I'm picking up a Great Planes Ultimate Biplane .40 kit this week.
From everything I've read, the Ultimate really requires a bigger motor than a .46.
I'm looking at a Super Tigre .61 or GMS .61 for the motor.
Really leaning towards the Super Tigre, my LHS carries this motor and I will purchase
it from him vs online.
Any thoughts on either motor? Any other choices? Prefer to stay with a 2 stroke
and also "around" the $100 range for price.

Also, will the Super Tigre mount to the Biplane ok?
Are there any after market cowls anybody is using? I've read this is another weak point
on the GP Ultimate.

This is my third build.
I've built a 4 * 40 and a Somethin' Extra from Sig, but that was around 3 years ago.
Just got all the planes and gear back out after a 3 year hiatus.
We had gotten a new addition to our family back then and I didn't
have much time for the hobby, but I'm now back.
I enjoy building as much, if not more than flying.

Thanks for any help!
Don J

Dude , I put a O.S 50 ringed on mine unlimeted vert, And a bullet !!!

You also should consider a YS 63 four stroke. I have used it on .40 size bipes with much success. You use a large low pitch prop. Great vertical and it keeps the speed down.

Hi Don,

There isn't any reason you couldn't use the 61ST with careful throttle management, otherwise the sound of flutter will be immediately followed by a dull thud and cursing.

If I were going down this path, (I have 125A Saito in a CG 10/300 Ultimate), I would use Robart hinge points, 4/40 slop free linkages and balance with servos and battery before fixing anything, (including the motor), in place. I would try and stay away from adding weight to balance if at all possible.

Cheers,

Colin

Don J:
Congratulations for this new acquisition, Biplanes need more trust than monoplanes because of the drag, then you should use the biggest possible prop. Also you should end with a very light airframe to enjoy the ultimate capabilities thus you need to look for the most powered and lightness engine. I do believe that Super Tigre is not the lightest engine on the market even that it is very reliable. If you decide to stay with a 2 stroker you could take a look to the .75 size Tower Hobbies engine which is very powerful and I believe that is much lighter than the Super Tigre. Building this kit will take some time and maybe at the end of the building you will feel that your biplane could deserve something else, then you could think on get a Saito .82 which is the one that I would choose for this nice biplane.
Good luck.
Alfred.

I think it's illegal in most states to use anything but an OS 70 in that plane - or at least it should be!

But if you MUST go 2-stroke, look into the Magnum 52. It's relatively cheap and mine is a real powerhouse

Thanks for the replies.
Looks like the general consensus is to install a 4-stroke.
I will give it some thought, but due to cost, it will probably have to be a 2-stroke.
I will also start comparing engine weights. I do plan on using a Pitts muffler
or possibly a Macs. I see that the Super Tigre has an extremely heavy muffler.
I will probably work on the build and give more thought to engine selection.

Crash Campbell, reference the thud you speak of in your post, are you referring
that the Super Tigre is possibly too much for this plane? Possibly separating from the plane?
I'm looking for expert opinions, my only experience has been with .40 and .46 motors.

Thanks,
Don J

My first choice is the OS 70 four stroke but after trying the SK engines from Kangke any time I need A two stroke the SK is my go to engines. Can't say enough good things about them. Best thing I have found in the under A hundred bucks engines. I have the SK 90 in my 60 size aeromaster after yanking out the 68 MDS and it turned it into A complete new plane. They come with A good muffler but I have gone to the PITTS type.

Hi Don,

No I'm talking the thud you hear after the flutter induced by too much on the down-line with the ST61. It is a great motor but you need to exercise cautious throttle control. WFO on the up is fine but back off when descending. The beauty of STs is they will tolerate most after market mufflers. The stock unit is large and difficult to fit/hide in the cowl without much Dremel work.

Cheers,

Colin

Considering the significant weight of most .60-sized ball-bearing engines, you might want to consider the O.S. .65 LA. It actually out-turns the .61 FX on a lot of props, but it weighs about the same as a .46 AX. It will give you the power that you want without making the airframe impossible to balance.

I wouldn't worry about weight. I had an OS 70 Surpass in mine with no balance issues.

If you're thinking 4-stroke, but cost is an issue, here's a good little 70 for $129:

http://www.hobbypeople.net/gallery/210945.asp

Mike's right about that. A Magnum 4-stroke would be great. I had an old used .80 that performed flawlessly. Easily worth the extra $ over a 2-stroke.

-Scott

OK, now I'm seriously looking at 4 strokes.
Thanks for the link Mike!
I am not familiar at all with 4 strokes.
What are the advantages to the four stroke versus a 2 stroke?
I would guess more torque at lower RPM's ?

As you can probably tell, I want to over power this plane, or I should say, I want this plane
to have plenty of power with a little extra to spare.
I also do understand that there is a limit. I'm just trying to find that happy medium.

When I began this hobby around 2001, my impression of 4 strokes were
that they gave a more realistic sound to the plane and this was there primary
purpose.
I got away from the hobby in 2004, (new son) and am starting back up again.
Boy has alot changed!


Colin thanks for the heads up on the 61ST.
The first thing I would probably do is change the stock muffler out for a
Pitts or Mac.

My kit is scheduled to arrive on Friday and I can't wait to get started!
Time to start getting the bench ready.

Don J

The sound alone is a good reason to use 4-strokes, but as you said, you'll get more torque at lower RPM, plus they burn less fuel to do it.

They also don't leave slime all over your plane like a 2-stroke does.

There is a myth that they are more difficult to tune than a 2-stroke, but I have never seen it.

Just use 15% fuel and an OS "F" glow plug. That's about the only thing I can think of that you need to do differently.

Think of it this way: If you're building a dirt bike, use a 2-stroke. If you're building a harley, use a 4-stroke

To add to what Mike said, I personally think they are easier to start than 2 strokes. Once warm, mine will ordinarily start with one backflip. Definitely more fuel efficient and less oil residue.

I just got one of the Magnum 70's for a 40 size pitts for the $129 and it runs really good, I have a Mag 91 too and that one runs great. Magnums need a little more break in than a OS but a little extra break in time is well worth it for the price difference from the OS, and it seems to run just as strong as my OS 70fs I used too have (wish I never sold it DOH who knew I would need it again)

Dauntae

First he says OS is better than Saito, now he says Magnum is a "good little 70". Oh for the love of God!!! To think I used to like this guy, I may have to go back to my first impressions.

Let's see...

Mediocre performing 72 - $224.99

Great performing 70 - $209.99

Imitation of great performing 70 $129

It all adds up to me

Mike,
I'm down to the Magnum 70 for $129
or the Super Tiger 61 for $90.
Going to start the build tomorrow.
I'll concentrate on the motor next week.
Suppose to be raining her most of the weekend, perfect!
Thanks for the help!

Don J

Just a fair warning... Once you go 4-stroke, You'll never go back!

hands down, for $149.00 the OS55AX put you outa site!

I have a Saito 72 on mine. Plenty of power, and balances well. The OS 70 would certainly be good also. I really don't see why one would want more power. The Ultimate Bipe is a hoot to fly and a great airplane but it is not 3D capable. You won't be needing to blast out of hovers with the Ultimate.