Re: Query about high-performance design
- From: Alan Jones <alanvj@xxxxxxxxxxxxxxxx>
- Date: Thu, 03 Nov 2005 17:24:54 GMT
On Thu, 03 Nov 2005 11:04:48 GMT, "Kevin OClassen"
<kevinNOrats@xxxxxxxxxxxxxxxxxxxx> wrote:
>I'm in the very beginning of planning a high performance rocket, based on an
>H650 or I700 motor system, and am quite concerned about airframe failure.
>I'm wondering at what point people start reinforcing airframes, and the
>benefits of different materials. From what I've read, anything approaching
>mach needs to be reinforced with fiberglass, at a minimum.
Don't believe everything you read. MR has been measured to M1.42
using plain paper body tubes and 1/16" plywood fins. If you are
shooting for max speed with high thrust motors, minimum mass is most
important. You have to decide if your fiberglass airframe will weigh
less than an ordinary airframe of the same strength.
> What about
>effective gravity? I mean, at what point does reinforcement become
>"mandatory"? 35 Gee? 50 Gee?
Unless you have very poor construction, acceleration is not a problem.
It is the airloads at or approaching max q, that can cause your
airframe to fail.
>My first estimates suggest that this rocket will pull about 40G, but if I
>shrink the rocket a bit (a distinct possibility, chasing mach....) it could
>easily hit 65G+.
>
>I can see several different solutions. Obviously, buy fiberglass airframe
>tubing, and work from that. Are there different types of tubing? Any dealer
>recommendations? Any specific problems working with the product for a 3FNC
>thru-the wall rocket? I've worked with G10 finstock quite a bit, and suspect
>the material would be similar. (fins would likely be 3/32" G10, FWIW)
>
>Reinforcement of phenolic tubing is also in mind. I've looked at
>Aerosleeves, and like the look of the product. I'm particularly thiking in
>terms of carbon fibre, but wonder if that is overkill? Also, I read that
>fiberglass creates a product somewhat more flexible that CF. Does this
>matter?
There are lots of mate4rals and building techniques. It comes down to
an individuals choice of how much money to spend, what equipment is
available or required, what skills he has or wants to develop, etc.
Even if it is overkill for your rocket requirements, you can look at
this project as an opportunity to learn and develop advanced building
skills.
>Because I like to putter and have people willing to teach me the process,
>I'm leaning towards reinforcing an existing phenolic tube, so I'll ask-- any
>airframe tube preferred for this purpose? I've used mostly flexible phenolic
>from Red Arrow, so my exposure to other brands is limited.
>
>Any "DON'T do this" comments?
If you insist, DON'T violate the safety code.
>I'm still scanning the web, looking at what other folks have done, but
>figured I'd tap the expertise in here as well.
>
>TIA
>
>Kevin OClassen
.
- References:
- Query about high-performance design
- From: Kevin OClassen
- Query about high-performance design
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