Building techniques

[jander14indoor]

Since we have a dedicated board for WS now, I thought it might help to organize by kicking off topics around the typical WS questions. Content of string to be driven by subject line (I hope).

[blue cobra]

Where could one find a good scale?

[jander14indoor]

Where could one find a good scale?

See see response under weight discussion thread, lets talk about building techniques here.

Jeff Anderson
Livonia, MI

[blue cobra]

Sorry, I wasn't sure which thread would be best.

[danyalukin]

Would it be a good idea to make rolled motor stick and tail cone instead of a solid fuselage out of 5# 1/32 thick balsa? Or is it better to it the solid way?

What is the advantage of lowering the horizontal stab, positioning it several centimeters under the level of the motor stick, the way it is done with pennyplanes?

Should mylar be crumpled, or applied as is?

And last question: What is the advantage of the geodetic construction of the wing?

Please try answering some of those questions, couldn't get much info off the web...
Thanks!
~Daniil

[andrewwski]

Huh? No way you're going to make a solid fuselage out of 1/32" thick balsa. Unless you mean using 5 sticks of it? In which case it's still not going to be thick or strong enough.

If you use a solid motor stick, I'd recommend at least 1/4" by 3/16" or so. You don't want it to bend at all under a wound motor, or it's going to adversely affect performance.

There were some discussions about using a rolled motor stick last year - my personal opinion is that it's not worth it in Wright Stuff, as you have plenty of weight to play with. You can easily make a minimum weight plane using a solid motor stick.

I don't think Mylar contracts like Japanese Tissue does, so theoretically you shouldn't have to crumple it. I've seen it done both ways, however. I find it hard to work with as it is, much more or less after being crumpled into a ball. I still built the majority of my planes with Japanese Tissue, however, but the minimum weight may be lower now (not sure of the current specs) so it may be tougher to use it.

Not sure what you mean by geodetic construction, are you referring to the curvature of the wing? I've never heard that term used before.

[danyalukin]

Huh? No way you're going to make a solid fuselage out of 1/32" thick balsa. Unless you mean using 5 sticks of it? In which case it's still not going to be thick or strong enough.

Not sure what you mean by geodetic construction, are you referring to the curvature of the wing? I've never heard that term used before.

No, I meant if it is worth using 1/32 for the rolled motor stick...not the solid one..

And geodetic construction is the one where ribs are positioned diagonally, as opposed to perpendicularly, to the spars... I know that this years 2nd place and winner last year at nationals had that construction. Im not sure if its worth trying....
Thanks,
daniil

[smartkid222]

I've never rolled motor sticks. could someone explain what this is and briefly describe how to do it??
i think he meant 5lb/ft^3 1/32" for the rolled sticks not the solid.

Lowering the horizontal stab was briefly talked about in last year threads but i dont remember what the benefits are.

I would crumple the mylar.

geodetic construction... yea... didn't you win NY states last year? i think you should be teaching us instead of us teaching you lol (that was a compliment in case that wasnt' obvious)
i've never heard of that before. according to your description of it, i've seen it done before, but i have no idea what the advantages are. if you find out let me know haha (:

*edit* do you make any indoor FF models? if you dont' and want to try contact carneyf1d and see if he can set you up or something.

[jander14indoor]

If you are already getting good times, you might be able to get a little more out of your plane with a rolled motor stick IF you use it right. The advantage would be in having a lighter, but still very stiff motor stick. Then you can transfer weight to the wing and tail spars to stiffen up those surfaces. Done right you can improve your plane. But this isn't something to mess with until you have the basics down. You can build a very good plane with a solid motor stick with a LOT less effort. Trick is to use very light balsa and a large cross section.

I've seen various theories about what the advantage of a low tail (gets it out of wing wash, prop wash, improves balance, etc). But frankly, even though I tend to build my planes that way, I'm not really sure it has any real advantage. High tail can be tricky, because it can actually get into wing wash in such a way as to mess it up completely. Hmmm, maybe I'll have to build this years demo plan with even wing and tail just to mess folks up.

Biggest reason to crumple mylar is to kill the static and make it easier to handle. There's been some discussion about which is better aerodynamically, but no real data. I've seen both fly very well. Frankly, to make the point that covering is over-rated, I've taken to covering my demo planes with plastic grocery bags. By selecting the lightest and flimsiest in my area I get a very suitable covering to build minimum weight planes and have a pretty logo to decorate my planes with. And my demo plane can keep up with the national winners. Its limit is more the amount of time I practice, not the plane.

Geodetic construction. Again, an advanced technique. Its advantage is to make the wing stiffer in twisting. Stiffer is for the most part better so again it can make a better wing. But it's a lot of trouble so unless you are already good with a basic wing, don't sweat this one. You'll get much more stiffness, much faster with careful wood selection. Do that first.

Jeff Anderson
Livonia, MI

[jander14indoor]

See the following for rolled motor sticks. A big advantage in very light indoor models, where allowed. Not so important in SO.
http://www.parmodels.com/Techniques_and ... 0Stick.pdf
http://www.indoorduration.com/INAVMotor ... uction.htm

The following shows a poor description of a rolled motorstick, but a very good description of what it takes to build an ultimate indoor plane, an F1D, by one of the masters.
http://www.indoorduration.com/BuildingF1D.htm

Jeff Anderson
Livonia, MI