theo63

well here is a picture of the elevator hook up and i think i am ready to close in the rest of the fuse and get as much done as i can and hope my motor shows up soon

theo63

well i got the bottom all covered up and progress is slow and i have not had much time to work on it

then today i finally got my jet 90 and she looks sweet and now i think that will kick me into overdrive to get more done

theo63

wow what happened to all that was building i seem to be talking to myselve lol well anyway i got the motor mounted and i think it looks pretty sweet on the nose

theo63

4 got the picture

nchrome

looking okay there mine is waiting for spring to arrive sos I can check out the new engine I have on mine(can't afford a jett engine)

ser00

Hi everybody,

I love this forum! So much so that I have two SU-27 kits coming in on Feb 19th . I have several questions for everybody. First, has anybody thought about doing flaps on this plane? I do not see why the ailerons couldn't be extended out and flaps installed. It should help slow the plane down on landing. I would appreciate the pros and cons on this idea. Also, I have found the choice of engine to be somewhat questionable. Since I plan on building this plane and the Juno RC F-18 kit at the same time, I have heard that the best engine for the plane(s) is a Jett 90 and that the OS 91 FX will barely fly the plane. Maybe I am ignorant but I do not see how an OS 91 can barely fly these planes. I do realize that the Jett engine turns higher rpms and would produce more thrust than the 91 FX. Let say that if I can run an APC 12x7 prop at 12,000-13000 rpms (stock muffler), than I should be able to run a 13x6 at the same rpm range. Using ThrustCalc (taking into account it does not use prop pitch in it calculations and it is only static thrust), I should get 11-12 lbs of static thrust. If I go with a Jett muffler on the OS 91FX, I could go to a higher pitch prop (12x8 or 13X7 at 12000-13000 range). Playing devil's advocate, let say that I only get 9-10lbs of thrust from the engine. I would still achieve a power to weight ratio of 1:1. Granted, I do not expect the plane to have any vertical performance but the plane should still fly without issue. It seems that if I have a Jett, then the plane flies like a rocket, but if I use an OS, then it barely flies above stall speed. Now, I am not trying to be a fanboy of OS and preach that OS is the best. I take each engine on its own merit and I have had great running Super Tigres, OS, K&B, Enyas and even a FOX engine. I have never had a Jett though (really too expensive for me at the moment). I got two OS 91FX NIB for $350. So, hopefully what I need is a better defination of performance expectations for these two planes. I know that the forum is call Extreme Speed prop planes. I am not looking to take these planes 100+ miles per hour. I would be extremely happy with 70-80 miles an hour top speed (though I am pretty sure that in the back of my mind I will be saying "Faster...Faster!). I am pretty sure these planes would fly fine at 50 miles an hour (but who wants to fly a SU-27 like a grandmother). Just curious, what is the landing speed of the SU-27? As always, I would greatly appreciate flight performance experience with the SU-27 from anybody on this thread. This will definately help me and anybody that comes after me wanting to build this beautiful plane.

Happy flying and soft landings!

Robert Strouse

Ser00,

Flaps are really not required on this thing. The landing speed is very very slow if you build it light and supply plenty of elevator. It will allow you to pitch the nose up with power on to control the descent and come in at a crawl. As for the OS91FX... that's what I'm using with a Jett Pipe. With the stock exhaust its tolerable but with the Jett Pipe it rocks! Lots of speed and long vertical up lines to a speck.

As for 70-80mph you're a bit low. Although I have never popped out the Radar Gun with a 12x8 its definitely cracking over 120mph. I know I know pitch x rpm... blah blah blah. But there are other forces at work here and we must not forget a non-airfoil prop would be terribly inefficient and the pitch x rpm ratio thingy would be darn close.

All that said expect performance with either powerplant. If I didn't have an OS laying around when I built mine I probably would have thrown a Jett in it. But I am anything but disappointed in the performance.

Robert

ser00

Thanks Robert,

That is encouraging. If I had both the Jett and the OS, I would put the Jett in without hesitation. If the plane will fly faster than 70-80 miles an hour, that is an added bonus. Could you please better define what you mean when you say that with the stock exhaust, it is tolerable. Are you talking from a speed perspective? I might be answering my own question here but I take it is easier to hit 13,000 rpms with the Jett muffler with an APC 12x8 than it is with the standard muffler? I really don't have an issue that this moment buying a Jett muffler for the SU-27. I am debating if I should buy one for the F-18. The only issue with the F-18 is that I am doing the F-18 as a Blue Angel (I know . . . not very original) and the red muffler kind of clashes. I am pleased to hear that it lands reasonable slow. Everybody at the air field says that I have a tendency to land kind of hot so I figure that landing the SU-27 and F-18 should be right up my alley. As always, thanks for your input.

Happy flying and soft landings!

Robert Strouse

ser00,

I'm not so sure the 13k on the powerbox is believable. But with the Jett pipe it the .91 really comes alive and winds up with some punch. On the stock muffler, the .91 is lethargic in comparison.

Although the landings, are slow the SU eats up some runway on takeoff. I flew it on the power robbing box originally and it flew well. But like you my mind kept screaming faster, faster and just had to get the pipe. I really didn't expect the increase I got since it wasn't a full length pipe. When the takeoffs became considerably shorter, uplines became considerably longer, and the overall speed increased that was an added bonus.

As for the F-18 I had a Cermark version in my hangar for a short while. And yes after the experience with the SU it got the pipe treatment as well. I say for a short while since it dug a trench in a rice field on the first day out. Long story short when the Blue Angels scheme gets below the horizon at any distance out you can't tell the difference between the vertical stabs and the wings. Its just a dark mass with things sticking out of it. Wouldn't have been a problem except I was hot dogging it low level around the field and it became unrecognizable coming around turn 2. Half a second later the rice field became a debris field.

Robert

bob27s

My Feedback: (19)

regarding your engine analysis above.....

OS91FX with jettstream and APC 12x8 about 12,700-13,000 ground peak rpm. Perfect setup in the SU-27.
There are a few flying like that, and they perform well.

Jett90L (Regular, not the LX) with APC 12x6 - somewhere over 14,000 peak ground rpm.

Either will take a 9lb SU-27 vertical with good authority.

Static thrust does not mean much. Do not dwell on it, we are not dealing with 3D or helicopters.
Also, with the tuned exhaust, flight rpm will be notibly higher than what you see on ground peak.





There is also a short video on here - a few years old but still a classic. [link]http://www.jettengineering.com/video/su27baker.wmv[/link] Click HERE
Might address some of your questions with regard to flight performance, landing speed, and such.

ser00

Hi everybody,

I wish to thank everybody for your patience and help with me on this. Robert, when you say pipe, you are talking about the Jett muffler, correct? Also, the 91FX does not use a Power Box muffler, it uses the muffler posted in the picture below. I think I better understand the issue with the mufflers. The Jett muffler will allow the OS91FX to hit higher rpms and rev up faster than the stock muffler. Therefore, the OS will produce more power(thrust) and produce it faster (hence shorter takeoffs). On a grass runway, how much distance is needed to take off? I like to use alot of runway (Don't like jerking the plane off the ground) so I do not think I will have a problem. Thanks for the video Bob. This is something I can show the little wife to help her understand my habit.

Happy flying and soft landings!

Robert Strouse

Ser00,

You can get the wife to understand it... You lucky dog! Anyhow I was referring to the Jett Muffler. I really can't comment on the grass since I fly off a crop duster paved runway. On that it still takes quite a bit of distance to lift off. I typically rotate at ~ 70ft.

Robert

theo63

well here is how she stands now seems like 4 ever building this thing but i am getting thru it

Steelie

My Feedback: (18)

theo63,
That plane is looking mighty good. Have you decided on your finish? Fiberglass w/ paint or iron on covering?

ser00

Hi Robert,

When it comes to my wife, I am very lucky. So you think 70ft is long before rotating? Sometimes I will let my P-51 run 200ft before rotation (it is somewhat difficult to try to keep it on the ground). Since you fly off a paved runway, I would imagine if I double the distance to 140ft, I should be safe to rotate the plane. Heck, I will probably push it out to 200ft to safe. Does the plane have any tendency to self rotate and come off the ground itself? I doubt it since everybody says that it needs alot of elevator. I saw a mod where a person increased the size of the elevator somewhat (not drastically). That might be worth looking into. I definately want to put a speed brake mod on the plane. I emailed Alex and he said my planes will ship out today [&o]. I was hoping to get them today. Oh well, something to look forward to on Monday .

Happy flying and soft landings!

theo63

steelie,thanks,i think i will be covering with iron on covering,i have never done a fiberglass job and this plan will be a chore i think doing it anyway ya go,i am not looking forward to it but once i start i think i will be okay

nchrome

serOO if you make the elevator fully funcunional this would give you the elevator that you are looking for A couple of the guys here have done that and I sure wish I did it on mine but I got what I got unless I order another one

ser00

Hi everybody,

I have a quick question in search of opinions. I get my SU-27s tomorrow. I was thinking about doing a mod that would convert the SU-27 to a SU-33/SU-27K/SU-35 (etc) with canards. I do not plan on making the camards functional (though I could by using a servo attached to a gyro along the pitch axis). Looking at the manual online, it seems that all I would need to do is replace the LEX with ones that have the correct shape and canard attached as one piece. I would then put some balsa on top of the canard and sand it to where the canard would have a flat-bottom airfoil. It might require cutting two pieces of sheeting to cover the LEX smoothly. My question to the great minds and modders is . . . how do you think this will affect the overall flight characteristics of the plane? Would it help or hinder overall takeoff and landing? The canard will have o° incidence. It would benefit the flying by providing additional lift (not much) but I do not know if it would cause any issues with airflow over the root of the wing during nose up slow flight such as when you are landing. Also, if anybody wishes to discuss the possibility of working canards with the help of a gyro, I will start it off. The canards would be attached together with a single rod and a high -torque servo would be attached to a horn on the rod. When the plane is sitting on the ground, the canards would have 0° incidence. As the nose is lifted, the gyro would active the servo, rotating the leading edge of the canards downword to maintain 0° (horizontal to the ground). So on takeoff or landing, the nose is high and the canards are parallel to the ground. This would help channel airflow over the wing better. If one allows the servo to move the canards full range of motion, you could fly high alpha with the canards flat, providing pitch control. I hope that is some food for thought.

Happy flying and soft landings!

jodini

My Feedback: (2)

Well, I think the canards would help. Definatly wouldn't hurt! You need full deflection on the elevator when landing this plane (4" up), so if you had something in the front to help pop the nose up it would be great. My only fear for you is this is already a nose heavy plane. You'll have to compensate with a lot of weight in the tail unless you ran the canards from a servo towards the back. Just something to think about.

I attached a picture of my SU-27 during the maiden...you can see the elevator pointing up about 45 degrees. I think canards would be really cool! Go for it!

ser00

Thanks Jodini,

If I did do the canards, they would initally be non-working, static only. The only weight added to the front is the additional balsa wood to increase the LEX size and the canards themselves. I have heard that the plane needs all the elevator it can get to take off and land. I think I will recut new elevator control surfaces and increase their overall size to give me for surface area. I believe I saw that mod earlier in this forum. When you say 4" up elevator, do you mean 4" total deflection (2" up and 2" down). It might be feasible to make the canards active without using the gyro to keep them @ 0° incidence, independant of pitch. Here is a new idea for everybody to think about. What if the servo controlling the canards mirror the elevator movement but at a greatly reduce deflection. When the elevator is deflected upwards, the canards rotate upwards and vice versa. Any opinions? This mod seems very feasible but I need the experience of modders out there to give their input.

Happy flying and soft landings!

jodini

My Feedback: (2)

4" in both directions!

I would think if the elevator would deflect up, you would want the front of the canards to deflect down...yes?

ser00

Hi Jodini,

If I am not mistaken, when the elevator deflects up, the leading edge of the canard rotates upward. This would cause the nose to be pushed upward. This would also make the loops tighter. But, the canard rotation / deflection would be very small though, as to not cause the plane to pitch rapidly and lose control. I am pleased to say that I now have my planes at home. Oh, the smell of burnt wood. Looking over the plans, the plane doesn't look 65 inches long. Also, the static canard modification would be easy to do using the original LEX part as a template to create the new part. If I have time tonight, I will make a test piece and post the picture.

Happy flying and soft landings!

ser00

I have another question for anybody. Does this kit come with the torque rods to attach the elevator and rudders to the plane?

Happy Flying and soft landings!

theo63

ser00,no you have to get them yourselve

ftjets

Has anyone tried full flying stabs yet? My kit is in the rafters waiting for free time so i can't picture how the mod would go on this one but i just put them on a scratch build F-14 with independant servos to program in ailevators. Can't see enough room for dual servos on this one but from your pics it looks like a single servo mod is feasable. It is time consuming and a bit of a pain to figure out but mine turned out pretty nice i think. That would have to solve any elevator issues. And, if someone would try it, by the time i get around to building mine they would have it all figured out.