Crazy recovery question.

[Bat-mite]

If you've seen my build thread, then you know I am building a MAC Performance Scorpion 3" kit. It has a 38mm MMT.

Sitting at home I have a Pro38-6G J410 I'd love to put in there. Here's the catch.

The booster is 22" long. The coupler is 8" long. Subtract 1" of the coupler for the switch band, and divide by two gives me 3.5" of coupler inside the booster. With me so far?

The MMT is 12". It sticks 1/2" out of the back of the booster for the retainer. That leaves 11.5". The top CR is 1/8" below the top of the MMT. So, 11.5 - 1/8 gives me the top of the top CR at 11 3/8" above the thrust plate/bottom CR.

Back to the 22" booster. Subtract the 3.5 for the coupler and 1/8" for the bulkhead, and it becomes 18 3/8". The distance from there to the top of the forward CR is thus 18 3/8 - 11 3/8, or 7".

I have 7" at 3" diameter to hold my recovery (shock cord, quick-links, swivel, drogue). Still with me?

Now, the length of the aforementioned J410 is 16.6" (roughly). That means it would stick out of the MMT by 5.1". I only have 7" of space. That leaves 1.9" between the forward closure of the motor and the bulkhead of the AV bay.

Now, HERE IS THE QUESTION!

Could I wrap the shock cord and drogue around the motor? Would I expect burns? Would they get hung up coming out? What am I not thinking about correctly? Anyone ever done this?

Here's the general idea, not to scale.

 

[Handeman]

I've flown with a forward closure within inches of the av-bay. I didn't wrap the chute and cords around the exposed motor. I z-folded the cords and stuffed them between the motor and BT, starting on one side and working around. I never put any length of cord more then halfway around the motor. It worked perfectly for me several times.

Wrapping the cord around the motor may work, but I would think it might tighten and bind if you do that.

 

[nute]

With my Estes Argent, I put the AV-bay in the tube coupler, giving me a very small area for the chute and cord on 29/360 motors. I wrap the cord around the motor, and fly drogueless. I'm 4/4 with those flights. It's not ideal, and I wish I could use a drogue, but that's the idea.

Nate

 

[Bat-mite]

Thanks, guys. Once I get this finished and launched (hopefully 6/13), I'll let you know how it went. If I can Z-wrap the cord, I will do it that way. If not, then around and around the motor it goes. Will it come out? No one knows.

 

[bobkrech]

Fan-fold or z-fold the shock cord with two loose rubber bands and position it beside the motor. If I were using a drogue, I would attached it with a short cord to the eyebolt on the altimeter compartment in a small d-bag and attach the d-bag to the airframe or shock cord at a position where the chute is out of the airframe before the bag is pulled off. Doing these two procedures will protect the chute from thermal damage from the motor and ejection charge, and prevent both from wrapping around the motor casing while insuring the chute will be pulled clear of the airframe before deploying and not get stuck in the airframe.

Bob

 

[ChrisAttebery]

Do you really need a 8" long altimeter bay? If not epoxy the aft bulkhead up inside the coupler a couple inches. I did this on my 3" Saab because I needed more space for the parachute in the nose cone. All of the recovery forces should be taken up by the all thread so the bulkhead to coupler joint only needs to be able to withstand the ejection charge.

 

[Onebadhawk]

Thanks, guys. Once I get this finished and launched (hopefully 6/13), I'll let you know how it went. If I can Z-wrap the cord, I will do it that way. If not, then around and around the motor it goes. Will it come out? No one knows.

John,,
For sure,, it's known..
Don't wrap the harness around the motor case.. It won't unwrap by itself when deploying...
1 long Z fold at a time, using a thin wood dowel,, insert all the way down to the top CR..
Then the next Z fold next to the first,, then the next,, working your way around the motor case..
I fly this way all the time,, no issues.....

Teddy