hi everyone im thinking of buying a kit SIG 1/4 Scale Spacewalker and putting a converted 38cc chainsaw engine with a 20 by 8 prop on it. ive read the sig 4 star 120 flys with a converted ryobi 31 cc engine easy and these two planes arnt that much diffrent are they, so im wondering what your thoughts are about what im thinking of doing. possable or impossable?

thanks for your input

brad burling
new zealand

Actually it's a great idea.

What engine does it recommend? I'm asking so we will know how much weight the airframe needs to balance.

I just put a 25cc Toro conversion on a 60 size Tiger moth biplane. It balanced perfect with no additional weight.

If the 38cc engine is to heavy you can shorten the nose. One inch means a lot.

The general rule is 1200 square inches for a gas conversion.

But the Space Walker is a slow flying plane that I believe could handle the weight.

By the way, you do know that 38cc engine is a real over kill.

Not that it matters any.

The 38cc engine would be a good match up for the larger, 1/3 scale Space Walker.

I have the Great Planes ARF 89" Spacewalker with a G26 converted to EI and lightened considerably. It balances perfect now but was quite nose heavy with the Zenoah all stock with mag. I removed about 1lb. and 2 oz. form the Zenoah when I converted it. The GP Spacewalker recommends a 120 size four stroke and with my Saito 91 it flew well but was tail heavy so I had to add nose weight. The plane now weighs 11.5 lbs. with the modified Zenoah and the engine makes 17.3 lbs of static thrust so it has no limits vertical. It will pull out of a hover which I know it can't maintain because it has no inboard ailerons but I just slow it down in vertical and when it starts torque rolling I punch the power and off it goes like a rocket. It flies just like the one in the RealFlight G3 sim. Kinda like a big Cub but more manuverable. Flies upside down as good as it does right side up. Just a very graceful, slow, fun bird. Relaxing to fly.

20x8 is a little big for a 38cc I would try a 18x8 or 18x10 on that engine.

Paul

sorry for the late reply, busy lifestyle at the moment

thanks for all your input fellas

i brought the sig 1/4 scale spacewalker 2 kit. would have prefured the sig 120 4star seeing this is my first kit build but well see how i go

it recomends a .90 to a 1.20 2 stroke ort a 1.2 to 1.6 4 stroke engine and has a wing area of 1110 sq. in.

like i said i have a 38cc engine i wanna stick in it. havent bench tested any props with a taco yet as the weilding quru hasnt finished my mounts. but ive read many a foroum and am thinking a prop size around 18 by 8 to a 20 by 8 would be some where good to start?

does everything sound sweet so far?

the engine weights almost the same as my brothers converted ryobie 31cc engine with out the mounts if this helps?

will the 38cc be to powerfull? is there any thing wrong with to much power?

im not looking at flying this model as a 'scale' plane but more of a 'sport' plane, at the moment anyway

also, and this may be in the wrong thread thingge but i have futaba s3003 servos, the booklet states to use servos with at least 60 oz./in of torque. will my servos cut it?

any other tips and tricks from the master out there

thanks for all your help

brad burling
converting and kit building vergin

and shocking spelling too!

Here is a quote from a guy here on RCU that you may be interested in.
"Saito 1.20 4s vs. G-23
By: Mike Cunningham - 1 Kit Tip Posted | 1 Product Rated
Posted: 10/12/02
I have had both engines installed in mine and the only real difference is that the landing speed is slightly higher with the G-23 due to the extra weight. It is a near crawl with the 1.20 though and is still fairly slow when carrying the extra weight of the gasser. The plane requires some lead in the tail to balance with the G-23. It is hard to say which is the better choice."

This was found on RCU by first looking for Spacewalker in the sell pages then following the link to the review section.

If your going to fly it as a sports plane then the S3003 will not do.

Try the Hitec 475. They should do nicely.

If you were just going to go out an float around and drive like, well like somebodys grandma then the S3003 would work.

The 38cc engine is going to be pretty heavy.m A Saito 125 only 28 ounces. Your looking at close to 3 pounds or 48 ounces.

Start off with the battery, servos and reciever in the tail section and shortining the noce by an inch or so.

thanks raiph for your help

im still getting a little used to searching for info on this web site, but im getting there

ive noticed you reply to a lot of peoples questions, i dont realy have a local culb of guys to learn of so the web site is helping me alot

just weighted me moto in at 1600 grams, 56 ounces and still have me mounts to go.

i see the g-23 is around the same weight and i had planed on having my servos and other electro gear as far back as possable to allow for the heavy nose

im dead keen on a gas engine. cant stand the glow engines. to tepramental for a young chap like me who has no paticance

havent looked over the plans to a major extent but will deffenatly look at making the frount end a couple inchs shorter

thanks for the low down on the servos. im not planning on flying it like granmar, maybe only on the first flight

The G-23 weighs in at more than I had thought.

General Specs:
- 1 cylinder
- Displacement: 1.400 cubic inches
- Bore: 1.300 (in.)
- Stroke In: 1.100 (in.)
- Shaft: 8 x 1.25mm
- High RPM: 9000
- 2.000 bhp @ 9000 RPM
- Weight (no muffler): 51.00 oz.


Ya know this projest just be a little more reasonable than I had first thought.

The G-23 only needed 6 ounces in the tail to balance.
Built with a heavier engine in mind you may not have to add any extra weight.
But the battery will have to go as far back as possible.

I do hope that you don't build as slow as I do.
It took me a year to build a Birdi Old Timer.
But it was truely a box of sticks, and the plans were not for a person who had not built before.
But you do have all winter.

Good Luck

Guys, like I said above, the G23 and G26 are virtually identical engines as far as weight goes and after I converted my G26 to Electronic Ignition it came up a little over ten oz. less. I cut off a bunch of other dead weight (The back of the crank is steel and is not needed - that is a lot of weight right there) and got nearly 8 more oz. off. I don't need any tail weight now and it fly's much like it does with a four stroke on it. Take the six oz off the tail and a pound off the nose and it makes a significant difference in the way she flys. The G26 is a lot stronger engine than the 23 and almost as strong as the G38. Mine has a better exhaust with slightly more compression and not that it makes any more power but it also has the EI. It turns an 18X6 9600 rpm's on a bad day and 9800 on a good one. Those numbers produce close to 18 lbs of static thrust and that is a ton on an 11.5 lb plane. The plane I am refering to is the one in my avitar. The only negative I see with the G38 is weight. It weighs more than the G26 by a fair amount and stock the G26 is already just a tad heavy for this plane unless you shorten the nose. The G38 may need some pruning to make it work out good.

ok just to make sure im converting a mac chainsaw 38 cc engine not a proper rc plane engine

the plans state to mount the engine with no down thrust and no side thrust but thats with a 120 os motor, as my engine is a converted do i have to allow any kind of thrust in any direction

fingers crossed it balances ok with out any weights as i can now see this plane might be a flying brick!

brad burling
new zealand

1100 sq, inches is a little on the small side, but only by 100sq.

Built right, so you don't have to add weight, it should be okay.

Landings MAY have to be a little fast, but flying should be a joy.

I have a 35cc engine on a plane that was designed around the old ST-2500.

Haven't flown it yet, but it balanced perfect with no additional weight,
I may of added 6 ounces to the tail, I'd have to look to be sure.

Anyway the Spacewalker is known for being an easy flier with great flying carateristics.

It should be a good flier.

thanks ralph

ill let ya know how im getting on along the ways

brad burling
new zealand

Hi Brad,

I built the Sig Spacewalker 2 (1/4 scale version), and power it with a stock zenoah G-38. The prop I use is an 18x6-10. I fly at 4100 ft, and this is a good combination. To accomodate the engine, I set the firewall back 1 inch. Additionally, I had to add a heck of a chunk of lead to the tail to get it to balance. The G-38 is not light. However, even with this added weight, she still flys very nicely. I typically fly at 1/2 to 3/4 throttle, and landing is fairly slow. The engine fits perfectly inside the cowl though I did have to put a hole in the side for the carb to protrude.

The 18x6x10 prop has good ground clearance.... I would be hesitant to use a larger prop, if you plop down a little hard on landing, the gear flexing could let the prop strike.

If I lived at a lower altitude, I would be tempeted to use the newer generation G-26 engine instead. Whenever I go to a meet that is close to sea level, I can see that the G-38 runs with so much more power. But on the other hand, if you already have a 38cc ready to use.... that is a bird in the hand. I would work on ways to lighten it as much as you can to reduce the amount of tail weight needed.

Hello Brad

Did you move the servos and battery to the tail of the plane?

Than usually makes a big difference in over all weight.

Also loosing the flywheel helps a lot also.

Just some ideas for Brad to concider.

Hi all. I converted chinese noname chainsaw 38 cc. I installed self made CDI and with LANYU wooden prop from UH it turns at 8100 rpm.

O-o-ps .. forgot to note: the prop is 18X10

hey ralph

sorry its been so long

yup im in the process now of installing me servos as far as possable in the tail

its still a long way from finished

its winter in new zealand and is dam cold in my shed so i dont get out there much

but ill keep you up date and how it looks

all so im using sig koverall as covering

ive never covered a plane befor

where is the best place to learn and ask questions about this topic on this web site

thank

brad burling
new zealand

It has been awhile.

As far as learning to cover on the web this is as good a place as any.

I think Coverite is about the easiest. I've never used the Sig covering.
But Sig does make some good stuff.

A friend showed me how to cover.
You will need an iron and a heat gun. Sig makes those too.

To bad you don't have a mate close to show you the ropes, and borrow his stuff.
It sure would make things easier. A beer or two while you watched him do it
really is the best way to do your first plane.

Good Luck