Dual deployment modification for PML Eagle

[mosh1]

Hey guys,

I have a PML Eagle (Hybrid ready kit). Because of the really long booster section for hybrid motors, as well as an anti zipper coupler on that - there's not much room for dual deployment.

However I really want to try to make dual deployment work (with two chutes, not with other methods such as burrito).

I've attached a pic of the layout of the rocket.

As you can see, the only room I have for a drogue is in the actual nosecone itself. I can pop the nosecone out with a charge on that side of the ERM assembly.

Here's what I'm thinking of doing:

- Expoxing the end of 9/16" tubular nylon to the end of the nosecone (this should be ok, if I have a big enough glob of epoxy?

- Eye bolting a 1/4" kevlar cord from the front ERM assembly centering ring, and attaching the other end to the nose cone tubular nylon.

- Attaching a small 12" drogue chute on that.

- Shear pins on the center payload section (where the main is), since the shock from the drogue may seperate the center payload.

Obviously, this is reverse from the standard setup of drogue in center payload and main in nosecone payload.

The 12" drogue I'm thinking will be the spherachute from giant leap rocketry (single piece chute). Hopefully this will be strong enough. The decent rate on this 5.5lb rocket will be pretty quick with the 12" but I'm not sure I have enough room in the nosecone for a larger chute (and I don't want to make the rocket longer by adding another payload section).

What do you guys think?

 

[jraice]

are you willing to scrap the PML alt bay setup and just make the rocket a bit longer? Could make your own bay and do a nice dual deploy setup, would probably only need 2-4"s for the drogue (whats the body diameter? you could go without a drogue and easily fit 1/8" tubular kevlar in there, I fit 20' in a 3" by 54mm tube)... then have the main chute in an extended body tube... could even use some of the space in the nose cone for the main chute.

 

[mosh1]

Well, as I mentioned - I'm not really into extending the rocket, unless its absolutely certain that what I want to do isnt a good idea.

One thing im worried about is if a 12" cute will stop the rest of the rocket from still coming in ballistic, as the rocket without its nosecone is still pretty stable.

 

[denverdoc]

Originally posted by mosh1
Well, as I mentioned - I'm not really into extending the rocket, unless its absolutely certain that what I want to do isnt a good idea.

One thing im worried about is if a 12" cute will stop the rest of the rocket from still coming in ballistic, as the rocket without its nosecone is still pretty stable.

in response to your first post, I'm not sure how much epoxy would be a big ebuf blob that I'd feel secure in attaching nylon to plastic. At the least I would probably line several square inches of the cone with FG or kevlar and try attatching the line to that. The increased surface area of the contact patch should help, but still not my method of choice under such circumstances.

You tie the chute to the shock cord, obviously so in the event of separation you lose the cone, otherwise you're right: expect at best a death spiral of some type. 12 inch drogue is marginal, but can't see that coming in "ballistic"--hard yes given the break point.

Finally not all hybrids/altimeters combos are created equally when it comes to reliable launch detect. Use a apir that are known to work together.

Hope this helps,
JS

 

[mosh1]

Thanks for the help. I'll try everything out and post back how it works out!

 

[denverdoc]

please do and best of luck. I'm hoping to fly some hybrids this year.
JS

 

[Sailorbill]

Replies are inline.

Originally posted by mosh1


- Expoxing the end of 9/16" tubular nylon to the end of the nosecone (this should be ok, if I have a big enough glob of epoxy?

As the nosecone is plastic I would agree with denverdoc and use a piece of fiberglass over the TN to help it stick. Also really rough up the surface and make sure it is really clean.

- Eye bolting a 1/4" kevlar cord from the front ERM assembly centering ring, and attaching the other end to the nose cone
tubular nylon.

Looking at your drawing I would suggest making a loup in the end of the Tubular Kevlar by running the end back through the cord using a pen or pencil to to open up the weave. Pull several inches through before you exit. This will form a "chinese finger torture" style attachment point. The harder you pull the tighter it gets. For added security you can run severl stiches of heavy thread through the TK. Then you can use Quick Links to attach everything.

- Attaching a small 12" drogue chute on that.

Should work. I use a 12" on both my grandsons 5+ lb Endeavour and my 8+pound Endeavour. Mine came from Aerocon and is a demilled flare parachut. Really tough with wide nylon straps for shroud lines that go over the top of the chute.

- Shear pins on the center payload section (where the main is), since the shock from the drogue may seperate the center payload.

Good idea just started using them myself. I discovered the hard way that the screw you use can be to long. I didn't want to cut the #2-56 X 5/8 nylon screws I had and used them full length. They didn't shear and my main got hung up in the tube.

Obviously, this is reverse from the standard setup of drogue in center payload and main in nosecone payload.

There are many paths to the same goal and it is all good when it works.

The 12" drogue I'm thinking will be the spherachute from giant leap rocketry (single piece chute). Hopefully this will be strong enough. The decent rate on this 5.5lb rocket will be pretty quick with the 12" but I'm not sure I have enough room in the nosecone for a larger chute (and I don't want to make the rocket longer by adding another payload section).

Coment above on the chute.

What do you guys think?

 

[denverdoc]

The chinse finger trap is pure genius IMO, a knot w/o a knot.

Sailorbill, curious about the too long shear pin comment, guessing it sheared but leaving the long ends sticking in the middle looking like a bull towards the end of its "fight", and the chute hung on those?
JS

 

[cjl]

I too am curious...

I used full length 4-40 x 5/8" shear pins on my Deuce and had zero problems - all 7 on the rocket sheared both on the ground tests and the flight perfectly...