260 Space Booster Started!

[hcmbanjo]

I've just started the newest build of the
260 Space Booster
on my blog at:
www.modelrocketbuilding.blogspot.com

This was a feature plan from a 1965 Estes Model Rocket News, volume 5, number 3.
Should be a fun build, it's got a big two shroud nozzle. I'll try to add clear fins the way it was done on the Thor Agena B and Gemini Titan models.

Stop by and follow along!

 

[El Cheapo]

That's cool. Looks like it'll be nice and clean with no excess junk. I like that. I assume the clear fins will mount above the nozzle. Why not make the nozzle into a booster. Semroc makes that little 13mm deal that is pretty sharp. I upscaled it and have used it on my boys Executioner. Works like a champ and seems to get some nice comments.

 

[Micromeister]

Neat and Clean Looking.
I think it may make a fairly quick and easy micro model as well.

 

[hcmbanjo]

That's cool. Looks like it'll be nice and clean with no excess junk. I like that. I assume the clear fins will mount above the nozzle. Why not make the nozzle into a booster. Semroc makes that little 13mm deal that is pretty sharp. I upscaled it and have used it on my boys Executioner. Works like a champ and seems to get some nice comments.

Thanks ElCheapo,
I hadn't thought of that. The BT-60 (1.637") and ST-16s (1.640") are really close in diameter.
I've built the Semroc booster but haven't used it.
I pulled it out to check them side-by-side and it's almost a perfect fit!
The upper shroud and centering ring needs a little shimming, but it's real close.
The Semroc Booster 16 is made for a 13mm engine, you could leave that engine mount tube and slide in a BT-20 with the right centering rings.

The Semroc booster doesn't have the 1/4" space between the two shrouds but that could be adjusted. The Semroc booster coupler is a little short.
But, for somebody not wanting to mess with printing their own shrouds, this could be a viable substitution.

 

[El Cheapo]

Oh, I wasnt suggesting the 13mm motors but adapting for 18mm since you already have to do the shrouds. You may have to recess the sustainer motor a bit but it would be really sweet. Plus, you'd have a slap on 18mm booster for all your bt-60 rockets.

You have skills. I have faith. Make it happen' Capin'

 

[JAL3]

Where did you get the plan/MRN. I couldn't find it on Ninfinger or YORF

 

[BobH48]

Where did you get the plan/MRN. I couldn't find it on Ninfinger or YORF

It's on Jim Z's site. here

I built one when I first got my copy of MRN just because I really liked the big nozzle.

It has four big clear fins that reminded me of Big Bertha fins but they extended far enough back to protect the nozzle from damage on landing.

But I seemed to pop one loose every time I flew it. I never had much success using butyrate dope as glue on the clear fins.

I didn't think at the time they needed to be that big.

 

[JAL3]

It's on Jim Z's site. here

I built one when I first got my copy of MRN just because I really liked the big nozzle.

Thanks. I thought I had checked JIMZ also but I guess I messed up.

 

[hcmbanjo]

I flew the 260 Booster today at the Orlando R.O.C.K. monthly launch.

This time with an Estes C6-5.
50' feet up it did a very tight loop then went vertical again!
It lost a lot of altitude in the loop, I would guess it may have peaked at about 350'.
The 15" nylon parachute ejected and landed in the far corner of the field.

I expected to find it with a fin or two missing, maybe they were left at the launcher.
(These are clear fins mounted (glued) onto a clear tube slid on outside the BT-60 lower body.)

All four root edges were still on the clear oustide "coupler". One fin was lying next to the body, cracked in two, it's root edge still glued to the clear coupler.
Last night I did reinforcing fillets with medium CA. (Yeah, I know they'll eventually get brittle and fall off!) But, they sure held strong for today's launch.
Too bad the rocket was unstable with the C6-5. Last September it flew fine with a B6-4. The old Estes plans make no mention of nose weight.
Oh well!

 

[mwtoelle]

The C6-5 is 0.2 oz. heavier than the B6-4. I would keep in mind that the B.8-4 was the largest single stage motor available in 1965. Comparison with an old 1967 Estes catalog shows that B.8-4 and the B6-4 supposedly have the same initial weight. YMMV.

 

[hcmbanjo]

The C6-5 is 0.2 oz. heavier than the B6-4. I would keep in mind that the B.8-4 was the largest single stage motor available in 1965. Comparison with an old 1967 Estes catalog shows that B.8-4 and the B6-4 supposedly have the same initial weight. YMMV.

Thanks Mike - good point!
You would think a model that's 22.5" tall and with trailing fins (almost the size and span of a Big Bertha) would be stable with a C6-5!
But - I've been wrong about stability before!