New project... Plenty of questions...

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rabidsheeep

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Ive been juggling the idea around in my head for alittle, and i guess ill start on it...

Im thinking of a 2 29mm mount cluster... I have a body tube which, evidentally, came from the garbage... Its about 34 inches long, and 3.5 OD, so this things just begging to fly...

I did a really quick sim of it, with just some random fin design and nosecone for just some idea, and i got some pretty promising numbers...



Ive made plenty of smaller 24 and 18mm scratch rockets, but for this one im not quite sure about a few things...

1. What should i use for an engine block? WIth all other smaller ones i would just chop up a used estes motor... Is there a BT that fits inside a bt-52 (that is a 29mm mount right?)... How far back should i push the block? (3.75 rings some sort of bell...)

2. For a motor hook or just retainer does anyone have suggestions of what to use?

3. Fins: Ive heard of everything from Plywood to birch to basswood... I dont know what would hold up for a 29mm rocket...

As far as the nosecone, i guess ill ask sandman about it (once i have an idea what im making), and parachute, i have one from an my arreaux that i dont use...

Thanks a bunch

--Sheeepy
 

GL-P

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I use good plywood. I don't have any experience with basswood or birch. Might want to try G10.

I would take a coupler tube for 29mm tube and cut it so you have some engine blocks.

Don't know about a small motor retainer. I just use tape but the heat really does make a mess of it.
 

rbeckey

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Do a Google search for "Kaplow Clips." I prefer this method for Mid power retainers. I would not use an engine block for a 29mm rocket, due to various lengths of available 29mm motors. For single use motors like the G80, I either epoxy a thrust ring made from a slice of 29mm motor mount to the business end of the motor, or wrap it with masking tape to build up a thrust ring. Either method works equally well, in my experience. Aerotech reloadable 29mm motors have a built in thrust ring, so an engine block is not needed.

EDIT: 1001 posts! Yeeehaa!
 

rabidsheeep

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so that little overhang in the closure of an RMS casing can hold the engine instead of a block?

and are the clip style motor retainers they talk about here the same thing?

https://www.rockymountainrocketry.com/FrameProductsMotorRetention.htm

edit:

cant decide where to do with this one... i could make an upscale pheonix which im thinking of, or just a standard military design, or something retro-ish:



maybe add a boatail to that...
 

Stymye

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I like to use a block glued in for the longest motor I plan to use
than I just drop in spacers for the rest.I keep various spacer in the range box.
 

rbeckey

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Kaplow clips are made with T nuts, cap screws and a short piece of metal, sometimes from a screen door retainer. Hardware store parts, all very inexpensive.
 

rabidsheeep

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well, i decided to make an upscale pheonix... its gonna be about 40 inches long... i simmed it and it said on 2 a G64 it'll get about 1700...

For the front fins, do you think i should slot the airframe and glue them in secured to rings on the mmt, or can i just glue them straight to the tube (the rear ones ill have slotted in...

also, where can i buy or how can i print out decals for this thing...

im itching for a 3 29 cluster, but i think ill keep it at 2...
 

GL-P

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I'd say slot the airframe and glue the fins to the rings. It'd be heavy but the front fins on a phoenix are big enough that they are prone to breaking on landing unless you're glassing them. If you're glassing them, don't bother with thru the wall on the front fins.
 

rabidsheeep

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yeah, this thing is gonna be pretty heavy but meh...

i found something for decals, but does i think you need a laserjet not a deskjet

btw, 3/16 birch plywood for centering rings, should i use the same thing for fins?
 

GL-P

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Hey, I got a laserjet. If you want to you can send me the designs and I can print em off and send them to ya. I got an old laser printer that only does b&w (don't lasers only do b&w?)
 

Justin Horne

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I've got a b&W laser too..

They actually do make color lasers now, but they are freakishly expensive....:(
 

rabidsheeep

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i still cant figure out how im gonna decal this thing

anyone have a scan of the estes decals for it? i guess i can work from there
 

rabidsheeep

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Man, this thing is starting to worry me lol

gonna be heavvvy...

with the solid balsa nosecone, and 3/16 birch plywood fins, and centering rings, im wondering if 2 g's is enough to power this thing lol

after simming it, the altitudes went from 2200 to 1700 on 2 g's, and with how i build its gonna be even more...

anyone have a reccomendation on a lighter wood? or is this stuff light enough?
 

sandman

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So....what's wrong with 1,700'?

You can't really see it that well from launch distance anyway.

1,700' is up there for a heavy rocket with 2 "Gs"

sandman
 

rabidsheeep

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i know, id be happy if it got 1700 with the way i build

oh well, ill just try to work lightly
 

lalligood

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Weight saving recommendation #1:

Challenge yourself to use as little epoxy as possible. Remember: the goal is to build a cool rocket, not use as much epoxy as possible! :rolleyes:

Weight saving recommendation #2:

If using paper tubes & (any kind of) wood, use yellow wood glue (aliphatic resin) instead of epoxy for attaching those items together--particularly for all internal attachments & fillets. Can be used for external fillets too but might not look as smooth as epoxy fillets. (FWIW, I would only use epoxy to attach anything to/with phenolic or G10...)

Something to think about anyway. HTH,
 

loopy

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Keep in mind that when you cluster, you have to stay under H impulse, otherwise it's considered a HPR flight...

Sounds like a great project, but you might want to find a way to make it lighter.
 

rabidsheeep

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2 G64's is possible because it is 125 grams (62.5 each) meaning you can use it without a lvl 1 cert right?
 

iceage

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Originally posted by rabidsheeep
Man, this thing is starting to worry me lol

gonna be heavvvy...

with the solid balsa nosecone, and 3/16 birch plywood fins, and centering rings, im wondering if 2 g's is enough to power this thing lol

after simming it, the altitudes went from 2200 to 1700 on 2 g's, and with how i build its gonna be even more...

anyone have a reccomendation on a lighter wood? or is this stuff light enough?
My recommendation?

38mm and toss her up on a J330.

But that's just me ;)

Patrick
 

rabidsheeep

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ill just have to teleport 4 years in the future and get certed, no biggie...
 

Mark_Newton

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To keep it light, make fins with foam core board covered with either fiberglass/epoxy, 1/32" balsa, or cardstock(glue on, then coat with thin CyA). Your other option is 1/8" balsa fins, covered with either fiberglass/epoxy or cardstock soaked with thin CyA. Either technique can handle H motor impulses (I've seen several Level 3 cert rockets with foam/fiberglass fins).

As far as motor retention, I've made Kaplow clips, but my favorite is to make an upscale Estes-style motor retainer using brass strip from hobby shop. I cut and bend it into a hook with pliars. To attach it, I wrap duct tape around the motor tube, or glue it on with fiberglass/epoxy. Simpler to make than a Kaplow clip, and I've never had one to fail me in 5 years. I use them on 29-38 mm motors.

To keep centering rings light, make them from foam board or balsa. How they are designed is more important than construction material. Two rings spaced about 1/2" apart with some foamboard or balsa stood on edge between them is VERY strong, and very light as well.
 

rabidsheeep

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PROGRESS!

got my Nosecone from sandman... and of course i had to cut up some cardboard to try out the fins and see how it looks...



moving along nice and slow...
 
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