planning a Madcow mongoose build

This Mongoose a sweet 30" carbon 29mm rocket. To sure up the fins I would like to glass from tip to tip. Carbon is silly expensive. I have some 2oz BID glass and think it will do the trick after scuffing up the fins and tube. What do you all think? Will it look way to stupid with glass over carbon? Should I spring for 1 yard of carbon? I want this little thing to bust mach that's why the tip to tip glass.

Joel

My 54mm CF has busted Mach with no tip to tip and survived to fly another day. I think what you are proposing is an overkill and adding extra weight where it's not needed.

Thanks Tim. I just can't wait to get this little screamer!

I used a high temp epoxy (Proline 4500) on a modified Mongoose 29 for the initial fin-stick and fillets. You don't need tip to tip. Good fillets are way plenty to hold it together with any motor that'll fit in it.

Complete with your build time (if it is in fact worth anything), materials, motor, tracker, flight computer, parachute, club fees, gas to and from the launch site, insurance for the car, lunch money, and miscellaneous costs, you're looking at a solid $350 to get this thing in the air. What's another $20 for a yard of twill?

https://www.ebay.com/itm/Carbon-Fib...032690?hash=item1a2d5a2732:g:nAUAAOSwPCVYBfBk

GrouchoDuke said:

I used a high temp epoxy (Proline 4500) on a modified Mongoose 29 for the initial fin-stick and fillets. You don't need tip to tip. Good fillets are way plenty to hold it together with any motor that'll fit in it.

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Thanks Duke for the re-assurance and the Proline tip. In another thread I read about drilling small holes along the fin alignment line, slipping a petrolatum covered cupler in the body, then attaching the fin. This causes the epoxy to act like a rivet.

A single layer T2T, done under vacuum, with a breather, peel ply, and the correct amount of epoxy will add very little weight to your aft end, but it will add weight.

I am a big fan of T2T and I have done several that many TRFers also said was unnecessary, but I say build it the way you want. Having said that if you don't have the tools and are not prepared to invest in them then the T2T process could get ugly fast.

I have the OOP all carbon fiber 38mm Mongoose that I am just finishing up and I did a single layer 2x2 twill 3K T2T on her, I have one set of fins to go and hoping to have her ready for URRF4.

I also have the 54mm CF Madcow Tomach XL, I also did a single layer T2T on her. She has has been close to Mach 2 twice, broken Mach 1 five times, has fallen from 10K on a 12" drogue with a failed main landing on very hard compacted dirt (flight 6), and has a total 9 flights. She looks like new and I am not confident that I would be able to say that if I built it any less, but who's to say.

One other thing to consider which is very much the case with me. If you are planning on bigger and better flights as you get deeper into this hobby, the best time to practice building you skill sets is now. In other words before you get into a build that really needs this level of reinforcing, build your skills on rockets that don't, there is a learning curve to get it right.

I have had same experience as grouchoduke in using proline on several 29mm blackhawks. Fins stay on- even after coming in ballistic due to battery intermittent and pulverizing seven inches of forward section! Haven't found a motor that bothered it yet! happy building.

rocketman4h said:

Thanks Duke for the re-assurance and the Proline tip. In another thread I read about drilling small holes along the fin alignment line, slipping a petrolatum covered cupler in the body, then attaching the fin. This causes the epoxy to act like a rivet.

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Drilling a line of perforations in carbon fiber alongside a fin and then filling the holes with epoxy cannot possibly increase strength. Epoxy rivets might be useful if the epoxy has greater shear and tensile strength than the material removed by drilling.
Simply roughing up the surface so that the epoxy has more surface area to grip is usually sufficient. A strip of carbon tape for reinforcement along the joint between fin and body tube would be much better than rivets.


Steve Shannon

This one has flown every motor from an Estes D-12-3 to I-200 & I-204....H-399.


It fears no motor & only has small fillets. 10 yrs old and still flys on anything. Just glue the fins on, all the other stuff, not needed on this size.



Do what you wish, anything other than this is a waste, you thicken the fin profile & it's not needed.

PS. I have 75's that fly on M's with only a bit of carbon tape....under fillets. NO T-T.

I would like to thank all of you guys for helping me chill way down on the process. I just need to fall back on what I know. Hey Jim, what kind of altitude did you get on that I-204?

rocketman4h said:

I would like to thank all of you guys for helping me chill way down on the process. I just need to fall back on what I know. Hey Jim, what kind of altitude did you get on that I-204?

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I have no idea. I fly this one with motor eject, so I'm sure it's deploying while still going pretty fast, robbing it of some altitude.
I just stick motors in it with a tracker, never put an altimeter onboard.

Well actually I did have a tiny Pico in there, taped to shock cord. 2nd flight it landed in a pond in the woods, took several hours to find and turned altimeter to toast. So that...ended that....lol

First flight [with altimeter]was on a hobbyline G-something, that went 3800ft.
Friend flew his on I-200 to 7,880. BUT being motor eject with only 14 sec. delay, it also ejected while under a full head of steam. Had one of those clip on altimeters on board.


WARNING:

do NOT fly this without a tracker.......you will never find it!

I flew mine once, with out tracker on a F motor. Simmed to 12-1300ft. figured easy flight to follow. club launch many eyes on it. Motor was old, old single use [24 yrs old!] Took off like a bullet, no one saw where it went, this was on sod farm.

Found next day only 300ft from pad in 4-5inch grass barely visible! Lesson learned, black rocket...tiny 9inch chute...almost invisible...use tracking!. When these first came out, almost everyone flown with out tracking was lost on first flight!

I found this under my build thread............


Jeroen_at_CTI
Senior Member

At AIRFest this weekend a stock Blackhawk was flown on the new 381Ns Pro29-6GXL I224 motor. Altimeter recorded 9990 ft! An awesome flight. This was using the stock retainer ring, not the flush tapered closure. I think it was also max. motor deployment, so set for 15 seconds. It was probably still coasting.

Jeroen


That should answer it!