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Crash-n-Burn

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Hi folks,

This'll sort of be a build/fail/fix/fail retrospective and a possible V2.0 build thread. No timeline on the build but I can tell the history now.

I have not made it to a club launch in over a year, mostly due to weekend activity commitments for my kids. At some point I started getting itchy to burn some F/G motors and I have no non-club field suitable for such and activity... unless I devise a super draggy motor burner. That led me to build a spool rocket.

This was going to be a spare parts hero - scrap plywood and an orphaned Estes PSII 29mm MMT. The motor mount is an 8" long craft tube. I figured on 5 3/4" diameter spool ends through the highly scientific process of WTLO (well, that looks okay). A bit of bandsaw and router work produced two nice 1/4" thick spool ends. I sandwiched them, measured for the center, and drilled holes for the motor tube and for a 1/4" launch rod. Some 5 minute epoxy and I had a working spool after about an hour of work.

I decided to fly it later that day on an F44. Why I chose a 24mm motor that required an adaptor is a testament to me making things harder than necessary, but in the end I got everything friction fit and ready to go. That first launch was successful - up and tumble recovery down. Estimated apogee was 125'. Upon recovery, I found that the motor tube and crinkled along the spirals. Despite my kids imploring an encore flight, I chose to retire to the basement for modifications.

Several days later, I came across a $3 bag of Bondo fiberglass cloth at Wal-Mart. I've never glassed a tube before but this looked doable and cheap. This fg cloth feels heavy but in some way that makes it perfect for this project. I invested twenty minutes in watching Jon Coker's glassing a tube video, then measured out four wraps of cloth that would fit neatly between the spools. I spread West Systems 105/205 on the cloth (which was laid out on a piece of wax paper). After cleaning up the excess epoxy, I used the wax paper to start the rolling process. It worked surprisingly well; the spool ends gave me something to hold on to and steer with. After getting the tube wrapped, I wiped off a bit of excess epoxy, wrapped the tube in plastic wrap, and let it be for a while.

Next morning - this morning - I unwrapped my first glassed tube. I must say that it came out better than expected. This wasn't winning any craftsmanship contests, but I was pleased with a serviceable and strong tube. I loaded up the launch equipment, an F52 and a G76 and got ready for some fun.

My lantern battery was dead so I made a quick trip to the local hardware store and then there was nothing stopping this launch. My younger son gave us the countdown countdown and whoosh - perfectly straight up, nice tumble down. Touchdown, bounce, watch a spool end roll away. Dinkin' flicka.

Observation of failure are pretty obvious - the craft tube delaminated from the force of hitting the ground. About 50% of the plywood fillet area around the motor tube delaminated as well. The two pieces do not fit back together nicely and there's no reason to think a fix would eliminate a repeat occurrence. So This G** D***** Spool is headed for the Frankenstein pile.

V2.0 will use a proper FG mmt from a DX3 mini (which will some day become a 38mm MD project now). I'll cut more plywood and try again. I might even rig in a small parachute and motor retainer on the next version. That really depends on my potentially waning interest in this project. i'll leave it to y'all to keep me motivated.
 

Crash-n-Burn

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Picture; apologies that my kitchen table is laying on its side.

image1.jpg
 

Tonimus

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I would suggest something thinner and lighter than 1/4" ply. 1/8" or maybe a plastic.
 

Crash-n-Burn

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I would suggest something thinner and lighter than 1/4" ply. 1/8" or maybe a plastic.
I'm not against the idea but can I ask why? I'm not concerned about the small weight increase in 1/4" ply - not sure high performance spool is what I had in mind. I am not interested in using plastic.
 

Tonimus

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It's not the up part, but the down that makes me think 1/8" ply would be better. About 1/3 less mass when it impacts the ground may be more conducive to staying together.
 
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