Tube for MP build

[rabidsheeep]

found a tube in the trash... its 37 inches long, thich (almost 2 mm) cardboard...

i weighed it and it came out 8 ounces, so im just wondering if i should use it for a 29 mm mpr or not... would it weigh too much to get altitude? if so, ill just cut it up and cluster some things in it...

(i also found some wood in the trash... about 10 sheets 32 inches long and 8 inches wide, that look almost like 3 layers, but are REALLy light and strong)

 

[Ryan S.]

nice pic LOL, put a 29 in there and fly it on Hs, or a 38 for versatility

 

[rabidsheeep]

cept im 14 so i have to settle with g's...

edit:

anywhere know a place i can buy a full "set" for a 29 motor mount?

 

[solrules]

You could get that to fly on a G80, or even better, 3 or 4 of them.

As far as I know, you can buy some casings together, but not the 'full' set. That's becasue if you want to get all 29mm, you have to get:

29/60
29/100
29/40-120 (consumer case and closures)
29/180
29/240
29/360
Closure set
Seal Disk

That would be super expensive. (although I have each one, and seven 360 cases). 29mm is my favorite motor diameter, as it is very versitale, letting you fly E motors up to small I's.

 

[ghp3]

All but one of my MPR rockets were built with scavenged mailing tubes, roll cores, etc. Usually they do weigh in at about 8 to 9 oz for a 30' tube. One thing that I have done to make them a bit lighter, as well as easier to finish is to carefully strip off the outer paper layer. It doesn't seem to affect the structural integrity, and takes an ounce or two of weight off. Then I "paint" the tube with a coating of diluted Elmer's Fill n Finish, sand it with 220 grit, then 320 grit sandpaper and I've got a nice surface for finishing. Another suggestion is to wick some CA onto the top and bottom cut ends to strengthen them and prevent unraveling of the paper fibres.

Biggest problem with mailing tube rockets is that stock nose cones and centering rings often don't match the mailing tube. I generally make my own rings out of 1/4" ply from Home Depot, drilled and sanded to fit, and nose cones turned out of balsa blocks on a hobby lathe.

I do use "official" 29mm motor mounts and have flown them all on F & G motors (so far, I'm not yet certified, but have built several mailing tube rockets to handle 29mm H motors w/ TTW fins, epoxy joints, etc.). My heaviest mailing tube rocket weighs in at about 1 1/4 lb and flies to 1500 ft on a G35.

A great way to pursue low-cost rocketry!

George
NAR 83277
Tripoli Pittsburgh

 

[rabidsheeep]

most my rockets are low priced... i.e. trash...

centering rings are no problem... nosecones i hope i can get custom made (cant afford a lathe for myself)

as far as mid power engine mounts im alittle shaky on them... i had a about 5 BEATIFUL 29 mm tubes my mom threw out (ughh)...

other than the tube, i would need an engine block, and an engine stop right?

ive seen various types... from ones that are just like estes d powered hooks, to stops built in with clips to the wood...

which would i need here? as far as i know not all g's are the same lenth... mid power confuses me too much lol...

 

[ghp3]

Yes, G motors are different lengths, ranging from Econojets at 3.875", Aerotech SU motors are 4.875", and Ellis Mtn SU's are longer (6.5"?). 29mm H motors are even longer, up to 10+".

You can glue a thrust ring for a motor block (cut a piece out of used motor casing is cheapest) inside the mmt tube, but that limits you to whatever point you put the block in. I used a block for my first MPR, set at 4.875" for a Aerotech SU, which is fine, but now I'd like to be able to use an H in it and can't.

What I use now are piano wire hooks, usually two. I got a 36" length of 0.55" piano wire from the local hobby shop (only $0.75) and cut it to about 6" or 7". Using pliers, bend a 1/4" length 90 degrees on the aft (nozzle) end of the wire (for motor retention.) Then...and this is the tricky part...bend a 3/8" length 90 degrees in the EXACT OPPOSITE DIRECTION on the forward end. (Sorry, I don't have pic to show you right now, think zigzag.) Next, cut a groove in one of your centering rings. The bent forward part fits in the groove and will both hold the piano wire hook in place and keep it from twisting loose. Generous epoxy helps. I usually use two hooks on my rockets for redundency.

You will still need to use masking tape as a thrust ring at the nozzle end of your motor to keep it from thrusting forward, but you don't have anything in the mmt tube to limit your motor length.

Kinda rough, but it works on my rockets.

As for a lathe, you gotta variable speed drill?? I've done nose cones up to 3" in diameter by drilling a hole in the center of a balsa block, gluing in an oak dowel (gotta be oak, pine or poplar will shread), trimming the corners, then putting the dowel in the chuck of the drill and turning away. A 60 grit sandpaper block or wood rasp does a nice job of shaping quickly, emory boards are best for fine work.

George

 

[sandman]

This was my Level 1 Nike Smoke.

Made from all scrap material.

3.25" mailing tube, two 2x6's glued together for a nose cone (then turned on the lathe). Luan ply centering rings and fins, glassed with left over glass and cloth from my last boat.

Even borrowed a parachute and motor case from Carl!

Carl did "give" me some nylon strap for a shock cord.

The only thing I bought for this project was 3 spray cans of paint!

I looked everywhere...I just couldn't find any scrap spray paint!

sandman

 

[BlueNinja]

I don't think you need a motor block, as you want to put HPR motors in this. Right? Right?

 

[rabidsheeep]

actually, no. im 14, i got 4 years till i can even get my liscence (sp), and im broke.

as for the engine tube lenth i dont understand something...

ok, on estes single use motors, you need an engine hook and block... without the block, the engine would shoot up into the rocket... without the hook the engine would fall from 1500 feet onto somones head after the ejection charge (with some acceptions like misquito, twister etc.)

for mpr i was looking, and it was basically the same type looking thing... block on the inside, with a hole for the ejection charge, and a hook so it doesn't come out...

what i dont understand is how far your supposed to put the bottom part of the hook from the block... are you supposed to use only one type of engine?

edit:

got the tube patched where there was a dent, and sanded, down to 7 ounces

 

[rabidsheeep]

pardon my double posting...

i was looking at the pheonix project pictures stones put up... i noticed a couple things i didn't understand...

1. the engine tube extending the lent of the rocket?
2. i see the motor retainer... but umm... im alittle confused... does the retainer keep the motor from shooting up to the top or out of the bottom of the rocket...

better yet, does anyone have a pic of an motor mount tube where i could see how it works..

thanks...

 

[BlueNinja]

On HPR rockets you *generally* don't use either a motor hook or block, on the HPR SU motors they use a ring of masking tape. I've seen it used on an O motor, so for H and I motors it will be fine. Matter of fact I saw a minimum diameter Spring upscale designed for I70s or something like that fly on a I220, used a tape thrust ring and it would have flown fine had the motor had a little lower average thrust... It shredded

Blue

 

[Stymye]

tape works ,,I've tried it ..but don't care for it
I put a forward block in all of my motor tubes for the longest motor I plan to fly.. of course it's not needed for reload cases but ,,I simply make motors spacers for single use motors and keep them in my range box..it's too easy to just drop a spacer in if needed..done!

If I spend alot of time making the rocket look all pretty ..I don't care for a wad of masking tape sticking out the end of it.."is it tight enough ,,,is it too tight ..it gets sticky ..

I just usually use t-nut retention or make 29mm motor hooks for aft retention..

.lots of ways to do it,,