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light and sturdy

Old 12-25-2005, 05:36 PM
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MishaParem
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Default light and sturdy

When building a plane using anything from balsa to plywood, which is best to use in what manner?

I know the T-34 uses balsa framing with balsa sheeting and ply cross-sections of the fuselage, but the Mach 2 uses ply frame and cross-sections with no sheeting and its lighter.

The Lanier (<< I think) Viper has foam core wings with balsa sheeting making it extremely sturdy, but are built-up wings lighter?

The Mach2 has a very square shape perhaps due to the use of plywood, on the other hand the Pheonix Su-31 uses a lot of balsa and has a smooth shape.

Basically what materials used in what fashion makes a plane sturdy, smooth, or light.

I'm not into using Carbon fiber and fiberglass for base construction.
Old 02-23-2007, 04:50 PM
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speed lover
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Default RE: light and sturdy

I am currently designing a caudron c460 and plan on using a very similar construction but it is my first design and I have been asking myself the same sort of questions. But I think I am going to use balsa as much as posible instead of ply and lite ply. The reason is for the smooth finnish and also the lite weight issue. I have heard plywood can be very heavy and also the strength is not as great as most people think for the weight also you only need strength in the parts that need be strong for when it is in the air. I plan on using the frame work out of balsa from the tail to the firewall with sheeting on the out side to behind the wing with spruce spars running full length on each side under the sheeting but still thinking of other ideas.
Old 02-24-2007, 08:16 AM
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Default RE: light and sturdy

What it really comes down to is how much strength do you need to do a specific job. Balsa wood is a whole lot easier to work with, so I tend to use whenever possible and save the plywood for situations where you just can't use balsa such as firewalls and landing gear mounts etc. Foam core wings have benefits and issues as well, but the main thing to consider is you need the cores which most people do no have the equipment at home to generate therefore a built up wing is the way to go. If you look how enough planes are built, you will get a feel for what works and what does not. ARF type planes are very dependent on assembly line building techniques which may not be the best thing to look at when doing a home project. I would look at some plans and kits instead.
Old 02-24-2007, 01:12 PM
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speed lover
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Default RE: light and sturdy

Have been looking at this plane and would love to use a similar construction but could you tell me what you think the wing sits on do you think it is ply or hard balsa I was going to use the frame work to the fire wall then put the spars on then sheet over it to get the curved sides do you think it would be strong enough where the wing is
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Old 02-24-2007, 02:00 PM
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Default RE: light and sturdy

Not sure what your asking for but if your wondering what a typical wing saddle is made up of. A .60 size plane is usually a sandwich of balsa and light ply. Sounds to me like you need to build some kits and do some plans built planes before jumping into scratch building. You need to walk before you can run as they say.
Old 02-24-2007, 02:14 PM
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Default RE: light and sturdy

Most planes for RC use a ply doubler at the front from firewall to a little past the wing. 1/32 is normal on a 40 size model. This is then covered by the balsa fuselage sides or longerons and stringers. The wing seating often has a trebler of perhaps 3/16 balsa.
You should copy the methods used in successful models of the same type and size. Study a few of the free pull out plans in most British RC magazines. They should show the optimum construction - just strong enough for any flying stresses but light enough to fly well.
Also read books such as Gordon Whitehead’s Radio Control Scale Aircraft Models for Everyday Flying published by RM books Guilford Surrey 1980. Unfortunately this is out of print and selling at ridiculous prices secondhand, but your local library should be able to obtain a copy if you reserve it. This is the best book on the subject for sport scale models.
There is also Designing Model Aircraft by Peter Miller published by Traplet price ÂŁ7.95 which is a current book www.traplet.com

Most clubs have someone who can cut foam wings, -ask!
Old 02-24-2007, 03:52 PM
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Default RE: light and sturdy

Thanks for the advise and help I think I do need some experience and more knowledge about design but I don,t realy want any other plane and have already comitted to working out numbers and figures to make it an advanced sport trainer I can not find any kits or plans for this plane anywhere not at 91 2 stroke engine anyway. I was going to make it 71" or so but I think I will research a bit more. I have a pretty good idea of how to build a good strong and lite wing and fuse but where the wing bolts on I think I could do with some more info on different methods basicly would it be sound to bolt it onto hard balsa sides with the blind nuts secured into ply.
Old 02-24-2007, 04:27 PM
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Jim Thomerson
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Default RE: light and sturdy

One technique which is becoming very common in control line stunt airplanes is to mould shapes out of balsa sheet, either single layer or laminated. I've made one leading edge this way and found it easy to do and very satisfactory.
Old 02-24-2007, 04:36 PM
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Default RE: light and sturdy

what exactly do you mean do you cut strips then put them in a mould so it takes the curve of the aerofoil then build it up strip after strip
Old 02-24-2007, 06:49 PM
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Jim Thomerson
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Default RE: light and sturdy

This link will give you some idea and give you some names of folks who do this kind of construction. Bob Hunt has a video on it, as does Al Rabe.

http://www.clstunt.com/htdocs/dc/dcb...ng_type=search

In my case, I was building a Dmeco Sportwing for CL Old time Stunt. The plans call for a solid shaped symmetrical leading edge with 1 inch wide 1/16 sheeting behind top and bottom. I carved a form out if a balsa stick. I wrapped the stick with saran wrap. I cut pieces of A-grain 1/32 sheet to size. sprayed some water and a spritz simple green on my glass building table and washed the 1/32 around in it, turned the sheets over and did some more. The sheets got limp in a minute or so. Wrapped them (two sheets, i. e. two layers) around the form and held them down with ace bandage. After they dried, I took them off and applid slightly thinnned down tite bond between them and rewrapped them. After competely dried, I cut the ends to exact size and glued them to the wing framework with CA. Then I made a vertical 1/16 sheet web to make a D-tube. Worked nice and looked like the original construction when covered. I was real pleased and surprised at how easy it was to do. Next time I will do the gluing as part of the first molding.
Old 02-25-2007, 10:41 AM
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kdc
 
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Default RE: light and sturdy


The Caudron C460 looks an interesting project at first glance, however the highly tapered wing is certain to make it a very tricky flier. It is sure to tipstall especially if not built really light. So for a first own design consider making it much wider at the tips and with some washout. It can still look fairly scale but might stand a chance of flying properly.
You would also need to be a very experienced flier of this type of model ( WW2 fighters etc ) to even consider building and developing this type of design.

This site contains details of a 1/3 scale Caudron model http://modelairclub.ch.free.fr/?p=4-1-1-2&lang=fr#1

The following sketches show the usual extent of fus side, ply doubler and trebler. Also a suggestion for a revised wing shape for better flying but still looking fairly scale.

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Old 02-25-2007, 11:35 AM
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Default RE: light and sturdy

Hi!
The original wing planform will be no problem as long as you build in slight wash-out in the wing and keep the airplane light.
A scale model should have scale flying surfaces.
Old 02-25-2007, 01:21 PM
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Default RE: light and sturdy

Yes a scale model should be scale, however he stated he wanted it to be an advanced sport trainer and he is a novice designer! So it is better to have something that might fly well rather than something that would be as tricky to fly as a Spitfire. Anyway most so called scale ARTF models are very semi scale and seem acceptable for normal flying.
Old 02-25-2007, 03:53 PM
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speed lover
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Default RE: light and sturdy

thanks again for the websites and the pictures these have helped me a lot. you are all right it is a hell of a taper and at scale wing area there is not much of it even at 71" wingspan so it will have to be light. I managed to work the numbers to a 25oz/ft wingloading which is about right for an advanced trainer or so Im led to believe. but after all your advise I think I am better to think a bit simpler and build this plane for a 46 size engine and make it semi scale as kdc suggested. But keep the 71" for another time so its back to the drawing board and calculator I have a spitfull plan and would like to use a similar design just wondering if anyone could tell me what amount of washout is usually used and is it realy needed if the wing loading is 25 or under.

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