New addition: Estes "Exocet MM 38" clone

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:



View attachment Estes %22Exocet%22.ork

View attachment Estes %22Exocet%22.rkt

Cool!

VERY nice bird- clean and mean!

GDJ said:

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:

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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.

Handeman said:

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.

Click to expand...

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.

Doing something similar...

Standby.

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!

Very. very nice ! Good luck on the cert.

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).

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

Rex R said:

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

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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.

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

Andrew

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.

It should easily take an F39 24mm reload.

Andrew

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?

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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.

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

RocketT.Coyote said:

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

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That I did not know. Cool! Another project!

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

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.

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!:wink:

Pat.H said:

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!:wink:

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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.

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.

One of my first Kitbashing experiences was with the Estes Exocet 38mm 18mm motor powered design. I redshifted it to accommodate "D" engines, and managed to launch it only once. It was very windy, and I was on the upwind side of the hill in Phoenix Oregon, launching from the old lumber mill that was next to the tracks. I fired it off at a 30 degree angle into the wind, and it weathercocked pretty bad. The parachute came out about 150' (eyeballed guess) off the ground, however the wind carried it over my head, and the updraft from the hill caught it.

That rocket hung in the sky for the better part of 25 minutes stuck in that updraft (despite the 6" hole in its 18" parachute) as I ran around that hill. I saw it go down in the farmers field behind Farmer's Market. Of course, the field was just plowed, and the rain made the clay sticky. I had 4" thick soles on the bottom of my shoes before I got out of the shoes. The rocket lost two fins. It has never flown since, and it's replacement has serious flaws. Now if I could only find that nose cone again. I'd start over.

I would build a new one. It's a great flier once you have the nose weight fine tuned. So far I have launched mine 12 times with E9 motors. Not quick off the pad, but the 3 second burn compensates for that nicely.


......

Really nice job.

I won a 4" Binder Design kit at LDRS in 1997 and then designed and built a 5" Dynacom upscale in 2001. They both needed quite a bit of nose weight to get 1 caliber of stability. They really stand out at most launches.

ChrisAttebery said:

Really nice job.

I won a 4" Binder Design kit at LDRS in 1997 and then designed and built a 5" Dynacom upscale in 2001. They both needed quite a bit of nose weight to get 1 caliber of stability. They really stand out at most launches.

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Please scan the instructions... It appears that they are lost. I really wanted to build one that hung around Tammie's Hobby Shop in Beaverton, but before I could afford it, it sold... Never to be stocked again.

In emails to Mike Fisher, it appears that the design somehow was lost, or didn't make the transition from the previous owner.

Thanks!
Jim

Sorry, they are LONG gone. The Binder kit core sampled at Black Rock around 1999. You can see the 5" version in my avatar pic.