Lawn dart repair?

BAR learning the hard way again.

Forgot to tape the motor in. Motor ejected MultiRoc Lawn Darted. Crinkled several joints about 1/4 inch.

Right now I straightened everything as best I could and used CWP and CA and working it back down to some symbolence of normal. Will prime/sand till it looks ok.

Any other ideas for next time? Oh yeah, I do expect some injuries as I learn the little (and big) things again.

And don't you just HATE it when it's on it's first flight after MANY hours of TLC! A 20hr Big Daddy killed me last time 20 years ago. But grandkids make a GREAT recovery team!

Phil.

Gluing an internal body tube sleeve (aka coupler) inside the rocket makes the repair super strong. Vendors such as https://www.balsamachining.com can hook you up.

Easiest way if damage is extensive: Cut off the damaged tubing. Get a new tube and coupler. Cut tube to length and glue together. Good as new.

lakeroadster said:

Gluing an internal body tube sleeve inside the rocket makes the repair super strong. Vendors such as https://www.balsamachining.com can hook you up.

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This is a great idea, but if you have some body tube lying around of the same diameter as your rocket, you don't need to buy something new. Just take a length of the spare tube a bit longer than the damaged section, make one cut down the length and slightly roll the tube. This will make it fit inside the rocket and can allow you to get past the shock cord mount if you have it glued to the side. Once it's in place, the roll will naturally spring tight, and then just soak it in some thin CA to set it in place. You could also smear a band of wood glue inside the rocket where the crumple is and then insert the sleeve to meet the glue.

kuririn said:

Easiest way if damage is extensive: Cut off the damaged tubing. Get a new tube and coupler. Cut tube to length and glue together. Good as new.

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This is often the best option, and what I usually do, but then I have to redo the paint and decals. But as a bonus, that gives me the opportunity to add features if I want. I had my QCC Explorer land in a pond and the body was pretty bad after all that soaking. I cut off the body just above the air scoop fins, and rebuilt the whole front end with a payload bay that the original kit didn't have.

ebruce1361 said:

This is a great idea, but if you have some body tube lying around of the same diameter as your rocket, you don't need to buy something new .......

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That's an option, a weaker option. Couplers typically don't have the glassine coating like a body tube (which is better for glue adhesion) and couplers are typically a thicker wall and therefore stronger.

@lakeroadster good point on the glassine coating. I always sand the body tubes where the fins and lugs will go to promote glue adhesion, but I hadn't thought about doing so for much else. A coupler missing that coating will grab the glue inside better, but the scrap tube gives you the ability do a repair sleeve in whatever length you want whereas coupler tubes are usually specific lengths (but if needed, I suppose one could stack several couplers).

Coupler tubes can be bought in lengths as long as 34". IIRC BMS stocks them.

kuririn said:

Coupler tubes can be bought in lengths as long as 34". IIRC BMS stocks them.

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Well, you learn something new every day. I have only ever seen couplers as long as double their diameter. At any rate, I suppose you could still use the scrap tube method as a quick fix if you don't have the couplers on hand, or if you have to contend with a shock cord glued to the inside wall of the body. Even with couplers, you'd either have to cut the coupler or remove the shock cord and sand down the mount point smooth to get the coupler past it.

If the rocket is a smaller Estes style rocket - A,B,C motor flyer. I've taken an x-acto blade and scored perpendicular to the crinkle, allowing the scores to be about 1/16 - 1/8" apart. Then I wick in some thin CA adhesive. The scores give the CA something to grip. I've repaired my kids'(6 and 4) rockets quite a bit this way from events ranging from rough handling to less than nominal flights. Anything flying on a larger motor, I would look at some of the other alternatives, like adding an internal coupler tube for more strength. The smaller rockets don't incur high enough flight forces to worry about with the method I outlined though.

ebruce1361 said:

Well, you learn something new every day. I have only ever seen couplers as long as double their diameter. At any rate, I suppose you could still use the scrap tube method as a quick fix if you don't have the couplers on hand, or if you have to contend with a shock cord glued to the inside wall of the body. Even with couplers, you'd either have to cut the coupler or remove the shock cord and sand down the mount point smooth to get the coupler past it.

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Or simply just cut the rocket body tube, insert the coupler and then re-assemble. Trying to slide and glue a coupler deep into a body tube is problematic... bordeline nightmarish.

I did use the "body tube in a body tube" as the shock mount on my X-Wing. It worked but was tricky. Next time I'll just cut the body tube. As a side note: Burying the shock chord mount deep in the body makes the pathway clear for the chute to exit the tube at ejection.

dvdsnyd said:

The smaller rockets don't incur high enough flight forces to worry about with the method I outlined thought.

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Until they lawn dart

I saw "Lawn Dart" and thought I'd see a Big Daddy in here... Looks like I was right.

https://www.rocketryforum.com/threads/big-daddy-lawn-darts-show-of-hands-please.131851/

General consensus is that the "ramp" that is on the shoulder vents the ejection gasses under the wrong conditions (drag seperation?), preventing the laundry from being deployed. I plan on modifying my BD's nosecone to eliminate the ramp, and prevent myself from having this problem.

K'Tesh said:

saw "Lawn Dart" and thought I'd see a Big Daddy in here... Looks like I was right.

https://www.rocketryforum.com/threads/big-daddy-lawn-darts-show-of-hands-please.131851/

General consensus is that the "ramp" that is on the shoulder vents the ejection gasses under the wrong conditions (drag seperation?), preventing the laundry from being deployed. I plan on modifying my BD's nosecone to eliminate the ramp, and prevent myself from having this problem.

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CRAP! If I'd known we had started a special group for that maybe I would have stared at that thing for months from a different prospective. SERIOUSLY! That broke my little rocket loving heart! I think I even cried! If I ever find that box in the attic, I bet it is still there, just because of those BEAUTIFUL fillets I invested HOURS in. I was so proud of that rocket, I flew it before painting, and then a funeral! This has become a rejuvenating thread for me. What killed me, has brought me back to life. I left the busted nosecone right where it was, about 4" aft of launch position, body tube split like a ??? Like an overloaded icecream cone! My first big engine rocket too. I found the 3 packs of Ds and Es still waiting for it when I got up the courage to play with these toys again.

Now it's in a place of honor, rather shame!

THANK YOU SO MUCH! Really.

Phil.

Phil Hasty said:

CRAP! If I'd known we had started a special group for that maybe I would have stared at that thing for months from a different prospective. SERIOUSLY! That broke my little rocket loving heart! I think I even cried! If I ever find that box in the attic, I bet it is still there, just because of those BEAUTIFUL fillets I invested HOURS in. I was so proud of that rocket, I flew it before painting, and then a funeral! This has become a rejuvenating thread for me. What killed me, has brought me back to life. I left the busted nosecone right where it was, about 4" aft of launch position, body tube split like a ??? Like an overloaded icecream cone! My first big engine rocket too. I found the 3 packs of Ds and Es still waiting for it when I got up the courage to play with these toys again.

Now it's in a place of honor, rather shame!

THANK YOU SO MUCH! Really.

Phil.

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Sorry to hear about your loss.

I really wish that Estes would get it through their heads that there is an inherent flaw in the combination of that nosecone with that kit. The numbers of people who report that their BDs have come in ballistic is significantly higher for that kit than any other kit I've seen (despite it being used with other kits). I think that those big draggy fins, and lightweight sustainer, are a major part of the problem. After boost, the mass of the nosecone wants to keep going, but the fins pull the body back and there isn't enough mass in the body to resist the drag. The body slides back, and when the conditions are just right, it opens the vent enough for the ejection charge to fail to split the rocket. The rocket then turns turtle at apogee, and "LOOK OUT BELOW!!!"

While it may be possible to prevent drag separation by just using pieces of tape to snug up the shoulder, I want to make sure that I eliminate the real source of the problem... That ramp. For my modification, I plan on using a piece of body tube, cut down to create a tube coupler of sorts. Cut away the ramp, and the bottom of the shoulder, then fit the tube coupler in and glue it in place. Finally install a bulkhead inside the coupler to attach the hardware for the shock cord and parachute. I believe that this will do the trick. However, it's going to be a while before I can do it, as I'm *STILL* having problems securing all the supplies I need to build rocket here in the PRC (nearly 4 years after arriving). You'd think you'd be able to find everything here (it's all made in China right?) but NO!!! Good luck finding filler primer, automotive body filler, wood hardener, etc. Hobby shops? I live in a city with 6.9 million people, and I have yet to find a dedicated hobby shop.

Pointy Side Up!
Jim

Looks like a great candidate for a cluster of 2 or 3 D motors... more motors, more ejection power too.