From: barrett@add.itg.ti.com
Subject: Re: HPR Attitudes Towards Model Rocketry
Organization: Arizona State University, Tempe AZ
Date: Thu, 23 Jul 92 21:24:16 GMT

In article <1992Jul23.142755.2177@axis.dsg.ti.com> you write:
<stuff deleted>

>on his models and was quite proud of them (as well he should).  I asked
>him if he had made the "appropriate" modifications to the kits that
>would make them "better".  He did not understand and then I went on to
>explain my experiences with Aerotech models and how I had figured out
>some simple changes to the motor mount/engine-hook/baffel-system that
>would increase reliability and flexibility.  I also explained that I had
>lost 2-3 models in the process of learning this information.  He was not
>
<stuff deleted>
I plan to purchase and build my first Aerotech kit this Fall.  Could you
tell me what these modifications are, or tell me where else I can get a
copy of the modification procedures.  Thanks.
--
  Greg Elder               | "Artificial intelligence?!!!  I'd rather
  Dept of Computer Science | have real intelligence."
  Arizona State University |                      -- Ann Elder
  elder@enuxha.eas.asu.edu |
=============================================================

Since Greg thinks this may be useful, I'll post it to r.m.r.

  I first thought that the overall design of the kits were quite good,
however, I did have some problems that I figured out fixes for.

  - The internal thrust ring is a real pain.  The spacers tend to get
welded to their cheap motor mount tubes (Buzz, note I didn't say engine
;-)).  Don't use it.  Instead, use an external thrust ring at the base
of the engine.  I use 1/2" masking tape or I epoxy a 3/8" piece of MMT
to the end of the engine.  This allows for longer engines anyway (e.g.
H70, H100, G42, etc).

  - The motor rentention "hook" gets the big heave ho.  I had a few
motors come out; even a re-load :-(.  I extent the MMT 3/4" behind the
aft bulthead and then use tape (straping tape if a reloadable motor is
involved) to keep the engine from coming out at ejection.  This means
that you will have to move the Fin Lock rings forward a corresponding
distance.

  - The Aerotech MMTs are really poor.  After a few flights, they tend
to burn up!  I use Phenalic(sp?)  MMT on all my rockets now.
Unfortunately it is real hard to get the Fin Lock rings to fit a 29mm
Phenalic tube without lots of sanding.  I would paint the outside of the
MMT with some finish coat epoxy (after you glue the Fin lock rings into
position) in order to give it some added durability.

  - I would also coat the aft end of the MMT with Epoxy so that it is
reenforced to stand up to many launches/motor insertions.  Even a thin
coat on the inside would help. You will have to sand after it dries
before a motor will fit.

  - The baffle system needs to be inspected before EVERY launch.  It
tends to get clogged up and will eventually cause the ejection to vent
side ways through the side of the rocket (which then becomes a lawn
dart!).  Take a 1/4 wooden dowel and drill a hole in the end and epoxy a
1" pin or small nail to the end.  Poke holes in the wire mesh to keep it
porous.  You will have to replace the wire mesh with a "chore boy" after
6-10 launces.  Unfortunately the old mesh tends to weld itself to the
plastic piece at the top so this is a pain.  You really can't use
wadding because the shock cord is attached to the forward bulkhead
(unless you move the attachment point ala LOC).

  - Don't tie the shock cords to either the nosecone/payload section or
the parachute; use small quick links instead.  This makes for easier
tranportation and more flexible interchange of parts.

  - Use Epoxy on everything!  CA should only be used to tack a piece in
place (the spray CA accellerators work GREAT for this).

That should do it.  Aerotech models are a good first step from the Estes
arena, however, they really can't be considered a durable HPR vehicle.

P.S.  CD, I realize now that my example of the guy who was not too
enthusiastic at my suggestions may have sounded like a "who asked you
anyway?" situation.  Fair call on your part.  I really was trying to be
helpful.  Maybe too helpful?

Stu Barrett TRA# 1277 NAR# 4341
-- 
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