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  #11  
Old 01-02-2021, 12:04 AM
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georgegassaway georgegassaway is offline
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Quote:
Originally Posted by olDave
I thought the addition of clear plastic fins for improved stability was OK in PMC competition? Not so?

Oh, clear plastic fins are definitely OK. But it is an added challenge to actually attach clear fins in a manner where they are not only strong enough, but that the joints are NEAT and no paint smudges or whatever.

For example, if you "butt glue" a clear fin to the surface of a plastic model, it's not going to be a very strong joint. If you added fillets.....judges would take points off (also epoxy does NOT bond to plastic very much). The best structural way to add a clear fin is to cut a slot *exactly* the width of the clear plastic fin, and have a tab of the clear fin that goes inside of that slot and inside of the body. And by drilling some holes thru the tab that is inside, use some resin inside to structurally lock everything together. That is quite a challenge to do, to cut a slot that well, and pretty much glue the fins in place before even assembling the model.

I never have done it with a plastic model. I did do it with my 1/72 scale Space Shuttle, but it took some time and planning and jigging to work out a way that worked well enough (I was very pleased how the finished parts looked and never broke a clear fin - fins were .06" Lexan). In the photo below, the root tab of the clear fins went inside of the SRB aft skirts. The part of the clear fins above the aft skirts were not glued to anything, an open-air gap of about 1/16".



But let's say a person does add clear fins to a Snark, as in a pair of horizontal stabilizers to move the CP behind the wing. Well, now it's also got a fundamental problem of converting plastic model winged jets. The wing and the stab need to be at zero incidence to each other, otherwise it will want to pitch aerodynamically.

IIRC, a 1/48 F-15 jet I converted to two C6's, the kit's horizontal stabs were maybe 2 degrees "up" incidence compared to the wing. It would want to pitch up aerodynamically. My fix for that, was to skew the engine mounts so the thrust would cause it to roll going up, evening out any pitching. And fiddling around like that, I definitely built an unpainted boilerplate first to see if it actually flew properly.
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Last edited by georgegassaway : 01-02-2021 at 04:42 PM.
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  #12  
Old 01-02-2021, 09:27 AM
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Sounds like too much work to PMC the Snark. Id just build it stock and fly it around the house like I did with mine back around 1959 or 1960 ...
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  #13  
Old 01-02-2021, 04:21 PM
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Aww, C'mon noww.
I want to see a PMC Snark POWR-PRANGG !
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  #14  
Old 01-02-2021, 04:38 PM
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georgegassaway georgegassaway is offline
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Quote:
Originally Posted by ghrocketman
Aww, C'mon noww.
I want to see a PMC Snark POWR-PRANGG !

Well, let olDave know how many Snark kits you want to him to get for you.

Post a video of the results.

Show your actual rocketry skills, rather than just type, type, type.
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  #15  
Old 01-02-2021, 05:52 PM
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Feeling "Snarky" ?

Dave F.
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Last edited by Ez2cDave : 01-02-2021 at 06:41 PM.
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  #16  
Old 01-02-2021, 07:22 PM
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I guess this would be good for when a PMC of the Snark plastic model just feels too simple ...

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  #17  
Old 01-02-2021, 11:05 PM
SCooke123 SCooke123 is offline
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I'll watch from a distance!!
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  #18  
Old 01-03-2021, 07:22 AM
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Quote:
Originally Posted by SCooke123
I'll watch from a distance!!


It is actually safer being closer. The models have less time to gain velocity before getting near you.

At NARAM-17 ( I was 14 ), I was struck in the back ( while running away ) by a PMS Klingon Battle Cruiser built by, I think, Mark Bundick. It came off the rod, did an instant 90 degree turn, regained stability and, literally, start flying level, under power, straight at me. I turned and started running, just before it struck me in the back . . . I was not injured.

Somewhere out there, there is an 8mm film of the incident.

I love PMC !

Dave F.
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  #19  
Old 01-03-2021, 07:34 AM
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A few more SNARK images . . .

Dave F.
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  #20  
Old 01-03-2021, 05:15 PM
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Those things are supposed to have a DESTRUCTIVE flight profile.
A POWR-PRANGG should get BONUS flight points. Intact recovery should be NEGATIVE flight points.
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