L1 - Help needed!

[Chilly]

Okay guys, the big day may be here sooner than I thought. Our TRA prefect is going to loan me a 29mm casing at next weekend's launch, and I'm gonna get an H128 or H180 reload for it.
Here's the problem. I recently built a VB Javelin intending to certify with it, but screwed up and built it PER INSTRUCTIONS. So the motor mount was assembled and epoxied in place, before putting the fins in - so no internal fillets! They are epoxied at the root and I made sure to put solid external fillets on it. The fins feel plenty firm but I'm worried anyway.
What I'm thinking is to drill three small holes in the aft centering ring (between each fin), and fill up the cavity with expanding foam. Do you guys think that would work, and if so, what brand of foam? Can I get away with the Home Depot stuff or should it be the 2-part hobby foam? And should I worry about plugging the holes after it's done?
I'd really, really appreciate some advice here. And I PROMISE to post pics of the cert flight.

 

[loopy]

I think that sounds like a plan, but I don't have much experience with the foam. I've heard alot of good things about the PML stuff though. Have you thought about just fiberglassing the fins on the outside of the rocket? Might be an easier solution. Especially if the fins aren't swept back behind the rear end of the body tube, I think just putting fiberglass strips at the base would hold them just fine...

Loopy

 

[llickteig1]

Chilly,

If you built the rocket per the instructions and the manufacturer recommends either of the two motors you mentioned, then you should be OK. Also note, there are L1 rockets that use surface mount fins and hold up just fine. You are certainly no worse off than that if you have added good external fillets. More than likely, the problem will be on landing, not on boost.

I would stick to the H128, though, just to avoid that added stress on the airframe.

Please note, you should not use the home improvement, construction-type aerosol expanding foam for anything in rocketry. #1 it requires air to cure and inside an airframe it can't get that air. #2 it is more likely to continue to expand under temperpature extremes much later. If you want to use foam, use the 2-part expanding foam. The brand doesn't matter it is all the same and repackaged under different brands.

HTH, --Lance.

 

[PGerringer]

The VB Javelin is suggested for F50-6, G40-7, G80-7. I think you will be fine with your rocket as is. The fiberglass fins should be sturdy enough and added external fillets will ensure a sturdy fin can. I would worry less about fins and more about the motor mount. Did you epoxy it strong enough as to not come loose and push up through the body? Sounds like you did. I would fly it as is. Just a note from your uncle Phil.

 

[PGerringer]

Oh, and good luck with your cert bro. Can't wait to see the pics.

 

[n3tjm]

You will be fine. I love the H128's. I am hording 4 of them now None of my rockets in my current fleet have foam enforced fincans, however when I plan on flying supersonic... those extrasteps should be concidered.

 

[Rocketmaniac]

I built my L1 rocket (ISP Caliper, whiched turned into my L2 rocket) with external fillets only......... Your rocket should be fine......... Good luck, bring back lots of pics.......

 

[Chilly]

Thanks everyone!

The Jav's test flight was last weekend on a G35-4 and it went very well. It had a nice trip to about 1200' and recovered fine, but the chute was definitely too big. I was very uncomfortable with the "hang time" (could've easily lost it) and will replace it with a 24" chute for the cert. Rocsim predicts 1600' on an H128 and that's probably what I'll use. If it's successful maybe I'll pick up an H180 from Ross and fly the Stovi on it!

I was very generous with epoxy on the motor mount. The forward ring has a good fillet from pushing up thru the epoxy, and I slathered the aft centering ring with the stuff. I won't lose any sleep over foaming the can, but will certainly remember it for my next build.

I'm probably gushing, but this is more exciting than I imagined it would be. I've waited long enough! And it's a real privilege being able to fly in Ohio with people like Barry Lynch there. Makes up for the lousy weather...

 

[PGerringer]

Originally posted by Chilly
I'm probably gushing, but this is more exciting than I imagined it would be. I've waited long enough!

LOL, Sounds like you are catching the Thunder Lust. After you do your Level 1, get ready for a great ride cause there are many, many wonderful kits at the H-J level.

 

[greg_g]

I understand what you are going through. Planning on my L1 cert on 11/23. I'm thinking of all the bad things that can happen. If it was easy everyone would be level 1.

If you really are not comfortable with the current situation I would do this. Attempt with the way it is. Should the fins loosen as a result and cert denied then reglue fin/repair filet with 5 min epoxy. Drill three holes (one between each fin) at least 1/4 dia to pour in 2 part foam (I use PML - don't use the spray in stuff). Pour in enough so expanded foam excess oozes out. It takes less liquid than you think and if you guess less than you need multiple pours in say 5 minute intervals is ok. Trim when cured (about 30 min). Dont worry about sealing the small exposed surface. Present to the RSO and try again. Foam really tightens up the fin can. You cant believe the difference.

By the way my cert bird is a PML Tethys (full foamed fin can) going up on a Pro38 247H143 Smokey Sam. Good luck to you and hope we can swap 'hero pics' soon.

 

[Jase]

Best of luck with the cert Chilly!

I agree with the other guys. I think you'll be fine with this bird as is.

When you do get to playing around with the foam, I have had great luck with the foam that PML has. I used it in a couple of my birds now and it makes the fin can hard as a rock!

The H128 is an awesome motor. That's what I used on my cert flight.

Pics, pics, pics!

 

[Rocketman248]

Hey Greg, nice choice on L1 bird. I used the same one for my cert. I used an H153. At NARAM, I flew it on an H143SS. It was pretty sweet.

 

[gerbs4me]

good luck one the cert

just go with the foam like th other guys have said, and you will do fine

Greg>good luck to you too, I se your from Lansing Illinois, are you a member of TQC's message board?

 

[greg_g]

Gerbs
Yes part of the message board. Was one of the first posters and made comments to the web master to help with the look. May have actually been the first to use the chat room attached. It is sweet. You coming to the TCQ launch on the 23rd?

 

[gerbs4me]

I might be able to make it, but I doubt it.

 

[Minimag54mm]

I'm right there with ya on this one Chilly!! Going for L1 on Nov.22 myself. However, since I love the rush and the whole nervousness thing, I thought I would do it again...for the 3rd time Got the "up" part figured out, just have to dial-in the "down". At least I'm not nervous anymore
Anyways, good luck and may the force become you....
Sounds to me like the Jav will do fine. If your still doubting the fillets( little subliminal voice that gets louder the nearer launch day gets), go ahead and drill your holes in the aft CRing. Pour some 2-part, 30 min. epoxy in !!! Foam is messy and if you put in too much you run the risk of having "too" much internal pressure(on both the airframe and the motor tube) since your aft CRing has already been installed. Normally foam works better in the "finbay" area when the foam is allowed to naturally "grow" out the aft, then trimmed back allowing the last centering ring to be put in. As mentioned, the launch won't effect it as much as the landing~~~~~~~~~~~~~~~~ >>>====> Fly High




If "everyone" knew how to do rockets then "everyone" would be!!



Chris Emich
Cronic Blastitis

 

[Chilly]

Sounds like a lot of us have the same thing in mind for next weekend. Should be some interesting posts the following Monday! Hopefully the weather will hold off (always a problem here).

I may just forgo using a borrowed casing and go pick up a 29/180 at Magnum this week. I need to get that 24" chute anyway. I'd like to get a full 180/240 set but it's not in the cards right now ($$). In the long run I'm probably better off with two full sets of casings & closures anyway. There are LOTS of 29mm HPR kits I want to build right now! The MiniBBX is calling my name...

 

[daveyfire]

Originally posted by Chilly
There are LOTS of 29mm HPR kits I want to build right now! The MiniBBX is calling my name...

Oh... sure... I see where this is going...

Before you know it, a 38mm kit will look reallll good to you too. And so you'll get a full set of Dr. Rocket 38mm casings. But then you see the 54mm line out there and just say, "Oh well, what harm could a 54/852 do? It's only four J motors... the entry level to 54mm?" But you don't realize it... you're stuck waist-deep in AP. Soon, you'll have your eye on the 10240 n/s 98mm casing. "Gotta get one of those," you'll say. And you do. But this puts you into debt and you go back and fly 29mm and 38mm until the credit card bills get paid off. Then back to 75mm and 98mm... and it goes downhill from there. Soon the voices in your head will be whispering things like "N" and "O" and you'll start designing that all-carbon 10.25" Q motor project!

We got ourselves another one!


(and don't think this won't happen... I didn't think so either when I bought that 38/240-480 set!)

 

[Chilly]

Actually, I was thinking of Pro38's since the casings are cheaper! I have a whole plan budgeted for the next year...

First, certify ASAP and treat myself to a MiniBBX and 29/240 casing for Christmas. Then I'll pick up a Binder Stealth (54mm version just in case) and Pro38 4-grain for my 40th b-day in Feb. That'll make a nice L2 flight when the time comes.

Once that threshold's been crossed, it's time for the PML Terrier booster (it does need a BIG 38mm motor, after all) and electronics. By the end of the year I hope to have the full Terrier/BBX stack ready to fly two-stage. I REALLY LIKE staging . If it works there's probably a Quantum Leap in my future too.

By the way, I was just cruising the Tripoli Mid-Ohio website and found the esteemed Mr. CTulanko is a member too. Can't wait to meet you, and see some of your work in person!

 

[Chilly]

Originally posted by daveyfire
Oh... sure... I see where this is going...

..Soon the voices in your head will be whispering things like "N" and "O" and you'll start designing that all-carbon 10.25" Q motor project!

We got ourselves another one!

My wife would immediately quip that "N" and "O" spell NO! She says men's hobbies all cost too much.

I tell her that at least it's cheaper than flying, and there's less chance of me getting the whole family killed.

 

[rocwizard]

If Ns and Os wont work, then how 'bout Ns and Ps!

Sounds like you have yourself a good plan there. We all look forward to hearing about your progress into the world of HPR! Just be sure to keep the pics coming or someone is going to get a visit from Vinny and Tony:kill:

 

[Chilly]

In my haste to take advantage of the TRA special offer, I just realized something...my membership card and # probably won't be back in time for next weekend's launch!

Our prefect is seeing what we can do about it. He's shown great patience answering all my questions and this will truly be "above & beyond" if he can find a way around this.

Well, if it doesn't work out I've got a couple of Ellis Mtn. long-burn G35's that'll be fun to fly. And I'll try not to drool all over everyone else's stuff...

 

[Rocketman248]

My Dad had the same thing happen to him. He just called them up, and they gave him the number over the phone.

 

[Chilly]

...and I'm not kidding! Both Weather Channel and Intellicast are calling for high winds Sunday. Well CRAP!

I should know better by now than to trust any forecast more than two days out this time of year, but that's how my luck was with last season's club launches. I work Saturdays so right off the bat my flying opportunities are cut by 50%, and the other 50% were usually cruddy.

Well, I'll just keep hoping for the best. Called TRA and got my membership number today, and it looks like the casing & motor are falling into place. I am psyched and ready to rock.

 

[greg_g]

Chilly
How did your cert flight go? Mine was picture perfect. Now I can spend even more getting ready for L2. The Tethys was a magnificent bird for certification; big enough to see all the way and even easier to see laying on the ground for recovery. No damage of any kind. Wife was amazed at the condition of the bird after flight. Other that a small dab of mud it still looked brand new. Pics to follow if I can find someone who captured the flight.

Greg
New TRA L1 (oooh that feels so good)

 

[Rocketmaniac]

Originally posted by greg_g
New TRA L1 (oooh that feels so good)

Congrat Greg!!!!!!, Hope we can see some pics......... Will you be using the same rocket for L2? I was able to do both L1 and L2 with my ISP Caliper.....

Again congrats.......

 

[Chilly]

Congrats Greg! Wish I could share the excitement but it didn't happen (see my post on the TMO season opener). My Javelin was ready, and I had a 29mm casing and H165 Redline at my disposal. But the winds were BRUTAL yesterday, and our Prefect finally scrubbed the launch at about 11AM.

He at least was able to inspect my rocket and gave it a thumbs-up. Hopefully we'll have better weather at next month's launch.

 

[MaxQ]

Ah yes...the weather gods intervene.
Best of Luck to you on the Cert 1 AND the winds.
BTW:

"Then I'll pick up a Binder Stealth (54mm version just in case) and Pro38 4-grain for my 40th b-day in Feb. That'll make a nice L2 flight when the time comes."......
-----------------------------------------------
I'm finishing a Binder Stealth right now..set up for a night launch w/ Strobes and formation lights. Nice kit.
I've used the Pro 38 4 -grain in a Binder Raptor (aka.Cobra). You should hear those fins whistle all the way to apogee after burnout. Awesome.

 

[MaxQ]

Oh...almost forgot.
Here's a pic.

 

[MaxQ]

...and the "lights out" shot: