How to convert a built rocket to dual deploy

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astrowolf67

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I have a PML Endeavor (Quantum tube version, in my profile pic), that is built completely per the instructions, with the only modification being a foamed fin can. What would be the best way to convert this to a dual deploy, with as little destruction as possible?

David
 
I would just call Frank at PML and he will set you up with the parts you will need to fit the Endeavor kit. main chute tube, coupler, bulk plates, some type of altimeter

Good luck
 
Okay, that was a very general question, and, I should list some of the modifications I'd like to make. First, I would like to remove the piston ejection system, and, add a shock cord anchor. Removal of the piston and strap would be the easy part, just cut and pull. The new cord anchor is one area I'm stuck on. I've come up with some possible solutions. One, just remove the piston, and sew a loop in the piston strap, but, I'm concerned about the strength of the loop. Two, remove the strap and piston, and install another CR with an eyebolt down there, but, with no support in the center, would it hold up to the ejection forces? A third, try to drill and screw an eyebolt into the upper existing CR, if I can get my arm in, but, would it hold with no washer or nut on the opposite side of the ring? Any other ideas that I haven't thought of?

Now, for the e-bay, the payload section has the coupler and a bulkhead with eyebolt epoxied in. Any suggestions on how to modify it for a removeable bay? I'm looking to do a mid deploy drogue, and, main out the top.

Again, thanks for any push in the right direction.

David
 
David,

If the piston shock cord is not heat damaged, i would just cut it below the piston and have a secure loop sewed at the end of the cord. Add a nomek sleeve protector and quick link to the end of the piston shock cord then attach 15' or 20' of shock cord to the quick link. If your going to attach an eye bolt to the top CR you can cut an access hole below the CR and secure the eye bolt with a lock washer, nut and epoxy.

Good luck...
 
The new cord anchor is one area I'm stuck on. I've come up with some possible solutions. One, just remove the piston, and sew a loop in the piston strap, but, I'm concerned about the strength of the loop.

I'm not familiar with the Endeavor; however the PML BullPuppy instructions note to fold the nylon strap over itself and epoxy, so if you're going to sew a loop and you're worried about the stitching, you can probably also epoxy for extra strength. I myself have thought about using a pop rivet or two as a precaution, but haven't tried it yet.

Here is a link to someone who converted their Endeavor to DD:
https://www.rocketreviews.com/public-missiles-endeavour-by-gene-wolski.html

Good luck on your endea....um...project! ;)
 
If you need a new anchor there are a few ways to do it. Many have done an anchor similar to the Estes using webbing and epoxy. I have seen instructions for high power saying to simply epoxy a few inches of webbing to the inside of the tube.

If there is room, some have drilled a hole the length of the fin can and put a bolt clear out the bottom.
 
Spicer:
The piston strap, appears to be in good shape, but, does have the typical crusty feel to the surface. It would probably be fine with a sleeve added to it.

Ken:
That's a great review of the Endeavor. It is pretty much built like any of the PML kits with piston ejection. But, that's the problem, it's built, lol. At the time I built it, dual deploy was an afterthought. I guess that'll teach me in upcoming builds, to alway plan ahead.

1tree:
I had for a split second, considered a Estes, or LOC style anchor, but, I would not trust one in a Quantum tube air frame. However, that got the gears turning, and, one possibility would be to "weave" a strap through a coupler, then install the couple down in the airframe. I also considered drilling the fin can, but, the eyebolt would need a very long shank to reach out the bottom. It's approximately 14 inches between the upper and lower rings.

David
 
You could always glue another centering ring down on top of the first. Ads your hardware to it then glue it in. Or you could make a baffle and attach the hardware to it.
 
This speaks mainly to recovery attachment...

One option, if you seek to go with strictly electronic deployment, eliminates use of any motor eject as a back-up. You can use a tapped forward closure with a cast eye bolt, and attach the recovery harness to the front of the motor. Properly installed with a jam-nut, it's the strongest point in the rocket. You'll find that a large number of larger birds are built this way.

The drawback... No motor back-up. Do those electronics right. Once it leaves the pad, it's up to your build and prep to get that laundry aired out. Make a check list, and double check absolutely everything.

Electronic dual deployment... Ground test, ground test, ground test. KNOW that when those charges go off, it will first split and destabilize the airframe, and later deploy the main recovery system in an orderly manner, allowing it to bring the bird back safely. Engineer failure OUT of the equation.

Good luck with the conversion. There's a lot involved with going to strictly electronic deployment, but it is the way to go. Hard to beat properly executed dual deployment. :wink:
 
You could use a threaded forward closure with an eyebolt to attach your drogue recovery.
 
and sew a loop in the piston strap

How about just tying a loop in the end of the strap instead of sewing it?

the coupler and a bulkhead with eyebolt epoxied in

Is the coupler epoxied in? If it is, I don't see how you could make it into a removable AV bay.
 
The problem with gluing another CR in would be getting the top end of the motor mount and adjacent body tube clean. There will be soot in there from previous flights, you would want to be able to sand in there.
 
Can you provide pics of the parts? Would probably help us who can't read too well. :wink:

Well, since you asked, lol. It might help to see how it's currently built.

The Endeavor
IMAG0357.jpg

Looking at the piston strap attachment, note, no motor mount extending past upper CR
IMAG0355.jpg

The Piston
IMAG0354.jpg

The payload bay coupler, which is epoxied in
IMAG0352.jpg

David
 
I'm thinking a forward closure anchor would probably be the easiest, most reliable solution, but, even that will present a couple of issues. One, no more motor ejection options. Two, with this thing having the quick change mount, motor length would be limited. I had thought about just putting a permanent 38mm mount inside of the 54mm, and adding another forward ring with eyebolt, but, there again, that severely limits motor choices. It only had 4-5 flights on various AT and CTI 38 mmmotors prior to my long break from flying, so, the piston strap really isn't that bad, other than the outer surface.

The main reason I want to convert to dual deploy is for flight experience. I am building a Weasel dual deploy, and, also have a partially built PML 1/4 Patriot that will be easy to convert. I have also considered a nose bay mounted setup for my Minnie Magg. I'm trying to get well seasoned by mid next year, with ambitious plans for a L2 project.

David
 
Rocket looks very nice! I'll have to admit that this one is beyond my expertise, so maybe someone else can chime in, but I'd think S6's suggestion of cable cutters makes sense since it means the least amount of change. :)

Good luck!
 
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My quick and easy method, proven across several rockets now -
1. Swap parachute for streamer
2. Build deployment computer into nose or payload bay
3. Re attach parachute, where bundled it can still flap around somewhat freely
4. Run lead wire out from payload bay to cable cutter
5. Bundle parachute with zip tie to be severed by cutter

Drill delay charges for apogee and you are set. Minimally invasive dual deployment retrofit.
 
How about this for the booster:
1) Cut the piston off the strap.
2) Cut the strap off as low as you can.
3) Get another coupler bulkhead, put a 1/4" X 20 u-bolt or eyebolt in the new bulkhead.
4) Drill some 3/8" holes in the new bulkhead and in the one in the piston.
5) Glue the new bulkhead in the open of the piston, making a sort of baffle out of your piston. The holes will allow the motor eject gasses to pass (if need). If you want, put a couple or 3 chore boys in there to trap the fiery particles. You can shake the other ejection remains out the MMT.
6) Rough-up the inside of the BT down as far as you can and sand the dickens out of the piston/baffle assembly to remove all residue. Do this like PML suggests with QT.
7) Epoxy the piston/baffle in the rocket with the new bulkhead and ubolt/eyebolt forward. I would use some filler like chopped fiberglass or silica to reinforce the bond to the QT.

Only parts required are a coupler bulkhead and eyebolt/ubolt.

I'm still thinking about the payload bay.

--Lance.
 
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I think if I wanted to convert this rocket to conventional dual deploy, for the upper part, I might cut the existing coupler off about 1/2" or 3/4" - whatever is required to get that bulkhead off. Thin build an Av bay in a 3" tube that would slide up into the coupler.

There was a company called Smokin' Rockets who had a design feature called the Alti-Tube. That would be my approach. The details depend upon figuring out attach points, etc.

Just throwing out ideas ...

--Lance.
 
Great ideas Lance, for an added measure, I could even put screws into the baffle. For the payload bay coupler, I never thought about just cutting a half inch or so off. That would still leave plenty of coupler, considering I would be using shear pins. This is turning out to be easier than I thought, just need to implement a plan, get parts, and, go at it.

David
 
Watermelonman, I will probably be getting a cable cutter system, even if not for this rocket. Any reference to how they are used? I understand the basic concept, but, what secures them to the rocket, and, what keeps the recovery bundle from flopping around and destroying/unplugging the charge leads? Is there a steel cable or kevlar tether that attaches to the cutter somehow?

David
 
Simplest mod is to do it right. Remove the coupler & BP , to do so will destroy it...so what.

I have done this many times with Q-tube, epoxy does not stick worth a darn anyhow. Cut, bang-out, remove the BP. Peel coupler out from inside.
Just as you have peeled a layer of paper off the outside of tubes.......now do it from inside. You may need to grab a corner with needle nose pliers and wind it out that way. Sand epoxy residue from tube.

Now just start fresh with new coupler-BP's-threaded rod etc & make a Removable av-bay......done!
 
Thanks Jim, I have been eyeballing that option too, thinking the same, nothing sticks well to QT. Might just give it a go now. Worst case, I've got sanding to do, best case, I've got some sanding to do. Plus, it was built using Bob Smith/hobby shop brand 30 minute epoxy, so, it will likely be adhered better to the coupler, rather than the QT.

I think I need to get on the ball and start ordering some parts!

David
 
I have a PML Hydra, and left the piston out. I had already secured the strap to the motor mount as per the instructions when I decided not to use it. I ended up sewing the D ring into a loop at the end, I used 150# Kevlar thread and a BIG needle. I tied the rest of the stock shock cord to the D ring using the knot shown in the instructions. I have two flights on the rocket and the stitched loop is fine and shows no stress.
 
Thanks Mike, that is probably what I will do, to start with. I'll just keep a close eye on the condition of the strap and see how it holds up. Simple solutions first.

David
 
Watermelonman, I will probably be getting a cable cutter system, even if not for this rocket. Any reference to how they are used? I understand the basic concept, but, what secures them to the rocket, and, what keeps the recovery bundle from flopping around and destroying/unplugging the charge leads? Is there a steel cable or kevlar tether that attaches to the cutter somehow?

David

Most units have a tether that you can connect to the recovery harness. I then hot glue the igniter in to the charge area, and make sure the igniter leads are a good couple inches longer than the various tethers will allow the bundle to travel. Size it so that the bundle can move around freely but not so much that it can get tangled or bang around with high forces, and it should work well.

I recommend using it to deploy a second full size parachute, rather than the only one, at modest altitudes, to get the hang of the whole configuration before relying on it.
 
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