Scott and Warren and the Maytag man (ask Warren)

This topic has 32 replies, 9 voices, and was last updated 14 years, 4 months ago by Warren B. Musselman.

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May 6, 2011 at 3:36 am #41255
SCOTT EVANS
Went to Warrens place to do this last week. “We got in a big fight with the vac. bag.” 😡 But it still came out ok. I sanded it and gave it one coat of clear. A little rough yet, but I think the final product will be beeeeeutiful! 8)
May 6, 2011 at 1:08 pm #54291
Warren B. Musselman
Moderator
Turned out VERY nice Scott. How many coats of epoxy?
May 6, 2011 at 1:41 pm #54292
SCOTT EVANS
JUST 1
May 7, 2011 at 4:05 am #54293
greywolves
Hot, Hot, Hot! Looks real nice, great job! That should be a beast!
May 8, 2011 at 4:44 am #54294
Warren B. Musselman
Moderator
Make no mistake, this bird is the shit! Best fillets I’ve ever seen anyone bring me for a layup. (by the way, aerodynamically, 10% of semi-span is a minimum. 20% is closer to ideal in terms of resolving interference drag at the fillet.)

Two full-sized layers of 5.6oz carbon across fins made from Art’s autoclaved carbon plate on PF carbon filament tubing. This rocket will survive anything he can stuff into it. oh yeah, that finish layer looks killer.
May 8, 2011 at 4:58 am #54295
Chris LaPanse
Warren: I’d be curious to see a reference for that (the interference drag). Everything I know about interference drag (which is admittedly not much, but it at least includes the basic mechanism) and boundary layers (about which I know far more) would indicate that optimum fillet size would be independent of fin span, and would be more related to fin chord, length of body ahead of the fin, rocket finish, and airspeed. I don’t know any exact relations, but I can’t think of any way in which it would be related to span (especially for supersonic).
May 8, 2011 at 1:28 pm #54296
Warren B. Musselman
Moderator
Chris, I’m far from knowledgeable about this. I had the question myself a number of years ago and so I asked the venerable Henry Spencer (do a Wiki search on him if you’ve never heard of him…) I can probably dig up his reply which has all sorts of the math you’re looking for. Boiled down, what I posted is the essence of what he told me.

I have very little knowledge or interest in aerodynamics or mechanical engineering issues. I build things and quite frankly, I do most of it by rules-of-thumb, seat-of-the-pants or just a general overkill approach. Now electronics and software is a completely different matter.
May 9, 2011 at 3:22 am #54298
Chris LaPanse
That would be interesting if you could find it. I certainly am not that well-versed on interference drag, and I’d love to know more about it.
May 9, 2011 at 3:54 pm #54299
SCOTT EVANS
Warren: I’d be curious to see a reference for that (the interference drag). Everything I know about interference drag (which is admittedly not much, but it at least includes the basic mechanism) and boundary layers (about which I know far more) would indicate that optimum fillet size would be independent of fin span, and would be more related to fin chord, length of body ahead of the fin, rocket finish, and airspeed. I don’t know any exact relations, but I can’t think of any way in which it would be related to span (especially for supersonic).

What?! 😯 Look…Just put a bigger motor in it, and even that drag crap cant keep up!!! 8)
May 10, 2011 at 1:02 am #54297
Steve Jensen
Participant
Some day…

But keep sending the rocket porn!

Just gorgeous, drool…
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