obriendigital

My Feedback: (13)

I just finished up the Ultimate with an SV 26cc from Troy Built Models. I am running an 18x6 Vess prop and it doesn't have much power, the tail drops a bit. Try a different prop or is a 26cc just to much? Maybe I need to work on the motor a bit more.

cmoulder

Should be plenty of engine. Follow break-in procedure and tuned properly?

Is it tail-heavy? Even if it is underpowered it should still fly at the proper pitch attitude if the CG is correct.

CAT POwer

My Feedback: (61)

OBRIENDIGITAL, What are your RPM's with the 18x6 Vess ?

busted blade

I doubt that it is tail heavy with a 26cc gasser in the nose.

I had a Saito 125 on my previous one and mounted the receiver pack up in the hatch. CG was 13-14cm with that setup.

I also tried an SPE 26cc and didnt much like the power it made, It also was a tad overweight (around 12.5-13 lbs if I remember right) and didnt feel too good in the air. It felt like a brick in my opinion. Needless to say the gasser didnt stay on there very long.

I wonder if a 16x8 prop on that 26cc would help you out any?? I think the 18" prop might be a bit too much for decent rpm. just a guess though..

The thing about this airplane is it is built like a tank and is a little on the heavy side, even before you load it down with radio equipment and engine.

obriendigital

My Feedback: (13)

Yes, I broke it in exactly to the manual and am just about ready to switch the oil mix, I am wondering if that will help. It seems the CG is pretty darn close, but the tail just drops every once and awhile. I will maybe move that batteries forward for a flight or 2 and see how that helps. I was pulling pretty good RPM with the vess, I will tach it again tomorrow and post it here. I am going to try a 17x6 and maybe a 16x6 vess prop too, thanks for the comments on this. I will keep everyone posted here.

cmoulder

This part I don't understand... What are the conditions under which it drops?

If the plane is tail-heavy, it will fly with what looks like nice pitch with some down elevator trim, but the tail will drop when you slow down. Is this what is happening?

When flying inverted, how much elevator push is required?

Difficult to explain without more information![sm=confused.gif]

obriendigital

My Feedback: (13)

Bob,

You could be right, when i slow down it does drop a bit. I am changing the prop and switching the oil and will retune. We will see how that goes... I will post a video of the flight so maybe that will help too.

Thanks!

cmoulder

If it climbs when inverted, it really is tailheavy. Sounds improbable that it is tailheavy with a 26cc gasser, but it is what it is. This is rather a heavy plane... feels heavy even with my OS 1.20 4-stroke, but it seems to handle a little breeze very nicely and still is a very agreeable plane to land.

As for oil, you can break in and stay with Pennzoil Air-Cooled 2-stroke 32:1 for the life of the engine and save a lot of hassles, and get a noticeable power increase compared to synthetics. I would not have believed this had I not seen it on my DA50 and DL50.

goph

cmoulder
hi there i have the same engine as yours would like to know what prop you are runnng , i've got a 14-10 on it it fluy realy good but dosent have a real good vertical pull .

i had the tail droping when i droped of speed. when i had the wheel pants removed for repair.
the balance was good. i have just refitted the wheel pants and it has come good in flight.
i think they created a drag and keep it balaced in the air?

cmoulder

Hi goph:

I am also running a 14x10 and I agree that the vertical is far from spectacular, but perhaps more "scale-like".

Mine has only 3 flights on it and I haven't had a chance to fly more because I am away from home for work, returning the middle of next week. I plan to also try 15x8 and 15x7 props, which may be better for this model. Being a biplane, it is of course noticeably more draggy than a monoplane, so the lower pitched props MIGHT work better, though only actual trial-and-error will tell.

The tail doesn't drop on mine as you have described. My CG is at 13.5cm (from leading edge of top wing at the center), if that is of any help.

mudboger07

Iknow this is an old thread but for the people running a st90 in the plane were are they finding the best c/g between 12.5 and 15 cm?

Night Scream

Hi everyone:

I just got this plane and got it around 60% build.

I'll be running it with a Saito 150 in the nose..

Question I got though.. If anyone is using this same engine where are you setting up your CG [cause from the manual it says 12.5 to 15 cm] which I find extremely short.

But reading here I see ppl using the 12cm or 13 cm mark using saito 120 or similar..

Is that the correct range in cg for this plane?

Thank you

jimmymac52

My Feedback: (4)

Night Scream,
Check your other post on this subject, I and another person replied to you. But to summarize, I think you may have confused (cm) for (mm). 12.5 to 15 cm is correct. Mine is at 13.5 cm which is about 5-3/8 inch from the leading edge of the top wing measured at the middle rib over the fuse. Try that and I think you will find it close. I hope this helps.

eclipse3g

My Feedback: (5)

Mine CG is in the same place - the plane is flying beautifully with saito 125 and 15x8 APS. Tried 16x6 xoar - bad performance - not enough speed

captinjohn

where are the photos ????????

TimJohansen

Hello!
I am currently putting this kit together. I have an O.S. 120 engine. I am curious if the 140 mm dimension pertaining to the engine location needs to be modified due to the weight of the engine. Any other building tips available as well? Thank you for your time and knowledge👍