Newest design after 20+ years of absence....

I would like to offer just-in-case apology--

I hope you didn't take my comments about the previous fin design as some kind of "don't do it" or criticism, I was just trying to show you a way to make it work (and why)

This new design looks good, but the first one had some unique style. I hope you don't give up on it!

powderburner said:

I would like to offer just-in-case apology--

I hope you didn't take my comments about the previous fin design as some kind of "don't do it" or criticism, I was just trying to show you a way to make it work (and why)

This new design looks good, but the first one had some unique style. I hope you don't give up on it!

Click to expand...

No apology needed. Your data was excellent.
Haven't totally given up on the first design, but that design was veto'd by Genevieve. "Too swoopy" she said. The 2nd was her idea, and it was ultimately better.

Okay, Rocket is 1/3 done.

-Nose cone has carbon fibre look now (this was not that easy. Olgive shapes are hard to cut with scissors! )
-Body has a white/black checkerboard pattern on it (thank god for self adhesive films! )
-Fins are cut out from 3mm birch plywood, rounded at the front section, then the actual "wing" sections are airfoil shape, and height-wise the fins taper from 3mm to 2mm. 3rd fin is now glued and setting.
-Engine mount was done a couple of hours ago. Estes standard mount with a steel spring clip. Simple, easy, reliable.

Pics to follow......

GDJ said:

No apology needed. Your data was excellent.
Haven't totally given up on the first design, but that design was veto'd by Genevieve. "Too swoopy" she said. The 2nd was her idea, and it was ultimately better.

Click to expand...

Probably a moot point now, but places like Balsa Machining will laser-cut fins for you in a variety of materials based on RockSim data.

I had them cut my CN Tower fins which, because of the length & thickness had to be sectioned and laminated.

PhlAsh said:

Probably a moot point now, but places like Balsa Machining will laser-cut fins for you in a variety of materials based on RockSim data.

I had them cut my CN Tower fins which, because of the length & thickness had to be sectioned and laminated.

Click to expand...

What??? And deny this man's daughter of the toil and blessing of cutting your own? Please do not cause the stock to go down on X-Acto knives! I'll be destitute and there are no homes for old model rocket scientists.

:roll:

Rip said:

What??? And deny this man's daughter of the toil and blessing of cutting your own? Please do not cause the stock to go down on X-Acto knives! I'll be destitute and there are no homes for old model rocket scientists.

:roll:

Click to expand...

Well, she's a bit young to use a Dremel with Router attachment. :shock:

Here she is in all her glory, awaiting maiden launch!


Launch lug is placed <> CG and CP. Body is wrapped (I ain't that good with paint! LOL)


Carbon-fibre wrapped nose (oops. Missed a spot. Black sharpie will take care of that )


Wrapped the fins too! I love the carbon fibre look, Genevieve likes it too!

Flight simulations on measured dimensions, altitude corrected for launch site:

First one is with the Estes B4-4 (maiden launch engine), second is with a Estes C6 engine, third is with a Apogee D10-7 engine, which is the most powerful I can fit in the engine housing (can't get one up here in Canada, but I wanted to see what I can do with the rocket, pushing the envelope so-to-say! )

For fin strength, what about 2 ply 1/16 balsa?

Cut one with grain one direction, the other 90 degrees off. Glue the two prior to sanding.

Gives strength of 1/8 inch balsa, but in every direction of stress.

BABAR said:

For fin strength, what about 2 ply 1/16 balsa?

Cut one with grain one direction, the other 90 degrees off. Glue the two prior to sanding.

Gives strength of 1/8 inch balsa, but in every direction of stress.

Click to expand...

I may consider this on my next rocket.

GDJ said:

Here she is in all her glory, awaiting maiden launch! Launch lug is placed <> CG and CP. Body is wrapped (I ain't that good with paint! LOL) Carbon-fibre wrapped nose (oops. Missed a spot. Black sharpie will take care of that ) Wrapped the fins too! I love the carbon fibre look, Genevieve likes it too!

Click to expand...

That is one fine looking rocket!

qquake2k said:

Or laminate balsa with 1/32" plywood, if you can find it.

Click to expand...

Any advantage of using 1/64 ply over balsa ? Saw some local and thought it would be good to reinforce my Renegade D fins when I upgrade the MMT to 24/60 .

Know it is not as strong as birch or the thicker ply, but like paper adds a 2 layers of rigidity - goes together quick with CA . Personally like this type of laminate when a fin is made of 2 pieces or more like the SR-71 , having snapped one while sanding/finishing in the past .

Hope Gevevieve likes the rocket !Was thinking of doing a SANDMAN ' DER GROSSER VATI ' Big Daddy for the little girl , if I can them 'Pink Maxed' style

That came out real nice. I like the wraps.

Hmm, interesting discussion to follow.
That'll make a nice looking rocket.

BABAR said:

For fin strength, what about 2 ply 1/16 balsa?

Cut one with grain one direction, the other 90 degrees off. Glue the two prior to sanding.

Gives strength of 1/8 inch balsa, but in every direction of stress.

Click to expand...

On the "yes" side:
- a "ply"-balsa fin could be stronger

On the "no" side:
- it will be more work (compared to just cutting parts from a regular sheet of 1/8 th balsa)
- it will be heavier (with a glue joint up the middle)
- it will be more difficult to sand the edges of the cross-grain side (if you round the edges of the fin)
- it will be just as prone to warping as a single-ply sheet balsa fin (unless you go all the way to a symmetric ply stack with 3 or 5 plies)

Bottom line, whatever list you make up:
- for a low-powered model rocket, you just don't need it

Use 1/8 th, align the wood grain with the fin leading edge, it will be plenty strong enough, you'll be fine
And K.I.S.S.

Well gentleman and ladies, she had her maiden flight with a B4-4 engine. I did this without Genevieve (she went on a shopping day with mom and the other 2 daughters) so I could iron out any flaws or bugs with the design if need be before she gets to do her own launch (less disappointment....yadda yadda yadda....you other parents know the drill).

Flawless. Absolutely flawless. Straight up, no wiggles, no deviations, just motor ignition and it took off......like a rocket!

B4's took her to around 500 feet or so, and after 3 launches I swapped in a C6-5.

It disappeared. Literally. I had 4 spotters for it, and about 1/2 way thru the flight, it simply winked out of sight. Then a POP and my Stepmother saw the 'chute open up.
We all looked for about 30 seconds, then we all tracked the bright orange speck for about 2 minutes.

Then I lost it in a stand of trees......or somewhere in the neighbours adjacent 1/4 section.......we aren't sure where it went. It wasn't a big parachute, and OpenRocket calculated the descent at 4.5 metres per second. It was up in the air for a bloody long time.

So I'm building a new one. Exactly the same as the first one. Because it worked so damn good.

I just hope that I can build it before Gen gets wind of me losing the first one :/

Might as well build two or three while you're at it

And next time you launch with a C, try removing the chute and replacing with a short streamer....or nothing at all. Leave the NC tethered at the other end of the shock cord, and let the whole thing tumble down. That's called 'nose blow' recovery (and no, I didn't just make that up).

powderburner said:

Might as well build two or three while you're at it

And next time you launch with a C, try removing the chute and replacing with a short streamer....or nothing at all. Leave the NC tethered at the other end of the shock cord, and let the whole thing tumble down. That's called 'nose blow' recovery (and no, I didn't just make that up).

Click to expand...

The first 2 recoveries were from trees, and the rocket showed no signs of damage even after some pretty violent shaking of the tree. It may survive a no-streamer or no-parachute descent. It appeared pretty damn tough.

Yeah, I think I will get enough parts for 2 more.

After running thru the numbers, OpenRocket might be in error for the descent of the rocket. It's possible that it calculated it's descent with a fully loaded rocket, not with a rocket with a spent engine (which would be much lighter). The 'chute I had looks like (from observations) that it was oversized by at least 20%. It was falling far slower than the 4.5 metres per second projection (more like 2.75 m/s) which didn't help.

So, the streamers only or nosecone only descent might be what's needed here. The rocket with a spent engine is quite light.

Ya know, us low-power fliers face many of the same problems that high-power fliers have, just on a smaller scale. Everybody wants to get their rockets back, which has led to development of the 'dual deploy' systems for high-power where an apogee event releases a small drogue device and a lower altitude trigger releases a main recovery system for the actual landing.

But

If we use a separate blackpowder-based deployment device for the second, low-altitude deployment, our simple (and low cost) low-power hobby turns into complicated and expensive licenses, lockers, permits, paperwork, and inspection intrusion.

Sure would be nice if some low-power motor manufacturer would try to come out with a pyro-based, pre packaged dual deploy motor. Such a motor could be built as already done, with the first ejection charge venting out a port in the side of the case. The first ejection charge could also ignite a second pyro delay in the front of the motor case, which would finally ignite a second ejection charge maybe some four or five seconds later. Technically, I think it is quite do-able. Business-wise, I'm not sure how much demand there would be.

One other option would be to offer a pre-packed kit containing the second delay and ejection charges, stamped (as now) in the same kind of cardboard motor casing. This auxiliary device might be mounted 'gap staging' style to vent the first ejection charge as the second delay is ignited. A separately packaged auxiliary delay/ejection device could be built using the same components and chemicals, would not mess up the business of the current motor offerings, and could even be done on a smaller scale by a manufacturer who is not interested in making these devices by the million.

Just wishing.....I'll put it on my Christmas list

The neighbours in the next 1/4 section south of my dad's found it. It became separated from the 'chute and nosecone and I was chasing the stupid nosecone and parachute. That's why it came down at such a slow pace (didn't have my prescription glasses on, and I was chasing a slightly fuzzy orange "object" that looked like the parachute). Didn't catch the rest of the rocket not being attached. Kinda feel dumb here.

No damage due to the freefall, no water damage (it was sitting on top of some very tall grass, not buried in it), no cracked fins. New nose cone, better shock cord (no more Estes crap) and a better parachute or long streamers and she's good to go!

Genevieve's Missile #2 and #3 will have some better changes to the shock cord mount, better recovery system.

Great news that you found it! Way to go, neighbors! Now she gets to keep the original. Nice happy ending.

It is indeed good news, but I am continuing #2 and #3, and using the original as a benchmark, and they will be improved particularly in the recovery system (which was spotty in the original). Everything else on the rocket was fine.

#2 is built. Identical to the first one (body, nose, fins) but with a heavier shock cord mount and 1000mm of heavy string then the shock elastic is tied to that. Parachute is slightly smaller. Flight sims are nearly identical to the prototype (within 3 metres).