New addition: Estes "Exocet MM 38" clone

[GDJ]

Yep. This is a 1:1 scale clone of the Estes kit #1925 "Exocet MM 38". This rocket is a scale-down test for my L1 model (3" bodytube. Literally a scale-up of this kit).


So far just the basics are done so far. Cut out all the fins out of 1/8" Birch plywood, Airfoil profiled. I have the MMT (24mm) installed as with the retainer. All fins are TTB constructed (MMT extends all the way up to the front leading root of the front fins).

This isn't a exact clone since it's made entirely of Quest Aerospace parts, but the bodytube within 1mm of the original Estes plans for length, within 0.5mm diameter. It's overbuilt to maintain a 10:1 power/weight ratio which will be similar to the 3" model. Also this one is going to go VERY fast for a small mid-power model, hence the birch fins and TTB construction on all the fins.

Simulated and planned around a E-15 engine, it's just stable enough to fly a 24mm F21 if need be.



Here it is so far:

[WizardOfAZ]

Cool!

[fyrwrxz]

VERY nice bird- clean and mean!

[Handeman]

Also this one is going to go VERY fast for a small mid-power model, hence the birch fins and TTB construction on all the fins.

Simulated and planned around a E-15 engine, it's just stable enough to fly a 24mm F21 if need be.
Here it is so far:

I don't necessarily disagree with the birch fins for durability in landing and handling. What I think you'll find is 1/8" balsa will hold up to flights just as well as the birch ply and be much lighter.

I have a Estes Renagade D with the big fins and pods that is stock build with balsa fins and no laminations at all. It held up just fine to a 24/40 E18W flight and I expect it to work just as well with a F24W. It has snapped two fins off on landing, the paper on the tube peeled off with the fin both times. The tube is the week spot but you won't have worry about that.

Good luck.

[GDJ]

I don't necessarily disagree with the birch fins for durability in landing and handling. What I think you'll find is 1/8" balsa will hold up to flights just as well as the birch ply and be much lighter.

I have a Estes Renagade D with the big fins and pods that is stock build with balsa fins and no laminations at all. It held up just fine to a 24/40 E18W flight and I expect it to work just as well with a F24W. It has snapped two fins off on landing, the paper on the tube peeled off with the fin both times. The tube is the week spot but you won't have worry about that.

Good luck.

All true, but in order to simulate the loads that my L1 version will be exposed to I'm doing basically a L1 build on a LPR kit (originally the kit ran with a C class 18mm engine). I'm just eliminating any differences in construction, minus the size of course. Everything on this rocket so far is scale.

'course that might change....the L1 version is still on simulation only.

[rifleshooter]

Doing something similar...

Standby.

[GDJ]

Got some more done on 'er. 3 coats of epoxy appliance gloss black and 3 coats of fireengine Red.

Unfortunately the rocket took a spill on some grass seed outside and some of the red got marred up on the nose and upper body tube. No biggie. Just wait until the paint dries, quick sand and buff, and repaint.

But she's 80% done!

[hornet driver]

Very. very nice ! Good luck on the cert.

[GDJ]

Thanks!

Paint is now all fixed. Now to build a 6.5" thin nylon parachute and elastic shock cord assy (already put in the stainless leader line to the motor mount).

[Aksrockets]

Sexy Beans!

Alex

[Rex R]

it is gonna hit the ground mighty fast w/ that dinky chute.

[GDJ]

it is gonna hit the ground mighty fast w/ that dinky chute.

Maybe, but I doubt it. So far the rocket weighs in at 97 grams (3.5 Oz) without a motor. OR predicted a 30 km/hr descent. Not too fast.

The L1 version will be dual deploy, with a 13" drogue and 24" main.

EDIT: Yeah, Rex you were right. I made the parachute a tad bigger.

[accooper]

Cool. I have seen a real one and yours looks close to exactly alike.

Andrew

[GDJ]

Thanks Accooper. Appreciate that.

The Nose cone is not quite the same as the original Estes Kit, but it does have a rather short taper profile, kind of like the real thing. I thought it was a good compromise.


Launch lugs are attached, Parachute has increased to 8" (Rex R was right. The other 'chute was too small), no other changes yet. Still plan to do the maiden on a E15, then a E30 to get the speed up. If it survives that, maybe a F21.

IF it survives a F21, apart from being a miracle, then I think this will be a good design for the L1.

[accooper]

It should easily take an F39 24mm reload.

Andrew

[GDJ]

Rocket is now complete with a recovery system.

Carvac posted a question in another thread:

Originally Posted by CarVac
What would happen if you attached a chute to the end of a streamer? Would that be good for reducing opening shock in the case of an early ejection?

The shock cord has a reflective pink streamer that is woven into the 5' of orange nylon string (2mm, 100 lb). Lets find out what happens.

I'm awaiting 2 E15's,and 2 E30 Econojets.

[RocketT.Coyote]

IIRC Estes offered the Exocet as a mini-motor kit back in the late 1970s.

[GDJ]

IIRC Estes offered the Exocet as a mini-motor kit back in the late 1970s.

That I did not know. Cool! Another project!

Mine is based on Kit #1925, which uses 18mm engines.

[GDJ]

Well, I launched it, and it was the most spectacular feat of aerobatics you ever saw.
I honestly didn't know a rocket could not only spin, but travel in a complete 3' loop several times, and quite well!


Yes, I'm being sarcastic.

The E9-8 was a bit too heavy and the rocket dipped into the negative stability margins off the launch pad. A E-15 is a better choice (physically lighter).

Added some clay to the inside of the nosecone to increase the take-off stability. We shall see how it goes later on.

[Pat.H]

hopefully it won't spin around and around like it did last weekend eh!
still exciting to have you out there trying new funny looking rockets with low stability margins, makes for some great heads up flights!

[GDJ]

hopefully it won't spin around and around like it did last weekend eh!
still exciting to have you out there trying new funny looking rockets with low stability margins, makes for some great heads up flights!

Yes, exciting, but not preferred.

I added just a hair over 1 oz in the nose cone (30 grams). That hopefully will settle things down.

[GDJ]

After a long delay and adding the nose weight way back in April, I finally got to do the retest flight on the Exocet model.

Nailed at least 1500 feet apogee on a E9-8 motor. Dead stable with a 26 km/hr wind today.

Descent was quick, but not bad. No damage with 3 flights on it today.

The Question earlier on in this thread was about attaching a parachute on the end of a streamer to reduce snap-back. My version was a streamer interwoven with a nylon and elastic shock cord. The results of each flight was absolutely no signs of snap-back into the rocket body or fins. So I would say the idea has merit and works.