Repairing broken fins on L1 rocket - Northern Colorado Rocketry

This topic has 10 replies, 7 voices, and was last updated 15 years, 10 months ago by pmscientist.

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October 19, 2009 at 3:53 am #40813
RichWallner
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I tried for my L1 at Oktoberfest, using my LOC/Precision NORAD Pro-Maxx, but my shock cord detached, and the boost section came down without a chute and broke 2 of the 4 fins. One of the fins broke off right above the epoxy fillet, and the other cracked right above the fillet.

Being a bit of a stubborn guy, I’d like to repair the rocket and try again. With this amount of damage, I figure that my only repair alternative is to fiberglass the fins — I’ll epoxy the fins back into place, and then fiberglass over the whole fin section. I figured that I’d have to fiberglass all 4 fins, because I assume if I just glass 2 of them, I’ll change the flight characteristics by having 2 “fat” fins and 2 “thin” fins.

The fins on this rocket are 1/8″ plywood, are about 3 3/4″ long, and protude about 3 1/4″ outside of the body tube. Here’s a URL with a review:

http://www.rocketreviews.com/reviews/all/loc_norad_pro_maxx.shtml

Will fiberglassing make the fins strong enough to safely launch the rocket on an H? If not, is there another alternative for repair?

Also, I have little experience with fiberglassing (I also figure this is a good opportunity to learn). I have some 3/4oz fiberglass cloth, which I’ve used to reinforce dented/kinked body tubes. When I’ve done this, I’ve used 20-minute “finish cure” epoxy with the fiberglass. Is this an OK combination to use for the fin repair? If not, what would you recommend?

Thanks for your help!
October 19, 2009 at 10:30 am #51438
SCOTT EVANS
Glass em tip to tip.
But you might want a little heavier glass.
20 min. epoxy is fine, but is an expensive way if your doing a lot.
October 19, 2009 at 2:26 pm #51439
new2hpr
Participant
I’ll probably get overruled, but I’d recommend cutting the fin completely out and putting in a new one by the original method. I’ve had similar damage happen with my L1 (also LOC), and repaired with more glass and epoxy each time, but it just keeps getting heavier, which leads to more landing damage and buying larger more expensive chutes, yadda yadda yadda.

LOC has VERY undersized chutes for our altitude, and I think you’ve found that their shock cords leave something to be desired.

BTW, I still have that damage to repair on mine, but I’ve got 3 layers of tip-to-tip glass to hack through as well. 🙄 😥

-Ken
October 19, 2009 at 3:35 pm #51440
Steve Jensen
Participant
to name a few have really undersized chutes for us.

I’ve given up using chutes supplied with the kits. I like the Skyangle chutes.

Grind out your fins with a dremel all the way to the motor mount and glue in new ones using slow cure epoxy.

I’ve done this on numerous rockets.

Then it’s the problem of balancing chute size for minimal damage against a long walk.
October 19, 2009 at 4:37 pm #51441
John A. Wilke
Participant
I think the root of the issue — no pun intended — is wooden fins. PML is a great, low-cost resource for cutting G10 fins. The fins are a bit more expensive up front, but when you calculate all the surgery you may have to do to fix a rocket, it seems to make sense to forego the wood and go with glass.

My L1 rocket was a Loc Vulcanite. I loved the rocket, but I got so tired of fixing it up that I created a rocket that I called the “Vulcanot”, which was the same rocket done without wood and without paper. It was far, far more durable and forgiving…

Regarding chutes – you are on the money there. Most are undersized for our elevation. I have a smattering of sizes that I move from rocket to rocket.
October 19, 2009 at 5:40 pm #51442
new2hpr
Participant
Excess in Moderation is a LOC Fantom EXL with G10 fins. I don’t know how it hit hard enough (it appeared to be coming in quite gently) to tear through the core and 6 layers of glass (3 t-t on each side). I think I started with too thin (1/16″) G10. I have a chunk of 1/8″ that will be used for the replacements (with no t-t).

Plus, with each repair, there’s less and less of Art’s paint job showing! Bah!

-Ken
October 19, 2009 at 11:18 pm #51443
SCOTT EVANS
I dont care what you all say! 😉 I repaired mine, just stuck the fin on with five minute, glassed it tip to tip with 20 minute. Flew it 2 more times before I lost it. 😆 See all that time I saved!! 🙂 Grinding…BAh.
sanding….Bah paint… who needs it? 8)
October 20, 2009 at 4:22 pm #51444
Steve Jensen
Participant
Sorry you lost it.
October 20, 2009 at 4:48 pm #51445
mule
Participant
I like using the Dremel with the little cut off disks on them for fillet/epoxy removal. It makes a surgical cut w/o taking too much material off.

I concur on the LOC fins, holy cow they just don’t seem strong enough w/o glassing. I have a new I-Roc that I’m thinking about taking the wood ones off of and putting in some G10 ones. A 5.5″ bird just shouldn’t have bare wood IMO…. Plus, it really needs a 38mm motor mount not 29….

Where are you at Rich? I have a big sheet of 1/16″ G10 we could cut some fins out of, it is a bit thinner than you may like though…. Or, check out Giant Leap’s or PML’s fin pages. Both are fast shippers and good people.
October 21, 2009 at 1:13 am #51446
SCOTT EVANS
Sorry you lost it.

Ah look at the bright side I dont have to store it any more!
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