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

Sportsman Aviation F-20

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Old 10-27-2005, 10:59 PM
  #1  
setxws6
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Default Sportsman Aviation F-20

Hello all. This is my first post on RC universe, and I'm a speed freak. I started flying RC glow planes in the mid 90's and then took a break from it for about 4 years so that I could continue my quest for speed, modding my 2002 Trans Am. Now I'm starting to get back into RC.

I have a Great Planes big stik 40 that I recovered with my own trim and color and built it back around 2000. It has a Thunder Tiger Pro .46 and a Futaba 4 channel.

After flying it now, it's just not fast enough for me. I have always like the look of the DC F-20, but after finding out they went out of business, I started search for someone else that made the same design and found Sportsman Aviation. So I order the ARF (with plans of recovering it with my own monokote) in hopes that it will quench my speed need.

I have noticed that there are a lot of complaints about rudder flutter. If I understand correctly, it's because the hinge line is vertical up and down with no angle or sweep in it? Is this right? I really don't want to go without a rudder, as I like to use it for take offs and a few maneuvers. So what are some options? Give the rudder a rake to it?

Also, if there are any other tips to watch out for while building, give me some hints...

PS...where can I find a real pointy spinner like this???
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Old 10-28-2005, 08:48 AM
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bob27s
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Default RE: Sportsman Aviation F-20

Hey there... welcome

First - the spinner - Tru-Turn makes very nice "Ultimate" spinners in a variety of sizes. They are the long, skinny ones. Most folks tend to use those on the jets. There are some other profiles that work better on some of the jets.
http://www.truturn.com/Spinners/By_Shape/by_shape.html

The DC F-20 is actually available (of sorts). They are now being produced by Juno RC down in texas, along with the DC F-18, and Tsunami.
[link=http://www.junorc.com/gpage3.html]www.junorc.com[/link]
The company recently moved to a new facility, but they should be up and running with production here soon. Check the web site. The DC F-20 has the advantage on accomodating retracts - and from what I have seen it tends to build up lighter. Flys excellent.

The Sportsman F-20 is a good plane. Flys well. Your existing TT.46 will power it ok if you desire. No provisions for retracts, but it flys nicely with the fixed gear. If desired, you can install at least main gear retracts - an leave the fixed nose gear. (some other threads on here about this airplane too)

The flutter has less to do with the hinge line than it does the long torque rod linkage. The linkage to the rudder is a torque rod (similar to an aileron torque rod) which is somewhat long - and it simply winds up, and becomes a tortional spring. Plus it is unsupported for a bit too much of its length. Any excitation, and its can really buzz. If you seal the hinge gap, that takes the control surface line out of the equation. Use a heavier rod, and a different arrangement for rod bearing - helps a great deal.

Bob
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Old 10-28-2005, 12:04 PM
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Default RE: Sportsman Aviation F-20

Thanks for the reply back Bob. The aluminum spinner looks better, in my opinion, I was just worried about the added weight over a plastic on. I figured that's on reason for some F-20 being nose heavy. Also I'm worried about rotational weight, and the heavier the spinner the less rpm's you may get???

Wow, the Juno kit is like 100 buck less than the sportsman kit, why is that? Did I get ripped? I know the sportsman is covered, but I was planing on recovering it anyway....and I don't plan on retracts for cost and simplicity. I plan on making rough landings at times, like we all do.

I will use my TT .46 for the time being, I figure with the right prop and muffler, it should still scream. So use a stronger rudder linkage to the rudder? Is there any other linkages to watch out for or any other flutter?
Thanks, Brian
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Old 10-28-2005, 12:32 PM
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Default RE: Sportsman Aviation F-20


ORIGINAL: setxws6

Thanks for the reply back Bob. The aluminum spinner looks better, in my opinion, I was just worried about the added weight over a plastic on. I figured that's on reason for some F-20 being nose heavy. Also I'm worried about rotational weight, and the heavier the spinner the less rpm's you may get???
Spinner mass is not an issue for performance. If anything, more mass means you get a better idle (flywheel). They weight a bit more than plastic, but not much. Good aluminum spinners like tru-turn are balanced well, and they can withstand much higher rpms than most plastic spinners. For the TT46, a plastic spinner is ok. My opinion is not to use a plastic spinner if the engine will exceed 15,000 rpm.

Wow, the Juno kit is like 100 buck less than the sportsman kit, why is that? Did I get ripped? I know the sportsman is covered, but I was planing on recovering it anyway....and I don't plan on retracts for cost and simplicity. I plan on making rough landings at times, like we all do.
The difference is, the Juno kit is a KIT. Box of wood, plans - you have to build it. The Sportsmans is ARF - framed up, covering is done (its not that bad - could be better) and comes with most hardware, fuel tank, stuff like that.

I will use my TT .46 for the time being, I figure with the right prop and muffler, it should still scream. So use a stronger rudder linkage to the rudder? Is there any other linkages to watch out for or any other flutter?
Thanks, Brian
The rudder post and torque rod is the only real issue consistantly noted. The elevator and aileron linkages are pretty straight forward. Use your best modeling judgement and experience with the control linkages and hardware utilized. Use a 9x7 or 9x8 on the TT46 and the plane will fly well for you.

Bob
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Old 10-28-2005, 12:40 PM
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Default RE: Sportsman Aviation F-20

slap a Jettstream muffler for 50 bucks on that TT 46 and you will like the sound and rpm jump. Add air whistles from i4c to get rid of that bearing sound too.
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Old 10-28-2005, 01:11 PM
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setxws6
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Default RE: Sportsman Aviation F-20

I'm not sure what the highest RPM is with the TT Pro .46? Is it over 15k? Bottom line, I'll get a true turn if it will be better performance all the way around.

I have noticed a lot of F-20's use the red colored Jettstream muffler...are they similar to one of these two Mac's systems???
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Old 10-29-2005, 03:18 PM
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Default RE: Sportsman Aviation F-20

Hello setxws6 I have a sportsman aviation f-20 and im powering this with my magnum xls 52 with Macs tune pipe I’m getting around 15k with apc 10x7 prop On ground. My f-20 was nose heavy but I solved this by placing my receiver battery at the tail pipe and balance well with no added weight here are some of my pics

I use different kinds of muffler on my engine I tried the tower hobbies muffler give me about 600-700more rpm I tired the Macs tune pipe Like in the picture and boy this was a bullet on the air.

I never had any flutter on my rudder. All I can say is that you will love the way it looks and fly on air. I added an IC product whistle under my wing and give me a turbine like sound on a low high speed pass. Amazing,
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Old 10-30-2005, 03:49 AM
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Default RE: Sportsman Aviation F-20

I can see why you'd get more power from a tuned pipe. But they still look a lot heavier than a normal sized muffler. Of course I've never held one to really know.

When you put your receiver and battery out back...did you have to use cord extensions to the servos?
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Old 09-15-2006, 04:22 PM
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Default RE: Sportsman Aviation F-20

Hello-

Where can I find the whistle? Thanks.
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Old 09-15-2006, 06:42 PM
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Default RE: Sportsman Aviation F-20

Juno R/C also has the aluminum "Jet" spinners. $10 + shipping. A real bargain.

www.junorc.com
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Old 09-15-2006, 08:17 PM
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vicman
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Default RE: Sportsman Aviation F-20

i4C products. They work very well.
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Old 09-15-2006, 08:34 PM
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Default RE: Sportsman Aviation F-20

ORIGINAL: alqwad

Hello-

Where can I find the whistle? Thanks.
i4c products
I have a pair of them on my big Dago. Work great but they do have issues that I went through to get them right. They need "clean direct air" to work right. Last year when I installed them, I tried them on the wing at the CG. I also moved them around the general area.

What I got from it all was a whistle but only at certain parts of the flight like landing or something where the attitude of the plane was different. I was not too happy with it all.

Then last winter I rebuilt the whole plane and clipped the wings back. I then mounted the dumb things right on the flat surface with direct air and these suckers are singing from start to finish and loud!. I'm not at the house right now but I get a photo of it tomorro am.
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Old 09-18-2006, 08:21 PM
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Default RE: Sportsman Aviation F-20

How much did Futaba pay you to advertise them on your airplane?

I can't help it down here we don't put nobody's name on somthing unless they pay, must be a NASCAR thang.

My wistles worked at the wingtip similar to CH's. I did mount mine on the bottom of the wing on the outside near the L/E.
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Old 09-18-2006, 09:30 PM
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Default RE: Sportsman Aviation F-20

Whos name do you have on yours? "Ricky Bobby?
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Old 09-18-2006, 10:02 PM
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Default RE: Sportsman Aviation F-20

No body but the Revver B-Hood my man + my Revver # dam straight![sm=48_48.gif]

No free rides Boyeee!
I got cured fo free sponsorship a while back. In the racing days, yep I did. Futaba, OS, MVVS or none of the others have done squat that I haven't paid for!
Airborne hobbies(now closed unfortunately), The Great Escape (in Greenville SC) and the B-hood are the only ones that have hooked me up to date. You want free ads ya better be givin me something for it![>:]
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Old 09-19-2006, 01:15 PM
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Default RE: Sportsman Aviation F-20


ORIGINAL: vicman

No body but the Revver B-Hood my man + my Revver # dam straight![sm=48_48.gif]

No free rides Boyeee!
I got cured fo free sponsorship a while back. In the racing days, yep I did. Futaba, OS, MVVS or none of the others have done squat that I haven't paid for!
Airborne hobbies(now closed unfortunately), The Great Escape (in Greenville SC) and the B-hood are the only ones that have hooked me up to date. You want free ads ya better be givin me something for it![>:]

I thought you were older than that

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Old 09-19-2006, 04:13 PM
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Default RE: Sportsman Aviation F-20

Hey Bob (or anybody else),

Is it possible to support the rudder linkage in some way BEFORE epoxieng the tail on? I seem to recall doing this to one of my Cermark F-20's. It may have been the 40 size (many years ago )

It also seems I made a "new" heftier one for my 60 size. NEVER had flutter with either.

Gary
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Old 09-20-2006, 10:16 AM
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Default RE: Sportsman Aviation F-20

Flour even gave me the hat![>:]
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Old 09-20-2006, 10:19 AM
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Default RE: Sportsman Aviation F-20

Flour the contractor? Cool
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Old 09-20-2006, 10:24 AM
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Default RE: Sportsman Aviation F-20

I got it right Flour is a huge contractor for the Govt. They are one of the main contractors rebuilding New Orleans. Or at least attempting to.
41.5's plane was supplied at cost when Airborne Hobbies realized it was for the little guy.

So there! I will cease my rant thank you.

Nice looking plane CH
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Old 09-20-2006, 01:40 PM
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Default RE: Sportsman Aviation F-20

I am currently flying the Sportsman Aviation f-20, I have install air retract in mine, the engine I am using is the YS-45 with the special performance urntrust tune muffler from Performance Specialties, www.pspec.com, just last weekend at our flying field it was clock in a dive using my radar gun at 143 MPH, I am also using 30% glow fuel. The nose gear, vertical stab and the rudder needs to be beef up. The wing section is very strong and easily accommodate retracts. Where the vertical stab mount to the fuslage needs to be beef up, the nose landing gear is very weak on the original ARF. This is a very fast aircraft with the above setup.
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Old 09-20-2006, 01:49 PM
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Default RE: Sportsman Aviation F-20

Yes I forget, the prop I am using is a APC 10/7, the Dave Brown Alumimum spinner is cheaper than the Tru Turn spinner, with the same quality. I love the aircraft, and it is a blast to fly.
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Old 09-20-2006, 03:29 PM
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Default RE: Sportsman Aviation F-20

TUNE- Where do you fly? I am in the San Diego area...
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Old 09-20-2006, 04:38 PM
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Default RE: Sportsman Aviation F-20

Can you post a pic of the nose gear?
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Old 09-20-2006, 08:52 PM
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Default RE: Sportsman Aviation F-20


ORIGINAL: TUNE

I am currently flying the Sportsman Aviation f-20, I have install air retract in mine, the engine I am using is the YS-45 with the special performance urntrust tune muffler from Performance Specialties, www.pspec.com, just last weekend at our flying field it was clock in a dive using my radar gun at 143 MPH, I am also using 30% glow fuel. The nose gear, vertical stab and the rudder needs to be beef up. The wing section is very strong and easily accommodate retracts. Where the vertical stab mount to the fuslage needs to be beef up, the nose landing gear is very weak on the original ARF. This is a very fast aircraft with the above setup.
Now this I believe since I have seen that combination fly here. Good combination
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