40% Turbo Laser (scratch built)

[forgues research]

	Quote: Originally Posted by BTerry
	Roger, I believe your spar caps are 1/4" square but what is the thickness of the shear webs?

On the 40% they are 5/16 square, the shear webs will be 1/4 inch.

Roger

[Sukhoikid]

	Quote: Originally Posted by jack strickland
	Hello Cracky You, among a few other staff members seem to have a positive outlook on misunderstood ideas, so I will just inject a thought about boost tabs on ailerons while torque rolling. Its my understanding that ailerons are not used during this helicopter type thing. Now if this is not factual please inform me as to the truth. Thanks Jack

Ailerons are used to stop the torque roll and maintain in a stable hover for some planes. They can also be used to make the plane spin faster while in a hover.

I can say this this nose down hovering with the variable pitch prop thought would never happen and someone made it and made video and look where it is now.... Not used a lot in the gasser world but in the electrics yes.

[jack strickland]

	Quote: Originally Posted by BTerry
	Roger, I believe your spar caps are 1/4" square but what is the thickness of the shear webs?

Hi Brett
If I may, the "shear webs " are not used in this wing's spar. the webs are in compression between the spars, vertical grain between the spars, this is a very important detail. They can be as small as 1/8 inch to 1/4 inch. I usually install 1/4 out to about half way to the tip from where the tube ends, then finish with 1/8 to the tip. These compression webs must be fitted very carefully and glued with thin ca. This I beam spar is extremely strong and will hold up to pylon type 180 deg. turns, at wide open throttle (130 mph) with no failure, because the spars cannot cripple under high loads. Sorry Roger did not mean to butte in here, but when the tearm shear comes up I just have to jump on it. Shear webs have no place on models of this size and weight.
Cheers

[forgues research]

	Quote: Originally Posted by jack strickland
	Hi Brett If I may, the "shear webs " are not used in this wing's spar. the webs are in compression between the spars, vertical grain between the spars, this is a very important detail. They can be as small as 1/8 inch to 1/4 inch. I usually install 1/4 out to about half way to the tip from where the tube ends, then finish with 1/8 to the tip. These compression webs must be fitted very carefully and glued with thin ca. This I beam spar is extremely strong and will hold up to pylon type 180 deg. turns, at wide open throttle (130 mph) with no failure, because the spars cannot cripple under high loads. Sorry Roger did not mean to butte in here, but when the tearm shear comes up I just have to jump on it. Shear webs have no place on models of this size and weight. Cheers

Nothing to be sorry about Jack, you explained it better then I did, thank you.

Jump in anytime, please.

Roger

[jack strickland]

	Quote: Originally Posted by forgues research
	Nothing to be sorry about Jack, you explained it better then I did, thank you. Jump in anytime, please. Roger

I am truly sorry about jumping on flatout about the camera thing, just hit me wrong that we were being accused of not knowing what a video was.

[forgues research]

here is two ways to look at webbing , you can see the difference of what Jack is talking about

Roger

[forgues research]

	Quote: Originally Posted by jack strickland
	I am truly sorry about jumping on flatout about the camera thing, just hit me wrong that we were being accused of not knowing what a video was.

No worries, he deserved it.

Roger

[BTerry]

	Quote: Originally Posted by jack strickland
	Hi Brett Shear webs have no place on models of this size and weight. Cheers

Yes, I call them "shear webs", but they are actually loaded in compression. They prevent the spar caps from buckling by transferring the shear load between the cap under tension and the cap under compression. They prevent the spar as a system from shearing diagonally.

You are correct, the spar system cannot rely completely on the shear strength of glue. I have seen 12 oz sailplane wings fail under flying loads because the builder "didn't think the webs were important".

[jack strickland]

	Quote: Originally Posted by BTerry
	Yes, I call them "shear webs", but they are actually loaded in compression. They prevent the spar caps from buckling by transferring the shear load between the cap under tension and the cap under compression. They prevent the spar as a system from shearing diagonally. You are correct, the spar system cannot rely completely on the shear strength of glue. I have seen 12 oz sailplane wings fail under flying loads because the builder "didn't think the webs were important".

Hi Brett then the word crippling is not the right tearm?

[BTerry]

The term "crippling" reminds me of Tony Soprano kneecapping somebody (or Tanya
Harding/Nancy Kerrigan). Just kidding! I know exactly what you mean, and you are correct to use it. The term "crippling" refers to the buckling of the flanges of a beam under a bending load, while buckling of the entire section is called Column Buckling (Euler buckling).

The spar system itself is an I-beam, with the upper and lower spar caps acting as flanges and the web is of course the web. You are also correct in stating the spar MUST have an I-beam cross section, as opposed to a U-channel cross section. We don't want the flanges to rotate under a load! Balsa wood in compression and tension is significantly stronger than in shear, and the channel design will just cause a local shearing of the glued section to the spars. Of course that would lead to a catastrophic failure of the wing.

Thank you very much for the dimension of the spar too. I can see it is a very strong wing design. The one thing I was contemplating changing would be to remove the foam rib portion in way of the spar web to maintain continuity of structure in the spar itself, but actually leaving it the way you designed it has advantages as well in transferring the load into the ribs themselves.

Brett

[BTerry]

	Quote: Originally Posted by forgues research
	here is two ways to look at webbing , you can see the difference of what Jack is talking about Roger

The U-channel section shown here, when placed in a bending load, would allow the flanges to twist away from the web. This would shear the balsa web away from the spar caps (flanges), which would eliminate the method of force transfer. Immediately the upper flange would buckle and cripple, followed by the lower flange, without the presence of the web to transfer the forces.

[forgues research]

	Quote: Originally Posted by BTerry
	The one thing I was contemplating changing would be to remove the foam rib portion in way of the spar web to maintain continuity of structure in the spar itself, but actually leaving it the way you designed it has advantages as well in transferring the load into the ribs themselves. Brett

Brett, I understand you're point, and this has been discussed before in the other thread I had about the smaller laser , it was deemed to be absolutely unecessary


It would not hurt you doing this , but simply more work.

Roger

[SmoothFlying]

	Quote: Originally Posted by jack strickland
	Whats a video camera?? We are all to dumb to know anything anyway, because we don't live in Ga. Give it a rest why don't you. Good grief

A video camera is usually black or silver in color. It takes live shots of things you would like to look at on a different day to remember what you did on that particular day. Now a days they come in several different ways. A lot of digital cameras have the option of taking regular still pictures and video also. Pretty much all of them will work at your local flying field. I do understand it might be a little hot now a days. Fear not the camera will not be affected by heat, maybe rain though. Video cameras are perfect for those individuals who are having a hard time proving to others how boost tabs work in the air on an RC model, particularly on all surfaces not just one. I probably speak for a lot of FG members. We want to see how they work in flight because none of us have seen them work except for you and your counterpart.

[forgues research]

Will the moderators please remove this guy as he is distracting from the intended thread, thank you

Roger

[Cracky]

Roger, Click on his screenname and his profile will show up. Click on User List and then click on Add To Ignore List. You won't be bothered by him anymore.