Acquired a Super Skybolt kit that is nearly finished. LUCKY ME!

One of the major things I have to do is decide on an engine. I have two possible candidates sitting on my bench. A Magnum 2 stroke 61 or an old, but very clean, OS 90 4 stroke (rear push rods circa late 80s).

Both engines are within the GP recomended size. My concern is with using this older OS that I ave zero experience with. Anyone have any comments? I would prefere to use the 4 stroke but just not sure.

Not looking to burn holes in the sky or do unlimited vertical. I was very lucky to buy this plane in the condition it is in and want to enjoy it in the air eventually. Basic to intermediate acrobatics.

Thanks,

GrumpE

The 90 will fly the plane and it will sound better. I'm sure there is someone you could ask for help with the four stroke, it's not hard. I finish my Skybolt and I installed a Saito 120.

It seems to me that an 80's vintage 90 4-stroke might be a little anemic for your Skybolt. Go with the .61.

I agree, the older model 4-stroker will probably be too weak. Ideally, I'd recommend a Saito 1.50, but if you have the .61 and don't want to get a new engine, go with what you got.

Pilgrim

That is pretty much what I was thinking. Basically wanted to bounce it off those more experienced.

Thanks a bunch.

I used the 120 because I read here on RCU that the plane comes out very tail heavy. SO instead of lead I installed power, the plane balanced perfectly

Now that is an approach I didn't think of. Extra displacement vs lead. Me likeee. [8D]

Ask MinnFlier

Who me???

I was just about to chime in...

The original engine in my GP Skybolt was an original OS 90 (Pre Surpass) and it flew the plane very well. It didn't have unlimited vertical, and you weren't going to burn the sky up, but it was still an excellent flying plane.

I had an OS 61 in a GP skybolt at one point in time. it was a dog. If I were you, Id find a way to get my hands on a 4cycle 1.20.

Chris

MinnFlyer,

Was it the rear cam OS FS-90? This was the engine that I acquired with the plane. It was mounted in an old lanier and the owner said he had intended to switch it to the Skybolt. It looks to be in great shape after I cleaned it up a little and freed up the lifters (old post here). Runs well and I wouldn't mind running it IF it will be enough engine.

Again not looking to rip the wings off and do 3D type stuff. I think the Skybolt is a really cool airframe and I really just want to fly basic arobatics with it. Eventually maybe I would change out to a 1.2 but for now the financial aspects of using what I have are appealing.

That said there is one going for around $150 on e-bay that looks to be in similar or slightly worse shape. I could sell it, switch my Magnum 61 with pitts muffler over to the skybolt (currently overpowring a GP P-51 ARF) and get a brand new 40-50size 2 stroke for my P-51 AND pocket some cash for my trouble and both planes might be happier.

Thoughts?

GrumpE

Grump, I'd go with the 4 stroke, it will fly fine. If you decide to go to the 120 it will be an easy switch.

Ditto, I flew my skybolt for several years with that engine (Yes, it's the same as the engine you have) before switching to a YS 91.

It will fly the plane very nicely.

Have GP Skybolt with Saito 150. Flies well; unlimited vertical. Only problem is prop clearance. Use 3 blade 14x 9 Master Airscrew prop. Balances perfectly with that setup. Weight of 150 and 120 is almost the same. If I started again, I would probably go with 120; nothing smaller.

Thanks for the opinions guys. Hedging toward the OS 90 I have. I am now more comfortable with the notion it will be enough. May change it out later. Who knows.

Hope to get it all together by the end of the summer. Will post a pic or two and let you know how the old OS does.

GrumpE

I had a heavy OS 120 surpass III in mine and still needed almost 1 pound of lead weight in nose.

Plane comes out to about 10lbs flying weight, so the 120 pulled it quite alright.

Bill

What about a os 91 or 1.08 two strokes any thoughts?

Thought about several options like this too.

BUT.

I have the old OS four and a basically new Magnum 61 2. Making the most of my hobby budget has pretty much made the OS 90 my choice. Should be a fine match for me for a while and then hopefully I can re-engine down the road.

Eric

I hate to brag.....but mine came in at under 9lbs.

With the 120 FS

Yup and it balanced out perfectly. I had to install the battery right on the CG

I don't understand the "tail-heavy issue" either.

With an old OS 90, I had the battery behind the servos. With the YS 91, I had to put the battery in the tail (Even before the smoke system was added)

Mike,

Speaking of the smoke system.................

How much did the added weight affect the plane. Have searched a little on RCU and it seems to be a mixed bag of feelings on it. Also have read it is easier (of course) to install before you are done with the airplane.

I know it looks cool. Would love to do it. Since you have done it I was wondering your thoughts on when to do it and which system you used. For matter of discussion the fuse is basically ready for final sanding. No electronics or engine equip (save fuel tank) is installed yet.

Eric

Eric,

First, I should mention that my Skybolt is over 10 yrs old, and as such, it has a few "Nicks and Dings" (Translation = It has so many holes, I don't know what's holding it together)

That in mind, The piece of sheeting under the nose (Between the Firewall and the Langing Gear) is missing, so I installed the pump there. It would be very easy (Especially since you haven't covered yet) to add a Hatch there for just that reason.

The Smoke Tank is located where the Fuel Tank should be, and the Fuel Tank is right behind it (In the radio compartment)

I am using a home-made system which ueses a windshield washer replacement pump [link=http://www.jcwhitney.com/webapp/wcs/stores/servlet/ProductDisplay?productId=1255&catalogId=10101&lang Id=-1&storeId=10101]available here for 10 bucks[/link]

It is basically the same pump as the TME system. You just need a 4 (or 5 or 6) cell battery pack, and a way to turn it on and off.

For that, I use a servo that hits a microswitch (Radio Shack, about 3 bucks)

Finally you need a check valve (LHS) and a flow regulator. The flow regulator can be a spare needle valve, or one of those air regulators from a fish tank, or you can even make one yourself by drilling a hole in a block of wood (for the oil line to go through) and tapping a screw to squeeze the oil line.