I just bought an old sig skybolt and I was reading along but I find little info on the engine that would work on this plane good. I see that the GP uses up to a 120 since it is very tail heavy. Is the sig the same? I would like to keep the plane as light as possible but I rather put on a lager engine that plain lead.
With what engine would the plane balance with no added weight?

Thanks

A 1.20 would definitely be overkill for this aircraft.
I've had 2, the first with a 65 2 stroke, the second with a 91 4 stroke, pictures of bothare in mthe archive section of my website.
The 91 required me to move the firewall back from plans...
Both were well overpowered and torquerolled for ever.

So it is not as the GP skybolt.... nice to know...
Anybody else with some experience?

Well, I've got the kit, as yet un-started. Does that count?

The Sig is a bit smaller than the GP offering. It was designed around a 60 two stroke, and the cowl is a bit cramped for anything larger (such as a 91 four stroke). I want to put a four-banger in mine, and just may fabricate a Super SkyBolt cowl for it. The Sig is modeled after a regular SkyBolt, not the Super- which must have a larger engine.

I did some looking around. Here are my conclusions. I wouldn't like a .61FX because it is the same size as the .91FX so I rather have the 91. If going to 4 stroke I was thinking the Saito 100 since it is light and powerfull, and isn't much bigger than the 61 size we taked.
What do you think?
If going 2 stroke I would like some other engine other than the OS 91FX since I read so many problems with it I think it isn't a good choice. Any suggestions?

The Saito 100 is bigger than you think. I bought one expressly for the Skybolt, and sold it un-run to a pal when I realized some major surgery would be required to make it fit right. It is quite a bit taller than a comparable 61 two stroke. It is light, but IMO it is just a tad too much engine for this model. It needs a 14" or 15" prop, and aside from potential ground clearance problems, that large a prop would look a bit out of place, I think.

While poking around in the hobby shop the other day, I found a new-in-the-package Slimline Pitts muffler for a 61 FSR; one of which I just happen to have laying idle. So that's what I'll use, I think.

I've got plenty of time to ponder this; I just started a GP Super Aeromaster, and will finish it before I begin the Sig SkyBolt. And, as slowly as I build, that will be a while...

Thanks for the heads up. I also thought that the saito wasn't so big. Well I think that I will go with a 91 2 stroke then. It has the same size of a 61 and more power. I will have to find the correct engine for the model. I was thinking also the super tigre G90 I read a lot of good things about that engine, and non bad. Is it really that good?

I also have one of the SIG skybolts but have not built it yet but I did start the fusalage, how about a Saito 82, they are the same size as the 70 and about the same power as the saito 91.

It might be a good option but I will look into that one also. I was thinking of the super tigre due to the low price and the fact that all people that have it say that it is very reliable.

norbe, unless your model is over-built (i.e., heavy) power won't be a problem. The model will fly on a .46, so a .61 is plenty. The .91 two stroke, unless you just want unlimited vertical, etc., adds complications; you need a bigger tank, the engine is going to vibrate/stress the airframe more, etc. Plus, the almost-mandatory Pitts muffler will be larger; and you don't have much room in that cowl at all.

I don't like Super Tigres, but that is purely a personal observation. You do know they are made in China now? And I didn't like them when they were made in Italy, either...<G>

a340's suggestion of a Saito 82 might be the answer for a four stroke. I haven't seen one yet, but by all accounts it is a typical Saito (i.e., good) and should have plenty enough power. If I recall, the Saito 91 is a bit smaller than the OS .91 Surpass; so something that size should fit fine. For an idea of just how big the Saito 100 is, check out the photos, in the ARF forum, of the Pacific AeroWorks Edge 540 60 size ARF. It has a pretty big cowl- MUCH bigger than the SkyBolt- and still needs two holes cut in the side to clear the rocker arm covers.

On the subject of power, we tend to become spoiled by sport planes that have a power-to-weight ratio far above one. IOW, we think we NEED the ability to go straight up forever, leap off the runway in ten feet, etc.

The Sig SkyBolt hails from an earlier day of model design; it is intended to fly on its wings, not the engine. It may do well at the ever-popular 3F (Flip-Flop Flying) that seems to be all the rage these days, but consider this: it is a very complex kit, requiring many hours and much patience to build. Why risk all of that with gyrations and antics and attempts to emulate a helicopter??? Buy one of those electric foamie things or a profile fun-fly plane if you have the urge to flip-flop around, and save the SkyBolt for days you want to FLY...

Anyway, my point was that overpowering this particular model might cause more problems than it solves. Just my opinion; and I'll get off the soap box. Sorry...

Amen Brother! [8D]

"The .91 two stroke, unless you just want unlimited vertical, etc., adds complications; you need a bigger tank, the engine is going to vibrate/stress the airframe more, etc."

not to mention ground clearance for the 14" prop....

[:-]

Steve thanks very much for all the info. I was lead to buy a 91 since the engine has the same phisical dimensions of a 61 (at least in the OS case) I was looking also for a 4 stroke and since NOW I know that the Saito 100 is too big I will look into a 82. In planes as the Skybolt, where you need a heavy engine to balance your plane, I would rather have a bigger engine than plain lead. As for the ground clearence, I can always use a 3 bladed prop, that would look even better on that plane. I will see what to do. As for the super tigre I wasn't aware that now they are built in china, but what isn't nowdays. Everything is biult there.....

Thanks for all the tips I think I got myself a good picture of what I have to do.....

I have an Sig Skybolt with a Saito 80 with a Slimline Pitts muffler. Flys Great. Had a Saito 91 with the same muffler. Flys greater. Go with a four stroke 91 size. (I have a Hog Bipe with a Saito 100 and I would consider it overkill in the skybolt, but fun.)

Stan

My kit is for sale in the MarketPlace, if anyone is interested.

I'm going to larger airplanes...

Mine flew fine with an OS 61fsr. It weighed 6 lbs 13 oz's. It is a great flying plane. Mine is still going after 17 years. I did not use the plastic deck as it will crack after a little use. It is designed around some old building techniques, but it is a great flying plane.

turbo

I have a Supertigre 91 in mine with slimline pitts muffler. Ground clearance is not a problem with the prop, I think I run a 13-8. I got rid of the plastic turtle deck and used balsa formers balsa sheeting. Most of the time I use 3/4 power, full power on take offs and if you want vertical. I suggest building the version with two ailerons. Mine weighs just a shade of 7 1/2 pounds. Be careful of the balance as you build to avoid excess weight in the tail. I didn't need to add weight, but had to put the battery under the tank to make it balance right.

I first saw this plane fly a number of years ago by an "old timer" who used a Webra 90. A 61 two cycle or 91 4 stroke would probably be fine, I just liked the extra power.

I am looking at my 85% complete Sig Skybolt with a Saito 1.20 4 stroke sitting on the firewall and it looks HUGE .. so much so that I had to lay about 3 lbs across the tail to keep it from nosing over.. way too much engine for the size of the plane. My 1st thought was to get a Saito .82 4 stroke and I think it will be my next purchase. That being said I have a Saito 1.20 4 stroke for sale if anyone's interested.