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Apr 14, 2011, 09:47 PM
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Troy's Avatar
Quote:
Originally Posted by Dbox
Awesome Troy.
Looks just like mine.
Yuri.
Our Woodies don't count. At least mine flew
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Apr 14, 2011, 11:21 PM
One Idiot is plenty...
Dbox's Avatar
Quote:
Originally Posted by Troy
Our Woodies don't count. At least mine flew
Mine does not fly ,but bites and barks
Yuri.
Apr 15, 2011, 03:01 AM
Speed King
MarkChinery's Avatar
looks like mine too

Apr 15, 2011, 08:51 AM
Caution:Makes sharp left turns
Troy's Avatar
Yes, yes, yes... Mine too.


But you're missing the point...


Handing off plugs to Dave on Sunday.
Apr 15, 2011, 08:59 AM
Registered User
epwierman's Avatar
.
Apr 15, 2011, 09:01 AM
Caution:Makes sharp left turns
Troy's Avatar
Quote:
Originally Posted by DownUnderPilot
Amazing! Are you guys just making your own and passing around the molds, or is someone actually going to make them to sell?

Apologies if this was patently obvious
Yes, yes, no. The original designers are too busy to produce these so they offered to lend a set of positive casts to a few of us who have been bugging to get an airframe. So we shipped them over here and now we're taking molds off of the provided positive casts.
Apr 15, 2011, 09:59 AM
Registered User
Pick up the plugs sunday, make some molds and then on to some serious pod design stuff. Should recieve the sawtooth drive system next week so we can build pod to accept our ultimate drive set up and then put a lower power set up in it for some R and D or C and B (crash and burn)

Talked to my machienest buddy and he is in for some design ideas I want to try

D.E.
Apr 19, 2011, 02:09 PM
hot air rises...
jfinch's Avatar
So, all this new interest in the 'bumm has renewed my interest as well. I've got a few questions for you all. I pylon race monthly with a bunch of local guys. In a nutshell, our rules specify a main wing area of 200 sq inches (12.9 dm2, just slightly smaller than a typical F5D wing) and we all use the same motor/battery/prop. Our planes fly right around 110 mph (177 kmp). The multibumm was obviously designed around a much faster speed. Would it still perform well at the slower speed? And would it be ok if I shrunk everything down to get the 200 sq inches of wing? Biber, do you have a cad file of the planform that you'd be willing to post (it would make the shrinking easier )?
Apr 19, 2011, 02:51 PM
Registered User
jfinch,

Some posts that might be helpful,

Flight #207
Other stuff you asked, #208, #411, #415

Went to Troys house and picked up plugs, we talked over some plans. Will start my mold set this weekend and will post some stuff here when it starts to get interesting.

SHOULD BE FUN

D.E.
Apr 19, 2011, 02:52 PM
Needs brain lubrication
biber's Avatar
Thread OP
I think, It might work, If you can build it that small and still accurately.
If there might be trouble caused by the lower Re numbers you should be able to correct that with zig zag tape tripping the BL flow.

Joe made a 3D file of it and was so kind to upload it.
You can find it in Post #415 in this thread:
https://www.rcgroups.com/forums/show...&postcount=415

biber
Apr 19, 2011, 03:58 PM
hot air rises...
jfinch's Avatar
I don't have Rhino and the conversion program to Autocad is too expensive. Guess I'll have to draw it up.

What do you mean by correcting with zig zag tape?
Apr 19, 2011, 04:24 PM
Needs brain lubrication
biber's Avatar
Thread OP
If the somewhat lower Re numbers (due to lower speed and shorter chord) may cause trouble, there's still the option to fix the issue by forcing the boundary layer flow from laminar to turbulent, just ahead of where laminar separation would occur.

Zig zag tape as a means to achieve that is used on a wide range of modern full size gliders.

See Martin Hepperle's site for a more info:
http://www.mh-aerotools.de/airfoils/bubbles.htm

biber
Apr 19, 2011, 04:28 PM
Speed King
MarkChinery's Avatar
in 1996/8 a German F5D pylon model called the little devil had the zig zag tape to turbulate. if I recal it was using the RK40 section.
Apr 19, 2011, 05:02 PM
Caution:Makes sharp left turns
Troy's Avatar
Quote:
Originally Posted by jfinch
So, all this new interest in the 'bumm has renewed my interest as well. I've got a few questions for you all. I pylon race monthly with a bunch of local guys. In a nutshell, our rules specify a main wing area of 200 sq inches (12.9 dm2, just slightly smaller than a typical F5D wing) and we all use the same motor/battery/prop. Our planes fly right around 110 mph (177 kmp). The multibumm was obviously designed around a much faster speed. Would it still perform well at the slower speed? And would it be ok if I shrunk everything down to get the 200 sq inches of wing? Biber, do you have a cad file of the planform that you'd be willing to post (it would make the shrinking easier )?
Does it have to be exactly 200sq"??
Apr 19, 2011, 05:21 PM
hot air rises...
jfinch's Avatar
No. 200 in2 is a minimum. But everyone builds to 200.


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