RE: 50cc Sukhette Build Thread, now in progress!!
 

Roboto65 to me it soumds like you have to much up thrust. The trimming guide that fishdeth posted will help solve any questions you would have about getting your plane trimmed out properly.




Rich

RE: 50cc Sukhette Build Thread, now in progress!!
 

Yeah have to get the right tools but going to check it out for sure !!!!

RE: 50cc Sukhette Build Thread, now in progress!!
 

To me it sounds like your tailheavy with both of your simptoms happening at the same time. She will porpoise on you if she's tailheavy, but to check your up or down thrust you can just prop the tail up on the ground to were the plane sits level and then stand back and eyeball the prop to the cowl. With such large props its easy to see if the engine is pointing up or down. Look for it to be level and then you can check a few other things.

Start by flying straight and level and then pulling up to a 45 degree line, hold for a second and then roll inverted and let go of the sticks. If she holds the 45 then your on the borded line of tailheavy, if she climbs then your definitly over the line. I would suggest that you set up your cg as such that she falls slightly on that 45 degree line. This will make the sukhoi very user friendly while your getting use to her. It will come in for landings without the ballooning, and fly much more predictable in upright flight. Inverted will require a good bit of down to keep level but like i said for know just fly it that way and when your more relaxed and use to her you can slowly move the cg back for a more neutral feel on the sticks for precision flying.

Another test for cg would be to fly straight and level and then bank close to 90 degrees and use elevator alone (no rudder to hold the nose up) to carve a nice shallow turn. In precision flying with a slightly tailheavy setup you will notice that even at this step bank the nose dosent really drop and you can pull lightly on the elevator to carve the turn without losing altitude. Once again this is not what you want at first, but it is another way of checking if your cg is to far back for know.

If you do decide to use the trim charts thats out there just remember one thing, They are meant to be used in the order they were written in, If you decide to change something like the CG later on you will have to redo all of the settings that precided it. This will mean any programable mixes as well. Trimming for precision can be a long an tedious process but in the end I have found that it is truly worth all the effort. Well trimmed planes fly on rails and give you a feeling of being totally lock in and in control.

RE: 50cc Sukhette Build Thread, now in progress!!
 

To check up/down thrust angle follow this procedure. Do this a few mistakes high, not close to the ground.

Fly along in front of you at full throttle, with the plane trimmed for straight and level. Then carefully close the throttle quickly without touching any other control.

The plane should continue on in the same orientation for a while, eventually as speed bleeds off the nose will drop but initially there should be no change.

If the plane climbs when you close the throttle you need to add some up thrust, if it dives suddenly put a little down thrust in, then re-run the test.

If thrust angle is way out of whack for some reason it will make adjusting the CG more difficult, the two things interact so it's really important to have one correct before adjusting the other.

TF

RE: 50cc Sukhette Build Thread, now in progress!!
 

Well for balance which I neglected to tell everyone sorry is right on the front edge of the wingtube. Thanks for all the replys I love this bird just want to make sure I have her correct and not lose her because of MY mistake and not making sure she is set up correctly and she flys true and it is my Dumb thumbs not setup which would also be my fault !!!:D:D

RE: 50cc Sukhette Build Thread, now in progress!!
 

Prop question. I need to buy a new prop for my DL50 because of the bad landing I mentioned in an earlier post. BTW, thanks for the suggestions on the firewall. I've been running 22x8 props, but see people recommending 23x6 for 3D. What performance difference am I going to see with the bigger diameter prop?

Chuck

RE: 50cc Sukhette Build Thread, now in progress!!
 

I've never seen a 23-6, but I would expect it to be very slow with lots of pull at low speeds. Without actual testing though that's just a guess.

TF

RE: 50cc Sukhette Build Thread, now in progress!!
 

Should I have said 23x8? Sorry.

RE: 50cc Sukhette Build Thread, now in progress!!
 

Roboto its actually on the rear of the wing tube... It is a bit tail heavy, but still changes pitch slightly with throttle changes, so it needs another degree of down thrust as well as a bit more of right since we have some right rudder dialed in for trim.

RE: 50cc Sukhette Build Thread, now in progress!!
 

Gee this is getting interesting, Ok my plane, in a vertical climb tracks very straight and just keeps going up and up and up ok good, looks great too!!
Now fly along full power and pull throttle back to idle, plane slows and starts to dive, increase throttle and plane continues on the the trck it had at idle, still good
so why from quater throttle, power up to full and the model starts to climb. At half power it still climbs but slowly. put in one click of down trim and the model decends not badly only enough to be annoying because I have to correct just a bit all the time. Would someone be so kind as to tell me why????? and or is it just that I need a small amount of down thrust put in. I must add that the landings of this plane are very elevator sensitive could this be the same problem. my CofG is right in the middle of the wing tube.
Regards
Lee

RE: 50cc Sukhette Build Thread, now in progress!!
 

As with Roboto's bird sounds like you need a bit of down thrust.
The weather conditions (winds) were a bit subpar for the initial 3 flights we put on Roboto's bird when I finished assembly to know what thrust angles were correct.

RE: 50cc Sukhette Build Thread, now in progress!!
 

Greg, Thanks for the reply, could you tell me how much do you use, say one washer on the top two bolts???????? would this be ok
Regards
Lee

RE: 50cc Sukhette Build Thread, now in progress!!
 

I am running a 23x8 Mejzlik on mine at present but I do not think that it is the best 3D prop out due to it's slow spool up due to it's mass, however it is very good for IMAC. There is a lot more to a prop than just its diameter and pitch. A lighter prop such as the PT carbon fibre or the Vess props are often better for 3D since they have better spool up but are not necessary the best props for IMAC. I have a Vess 23A that I still want to try for playing around a bit.

Cheers
Pupmeister

RE: 50cc Sukhette Build Thread, now in progress!!
 

This is the understatement of the week! There is so much more to props than just the size.

Yesterday I did some testing of an engine on the bench, a TOC-53 with a canister on it. I was initially just testing the canister, but I figured what the heck, I'm here and have a bunch of different props, lets see how they each work.

I tried a Vess 22-a and a 22-B first, putting up impressive numbers of 7350 and 7150 respectively. I already knew these props were high revving, I flew my Extra this past weekend with the 22-B and found that it was just OK despiote the high RPM numbers.

Then I tried a few others. A TBM 22-8 put up 6750, while the Bunny 22-8 turned 7000 even. Finally I tried a 23-10 Mejzlik, which only allowed 6450 RPM.

I think that my preference would be a Bunny 22-10 on a lightweight plane, I like the way the plane jumps with that prop, but most people prefer a 22-8. Static RPM should be around 6600-6800 rpm with the TOC-53, that puts the power just under the torque peak so when it unloads power is right in the sweet spot.

I think the Vess props are way too small for this engine. I don't know what it is about them that allows the engine to turn higher rpm, but at this size they are not transferring enough of the engine's power into actual motion and theyt just kind of seem like they aren't going anywhere. I was flying a 22-B, I can guess that the 22-A would be even more so.

BTW spool-up on the Mejzlik 23-10 was indeed noticeably slower.

TF

RE: 50cc Sukhette Build Thread, now in progress!!
 

Thanks for those test results Tom !
Good info for future use.

Jim

RE: 50cc Sukhette Build Thread, now in progress!!
 

Ive got a DA50R with a Mejzlik 22x8 and canister muffler and get 6940 rpm, tried a 23x8 and did not like this as much, Have been working through the trimming chart from Scotland over the past 2 nights. Got in six flights and have the thrust worked out now and are trying to get the screw out of the loops and bunts, it does seem to take a while cos its only me trying to decide whats happening. I do recommend you try this, it is working just seems to take time. But then hey I like flying this baby!!!!
Lee

RE: 50cc Sukhette Build Thread, now in progress!!
 

[quote]ORIGINAL: rctom


The 22A vess is not the prop for this plane. Tried one on mine 7200 rpm but the plane had no get up and go.

RE: 50cc Sukhette Build Thread, now in progress!!
 

I have a fellow clubmember who accidentally purchased two Vess 23A props instead of one. He is asking if I want to buy one of them. Should I? I have the TOC 3MM 53 in mine. I am new to gas and welcome your feedback.

RE: 50cc Sukhette Build Thread, now in progress!!
 

Can anyone help me with this. I got my sukhoi form Tom friday, I will be useing the DA 50 engine, heres the question I have what size stand offs were used on the sukhoi su-26 when useing the da 50 for power. thanks Marcus

RE: 50cc Sukhette Build Thread, now in progress!!
 

As I said before I did not like the Vess 22-A or B, the 23-A is probably even more so. It kind of depends on whether you enjoy experimenting and are willing to buy the prop.

TF

RE: 50cc Sukhette Build Thread, now in progress!!
 

You will want 3" standoffs for the engine, then you can add a little behind it witrh wood shims/spacers to get it out where you like it.

TF

RE: 50cc Sukhette Build Thread, now in progress!!
 

Nitromarc3
If you go back through this thread there is a section just talking about the standoff lenghts I used this as a guide and it worked well for me, I think its back about page 20-25 I could be wrong, this was gone into in some length. I run the DA50 and I think I added about 15mm to them.
Lee
Ps I could check mine if your still not sure.

RE: 50cc Sukhette Build Thread, now in progress!!
 

Marcus

Harden the holes around the mounting with thin CA and use fender washers! See my post 990 on page 40 and Tom's/others replies.

Chuck

RE: 50cc Sukhette Build Thread, now in progress!!
 

6 months later...

whoopee finally done. here is the final product . Engine runs great and My battery Placement had the CG right on the center of the wing tube which had me pretty happy as I didn't have to mess with much at the field one click up and was flying true. Got really windy and didn't want to land in a cross wind with the wind sock straight out so called it a day after maiden. It's a little heavy at 17 3/4 lbs but vertical was fine at 3/4 throttle. hoping to get to the field sometime during the week if the wind kicks down so I can just get a better feel for the plane and work on breaking in the engine.

:D

RE: 50cc Sukhette Build Thread, now in progress!!
 

Very nice job Don! Great job personalizing it.