Designs

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blue cobra
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Re: Designs

Postby blue cobra » November 11th, 2009, 6:14 pm

If you offset the wing to the right (looking from the front) that will give it a right turn, correct? But the planes will naturally want to turn left, so is this offset just to combat torque? Also, on the LE design, both the wing and tail are angled or offset for right turn, and only 2 degrees of left thrust to get the turn, so how does that kit turn?
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Re: Designs

Postby jander14indoor » November 12th, 2009, 7:19 am

No, longer left wing (right when looking from front) gives left turn (more drag on the left side). It is one of many controls to manage a consistent left turn. But the real reason for longer left wing, and washin on left wing is to make the plane fly closer to level offsetting propellor torque which tends to roll the plane strongly to the left if no other actions taken.
As for the rest of the LE design I think you are interpreting the drawing wrong. Prop is offset to give left turn (view is from bottom). Stab is angled to push it out to the right, giving a left turn. Wing is offset to left with left washin. This tends to keep the left wing up offsetting prop torque, while the higher drag on the left pulls the nose around to the left in a turn.
The only thing I don't see that's 'normal' on an SO plane is offsetting the stab so the stab boom angles to the left at the rear from the straight line of the motor stick.

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Re: Designs

Postby blue cobra » November 12th, 2009, 1:27 pm

Oh, thanks. I was thinking more wing on the left would mean more lift, creating a right turn, but I see how it would create left turn.
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Re: Designs

Postby smartkid222 » December 21st, 2009, 6:48 pm

I thought to post the kits available for WS as many people like to start off with them.

The Zeigler Fun Science 2010 kit http://www.freedomflightmodels.com/index.html
Cesar Bansk- Peck Polymers- Leading Edge 2010 kit https://www.a2zcorp.us/store/
Shrike AF-31 and Falcon AF-16 from Aeroracers http://www.aeroracers.com/bdivision.html

harlan no longer makes kits.

There are also free plans:
Chuch Markos 2009 http://soinc.org/sites/default/files/up ... ans2.0.pdf
Leading edge 2010 Plan only http://www.a2zcorp.us/freedownload/Lead ... nePlan.pdf

did i miss anything? hope this helps
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Re: Designs

Postby leetx » January 22nd, 2010, 5:46 pm

A quick question for those who are familiar with the Leading Edge kit.

I was looking at the kit plans online and saw the instructions for shaping the "broad" ikara prop blades and to set the pitch to 45 deg. My questions are:

- Does the "broad" ikara prop come stock with pitch greater or less than 45 deg?
- for the Leading Edge kit, what is(are) the recommended rubber size(s) for this prop/plane combination?

This is my first time posting. I recently saw this discussion forum, and I want to thank everyone for sharing their knowledge.

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Re: Designs

Postby clinto » January 24th, 2010, 12:31 pm

Does increasing the vertical distance drastically from wing to stab have any significantly positive affects? As in, if your looking at the plane from the front would look something like this and increasing this distance between:
___________
_______

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Re: Designs

Postby carneyf1d » January 24th, 2010, 1:22 pm

if you're talking about a droop boom?
It increases the lift of the stabilizer by the ground effect near the beginning and end of flights. It also decreases the moment arm, and decreases the pitching moment caused by the stabilizer.

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Re: Designs

Postby jander14indoor » January 24th, 2010, 7:08 pm

<SNIP>
- Does the "broad" ikara prop come stock with pitch greater or less than 45 deg?
- for the Leading Edge kit, what is(are) the recommended rubber size(s) for this prop/plane combination?
<SNIP>
Most props have a varying angle from very steep at the pitch to almost flat at the tips, this is called a helical blade. So they will have a 45 degree angle (not pitch) somewhere along the radius. Key is what radius the 45 degree angle is as this helps define the pitch. (Pitch is the theoretically ideal distance the prop will move forward during one turn, not an angle of the blade).

The plan is recommending the 45 degree angle be at a particular radius to give a particular pitch.

Never flown this plane, but from experience, it should be in range of .070 to .096 width. That's a very wide range I know, but it should be in there somewhere.

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Re: Designs

Postby blue cobra » January 25th, 2010, 11:55 am

Carbon fiber does mean carbon reinforced polymers, like this, right?

https://www.a2zcorp.us/store/Category.a ... Pultrusion
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Re: Designs

Postby jander14indoor » January 25th, 2010, 1:08 pm

Carbon fiber does mean carbon reinforced polymers, like this, right?<SNIP>

Wwweeeeellllllllllll, you knoooow, when the rules writers added that, I'm confident that's what they meant. But I can also see some less knowledgable (but well meaning) event supervisor saying otherwise. "It only says carbon fiber in the rules, not plastic, second tier."

Heck, last year one supervisor disallowed tape, which is only a combination of plastic film or paper and glue.... Required a clarification to straighten that out.

So, I'm NOT going to give you a definitive answer, but instead STRONGLY recommend you submit a rule clarification on the national site.

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Re: Designs

Postby leetx » January 26th, 2010, 10:00 am


jander14indoor:

The plan is recommending the 45 degree angle be at a particular radius to give a particular pitch.

Never flown this plane, but from experience, it should be in range of .070 to .096 width. That's a very wide range I know, but it should be in there somewhere.
For the large ikara prop, I know that a wider rubber is needed. We recently tested with a .093 rubber and got close to 2:30. I was wondering if others have experience using such a big prop with narrower rubber like .090 or .085 to increase flight times.

Thank you.

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Re: Designs

Postby blue cobra » January 26th, 2010, 12:30 pm

I'm not sure where to go from here. My planes specs are:

12.75cm chord wing
2 dihedral points with a middle portion 24 cm long and the tips angled at 20 degrees
28x10cm stab
6.93 grams
Also I'm using the 8-7/8in Ikara prop with .090 rubber with 90 winds (1350 turns).

It got just under two minutes and I really don't know how to improve. My WS mentor was with me when I flew, and he didn't really know where to go either. All he could suggest was ruby bearings for the propeller.
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Re: Designs

Postby jcollier » January 26th, 2010, 6:11 pm

I'm not sure where to go from here. My planes specs are:

12.75cm chord wing
2 dihedral points with a middle portion 24 cm long and the tips angled at 20 degrees
28x10cm stab
6.93 grams
Also I'm using the 8-7/8in Ikara prop with .090 rubber with 90 winds (1350 turns).

It got just under two minutes and I really don't know how to improve. My WS mentor was with me when I flew, and he didn't really know where to go either. All he could suggest was ruby bearings for the propeller.
How much have you played with wing incidence or stabilizer incidence to see how it affects the flight and time?

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Re: Designs

Postby jander14indoor » January 27th, 2010, 3:35 am

<SNIP>It got just under two minutes and I really don't know how to improve. My WS mentor was with me when I flew, and he didn't really know where to go either. All he could suggest was ruby bearings for the propeller.
The basic plane you have should be capable of more. And two minutes is very respectable.

Now's where it gets hard. Unless you have noticeable friction in your prop hanger (usually indicated by noise) I wouldn't worry about the ruby bearings, never heard of them being used, not necessary to hit three minutes.

You have to start playing with the variables systematically and figure out which ones to tweak to improve. The idea is to maximize energy storage and use (matching prop and rubber) and minimizing drag (look for skewed surfaces, play with wing and stab incidences as already mentioned, play with cg location, open up the turn if there's room, etc.). This is where the flight log becomes invaluable. Make small changes systematically and check for improvements. Keep records so you can go back if things degrade. etc.

As a hint, that rubber size seems a little large for these planes and most IKARA props. Try a much thinner and longer motor that will take many more turns. This is also the range where winding to torque, instead of turns, becomes useful.

Hope that helps some.

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Re: Designs

Postby blue cobra » January 27th, 2010, 8:51 am

I'll try some .080 rubber with 100 winds and see how it goes. Also, moving the wing forward is equivalent to increasing AoA with respect to flight behavior? So could I decrease AoA and move the wing forward to minimize drag?

I've gotten no gym time from school. That two minutes was at a college one and a half hours away. If I get any more gym time, I'll play with it some more, and report back.

EDIT: How does tail volume affect flight? I calculated my tail volume to be 1.6, which according to the table below is a bit high.

AMA gas models 1.0 to 2.0
Mulvihill rubber 1.5 to 2.2
Wakefield rubber 1.4 to 1.7
Indoor rubber duration 1.0 to 1.5
Hand launched glider .6 to 1.1
Full size 1913 Moraine-Saulnier, Type 'L' .16

According to the formula Tail Volume=(Tail Area/Wing Area)x(Tail Arm/Average Wing Chord) you can decrease tail volume by decreasing tail arm or by decreasing tail area, OR by increasing wing chord/area.

Assuming I want to decrease my tail volume, my best bet would be to decrease tail arm then, right? (Since I can't increase wing area with the laser cut ribs I'm using)
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