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Basic design concepts

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Old 06-17-2013, 12:01 PM
  #1
VUgearhead
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Default Basic design concepts

I'm currently attempting a project of enlarging a 1/2A planto tame the design, from a pylon racer to a suitable step up from a trainer (i.e. second plane). Anyway in my discussions with the more experienced members on that board, it became more apparent that just enlarging the design by scaling up isn't the best approach. While wing loading, center of gravity and such are familiar to me, other concepts of airplane design, such as control surface area and tail moment arms (length of fuselage) are new.

I came here to see if there were any guidelines in the form of stickied threads that might describe some of these design concepts. But there really aren't any basic design guidelines indicated.

Would you more experienced plane designers consider developing a guideline to place at the top of the forum to help us who are just starting out? The electric forum has an excellent example.

Ijust thought it might be a helpful addition to the forum.

Thanks.
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Old 06-17-2013, 02:34 PM
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Default RE: Basic design concepts

Use all this. Dan.
http://www.geistware.com/rcmodeling/cg_calc.htm#mac
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Old 06-18-2013, 08:32 AM
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Default RE: Basic design concepts

Dan,

Do you have part 2? The pages you posted are labeled part1.
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Old 06-18-2013, 10:33 AM
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Default RE: Basic design concepts

Good question. I can't find part two. As I recall there may have not been enough information in part two that was worth saving. You can use this part as a good starting point. I did and as the years went by I deviated from it quite a bit. I'll attach some images for you. You'll have to suffer with having me in them. Dan.
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Old 06-18-2013, 10:56 AM
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Default RE: Basic design concepts

I have an old small hardback book I still dig out and use occasional printed back with R/C meant reed radios. The stuff in it still works!
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Old 06-18-2013, 12:11 PM
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Default RE: Basic design concepts

When you double the size the areas used for the controls should be fine just as scaled. Most of the changes needed for this sort of project are internal in terms of totally re-designing the structural details. There's really no rules you can use since scaling up the structural materials and details just do not scale worth a darn.

The easy way is to look around for plans of models at the same new size and copy the wood sizes, spar arrangement, rib spacing, fuselage firewall and bulkhead spacing and tail construction details.
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Old 06-18-2013, 12:46 PM
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Default RE: Basic design concepts

If you google rcm plans and click on requested articles (lower left side of page, small print) and then on columns, you can find what you're looking for.
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Old 06-19-2013, 04:40 PM
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Default RE: Basic design concepts

Thanks for the advice. Those old RCM articles look terrific for the type of info I was hoping to find.

For the project I have started, I was enlarging the plan from a 24" wingspan to a 36" wingspan (50% enlargement). I imported the tileprint plan into CAD, enlarged it and started converting to CAD. I realize the materials would need adjusting dimensionally, but the fuselage just looks HUGE dimensionally for a 1/2A plane (6" tall and over 4" wide at the wing saddles)! It would probably turn out grossly overweight if I did it this way. Also, I wasn't sure if the control surfaces scaled proportionally to wing area/span.

I want something that looks like the original, is somewhat tamer and will at least fly!
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Old 06-19-2013, 06:03 PM
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Default RE: Basic design concepts

Vu, here's another resource. Dan.
http://www.amazon.com/Basics-Model-A...ircraft+design
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Old 06-20-2013, 12:53 PM
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Default RE: Basic design concepts

All day Dan,

What month and year of RCM was the article from? I have almost all the RCM from the 60s-2005 scanned and I can look for part two and post it here for FlyinginOK.
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Old 06-20-2013, 01:05 PM
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Sorry ser00 but I don't remember. Dan.
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Old 06-21-2013, 06:35 AM
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Default RE: Basic design concepts


Quote:
ORIGINAL: ser00

All day Dan,

What month and year of RCM was the article from? I have almost all the RCM from the 60s-2005 scanned and I can look for part two and post it here for FlyinginOK.

I would estimate between 1976 and 1983, probably closer to 1976.
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Old 07-18-2013, 02:20 AM
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Default RE: Basic design concepts

According to part one it indicates its after 1985.
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ORIGINAL: FlyerInOKC


Quote:
ORIGINAL: ser00

All day Dan,

What month and year of RCM was the article from? I have almost all the RCM from the 60s-2005 scanned and I can look for part two and post it here for FlyinginOK.

I would estimate between 1976 and 1983, probably closer to 1976.
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Old 07-18-2013, 10:16 AM
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Quote:
ORIGINAL: VUgearhead

...For the project I have started, I was enlarging the plan from a 24'' wingspan to a 36'' wingspan (50% enlargement). I imported the tileprint plan into CAD, enlarged it and started converting to CAD. I realize the materials would need adjusting dimensionally, but the fuselage just looks HUGE dimensionally for a 1/2A plane (6'' tall and over 4'' wide at the wing saddles)! It would probably turn out grossly overweight if I did it this way. Also, I wasn't sure if the control surfaces scaled proportionally to wing area/span...

Ah, now the picture is a little more clear.

You're running into the whole issue of gear size vs model size. On larger models it's almost never an issue. But when you scale up a 24 inch span model you run into the simple fact that the radio gear needed X amount of volume to contain it. And now you're blowing the design up to Y. But you end up with this great big cavernous opening for the gear.

That's where the whole thing falls apart to some extent...... Now you're faced with either finding an alternative structural method to hold the weight in check or you need to consider re-designing the model to make the fuselage more skinny.

There IS another option. The 1/2A page has plans or links to plans for a couple of models in this size range that are proven flyers. Two in particular are the LST (Lynn Sipes Trainer) and the shoulder wing stik style design named "Das Not Ugly". There's also some great old classic plans that can be downloaded from Dave Fritzke's website at http://my.pclink.com/~dfritzke/ . Any number of those would suit your needs. The Jr Falcon and Jr Skylark in particular are easily adapted to ailerons, if that is your desire, by halving the dihedral and adding a sub trailing edge to allow the original size of trailing edge to be used as strip ailerons.
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Old 07-19-2013, 04:28 AM
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Default RE: Basic design concepts

Holding the weight in check while scaling up our models is such an easy process because most all R/C models are so grossly over built from an engineered materials type and usage standpoint that they are completely out of scope with what the airframes should be in terms of weight versus actual strength requirements needed for flight, takeoff and landing loads, especially the old school stuff. If you are building from scratch then place everything you pick up on a diet prior to installation or assembly within the airframe, it is really that simple, and there is plenty of documented information on the internet to qualify this claim.

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