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repairing a scorched body tube

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jf_reinhard

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Money just got REALLY tight around my house, so I don't have the $$$ to buy lots of rocketry stuff (bummer) until about September.

Today, I flew my Edmonds Deltie B on an A8-3 instead of a B4-2 because a) Rob Edmonds recommended an A8-3 and b) on my last flight I almost had to chase the thing into the next county using a B4-2.

The rocket went up about 20 feet, immediately turned upside down and "lawn darted", causing the glider to break into a few pieces. Then the motor burned a hole about 1.5" long in the body tube before the ejection charge went off.

Instead of buying a new body tube and starting over, can I repair it with something and is it worth it?

Thanks,
Jim
 

powderburner

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IMHO, generally it is not worth it to me to do repairs after that much damage. But, that's just me-

If you want to repair it, I suggest you cut away the damaged BT on one side and "square" the hole so you can later insert a replacement section of BT. I would leave the hole open temporarily so you have good access to the inside, and I would roll (gently) some cardstock pieces so that each individual piece is just more than one inside circumference, and extends an inch or so beyond the cutout. Working fast, I would smear the inside surface with thin CA, slide in the cardstock liner, cover with more CA, and slide in a second liner. After that sets I would add the replacement BT to fill in the hole and bring the external surface back to contour.

Alternate liner material: order some "bulk" BT coupler stock from Totally Tubular and cut the length you need to re-line the damaged section. CA into place as above and add exterior BT patch.

Or, cut away the entire circumference and replace with a BT plug of the appropriate size. Line the inside with a couple layers of cardstock, or coupler material.

All this is a lot of work and extra trouble (at least, to me) compared to just building another model rocket. If it was an Estes motor it would at least be worth a try to call them and report the motor problem (you might get a free kit of some sort along with the motor replacement). I'm not sure what Edmonds' service policy would be in a situation like this but it might be worth giving them a call too.

And (at the risk of sounding like I'm shaking my finger at you) it might be worth it in the future to find a motor on the kit manufacturer's list of recommended motors?
 
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PemTech's Squeeze

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And (at the risk of sounding like I'm shaking my finger at you) it might be worth it in the future to find a motor on the kit manufacturer's list of recommended motors?
Oh come on, follow directions??? Where's the fun in that! ;)

Seriously though, keep playing safe. As my sweetie corrected me often when I was introduced to his hobby: Rockets go WHOOSH not BOOM.

Trudy
PemTech Art Department and sidekick
 
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powderburner

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attn: jf_reinhard

If Estes or Edmonds won't replace your glider, PM me. (I don't have a name starting with "E" but I am sympathetic to your predicament.) Or check your PMs.
 

jf_reinhard

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I thought I solved my problem - I cut off the burned part of the body tube, then reattached the glider "hook", launch lug, and the rip cord. Since I had had good luck with B4-2 on the first two flights, I decided to try it again.

As I was loading the rocket onto the launch rod, I noticed the rod wasn't as smooth as it used to be (motor residue build-up), but I figured, "Should be ok, there's enough engine thrust to overcome it").

Bad assumption! This time the rocket got a little higher (30 feet), but because of the drag on the rod, the engine was flaming pretty good at that height. The glider "popped" off, I thought it was ok. The pop pod was a total loss - the engine section burned up entirely. When I walked over to retrieve the glider, it was smoldering, but it still flies!

Next time I gotta make sure that rod is SMOOOOTH, eh?
 

dcastle

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I thought I solved my problem - I cut off the burned part of the body tube, then reattached the glider "hook", launch lug, and the rip cord. Since I had had good luck with B4-2 on the first two flights, I decided to try it again.

As I was loading the rocket onto the launch rod, I noticed the rod wasn't as smooth as it used to be (motor residue build-up), but I figured, "Should be ok, there's enough engine thrust to overcome it").

Bad assumption! This time the rocket got a little higher (30 feet), but because of the drag on the rod, the engine was flaming pretty good at that height. The glider "popped" off, I thought it was ok. The pop pod was a total loss - the engine section burned up entirely. When I walked over to retrieve the glider, it was smoldering, but it still flies!

Next time I gotta make sure that rod is SMOOOOTH, eh?
I'm curious as to how the motor could be burning up the pod at all. Do you a motor block inside the tube or is the motor free to fly up into the tube at least to some degree?
 

jf_reinhard

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dcastle,

I'm not sure why it's happening either. Rob Edmonds stated in the instructions that I needed to secure the motor to the pod with a small piece of masking tape, so that it extends from the end of the pod about 1/4 inch, and he also said to use one piece of wadding. My first two flights didn't create any scorching at all, even with the motor still in the tube. Come to think of it, I can't remember if the motor stayed in the tube on the first two flights, but I think it did. Since that time, I flew my Semroc Hawk about 6 times and that left a lot of crud on the rod. Then I flew the Deltie.

Without the tape, the motor would've fallen out of the pod on the launch rod, since the tube was very slick. If I build this model again, I'm going to try it with a smaller piece of tape and secure it very lightly so that the ejection charge will cause the streamer and nose cone to come out and the motor too.

Jim
 

dcastle

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dcastle,

I'm not sure why it's happening either. Rob Edmonds stated in the instructions that I needed to secure the motor to the pod with a small piece of masking tape, so that it extends from the end of the pod about 1/4 inch, and he also said to use one piece of wadding. My first two flights didn't create any scorching at all, even with the motor still in the tube. Come to think of it, I can't remember if the motor stayed in the tube on the first two flights, but I think it did. Since that time, I flew my Semroc Hawk about 6 times and that left a lot of crud on the rod. Then I flew the Deltie.

Without the tape, the motor would've fallen out of the pod on the launch rod, since the tube was very slick. If I build this model again, I'm going to try it with a smaller piece of tape and secure it very lightly so that the ejection charge will cause the streamer and nose cone to come out and the motor too.

Jim
I'm just a little confused as to where you are seeing the scorching. Is the motor moving forward into the tube and scorching the inside? Or is the scorching from the ejection charge? Do you have pictures?
 

hardinlw

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You do NOT want the motor to eject. If it does, it might not push the parachute out. The momentum of the nose cone and parachute ejecting out the front is what kicks the pop-pod off the rear of the glider, so it needs to work that way. The engine should be taped securely in place so it can't migrate up into the pod tube during thrust or eject when the ejection charge fires. Is that what is happening to cause things to burn? My experience is that after 20-30 flights you will see some charring of the inside of the body tube (or engine mount) from the ejection charge. The results of this charring can be as simple as just having to clean the tube to a complete burn through. I've never seen this happen in just a couple of flights unless the engine malfunctioned and split the casing.
 

jf_reinhard

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For both flights, I taped the motor to the booster using a small piece of masking tape. The charring/scorching on the booster on the first flight matched the outline of the motor perfectly, with a burned "V" directly opposite the "hook". On the second "charred" flight (flight #4), the body tube was "one B engine length" shorter than the previous flight. The area immediately surrounding the "hook" was completely burned away by the motor. I don't think the motor migrated up the tube. The streamer and nose cone popped off on both flights.

I'll see if I can retrieve the booster pod this evening from the garbage can in my workshop and take a few photos.

Jim
 

gpoehlein

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I have a couple of questions and a suggestion or two.

First, did the glider itself survive? If so, please go to number two:

Second, how much of the pod survived? Can you salvage the nose cone and the glider hook? If so, remove those from the destroyed tube for use later. If the hook is not salvageable, can you make another out of balsa?

Next the suggestion: How about rolling your own tube from cardstock or posterboard? Use a couple of spent motor casings as mandrels and a piece of cardstock or posterboard that is just a bit larger than wraps around the motors. Roll it around the motors and glue along the edge. Glue the glider hook to it, a new launch lug (you can make one out of a piece of index card if you don't have any spares) and glue in the shock cord.

As for installing the motor for flight, cut a piece of masking tape 1/4 inch wide and wrap that around the rear of the motor so it is flush with the back edge. This will act as a thrust ring and keep the motor from moving into the tube during thrust. The, wrap enough tape around the front of the motor to make it snug in the tube. If you wrap it around the middle of the motor, it might swell and will be difficult to remove - the front of the motor rarely swells and this makes removal a lot easier. A bit more tape wrapped around the back of the body tube and the exposed part of the motor will be added insurance. But be sure to use that "tape stop" on the back of the motor in a rocket that doesn't have a thrust ring.

Another possibility for replacing the pod (although a bit more expensive) is to use an inexpensive rocket kit like the Estes High Flyer - I can usually find those at Michaels or Hobby Lobby for around $6 - even cheaper if I use a 40% off coupon.

Hope this helps.
 
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