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Old Nov 08, 2012, 01:53 PM
So many projects...
United States, IN, West Lafayette
Joined Oct 2009
133 Posts
Help!
ARF survival

Folks,
I just bought one of Hobby Lobby's Super Dimona motor-gliders; when I opened the box, I decided I would not buy another 'ARF' ever again. Has anybody put one of these in the air and had it survive? If so, what did you do to the kit to make sure it would live?
The fuselage is an empty shell, being left/right halves of fiberglass joined down the middle. {And,as a bonus, mine has a seam to fill!} There are NO formers or bulkheads, not even a firewall to mount the motor to.
I'm afraid to peel the wing covering...
Any ideas, besides a lit match?

Thanks,
soarguy
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Old Nov 08, 2012, 02:58 PM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
13,773 Posts
Perhaps try radio controlled cars

Hobby Lobby's Super Dimona Powered Glider ARF Review
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Old Nov 09, 2012, 01:01 PM
So many projects...
United States, IN, West Lafayette
Joined Oct 2009
133 Posts
Thanks, but I have seen that review. It was a large part of why I bought the 'kit' to begin with. Problem is, the model that I got was not nearly as well set up as the reviewed sample. I know it's a 'made in China' thing, but, based on the review, it is now a much lower quality piece.
So, has anyone dealt with this 'empty shell' model?
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Old Nov 09, 2012, 01:21 PM
YAY the tourists are GONE
United States, MA, Sandwich
Joined Feb 2010
192 Posts
Welcome to the world of Chinese Q&C. The big companies will just send you another piece ie (wing, fuse, tail, whatever is missing or broken or ....
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Old Nov 11, 2012, 07:20 AM
Canadian Bacon
flypaper 2's Avatar
Kingston, Canada
Joined Jun 2004
13,177 Posts
The tube configuration is actually very strong. I still have a Yellow Aircraft Cap 10B 1/4 scale I bought around 95 with a fibreglass fuse with no formers in it. Its flexability is its strength. You can squeeze to sides in and it just springs back out. Gone through three wings with the same fuselage. I also have a Kyosho Zero fuselage out in the garage which is a plastic fuselage with no formers. Gone through two wings and can't get them anymore. Another to do build project.

Gord.
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Old Nov 17, 2012, 08:32 AM
UMs & parkflyers... for now.
davidterrell80's Avatar
United States, VA, Herndon
Joined Apr 2012
3,002 Posts
We often add extra structure because, well, that's what full-size planes have. But, I have invariably been able to whittle down structures after I've built them, keeping just enough strength to handle the loads I expect the part of experience.

Think about it... your plane might weigh 500 or even 1000 g... the 800mm span Nakajima Rufe I'm just putting onto flight test will fly at 550 g. I figured the 3 mm carbon tube I put into the wing will handle 15 times that in bending load.

For fuselages, the only loads other than air loads are those you get on landing. If you have a belly lander, you might need to make some "anti-plowing" accommodation like the canted bulkhead just behind the radome of the V-22 Osprey that will keep the fuselage skidding along the ground, If you are wheel or float landing, wheel loads get transmitted to the wing spar of fuselage frame.

I have added reinforcement to my two Polaris waterplanes because I often fly them on grass and tail strikes on the ground place stresses on the airframe where the designer never expected.

I'm planning my Blackburn Skua FF to RC conversion to be a belly lander... and am considering the addition of a stiff wire skid, sort of like a skater's blade, to keep the nose up upon landing. I'm taking a Rubber FF, essentially a powered glider, and turning her into a Sport Scale RC with as little changes as possible. I scaled her up 20% (span from 25 inches to 30) to keep the wing loading down as I add motor, battery, servos, and Rx... and beef up the structure to handle maneuvering loads that the FF would never experience. The half-height spar has become a full-height I-Beam calculated to handle 6G's of 300 g without sweating... and to stay together if I cartwheel her. Which reminds me... many times, extra structure is added not for flying purposes but rather for "crashworthiness" ... keeping the humans alive in a sub-optimum meeting with the Earth. I'm designing my Skua to become a repairable pile of sticks if I muck it up; but, the weight will be higher because I do... and the stall speed will be higher making the landing speed higher, making the loads on the spars heaver in high-speed pull up maneuvers, and on and on ... Oh, and I have to accommodate what the battery will do when inertia keeps it wanting to go forward if the aircraft stops suddenly on landing... so I need to handle a compressive load between the battery tray and the front of the fuselage... keeping the battery from wanting to meet the motor. Balsa construction really complicates things. I may build a second one, after the contest, using a empty fiberglass shell.

One of the major tenets learned from my years.. ahem... decades at Martin-Marietta, Lockheed, and Bell Helicopter is "Add lightness and simplificate." Things fly better and can be built less expensively when you do.

Perhaps those who designed your aircraft felt the same.
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Old Nov 17, 2012, 08:47 AM
Canadian Bacon
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Kingston, Canada
Joined Jun 2004
13,177 Posts
Like your Ideal Planes. How true. Those tube type fuses. are really monocoque configuration. I have a 1/4 scale Ercoupe and the back end is built this way.

Gord.
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