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Old Aug 30, 2009, 11:12 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,425 Posts
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Duration Bombshell for KIEF

KIEF is approaching, so I need an entry for the Old Time Climb and Glide event. Here are some pics of my progress on an 18-inch span Bombshell. It's made entirely from 050 Durobatics. Control will be Vapor brick and propulsion will be 7mm Pager. Projected weight at this point is between 16g and 17g. That should result in a plane about 1g to 2g heavier than a Vapor, and a wing loading of about 1.1 oz/sq.ft. If it's not competitive in the event I'll have a real floater old timer.

Gordon
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Old Aug 30, 2009, 11:14 AM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,425 Posts
Some construction pics. No equipment is in place yet, and wings will not be attached till control rods, brick, etc are all in place.
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Old Aug 30, 2009, 12:47 PM
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indoor_fr's Avatar
Paris (France)
Joined Jan 2006
842 Posts
Nice plane!

About the AUW:

Vapor brick 3.3g
7mm motor + gearbox+prop 5g
Battery 1.7g?

AUW = 17g means that the plane weighs 17-(3.3+5+1.7) = 7g?
Is that correct?

Thank you.
Frank.
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Old Aug 30, 2009, 01:23 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,425 Posts
Frank,
I'm not using a gearbox. It's DD 7mm. Prop is lightened Tri-Turbofan. The airframe with no motor currently weighs about 7.25g. But, CF wing struts, skinning the bottom of the fuselage, and push rods will add a bit. Battery will be 60mAh FR. I've spent a bit of time trying to keep it light. For example the entire landing gear assembly with wheels, struts, and fuse former mount weighs 0.50g with BSD hubs and keepers. Wheels are 1/64 inch ply.

Gordon
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Last edited by Gordon Johnson; Aug 30, 2009 at 05:11 PM.
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Old Aug 30, 2009, 02:37 PM
RIP Sheba :(
Robster's Avatar
Brentwood, CA
Joined Nov 2002
1,123 Posts
Very, very nice! Brilliant design, looks like a winner. How did you do the coloring?

Rob
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Old Aug 30, 2009, 05:09 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,425 Posts
Coloring is Krylon Short Cuts paint, dusted on. Painting templates are printer paper spray dusted with "stencil magic" to temporarily adhere them when painting. I've been using this method for years. I used to hand cut the templates, which works fine. These templates were laser cut.

Gordon
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Old Aug 30, 2009, 06:35 PM
del
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del's Avatar
north of Chicago
Joined Feb 2003
1,827 Posts
Good lookin' model Gordon!

You're giving me "laser-envy"...

And I like your idea of going for direct drive. Last year at KIEF, part of the reason why my Boomer Bus was so crappy in glide was that I couldn't get the prop to stop wind-milling. Going DD should put an end to that problem.

See ya at KIEF, stopwatch in hand...

--del
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Old Aug 30, 2009, 07:30 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,425 Posts
Del,
I think Ralph and I arrived at the same decision to go DD. Looking forward to seeing you and your stopwatch at KIEF.

Gordon
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Old Aug 31, 2009, 01:24 PM
MAD MEN QCRC
RCBilly's Avatar
Joined Jun 2006
604 Posts
Gordon, Very nice!! Looks like I will have to build something lighter than my Korda to keep it from becoming a Battle of the Bombshells this year Best, Bill
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Old Aug 31, 2009, 02:38 PM
TheyreComingToTakeMeAway!
derk's Avatar
USA, ID, Coeur D'Alene
Joined Dec 2003
5,442 Posts
i havent had the opportunity to attend KIEF yet, but has anyone flown a folding prop in the climb and glide, or is that not allowed?
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Old Aug 31, 2009, 03:38 PM
Hey y'all... watch this!
Rex A Lott's Avatar
Bellevue, WA
Joined Jan 2004
852 Posts
Gordon,
Would you be willing to share a little more information about your wing jigs and how you managed to create, cut, and glue your wing and it's wing tips?
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Old Aug 31, 2009, 04:08 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,425 Posts
Quote:
Originally Posted by derk
i havent had the opportunity to attend KIEF yet, but has anyone flown a folding prop in the climb and glide, or is that not allowed?
The problem would be obtaining a folding prop that small. K&P folders don't fold from gliding. I've tried. So, pretty much you'd have to make your own folder at this size.

Gordon
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Old Aug 31, 2009, 04:13 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,425 Posts
Rex,
The wings are cut from 050 durobatics with about 10mm extra at the leading edge. I carefully score and compress the foam where I need to fold the LE over from the back side. If I don't get it compressed thin enough then the foam will crack when folding. Then, I paint UHU Por on the underside of the LE where it will fold over and fold back on itself, weight it with a smooth board with a brick on top of it, and let it dry.

I curve the wing panels over a 1.5 inch dowl with my hands till I get the curve I want. I elevate the wing tip, line the other up with the edge of my workbench, and sand the end of the wing where they will joint together. This requires some repeating until the two wing panels will match up perfectly where they doing with one elevated. The, I apply UHU Port to one wing edge, press to the other wing panel, and let dry on the workbench. Note that this wing is not strong enough on its own and needs bracing via CF rods like my MacZip has.

http://www.rcgroups.com/forums/showp...2&postcount=78

Hope this helps.

Gordon
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Old Aug 31, 2009, 05:33 PM
Hey y'all... watch this!
Rex A Lott's Avatar
Bellevue, WA
Joined Jan 2004
852 Posts
Ah, so the wing jig holds the airfoil curve in place while you sand the edge of the wing. Getting good use out of the laser cutter I see.

Thanks for your reply.
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Last edited by Rex A Lott; Aug 31, 2009 at 05:38 PM.
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Old Aug 31, 2009, 05:54 PM
Registered User
Fairfax Station, VA
Joined Jan 2004
276 Posts
Hi Gordon,
I am building a similar model for the Climb and Glide (1930s Viking - originally for CO2 now electric and Depron). It will be quite crude compared to yours. I have been fiddling with design and build of a Cassutt for the Pylon race too. I am on the fourth build attempt. First with elevons, second with rudder and elevator, and third with rudder only. None flew right. I cannot get the wing angle of attack and adequate control using JMP and actuators. I hope to have something to compete or at least have some fun flying in the dome. See you there.
Al
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