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

Finished the F-20 (pics inside!)

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Old 11-15-2005, 01:36 AM
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setxws6
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Default Finished the F-20 (pics inside!)

Well I finally finished my Sportsman Aviation F-20, and boy is she a beauty! I havent' flown her yet, I still need to get the CG correct. Thanks for any help a lot of you gave me about spinners and mufflers and stuff.
I'm using a Thunder Tiger pro .46 with a JETT pipe turning a Tru-Turn. I'm a little nervous about it first flight, probably this next weekend.





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Old 11-15-2005, 02:14 AM
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crasharama
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Default RE: Finished the F-20 (pics inside!)

Looks great,
Have fun blasting holes in the sky !!!!

Tony.
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Old 11-15-2005, 04:29 AM
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0_CoooL
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Default RE: Finished the F-20 (pics inside!)

Very slick looking, Nice & Good Luck M8te
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Old 11-15-2005, 11:14 AM
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Default RE: Finished the F-20 (pics inside!)

Looks nice!

Awaiting that first flight report

Bob
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Old 11-15-2005, 11:25 AM
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Default RE: Finished the F-20 (pics inside!)

I hope you balanced the plane laterally....it will do a wicked dip to the right
on take-off if you didn't. I found this out the hard way. [X(]

FBD.
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Old 11-15-2005, 02:18 PM
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Default RE: Finished the F-20 (pics inside!)

Very cool ,is that stock covering ???
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Old 11-15-2005, 02:37 PM
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setxws6
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Default RE: Finished the F-20 (pics inside!)

Thanks for all the approvals! First flight report will come some....I've never balanced a plane laterally? Is one side heavier than the other?
If so, how do you balance it laterally the correct way and why would it dip to the right at full throttle take off?

Oh, and it is stock ARF covering. I just painted the canopy and cowling.
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Old 11-16-2005, 06:03 AM
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LDM
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Default RE: Finished the F-20 (pics inside!)

I have used a great way of balanceing a plane latterally . Your plane is totally finished so a screw with hook eye is out of the question (thats that typical way placed at the CG)and simply hang it from a string .
YOU can simply take two dowelsl , put pencil erasers on them to protect your plane , get a small piece of scrap wood 14"by 14" should be ok . Drill two holes in the wood 12" or more apart in a straight line .Draw a straight line from end to end on the wood where you intend to put the dowels and it should be centered to the base (example 14" base divide in two and 7" is the center . Drill two holes Glue the dowels in the base like two post , put the erasers on the tops of the dowels . Place a simple shirt button on the wood base inbetween the two dowels where your normal (front to back CG would be when your plane is sitting on these dowels) . Now place your plane on the dowels -make sure it centered to the line you have drawn on the wood base . YOU will see your plane tip left /right or balance just right .
If its tips , you can try to center your battery to make it balance but remember dont go out of the normal CG while trying to balance latterally .
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Old 11-16-2005, 01:26 PM
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Default RE: Finished the F-20 (pics inside!)

I've never had to laterally balance any other planes and they flew fine...so why would this type of model be so unbalanced? And if it is a little off on one side or another, why would it dip to the right after take off?
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Old 11-16-2005, 01:51 PM
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Default RE: Finished the F-20 (pics inside!)

The F-20 has a low-aspect ratio wing (short span). The engine cylinder and muffler are hanging on the right side of the plane, with that weight pretty much acting about the roll axis of the airplane.

On most sport planes, that weight inbalance would be fairly easily distributed in roll stability on a longer wing. The short wings do not distribute that extra weight offset quite as well - less moment arm to counter-act the weight with lift. Plus, the wing 'lift' can not correct the weight imbalance until the wing itself is up to speed and flying. So if you get into a situation where the plane leaves the ground at a minimum airspeed, that weight will roll the plane to the right. Once it the air and flying, yes the plane can be trimmed to deal with the weight offset, but its that low/slow situation where the lateral balance will get ya.

Chances are a small piece of stick-on weight strip (1/4 oz or so) on the left wingtip is all that will be needed.

On some of the racing planes, you will occationally see where some of us have taped quarters (25c) on the left wing for trip purposes. This is in part for the same reason. (quarters are flat and easy to tape on for trim flights - permanent weight is usually added afterward if practicle)
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Old 11-16-2005, 07:58 PM
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Mike Connor
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Default RE: Finished the F-20 (pics inside!)


ORIGINAL: setxws6

I've never had to laterally balance any other planes and they flew fine...
I pay as much attention to lateral balance on a model as I did on full scale and that is zero. I never felt any noticable effects of lateral balance on models or full scale. I would think spiral slipstream and p-factor would more then make up for the off center weight so close to center line.
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Old 11-16-2005, 11:33 PM
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setxws6
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Default RE: Finished the F-20 (pics inside!)

Well, we'll see what happens soon! I'll keep an eye on roll out and see how she handles. Thanks for all the advice.
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Old 11-19-2005, 10:14 AM
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Default RE: Finished the F-20 (pics inside!)

FBD,

Forgive my absence from the fold. However I think I've done pretty good to have moved 700 miles, gotten married, started a new job and still managed to find a place to fly in a matter of 6 months.
It's good to be back into the nitrous burning spirit again (just in time for the holidays ) I recently picked up a DC F-20 and was trying to locate the CG. I have a set of plans but being the skeptic that I am, would like to find out from the experts (and that's where u come in) what CG recommendations you could offer.

I hope to become more active in the universe in the days to come.


Rev on Bro's...................[>:]

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Old 11-19-2005, 11:59 AM
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setxws6
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Default RE: Finished the F-20 (pics inside!)

The instructions that came with mine said the CG should be between 5.5-6.0 inches back from leading edge of the wing next to the body. Mine's still a slightly nose heavy.
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