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Old Jun 05, 2006, 08:50 AM
Bernoulli+Newton=Lift
magic612's Avatar
Somewhere south of Chicago, IL
Joined Jan 2006
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Does this plane look overbuilt? Some dumb plane-from-plans ?'s

Hi all -

I'm a relative newbie to R/C aircraft, but have made a few stick-built rubber powered planes in the past. I've taught myself to fly from a 54" foam glider I converted myself, and now have a Slow Stick that I'm flying inverted / pulling inside and outside loops / etc., and haven't even crashed the Slow Stick once yet (in four weeks of lots of flying).

So... I thought I'd take another step into this rather addictive hobby. In addition to actually flying, part of what I enjoy is actually building kits. So I found some biplane plans I liked online, and started building it this last weekend (so far I've only completed the fuselage). I do have some questions though, having never built a plane strictly from plans before.

- Does this plane look over-built? I reducted the size of the stringers on the fuselage to 3/16" instead of 1/4", since the 1/4" seemed to be more than was necessary for the size of plane this is. Was 1/4" the right size, or will the 3/16" be strong enough?

- Also, the wing seems to have a lot of extra wood in it - is all of that really necessary for sufficient strength? There's 2 main spars, 2 front spars, a trailing edge spar PLUS trailing edge sheeting... see file for wing detail.

- Although this was likely designed for a gas engine, I'd like to make it as an electric - any thoughts on what size motor / prop should I be use?

- Is 1/8" thick balsa necessary on BOTH sides of the stabilizer surfaces? That seems like too much wood weight, when the surfaces could be made lighter going full stick built, or even covered with 1/16" balsa - or is 1/16" too thin considering the strength requirements of the plane?

- And what do I use for landing gear, and where should it attach, and how?

- Will micro / mini servos have enough strength to fly this plane, or should I plan on using standard servos?

For reference, the wingspan is about 37" (500 sq inches of wing area, both wings), and I've saved it in a PDF format for easier viewing.

Thanks for your help! (Sorry for all the stupid questions, and I hope I've put this in the right forum.)
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Old Jun 05, 2006, 09:43 AM
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It looks to me the reference as to twin 1/8" sheeting is being confused with the center core being of 1/8". The plans are not too good. There is great question as to how to complete the trailing edge of the Hoz-stab and elevators. Seems the drafter just drew a line where no material exists.

The choice of 1/4" spars could have been based upon the original designer having that at hand, compared to the 3/16" square. Then too, there could have been some consideration given as to rough handling.

The 1/16" sides to the fuselage may or may not be a bit light. 3/32" may be more appropriate if rough useage was thought of.

Some "rearrangement" of material sizes could be in order, and still result in same weight of an A/C.

Wm.
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Old Jun 05, 2006, 05:00 PM
Bernoulli+Newton=Lift
magic612's Avatar
Somewhere south of Chicago, IL
Joined Jan 2006
1,952 Posts
Yes, the edges of the stab surfaces are a bit sketchy on the plans, but I'm pretty confident I can work around that issue.

I'm assuming the 3/16 fuse runners will be okay, then.

1/16" skin on the fuselage is possibly a bit light? Is that because the main fuse runner on the bottom is missing due to the lower wing being there? In other words, additional fuse strength comes from that 1/16 or 3/32 skin on the forward section of the fuse?

Thanks for your help - definitely appreciated! Anyone with any other thoughts on the other questions welcomed, too.
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Old Jun 05, 2006, 11:10 PM
Kansas is windy.
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Wichita, KS
Joined Jun 2003
1,512 Posts
That looks like a pretty good plan to start with but you could do some lightening. I would definitely build up the tailfeathers instead of using sheet wood! Also the fuse formers don't need to be ply, and can be hollowed out a little. As you build you can make lots of modifications to suit your needs. It's not designed light like a FF airplane but it seems like a good basic design to me.
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Old Jun 06, 2006, 08:32 AM
Bernoulli+Newton=Lift
magic612's Avatar
Somewhere south of Chicago, IL
Joined Jan 2006
1,952 Posts
I am now planning on building up the stabilizer instead of using sheet. I already made the fuselage from the ply, but I also hollowed them out significantly to save weight.

More than anything, I just wanted to be sure I was on the right path as far as a lot of the modifications. I started building the lower wing last night, and I haven't put the leading edge, wingtips or ailerons onto it yet, but I'm amazed at how light it feels. So I suppose my concerns about the wings being overbuilt were perhaps a bit unfounded.

I still haven't figured out the best way to attach the lower wing - I'd like to make it semi-removable. And the plans offer no landing gear information, which I would like to add, so I'll have to figure that out too.

Thanks for the thoughts - most appreciated!
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Old Jun 10, 2006, 08:11 AM
Model Designer - AMA 667982
starcad's Avatar
Tucson, AZ, USA
Joined Sep 2000
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Very nice drawing. Almost looks like a concept model and very well detailed I think. Enough detail that could build it with no problems. Did you design this baby?
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Old Jun 13, 2006, 10:56 AM
Bernoulli+Newton=Lift
magic612's Avatar
Somewhere south of Chicago, IL
Joined Jan 2006
1,952 Posts
Nope - not my design. Found it at this site: http://www.aviationshoppe.com/airplane-plans/index.php

It's got enough detail to build it, certainly. And I have sufficient model building experience to figure out the parts that are not clear (building tail feathers lighter, attaching tail assembly, adding landing gear, etc.), but I liked the overall look of this plan, that being why I decided to build it. It just seemed a bit overbuilt - I mean, 1/4" thick balsa fuselage stringers? That seemed excessive to me, and some of the wing components seemed to be adding extra weight with little to no added structural strength.

But then again, I don't know - that being why I asked.

Update on this project, too: Both wings built, one covered. Tail assembly complete, fuselage built but not covered yet. Swapped 1/4" balsa fuselage stringers for 3/16" basswood, and swapped back three fuse formers for 1/16" ply instead of the 1/8" (yeah, now I'M the one overbuilding it, right? Haha!). I'll take pics and post when done - hopefully it'll be flight ready in a couple weeks.
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Old Jun 17, 2006, 09:53 PM
Electric Hippy
Brisbane
Joined Nov 2005
2,360 Posts
Looks somewhat like a pitts samson.
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