Designs

jander14indoor
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Re: Designs

Postby jander14indoor » January 28th, 2010, 5:54 am

Careful about changing multiple things at once. Unless you understand something called Design of Experiments, you can't correctly sort out which factor gave desired results or maybe undesirable.

Moving the wing fore and aft is NOT equivalent to changing angle of attack. It changes angle of attack, but also other things, possibly giving uninterpretable results. I'd stick with changing just angle of attack if you adjust that.

Bummer on the gym time, does your coach understand the importance of testing in this event? Its what the event is really about, not designing and building (though those ARE important).

Someone else will have to answer about tail volume, though I'd be leary about shortening tail arm. Just from observation, the short planes just don't fly as well. They tend to be VERY sensitive to changes in stab, and unforgiving to ceiling bumps (lose a LOT of height).

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Re: Designs

Postby carneyf1d » January 28th, 2010, 12:50 pm

Instead of decreasing tail lever arm by shortening the tail boom, what about having a slight droop boom?

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Re: Designs

Postby Frosti97 » January 28th, 2010, 1:42 pm

;) It is amazing we did it this year and won first place in the magsig

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Tail Volume

Postby calgoddard » January 28th, 2010, 4:45 pm

I don't like drooping tail boom designs. The reason is that the plane is more difficult to transport in a box, unless the tail boom is removable, which is really above the skill set of most middle school builders. I have not seen any evidence that a drooped tail boom will significantly improve performance of a WS plane. I also don't like the plane landing by first dragging its delicate horizontal stabilizer on the ground. A drooping tail boom could be a nightmare if the plane lands on a light fixture and you have to get it off with a balloon or pole. Our team has never been beaten by a plane with a drop down tail boom, so why bother?

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Re: Designs

Postby smartkid222 » January 29th, 2010, 10:20 am

leetx wrote:- for the Leading Edge kit, what is(are) the recommended rubber size(s) for this prop/plane combination?


It comes with three bags of rubber in the kit. I think they are something like .096-.106
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Re: Designs

Postby eta150 » February 3rd, 2010, 1:54 pm

I didn't know where to put this, but is there an especially safe way to transport planes to and from competition?
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Re: Designs

Postby jander14indoor » February 3rd, 2010, 3:00 pm

In a STURDY box, gently tied down so nothing is loose, and with NOTHING heavy in the box unless it is SOLIDLY tied down.

Its ugly what a winder loose in your box can do to a wing.

I use a long lawyers file box with foam rubber glued inside and cutouts to hold the plane parts.

Now,its convenient to have everything together so some like to have their flight log, repair kit (you do take a repair kit with you flying, don't you?), winder, extra rubber, etc so nothing is left back at your school or team room on the day of the tournament. I think its better to develop good personal discipline and keep a seperate flight box for the heavy stuff, but... So if you have to have one box, make sure NOTHING is loose.

I've heard and seen many horror stories about plane boxes being sat on and destroyed, so consider this when I say sturdy. Some teams use 1/4 inch plywood boxes with reinforced corners. On the other hand, I've been using the same cardboard box for my SO demo planes for 10 years now around hundreds (if not thousands) of kids with no damage (to the box, no comment on the parent who got too close to my plane!). Your plane, your choice.

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Re: Designs

Postby eta150 » February 3rd, 2010, 6:58 pm

I was using an extremely sturdy plywood box, but my new plane "outgrew" it. I'm using a large plastic roller box with the plane loosely attached by velcro straps. My wing in in a different box with slightly padded sides, and my supplies are all in a totally different toolbox. Does this sound safe enough?
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Re: Designs

Postby gh » February 3rd, 2010, 7:22 pm

I used a box shipped to me by Online Metals. One of the things I ordered was a 1ft by 2ft sheet of aluminum. The box that it came in fit it perfectly and was about 1ft tall. I never got around to using the sheet, so I left it at the bottom of the box and used the now aluminum-floored box for carrying my WS planes.
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Re: Designs

Postby SOCoach » February 12th, 2010, 3:29 pm

Can anyone speak to the lowered tail boom design? I've seen a few of them, but never noticed much of a difference in flight times between those and the horizontal tail booms. I suppose it goes back to how well built the plane is making more of a difference than the design??

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Drooping Tail Boom

Postby calgoddard » February 12th, 2010, 4:38 pm

See my January 28, 2010 post in this thread above.

I recall that Jeff Anderson's demo plane at Nationals last year had a drooping tail boom. See the photo of his plane in the Image Gallery.

Maybe Jeff can tell us if he thought it improved the performance under last year's WS rules.

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Re: Designs

Postby blue cobra » February 13th, 2010, 6:18 am

When you say a drooping boom, do you mean that the the whole tail boom angles down relative to the motor stick, or that your horizontal stabilizer is mounted underneath the tail boom?
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Re: Designs

Postby jander14indoor » February 13th, 2010, 9:45 am

There are folks who swear by drooped tail booms, I'm not one.

I do like low tail, high wing, but have no empirical data to back up any significant benefit. The only seeming benefit I've found is the plane seems more stabile.

I don't think it makes much difference drag wise whether you droop the tail to lower the rear stab, or use long tail posts. I suspect the drooped tail is better balance wise, avoids the long, heavy tail posts at the very rear of the plane, and replaces it with a slightly longer tail boom with its mass distributed evenly along the length.

There is fairly certainly no aerodynamic difference between drooping the tail and long tail posts (other than that affect on CG).

All-in-all, I suspect any effect is a far, far secondary factor in long flights. FAR behind minimizing weight, trim for low drag, and and proper matching of prop and rubber.

Jeff Anderson
Livonia, MI

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Re: Designs

Postby Taran » February 13th, 2010, 6:13 pm

Is the bonus worth trying? :?: :?: :?: :?:

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Re: Designs

Postby eta150 » February 14th, 2010, 8:01 pm

That's up to you. If you can make it work within this years much more generous bonus, then it's great, but you can only find that out through building one and flying one yourself.
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