Need Some Suggestions-

[11bravo]

While at AIRFEST, I purchased some phenolic tube (54mm and 38mm ID) and a plastic nose cone.
The 54mm tube is 48" long and will be the body tube for a rocket I'm calling the Warrior after my high school's mascot.
The nose cone is one of those blow molded, ogives that is about 9.5" long (from tip to shoulder).
I'll be using an Acme fin can and conformal rail guides (don't give me grief about them please )
Also planning on a 38mm SlimLine Motor Retainer from Giant Leap and a 29mm adaptor.
First question is,

How long should I make the body tube?

48" just looks too long. 30" or even 36" might be better. I know it's all a matter of what looks good, but I cannot decide.

Second question,

How big should the parachute be?

RockSim seems to think I need at least 48" of canopy; I guess I can't see that big as being necessary. This thing should be rather tough for landing purposes so I'd think a bit higher descent rate should be OK, but I'm just guessing here.

Attached is a .rkt file with a 30" body and 48" chute. The color scheme will be royal blue and white of some sort.

Thanks for any ideas,

Greg

 

[Stymye]

sounds like a good high performance design!

I 've been meaning to ask
Is it common practice not to glass phenolic tube when using it for body tubes ? ..I have used it for motor mount tubing quite a bit
but not for body tubes as of yet... the 29mm flexable phenolic motor mount in my black zombie completely shattered when a SU motor spit it's nozzle. and I had annother crack from landing stress so I've been weary of using it raw like that.

 

[11bravo]

I have the Non-brittle Phenolic Airframe Tubes.
I seems like a very tough card tube to me; maybe I misunderstand what it is.
Guess I don't know about glassing it.

From the Giant Leap Catalog-

Why is NONBRITTLE PHENOLIC better? Nonbrittle phenolic is strong, like the old standard phenolic But nonbrittle phenolic is much less prone to crack or shatter. Unlike paper tubes, it won’t easily crimp or buckle. Unlike plastics, will readily absorb CA’s and epoxies.

Hmmm? Maybe me need to rethinkest.

What do you think about the length?
I'm leaning towards 36" now.

Greg

 

[DynaSoar]

Originally posted by 11Bravo
How long should I make the body tube?

48" just looks too long. 30" or even 36" might be better. I know it's all a matter of what looks good, but I cannot decide.

Second question,

How big should the parachute be?

RockSim seems to think I need at least 48" of canopy; I guess I can't see that big as being necessary. This thing should be rather tough for landing purposes so I'd think a bit higher descent rate should be OK, but I'm just guessing here.

Well, I don't do Rocksim so I can't speak to those numbers. As you say, length is probably more a matter of looks than anything else. I happen to go for long rockets. They weathercock more, but to me that just says it'll head more upwind before the chute starts carrying it downwind. You could always buy a coupler and bulkhead, and turn the leftover tube into an optional payload section.

As for the chute: Yow! 48" of what kind? Even at 48" long, the rocket's not going to be over 3 lbs, is it? My Canadian Arrow weighs in at just under 3 lbs with a motor in it, and a 36" hemispherical (aerial flare type) brings it down right about 15 fps. A flex-phenolic tube and Acme fin can landing tail first is going to be about as fragile as a brick. 30 fps wouldn't be too much for it.

 

[11bravo]

Well, the length has been decided; I got out an old pipe cutter and cut it at 36" and guess I'll plan to use the other 12 inches for an electronics bay ifin' I were to want to dual deploy it as a 38mm might require.

I appears that the "biggest" Aerotech engine in the RockSim library will end up with a fully loaded weight of right about 60 oz, so just a snidge under 4 pounds.

With a 36" chute RockSim estimates a descent rate of 24 fps +/-.
As you said, the build should be about as "fragile as a brick" so that should be OK.

Now need to order the fin can and motor retainer from Giant Leap and the chute from someone.

Thanks for the input,

Greg

 

[DynaSoar]

Originally posted by 11Bravo
With a 36" chute RockSim estimates a descent rate of 24 fps +/-.
As you said, the build should be about as "fragile as a brick" so that should be OK.

Now need to order the fin can and motor retainer from Giant Leap and the chute from someone.

I've got a bunch of 36" flare chutes if you want to try one. I think they're actually a bit slower than a hemisphere because of the center shroud. If not, they're darn near disposable.

You might want to take a look at the Slimline tail cone retainer. The 54/38mm tail cone is $2 cheaper than the regular 38mm Slimline, looks better than a flat-butt, lower drag, and accepts the 29mm adapter as well.

They've also just come out with bell nozzle shaped threaded Slimlines. One of those with a PML urethane tail cone would make a sharp looking business end, but it'd cost about $50 as opposed to $20.

 

[11bravo]

I haven't been to the Giant Leap site for a while so will have to go have a look; I have last year's catalog downloaded so will have to double check prices.
Not sure about the tail cone idea, just not a look I've ever been "into" but something to consider if it does the same thing and especially if it's cheaper.
The bell cone thing I will definately have to look at.

How much would you charge me for a chute and shipping; my zip is 50468.

Was thinking today about what I would have to do to glass the tube. As the tube and nose cone are the same diameter and the fin can is made to fit that size tube, I'm guessing that I would have to peel a bit off of the outside of the tube. Not sure how much would have to be taken off, but think it sounds like a "dammit" waiting to happen.

Greg