EscapeFlyer

My Feedback: (1)

I'm building an ultra sport 60 from plans. I plan to compete, eventually, in sportsman class pattern with her. On selecting wood for my wing, what weight range/balsa grade should I aim for with ribs and sheeting to keep her light. I am not planning to build her crash-proof. I have made patterns and jigs to set this bird up, fully expecting to need them in the future. So I want it light, but sturdy enough to compete. I've heard this plane comes out stock around 9lbs. I'd like to keep her between 6-7 lbs. I think this is still a realistic goal. I think I will need to purchase a pump to keep the fuel tank directly on the CG, so there is some "extra" weight that I hate to add, but a necessary evil.

I'll ask about fuse wood at a later point. One thing at a time.[8D]

Bipes

Jimmbbo

Try these:

http://www.sigmfg.com/cgi-bin/dpsmar...FV4.html?E+Sig

http://www.sigmfg.com/cgi-bin/dpsmar...FV4.html?E+Sig

Cheers!

Jim

XTOL

My US60 built from the RCM plans came out just over 8 pounds.
The original construction article specifies 7-7 1/2 pounds.

I made no attempt to build light. In fact I probably over built
in some areas. OK...maybe in a lot of areas. So getting down
to 7- 7 1/2 should be no problem.

Lots of weight in that tail with all that 3/8 inch wood. I think
selecting lighter wood in the back and going with a lightweight
motor will go a long way.

Even as heavy as mine is it flies like a dream and I have no
problem flying the Sportsman sequence with it. Not that I
would ever compete but I think this plane would do very well.

Mike Hammer

XTOL

I see you were asking about the wing and not the fuse...yet.
There isnt really a lot to save weight wise in the wing.

You can hollow out the wing tips. They are solid balsa.
Sheeting with 1/16 balsa instead of 3/32 may save a bit
but would make the wing more fragile. If you do that I
would recommend keeping it 3/32 in the center where
you will be handling it most.

I think that most of the weight you are going to be
able to save is going to be in the fuselage.

Best of luck...

Mike Hammer

EscapeFlyer

My Feedback: (1)

Nice talking to you again XTOL.

I was surprised to find how strange the weight of balsa can be. I used a digital scale and weighed two identical sized sheets. One was 1/16 sheeting, the other 3/32. The 1/16 sheet weighed 29 grams, and the 3/32 inch sheeting weighed 17 grams! So I'll build according to the plans, just choose my wood selection very carefully with a digital scale.

I don't know how much 12 grams per sheet means in the grand scheme of things, but I don't think it hurts to try to keep things lean when I can.

I looked at Minnflyer's thread on his "Lite" build. Vey interresting.

I think balsa grade could be important when selecting wood for ribs. I've printed out several writings on the subject, and I've learned a lot about balsa. However, there seems to be a large difference of opinion as to which grades of balsa, or cuts of balsa, are best used for any particular part of the airplane. It seems to take experience and personal preferance to think these things through.


With all that said, I'm SURE I am making more out of this than I need to, I just want to be a great builder-as well as a flyer that can offer help to others also.

Jimmbbo

Sorry for the blind links... from the home page, navigate to the News and Information tab, then to the Interesting Facts About Balsa Wood, then to the "How Light Is Kiln Dried Balsa Wood?", "Selecting Balsa For Model Building" and the "Balsa Grain Chart"

Cheers!

Jim

da Rock

Don't use thinner wood in the wings to save weight. False economy and it'll bite you.

Do use contest grade for the sheeting. Use contest C-grain for the ribs.

And somebody suggested weighing the wood. Excellent, excellent idea. For two reasons.... well, maybe three depending on how you count.

Weighing lets you choose lighter wood. It also keeps you from using too light a wood. Very often the lightest wood of a type/size is actually the same false economy as using too thin wood. The other reason to weigh is a bit more subtle. You want the wing to balance spanwise, right. Use the heavier sheet from the root out. It's also the stronger sheet. Use your lighter sheet toward the tips. And when you weigh your wood, you insure that you don't wind up with all the heavy wood in one side of the wing.

da Rock

BTW, weighing wood is also a bit like checking props for balance.

EscapeFlyer

My Feedback: (1)

Thankyou everybody. This will help me. I'm looking forward to seeing what my results will be.