Peeled & Sealed Tubes

Peeled & Sealed Tubes

Post by Mark B. Bundi » Mon, 15 Jun 1998 04:00:00



Quote:

>After quite a searches, I can't seem to find step by step instructions for
>this method.  From what I can tell, you simply peel out most of the inner
>layers of a standard tube, then seal it with thin CA on the inside.  Is that
>all?  Any special tips would be appreciated.

I think you need to reverse the peeling when you use CA, i.e. peel the
OUTSIDE of the tube, then cover with CA.  I did that for a couple of
small SD models years ago.  It works fine to put on a good finish, but
it's terribly wasteful of CA.  You're better off, IMHO, by peeling the
tubes, then using clear dope to seal them.  Three coats of 50% dope,
50% thinner should do it.

If you're looking for the lightest tubes possible, however, I'd
recommend using drafting vellum, and rolling your own.  You can build
a short section of your model with regular tubing, enough to hold the
fins and the engine mount of your own, then replace the portion of the
model holding your recovery device with vellum and cut lots of weight
out of the structure.

============================================================================

NAR President     Carol Stream, IL  60188  http://www.nar.org

 
 
 

Peeled & Sealed Tubes

Post by Mark Johnso » Tue, 16 Jun 1998 04:00:00


Quote:

> If you're looking for the lightest tubes possible, however, I'd
> recommend using drafting vellum, and rolling your own.  You can build
> a short section of your model with regular tubing, enough to hold the
> fins and the engine mount of your own, then replace the portion of the
> model holding your recovery device with vellum and cut lots of weight
> out of the structure.

I second the above, although I use 2 mil drafting mylar rather than
vellum -- got a deal on several huge rolls of it at a drafting supply
store a few years ago. After some experimentation, I found that I needed
to use about 1.5" more than the motor length in conventional BT at the
bottom. Shorter than that, and the thin tube tends to melt. Of course,
this wouldn't be a problem with real vellum, but burning might be.

Worked real well for me last week -- 145 sec. flight in A SD, using a 13
mm
model, A2-5, and only a 4 x 30 inch streamer.

 
 
 

Peeled & Sealed Tubes

Post by Wolfram v.Kipars » Thu, 18 Jun 1998 04:00:00


Quote:

> BTW, what was the baseline length at Babylon-6?

It was 348 meters.  We didn't plan on seeing any "mile-high" flights.

--
Wolfram von Kiparski
NAR 28643

Get the rec.models.rockets FAQ at: http://www.ninfinger.org/~sven/rockets/rmrfaq.toc.html

 
 
 

Peeled & Sealed Tubes

Post by Ken Miz » Fri, 26 Jun 1998 04:00:00


Quote:





>> One other thing though, the 2 NS average thrust might be too low for some
>> events, especially in windy conditions.  All things considered and ignoring
>> cost, the B7 can be a better motor, even for B Altitude.  It is lighter (I
>> think so at least, the propellent weight is 1/3 of the B2 and the case is
>> lighter) and you are guaranteed a much more consistant burn and full 5 NS TI.

>Apogee's catalog lists the B7 with an initial mass of 9.5 and a propellant
>mass of 2.84.  The B2 has an initial mass of 11.25 and a propellant mass of
>6.07.  I must say that in windy conditions I think the B7 would insure a
>straighter flight.

B7's are a rare sight in altitude.  They require 30 to 40 gram liftoff
weight to optimize altitude.  Not easy to do in a 13mm rocket.  

B7 do make great motors, although pricy, for a 18mm to 13mm "old FAI"
style rocket with a big streamer in B SD.  Consistently got 7 minutes
without too much thermal activity.

Ken Mizoi