Aja

I was curious if there were any relatively simple and quick ways to modify my 4 star so it could become more agile and interesting to fly. Currently, I have an OS 40LA in it. In addition to the modifications, would a certain prop improve performance? Any suggestions are welcomed, but I would prefer ones that have been proven. Thanks!

Aaron

Ken Bryant

My Feedback: (10)

The first thing is yank that DOG of an engine. Go with a 46 or 50

Next is increase the control surface size.

Better servos help too.

The big thing you need to remember the 4* is NOT an aerobatic design. The other obvious thing to do is gut it and get something like a Twist.

Aja

Furyicon--
First of all, the engine does an adequate job of hauling the plane around. It doesn't have unlimited verticle performance or anything like that, but it will have to do for now.
Second, in addition to increasing the size of the control surfaces, is there anything else that I can do that will increase agility without compromising stability or strength? I was wondering if I could remove the dihedral, shorten the wing, etc.

Does anyone have any suggestions or pointers on these mods?

(I have a P-39 on the table with a ST90, so I'm just trying to get as much out of this plane as I can.)

Aaron

Ken Bryant

My Feedback: (10)

It already sounds like you have some good ideas on what to do. Try them and report back to here with how they went.

onytay

My Feedback: (1)

on my 60 size 4* I cut one bay off each end of the wing and eliminated half the diheadral, but this was all done on a kit

jrf

My Feedback: (551)

Shorten the wings one rib bay each. That's a well proven mod that makes the roll rate faster and takes some of the "ballooning" out of landings.

Don't reduce the dihedral. That makes high wings more aerobatic, but it makes low wings less aerobatic. The best dihedral for aerobatics is when the wing's vertical center is closest to the vertical center of the rest of the airplane. Note that aerobatic airplanes with a mid-wing like the Edge and Yak have no diheral, but low wing aerobats like the Extra and CAP have 2 or three degrees of dihedral.

A low wing with no dihedral will knife edge poorly and be more stable inverted than right-side up. That means smooth linear rolls will be harder to do than they should be as the roll will slow down during the inverted portion.

You might also experiment with 3D throws and exponential if your radio can handle it. Using separate aileron servos will make that easier.

The 4 Star has such a wide stability margin that it is a great airplane for experimenting. No matter what you do with it, you can't hurt it much.

Jim

G.W.

My Feedback: (22)

Before you do that Aja , consider this. I have a 4* 40 that weighs 4.25 lbs and has an os 46 la on it and it has unlimited vertical. I have a computer radio and have duel rates. I have tons of through on all surfaces. It has an awsome roll rate and snaps so fast you cant even count them. Furyicon, the four star is so an aerobatic designed plane. It will do just about everything you ask it to do and does it with precision. So I would try this before any thing else.[sm=thumbup.gif][sm=sunsmiley.gif]

Aja

Thanks for all the replies.

I think I will first shorten the wing by one bay on each side. This sounds very simple to do if I undestand it correctly. You just saw off the piece of wing at the end and recover that area, right?

I was also thinking about tearing (neatly of course) the rudder, and possibly the elevator, off and increasing the length about an inch or two. Will that noticably increase performance?

Aaron

G.W.

My Feedback: (22)

It should. Bigger means more fun. Right?

Aja

I guess your right hardcoreflyer.

I will test all of this out and report back on the results.

G.W.

My Feedback: (22)

I have a friend that cut the wings shorter. When I flew it I didn't see any difference except that you need to keep the speed up on landing.[8D]

Harry Landings

My Feedback: (8)

When you saw the end of the wings off, use some 1/8" or 3/16" balsa to make an end-plate for the wing to re-inforce it. Just trace the end of the wing onto the balsa and cut it out and glue it onto the end of the wing, then re-cover.

Don't change the size of the tail feathers till you have flown the plane with the wings clipped. You probably won't gain enough to matter and the size of the tail feathers is supposed to be proportional to the wing size and shortening the wings will change that proportion.

Go to http://www.btemodels.com/ and read Bruce's comparison of the Venture 60 and the 4* 60. He designed the Venture after he designed the 4*s and his comments about raising the horizontal stabilizer are very interesting. Doing that to a plane that is already built is probably too complex, but having the knowledge won't hurt.

Good Luck.

G.W.

My Feedback: (22)

If you do change the size of them you need to be careful not to give it too much throw or you will risk a high speed stall.

Aja

I did shorten the wings and am working on the tail feathers. I will make sure to keep the low rates reasonable as to not induce a high-speed stall. Almost done.

jrf

My Feedback: (551)

Aja:

Try one thing at a time and fly it in between changes. Otherwise you might overdo it and you won't know what to change back.

Jim

DTB

My Feedback: (15)

I have a 4*60 with several modifications. I would suggest putting a fuel hatch underneath the bottom. I modified my rudder with a counter balance, pull pull system, better tail wheel, 1" extra on rudder and elevators, dual elevator servos. Knife edge, hover, flat spins, inverted flat spins, inverted flight is great. I have really turn it into a 3D plane. I have a YS .91FZ up front. This supercharged engine pumps out the power of a 1.20. This plane loves extra power. Take the 40LA off and get atleast a 46FX, AX or 50. A Saito 72 or 82 would be amazing also on that plane.

Your 4*40 doesn't have dual ailerons servos like the 4*60 has, but that would be a great addition. Just beef up the wing and add a servo tray.

Here is a website I have seen several times, but it should be all that you are looking for concerning your 4*40.
http://renderwurx.com/rc/sig4star/

Enjoy,
DTB

Aja

I do have a Super Tigre 90. I guess that would be over-doing it?

DTB

My Feedback: (15)

A 90 2-strk on a 40 size. That is a little over kill and would probably be way nose heavy, but if it fits and balances, use it. Throttle management will be very important, but would be a ton of fun. You could damage the plane by going too fast and pulling up or down. You need to put tht 90 on a 40 size Diamond Dust. Not sure if the 4* wings can handle that type of load. Again, throttle management is key.

G.W.

My Feedback: (22)

Great covering job! Love it!

DTB

My Feedback: (15)

Thanks a lot, it definately took a while to cut out each individual checker that was flying off. I had to attach each cheacker individually; On the fuse, the wings and the elevator.

Last month at our spring fly-in, I had it in a flat spin and this plane will flat spin long after you try to stop it. So have plenty of altitude. I was too low. Needless to say, it went into the bushes and only had a broken leading edge on the wing. I couldn't believe it when I saw that. I honestly was thinking while walking out to see the damage, "OK, what can I put a YS .91 on now", but the plane was seating in some soft bushes that saved it. Unbelievable moment.

Thanks again,
Derrick

msu68stang

My Feedback: (7)

Yeah Derrick's 4* is really nice. I've flown with him and see him do some amazing stuff on it. I have a 4* 40 with a OS 46 FX with dual aileron servos. It's pretty much a twin of Derricks. My plane though is out to get me. It injured me this past monday....no fun.

Chris

britbrat

If your wings are not skinned with balsa up to the mainspar, I strongly suggest that you do that. It will stiffen & strenghten the wings & improve the stall characteristics (smoother airflow over the wing forward of the point of maximum thickness). The model will be somewhat more resistant to snapping out of tight turns & loops. You can use 1/32 sheet, or 1/16 sheet.

Be carefull about extending the size of the control surfaces -- the larger surfaces will be more prone to flutter, unless you do additional work, like aero-balancing, mechanical balancing, &/or making the control surfaces thicker than the fixed surfaces.

More power would be a good idea, if you can manage it.

rod2_hi

Just my 2cents
I maidened a 4* 40 ARF this weekend, and it flew sweet. I think it's a shame to tear into a plane that is reliable and experiment unless there are a few in the hangar that can be rolled out. I wouldn't take my only flyable plane and make it into an unpredictable dart. With the new ARF's it would be cheap to grab a U-can do or spectrum or something under $150 and have a plane that's designed to be unstable and keep the 4* docile for a go to plane when the others need maintenance or repair. It can get you to the point where you can get through most aerobatics as it is.

for what it's worth.

Good luck with the mods.

rod

DTB

My Feedback: (15)

Rod, I think we are on different pages. Mine and csdawggie Four Stars were kits. I built my kit about 1.5 years ago and Chris built his kit a couple of months ago. Kits are so much easier to modify. I agree with you that modifying the ARF version would be bad (harder).

I have a club member that is a police officer. One day he was at the field in the police car off duty. He took his radar and I did a low pass from a dive and registered 112mph. I guess to me that wasn't too bad for a supercharged 4-strk 60 size Four Star spinning a APC 15x6. I actually didn't try to make the plane into a dart, but it can be fast, but I don't fly it fast and that was the only time I have ever flown it that fast. With larger control surfaces and a aft CG, this means only one thing, 3D. 3D aerobatics is my main flying style and I have other 3D planes, but the Four Star plane is still very predictable and gentle. I didn't shorten the wingspan either or remove the dihedral and it will still torque roll easily. With flaps it will literally crawl. I didn't change the flying characteristics too much from the recommended. I did have a Mechanical disadvantage problem in the beginning which caused flutter, but I corrected that and the flutter is no more even with large control surfaces. Mechanical Advantage helps with large control surfaces that will tend to flutter sooner.

csdawggie, what did your plane do to you? I didn't know that you had an accident. Did the prop get you?

Derrick (DTB)