Twinstar flight charateristics  
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All Forums >> RC Airplanes >> Twin & Multi Engine RC Aircraft >> Twinstar flight charateristics
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Twinstar flight charateristics - 8/18/2003 8:06:52 AM   
jschenck



Posts: 393
Joined: 10/9/2002
From: La Vista, NE, USA
Status: offline 		Well I flew my twinstar with two OS FS30's again today.

I got quite an adrenaline hit. .. not a good one either..

I was flying a long downwind leg (no wind to speak of) and when I turned base, it snapped on me. It was nearing dusk, so I didn't recognize the problem right away. The airplane was fumbling out of the sky for a couple of seconds before I recognized I was in deep trouble. I full throttled it and pointed the nose straight down until I had some airspeed. Then I was able to pull it out and fly the best landing yet.

Lesson learned! --> the Twinstar does *NOT* like low speed high bank turns!

I think this is why one engine performance is bad. not that it can't fly on one engine, but you are not going to have the power to pull you through a turn == SNAP, ROLL, CRACK! ==

I have not had to try and fly on one engine. Other people at the field who have seen the twinstar on one engine tell me over and over, if one flames out, pull the throttle down and glide in or you'll wreck it!.
I would imagine that if I had a pair of strong 40 2-strokes and if one flamed out, you could fly safely with one engine. Provided you keep the wing horizontal and try steering with the little, tiny rudder.

Yea, the rudder -- wags the tail fine, does not MOVE the tail around. Perhaps a bigger rudder would help the base and final turns as I could use the rudder and keep the wing as level as possible.

The OS FS30's are enough to fly it and have some fun with it, but I am not comfortable flying it yet. There is not enough engine to pull me out of a momentary lapse in flying ability or a sight mis-orientation.

anyway, as much as I love the sound of 2 four-strokes, I'm thinking about selling one of them and getting a pair of TT-36's.

thoughts? is it possible that the problem may be a horizontal fin to wing angle problem (angle of incidence?). To all twinstar's snap (unfriendly snap) on lower speed maneuvers?

At least I am getting a feel for flying a war bird, eh?

Now I'm thinking a kit-bashed Ultra-stick would be a great twin - light wing loading and very maneuverable.
       Post #: 1

Twin Star - 8/18/2003 5:31:33 PM   
twinman



Posts: 1628
Joined: 1/19/2002
From: Katy, TX, USA
Status: offline 		If we assume that the normal stuff is fine, such as balance, you are flying a warbird trainer. .30 four strokes are on the light side. Have flown this bird with .25 two strokes and was not so impressed. Two LA 40's is a different animal, as is the TT 32's you propose.Lots of fun, but small fuel tanks.
I will admit that I have not flown this underpowered, but the plane does fly very well with only one engine...40 size.
I was not completely comfortable with your references to the rudder. Are you flying coordinated rudder and aileron ALL THE TIME?????? If not learn now. Do not fly twins and forget the rudder. Lose and engine and try to learn to use the rudder is not an option.
One other item on the rudder, if you think the plane does not respond to the rudder enough, set it for as much throw as possible. The rudder is how you will fly with one engine to avoid yaw of uneven thrust. Do not mix the rudder into the ailerons.
Once you get the power as you like and get tired of it as is......go to the post on Triple props and prop wash.http://www.rcuniverse.com/forum/tm.asp?m=1044125
You will find the tri-engine conversion near the bottom. Note, the wing loading goes very high with this, so keep the nose engine small......like .15
Good Luckk

(in reply to jschenck)
       Post #: 2

Twinstar flight charateristics - 8/18/2003 5:42:28 PM   
MajorTomski



Posts: 1401
Joined: 5/1/2003
From: Oklahoma City, OK, USA
Status: offline 		Are you talking the Hobbico Twinstar? I flew mine for almost three years, and retired it because I tired of it, it's still airworthy. I flew with two .25LA's and NEVER encounterd the negitive things you've said about this airplane. I've even done accidental single engine touch and goes because the single engine performance of this littel trainer are so docile. I was very much suprised to find that this aircraft at least with 25's for power has a Vmc that is below its stall speed. That is I could maintain directional control on one engine through the aerodynamic stall. It had all the power it needed to do the AMA pattern and sweet high speed flybys. I might suggest that you just pulled the power too soon on the down wind. Keep some power in until you're on final and lined up. then go tofull idle.

Tom Solinski
Aero Engineer
FAA AviationSafety INspector
Private pilot Single & Multi Engine land.
AMA 8026

(in reply to jschenck)
       Post #: 3

Twinstar flight charateristics - 8/18/2003 8:26:28 PM   
Edwin


 

Posts: 3423
Joined: 2/8/2002
From: Leander, TX, USA
Status: offline 		I flew my twinstar with TT.36 using apc 9x7 props. It was a wild animal with those engines. You're right about low speed high bank turns. I heavily modified mine. Basically glass the center section with 2 oz glass top and bottom and install dual ail servos with 1 1/2" wide ailerons instead of the stock 1" wide. On its second maiden flight after the rework, I lost an engine, and then discovered the other engine was stuck wide open. Mild panic at first but as long as I was on top of it, I was ok. Flew out the remaining tank of fuel and dead sticked in. I use quick links at the carb and the set screw only pinched the end of the throttle wire. My fault. But this says more about the planes ability to fly single engine than my piloting skills. The twinstar is about as perfect a twin trainer as I can think of. Love it.

Also love the unlimited verticle with those TT .36's.
Edwin

(in reply to jschenck)
       Post #: 4

Twinstar flight charateristics - 8/18/2003 8:55:38 PM   
krayzc-RCU



Posts: 6143
Joined: 3/26/2002
From: Kannapolis, NC, USA
Status: offline 		the twin star will not take a bank and yank turn on one motor well as i know this will stall the girl. i flew mine with 2-la 40 on 10 x 6 props. 7minute flights

(in reply to jschenck)
       Post #: 5

Twinstar flight charateristics - 8/18/2003 9:48:54 PM   
toucano


 

Posts: 212
Joined: 4/2/2002
From: city, USA
Status: offline 		"Now I'm thinking a kit-bashed Ultra-stick would be a great twin - light wing loading and very maneuverable."

I think your other points were addressed above, so I'll chime about the Ultra Stick.

You are correct.

I have a GP .60 size Big Stik (similar to the US, but it has tri-cycle gear) with two OS .46 FX engines. I also have a H9 .60 size Ultra Stick with a Magnum 1.20 4 stroke. The two planes fly very close to the same. Of course the twin sounds much better, but all aspects fo performance are nearly identical. If you are considering this route, I say go for it; you won't be disappointed.

(in reply to jschenck)
       Post #: 6

Tristar conversion - 8/19/2003 6:19:41 PM   
jschenck



Posts: 393
Joined: 10/9/2002
From: La Vista, NE, USA
Status: offline 		Twinman - your tristar conversion looks quite trick. Now I just need to find another 4-stroke to put on the nose - then velcro the battery pack to the tail. I'll bet the deadstick landings just about push the gear through the wing if you flair to early! - although I do hate to disturb the "Cessna 310ish" looks... If I wanted to get real cheap, I do have an OS 25FP laying around.... or a Magnum 40GP .... hmmm..

I have been teaching myself to fly with the rudder for a while. It took me 6 months to get the twinstar ready to fly because of time commitments elsewhere (work, family, house, etc...). I am to the point now where I use ailerons to keep the wing level on the approach and use the rudder to steer the craft in with my other airplanes. I'm even cross-controlling on base and final to keep the wing level and maintain directional control. What I found is the twinstar doesn't seem to steer with the rudder very well. I see the tail wag when I give rudder input, but the direction of flight doesn't change much. I have the throws set very high so I don't think that is an issue.

Tom - I take your point. This is probably a real good twin trainer - I have nothing to compare it to (yet). But it does require power through base leg. My experience with my other aircraft is to go to full idle just as I turn base and use the throttle to control altitude as I come in on final. My other aircraft float with light wing loading so the 'bank and yank' maneuvering on base/final is never been an issue for me. Part of my issue may be the *very* high elevator deflection I have setup. it's at least 25-30 degrees deflection from neutral. same with ailerons and rudder. I like the aircraft to move when I hit the sticks. This may be the wrong setup for the twinstar, or at least I may need to dial in some exponential curve into the elevator and ailerons.

I will get some pix as soon as I find my digital camera. I'd like to post a video of the twin fours , maybe I can borrow a digital camcorder and drop a video somewhere.

(in reply to jschenck)
       Post #: 7

Twinstar flight charateristics - 8/19/2003 9:30:17 PM   
krayzc-RCU



Posts: 6143
Joined: 3/26/2002
From: Kannapolis, NC, USA
Status: offline 		i would say its to much elevator i only fly 10 degress on everything low rate and the other rate is 3d. i would think you are not 3ding with the star so 8-10 degress is the ticket.

(in reply to jschenck)
       Post #: 8

twinstar - 8/20/2003 6:31:49 AM   
timrcpilot


 

Posts: 82
Joined: 1/14/2002
From: Wayne , NE, USA
Status: offline 		I have owned 2 Hobbico twinstars. The first I killed while flying inverted, too low to the ground, and I got a case of dumb thumbs. The second I still have. I had OS 25FP's on each plane. I have had no problems with it snapping, and have flown it on only one engine. Not exactly a powerhouse, but it was not falling out of the sky on me. I could have flown it as long as I wanted to.

I have had several planes snap on me on the base turn of final, and also at the top of the loop, in all cases it was too much elevator deflection. If I just toned down the amount of throw in the elevator, it quit doing it.

I enjoy my twinstar, love the sound. Yes I could put bigger engines on it, but it flies fast enough for me, and the length of flight is not something I have to worry about. The only thing I don't like is the crummy covering. This winter I will strip it off and dress it up a little, may also round off some of the corners on the boxy fuselage.

Tim

(in reply to jschenck)
       Post #: 9

Twinstar Conversion - 8/20/2003 7:40:06 AM   
twinman



Posts: 1628
Joined: 1/19/2002
From: Katy, TX, USA
Status: offline 		jschenck
UH.......That was not my plane......I just conned the owner in to doing it......then he is afraid of it ........and I get to try it out!!!!!
Life is good!!!!!!
Twinman

(in reply to jschenck)
       Post #: 10

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