bungee hook on an EDF- where?

[Frank v B]

I am assembling an EDF for a customer and have to install a bungee hook.  Does it go at the CG, ahead or behind? The model is like the KMP Avro Arrow with a 15 size EDF.  The same one Glenn built.


Anticipating Andy H's reply...."it goes on the bottom, you idiot".... even in Australia?


Frank

[sihinch]

I think from watching others launch it goes ahead of CG Frank.

[wollins]

I am assembling an EDF for a customer and have to install a bungee hook.  Does it go at the CG, ahead or behind? The model is like the KMP Avro Arrow with a 15 size EDF.  The same one Glenn built.


Anticipating Andy H's reply...."it goes on the bottom, you idiot".... even in Australia?


Frank

Hook position should be 50% to 66% of distance from nose to CG.  This should be verified by hanging the model nose up from a string attached to the temporary hook position and the model's nose should swing out (positive angle of attach) by about 15%. I'm sure Jeff will correct me if I'm wrong!

Colin

[Frank v B]

Thanks Simon and Colin.


Frank

[Wingnutz]

If Glenn's already done it, ...
I am no expert but I have " hooked" three EDFs for bungee launching. Hook locations are close to Colin's formula. All launch consistently. The two smaller models launch from a small Jetapult and hooks are about 3" ahead of the CG. Both are straight wing; a CT -114 Tutor 34" WS and a Cessna Citation 47" WS and the bigger one, a 55" Fly-Fly F-86 launches from the ground (no ramp)...the hook is 10" ahead of the CG.
Here's the little Tutor launching about a week ago...hook is about 2-3/4" ahead of CG...watching the video, hook could probably be farther forward
http://youtu.be/vs9UWCBXGJ4

[sihinch]

Hey Frank, did you do this hook? I'm thinking of doing one for the first time, on my Me-163.

What did you use as the hook and did you angle it?

@electroflyer where did you put your bungee hook on the 163?

[Frank v B]

Simon,


I have not installed it yet but I was going to do it via Colin's formula.  The hook I am using is a purpose built bungee launch hook from a two meter glider.  I had one kicking around.


Thanks for the video Bill Q.  I love the looks of that little Tutor.


Frank

[electroflyer]

  Hi Simon,
My 163 has the hook located below the motor but just above where the skid would be. There are not too many options on the Komet, but since you do not need to power up until it is airborne, it seems to work well.
  Glenn