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Little Dog Performance Rocketry Fiberglassing

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levi-rocket

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I am in the process of constructing the little dog by performance rocketry and had some questions about fiberglassing the fins. First of all, is this even a good idea and secondly, how would you do it. I have built 3 other high powered rockets but i have never fiberglass one before and would like to.
 

troj

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I'm assuming you mean fiberglassing the fins onto the body?

You have two options -- tip-to-tip, or just reinforcing the fin roots.

The first step will be to sand everywhere you're going to apply epoxy and/or fiberglass. Don't be shy; use 80 grit sandpaper in a sander, and wear a respirator -- the dust just isn't pleasant on the lungs.

Assemble the rocket as usual, including applying initial fillets to the fins. Then, lay the rocket down such that the tube is horizontal and supported. You want two fins up, forming a "V". Mix laminating epoxy and brush a thin layer onto the area where you're going to apply the cloth. Then lay the cloth over it, and if there are any dry spots, dab a small amount of epoxy onto the dry spots. Let cure, then sand and apply filler as necessary.

-Kevin
 

Handeman

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The method Kevin describes will work just fine. I just don't think it's necessary. Good joints and fillets should be all you need. Maybe some 1/4" chopped strands of fiberglass mixed in the epoxy fillets.

Looking at the flight reports from EMRR, the Little Dog seems a little heavy already for its diameter and length. My scratch built L1 cert rocket build from thick wall mailing tubes gets a consistent 5 - 10% higher altitudes with the same motors, I161W, I1299N, and J350W as reported on EMRR. I don't think I would want to add any un-necessary weight to the Little Dog.
 

n5wd

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I am in the process of constructing the little dog by performance rocketry and had some questions about fiberglassing the fins. First of all, is this even a good idea and secondly, how would you do it.
Like Handeman says, the Little Dog is built sturdily already, and a bit heavy, but that's one reason I like it - built like a tank and able to take anything you can slide into it. You're not going to be able to fit anything larger than a J in there, probably won't break mach, so at most I'd think that reinforcing the fin/body joint would be about all you'd need to do.

Be sure and consider adding a tracker inside if you start going for the big motors - you'll not regret it (he says, from experience).
 

blackjack2564

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I still have the first Little Dog DD prototype. It has dozens of flights on it and more abuse than 10 normal fliers could put it through. There is NO COMMERCIAL motor [yet] that it will not fly on that will cause it harm!

It was designed to fly as is on all available motors that will fit. No nose weight is needed either.

Fiberglassing the already g-10 fins is a total waste of time and will do nothing but add weight and keep you from utilizing small motors to the max.

The ONLY time I would recommend it : if you are converting to minimum diameter 54mm, then do it only to hold the surface mounted fins on.
 

Diosces

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As Crazy Jim says, the Little Dogs are very tough when built stock.

Here's Trio of Little Dogs build threadthat I built stock, used West Systems epoxy with milled fibeglass as an additive.
Close to a hundred flights all together with mostly just chipped paint damage and one recent flight had a fin fillet loosen when it landed back on the launch pad;)

Little Dogs with dogs.jpg
 

Bill P

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Absolutely NO NEED to glass it.
I agree completely.

Neither of mine were fiberglassed. The rocket and its fins are rock solid as-is.

The first one lawndarted and the fins were still securely attached:



I can't say much for the rest of the rocket:



The second one fell flat from over a mile after the shock cord tied the nosecone on without any damage to the rocket, including the fins:



As I said, the fins are rock-solid without any fiberglassing.

2009 04 18 Little Dog lawndart (718 x 539).jpg


2009 04 18 Little Dog dug up (816 x 612).jpg


knot closeup (1072 x 712) (804 x 534).jpg
 

UPscaler

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<snip>
The second one fell flat from over a mile after the shock cord tied the nosecone on without any damage to the rocket, including the fins:



As I said, the fins are rock-solid without any fiberglassing.
Wow, what are the odds of that?

I was looking at the Little dog DD. Looks pretty solid. Does it accommodate the new 1080 case?
 

blackjack2564

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It doesn't but the DarkStar and Wildman Jr. do! We made sure of that!
 

madmax

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Upscaler: I believe you are getting two cases confused. The 1080 case you mentioned is not new, it's been out for a few years. Used for the J570, J825, J575. I also believe this case just fits in the Little Dog. The 1320 case is the new one for the J510 is ~22" long and will not fit the Little Dog.

Forgot to add, wacky recovery mishaps always seem to crop up at the oddest times. A fellow flier failed on his first L3 attempt when the main harness tied a knot between the nose and the chute not allowing it to unfold. Came down under drogue only with the chute still neatly packed in its bundle. If it happens just keep flying! If you are afraid to put it on the pad, you're in the wrong hobby!
 
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Blue Skies

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I also have a Little Dog. It has survived everything except a complete lawn dart. It has landed in trees, it went swimming in a river for about an hour, and it fell sideways from 2000' under a very tangled parachute without any damage. I built mine with 30 minute epoxy fillets. There is no need for fiberglassing. If you still wanted more strength, you could add milled fiberglass into your fillets.
 

UPscaler

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Upscaler: I believe you are getting two cases confused. The 1080 case you mentioned is not new, it's been out for a few years. Used for the J570, J825, J575. I also believe this case just fits in the Little Dog. The 1320 case is the new one for the J510 is ~22" long and will not fit the Little Dog.

Forgot to add, wacky recovery mishaps always seem to crop up at the oddest times. A fellow flier failed on his first L3 attempt when the main harness tied a knot between the nose and the chute not allowing it to unfold. Came down under drogue only with the chute still neatly packed in its bundle. If it happens just keep flying! If you are afraid to put it on the pad, you're in the wrong hobby!
Oh you're right. It was the 1320. If they make a full power reload for that case, it should come out a baby K. That would be interesting in a little dog.
 
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