using hi-starts and the occasional winch, had no problems. Of course, my first winch launch was right after someone tried a zoom launch and had a wing explode on the way down before the last pullup. Got lectured on how to do it properly -- go downhill, stomp on the pedal, release pedal and pull up.

[DarthAnal]

Bookmarking this for reference when I get started on this.

Does anyone have some good photos on the inside and outside views of the bungee hook?

[Cougar429]

I can take some of my modded BAE Hawk if required, but used my typical method of laminating glass cloth between two sheets of thin ply to cut the hook and internal fuse brace out of. Light and very strong.

If memory correct location was 2/3 back between nose and CofG. Been a while so nice if someone can confirm.

[SARPLT]

For a hook I use a simple metal eyelet screw. Just cut about 3/4s of the ring off so you are left with the screw and a small angle, less than 90%. Screw this into the calculated location but make sure that you screw it into some plywood mounted to the inside of the aircraft. I use a small piece of 1/4 inch plywood. I have not used any reinforcement on the outside of the fuselage and this has worked well in my 70mm jets with no issues. Photos of the hook in my J10.

Cheers
Marty

[SARPLT]

I should have also mentioned that my preferred location for the hook is approximately 66% of the distance from the nose to the CG location. For example on one of my aircraft that has 12 inches between these two locations, I have mounted the hook 8 inches back. I have used this calculation on six models and it works great. If the hook is too close to the CG (too far back) then the aircraft will have a tendency to climb, possibly releasing early. If it is too far forward it will have a tendency to pull the nose towards the ground on launch.

Also don't forget to put some fabric or a small chute on the cable that goes to the aircraft hook. This creates some drag and will help pull the ring off the hook during release.

Marty

[j-c terrettaz]

I dont know our setup for catapult .
Im using a single cable : first hook to the release pin and to the jet with a small ruban like Marty said. Agree with Marty for the position of the hook ..some jet are a pain to bungee specially Delta and Mig 29....
The force for the pull are almost 5 time the weight of the model .

[SARPLT]

One last piece of advice is that what every you use for your release mechanism, make sure you have a safety. The photo of mine shows the vertical pin with a hole that I put a screwdriver through after the ring at the end of the bungee cord is put over it. When I am ready to release with my foot on the pedal I pull the screwdriver and the mechanism is armed. My first pin did not have this and after accidentally bumping the plane on the launcher, the ring slipped off launching my F20 into our safety fence. That was the end of that model.

Cheers Marty