Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Patriot Wing How Thin Can I Go

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Old 01-19-2005, 09:53 PM
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buzzingb
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Default Patriot Wing How Thin Can I Go

Concidering building Patriot from scratch and thinning the wing down considerably. How thin can I go without causing problems? I know the fuse can be trimed down considerably without too much problem. I have plans and will be useing same airfoil. How can I thin down the wing useing plans?
I have seen a patriot with wing clipped between last two ribs. It did help with speed and still was able to land but only faster. Has anyone altered a Patriot?
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Old 01-20-2005, 12:40 AM
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John A
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Default RE: Patriot Wing How Thin Can I Go

I've actually given this question a lot of thought, because I was planning on doing this for my next scratch built plane. So, let me go over the notes I've jotted down.

Start with the landing gear. If you are going without retracts, make it about an inch thick at the root and taper down to about 1/2 at the tip. Personally, I don't think I'd bother building a Patriot style kit without retracts, so you're going to need a thicker wing than that. The hobbico mechanicals are about 7/8" thick. Look around other suppliers if you want to spend the money on air retracts. You can get a little thinner with a few of those. I'm sure Bob from Jett would know who makes a good thin one.
To keep the wing as thin as possible, you will need to mount them as close to the spar (the thickest part of the wing) as possible. With the swept back wing, you've just created a tail dragger. To fix it, bend the landing gear back about 30 degrees where it has the shock coil wound in it. This moves the wheels further back in the wing when they are retracted, so you will need some thin wheels. Work gear doors into the design for a few cheap MPH. Adding a rocket nose cone backward in the tail, painted orange and yellow to mimic a flame, will help too.

As far as the body goes, servo width and configuration determines how skinny the body is. The servos themselves are 3/4" wide (standard size futaba or hitec) , but even the wheel type arms stick out a little over the side. About 1 5/8 to 1 3/4" Inside width is about the best you are going to get with side by side servos. Getting narrower than that in a .46 size or larger engine usually means an unusual fuel tank, too. You can go thinner if you use smaller servos, but you better get good metal geared ones at the speed you are intending to fly. Height is determined the same way. Lay the servos over the plan, and whack off the excess. The body is a whopping 4 inches tall at former f4 right behind the wing. You could cut that in half and still get standard servos in there, but I think you will detract from the looks if you go that thin. I've got it about 3 inches tall there in my rough sketch. I am planning on mounting the engine sideways and possibly using twin tanks with a YS engine, 45 or 53. Much of the weight you are shaving is going to be behind the CG, so I think I might lengthen the tail a few inches. The battery pack will end up ahead to the 4 servos in the back since there wont be any room behind or below them. That's where I stopped. I've got a couple drawings where I enclosed the pipe up top, but it looks just like a pattern plane that way, and really makes the fuel tank situation tricky. I'd thought of using 3 small tanks, with a couple in the leading edge of the wing, but figured it would dig into the reliability.

Keep us informed with your decisions along the way.
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Old 01-20-2005, 01:46 AM
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Default RE: Patriot Wing How Thin Can I Go

I had one with Split-Flaps, bought it that way--- They are almost always nose-heavy. Interesting notes--- I am no aeronautical eng. so dunno about rib thickness-

Keep us posted!
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Old 01-20-2005, 09:11 AM
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Default RE: Patriot Wing How Thin Can I Go

I like the look of the Patriot in the air but it is too slow because of drag. I think with some minor modifications it can be a lot faster with same look and flight characteristics. However, as far as I know there aren't any other airplane out there any better, so that leaves scratch building your own.
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Old 01-20-2005, 09:32 AM
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Default RE: Patriot Wing How Thin Can I Go

You have to cut down the aircraft frontal area and eliminate the parasitic drag. That will gain you far more than just thinning the wing.

some suggestions if you are going to dive into the paper.

general stuff:

1) RE engine - pipe through a tunnel over the top of the fuselage..... utilize no larger than a 2" spinner. Cowl in the engine as much as possible.

2) Cover all openings - gear doors if possible. (gear hole turbulance is KILLER drag)

3) well designed fillet at the wing saddle

wing:

4) 12% airfoil section at the root, 9% at the tip. It may look thick - aerodynamically it isnt.
Find and airfoil with the high point back around 35% for the root, and around 30% for the tip.

5) Increase the wing span by 2". That wing area will help a bunch.

6) wing must have 2-3 deg of washout at each wing tip.

7) use HEAVY 1/8" aileron torque rods (keep internal linkages). Ailerons 1.5" wide, 11" long, starting 3" outboard of the fuselage.

Other:

8) increase the vertical fin height about 1.5"

9) should weigh no more than 5.75 lbs when done.

Although this is larger, you may get some ideas from this thread
http://www.rcuniverse.com/forum/fb.asp?m=2510347
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Old 01-20-2005, 07:51 PM
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Default RE: Patriot Wing How Thin Can I Go

The Patriot wing looks like it could be cut out of foam. However, I don't have foam cutting experience.
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Old 01-21-2005, 11:27 AM
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Default RE: Patriot Wing How Thin Can I Go

Building these airplanes sure takes up a lot of time. However, the only way you can get one like you want is to build it and most of the time this takes making some changer from original design.
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Old 01-21-2005, 03:56 PM
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Default RE: Patriot Wing How Thin Can I Go

they can be cut from foam and Vac bagged I have made a couple for testing purposes (one white, one Pink and one Blue). Where I have a problem is that the ones that i have made were 3 part wings, the centre section that fits into the fuse then the actual wing with retracts. I haven't flight tested them yet, I just did the bend over the leg test and they looked fine with no spars.
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Old 01-21-2005, 08:03 PM
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Default RE: Patriot Wing How Thin Can I Go

ORIGINAL: bob27s

4) 12% airfoil section at the root, 9% at the tip. It may look thick - aerodynamically it isnt.
Find and airfoil with the high point back around 35% for the root, and around 30% for the tip.
While those numbers are great for a typical speed plane, they sound funny for the patriot. It has a huge 15" root cord, giving a wing that's still 1.8 inches thick at the root. Isn't that still way too think, since the stock wing is just under 2"? The tip is about 7", so you've got .63 inches whick sounds good. Shouldn't he keep about 9 at the root too, which is about 1.35? I know it's not ideal, but neither is the basic design to start with.
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Old 01-24-2005, 09:05 AM
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Default RE: Patriot Wing How Thin Can I Go

ORIGINAL: John A

ORIGINAL: bob27s

4) 12% airfoil section at the root, 9% at the tip. It may look thick - aerodynamically it isnt.
Find and airfoil with the high point back around 35% for the root, and around 30% for the tip.
While those numbers are great for a typical speed plane, they sound funny for the patriot. It has a huge 15" root cord, giving a wing that's still 1.8 inches thick at the root. Isn't that still way too think, since the stock wing is just under 2"? The tip is about 7", so you've got .63 inches whick sounds good. Shouldn't he keep about 9 at the root too, which is about 1.35? I know it's not ideal, but neither is the basic design to start with.
Lots of ways to do this, but doing a progressive airfoil and keeping the inboard thicker will help with stability. Aerodynamically, the drop from a 15% wing to 12% is pretty noticable. Plus, you need the wing thickness to install the retracts. Airfoil section tends to be more important to optimize for certain flight conditions.

As I noted, the wing is the least of the drag problem on a patriot. It has a lot of frontal area.

Least I might go would be 10% root and 7% tip. But you would have to build the aircraft VERY light. Remember, its going to weigh over 5 lbs. Retract and gear position would require serious review.

It is wise not to get confused by the very thin wing sections on airliners and fighter jets. Those aircraft/wings operate at minimum airspeeds that are FAR beyond our maximum airspeed.. and are designed for trans-sonic flight. We fly extreamly sub-sonic. Models are best designed with that in mind.
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