hello guys my question is would a thunder tiger 61 pro work well in the superskybolt arf? at this time its sitting in mytiger 60 which i call my airline planebecause of its size. this would be my first biplane. been flying my chapman 580 with a os 70 4 stroke and a couple hanger9 warbirds.,and a good old sig 4*with a thunder tiger46 which i really love to fly. thanks for the help keep flying.

A 61 2-stroke will be plenty for the Skybolt ARF

Funny you should ask.............

I just got back from flying a half hour ago... the first flights on my new Skybolt... with a brand new OS61 in the sucker...

A 60 size engine is excellent on that airplane. And that airplane is excellent with a 60 on it.

I was wondering about the engine size ever since reading some of the threads about the airplane. Eventhough the airplane built it's reputation as an outstanding airplane as a kit built 8.5 pounder with a 60 on it, there's a bunch who recommend bigger engines. After flying mine with it's 60, I got not the slightest idea why anyone would suggest needing more engine....

The airplane is a ball to fly with a 60.

Like I mentioned, the OS61 on my Skybolt was brandnew, just out of the box. The engine reads like an OS46AX on steroids. It is supposed to breakin the same way. Basically you run a couple of tanks through it on the ground while cycling the needle setting from a peak setting (to heat it up) to a rich setting (to cool it right back down). I did that, and it broke in just like my 46AXs have done. They seem ready to go after about 4 or 5 of those cycles, but I figure it's no problem to do what OS suggests, and it isn't.

The OS61 pulled like a bull with the 13X6 I had on it. The prop is a TopFlite wood. When I checked it for balance, it was already. I painted white and red strips on the tips and I got a feeling it's going to be a marriage made in heaven.

Only thing that wasn't perfect today was the wind and the sound level the Slimline Pitts muffler puts out. It's a tad bit loud. At what I paid for that muffler, I best get used to it. I'm running 10% fuel and got no complaints there. An IMAC airplane was up during my 3rd flight and the Skybolt blew by him like he was big and heavy..... hhmmmmm.... he was big and heavy....... whatever.......

My Skybolt came out at 7pounds ~4ounces, and with the OS61/pitts balanced right where the manual suggested.

Today was a bit too blustery to tell for sure, but the airplane actually felt a bit nose heavy. If she continues to handle like this when it's calm, I'm absolutely positive that I'll at least be moving the battery back from it's design location.

I was shooting touch and goes on the 2nd flight to try out different landing strategies and darned if I didn't forget about the way the wind was blustering. I was fat dumb and happy and trying to see how slow she'd go, and darned if the wind didn't quit. You know why they say you oughta always have some reserve speed on the airplane for windy landings? Momentum.... And all of a sudden, she didn't have any. And then all of a sudden she had a blast of headwind. Amazing little bird, she is..... And that engine ain't too shabby neither.......... Not even close to a close call..... no sweat...... only thing hurt was one of the guys. I think he pulled a muscle in his stomach or something from what I'm told was an AWESOME flinch..... She just sorta dipped when the wind stopped, and I swear she might have backed up in the almost immediate blast, and then flew on out............ excellent, excellent day at the field.....

oh..... gotta remember to dink with the lowspeed needle on the OS before the next takeoff. The transition is still stumbling from the factory safe rich lowspeed setting. It really was luck the engine didn't quit when I hit the throttle, after all, I think I bent the stick...

just like to take a min. out and thank all you guy for answering my question on the skybolt engine size. thank you

I know they all look alike, but they're all so cute, who can complain about another picture.


(AND if you look very closely at mine, you might just see something you'll probably not see on any of the others.)

Hello Darock. It looks like you put the control horn on top of the top wing. Was this intentional? By the way, I maidened my Skybolt earlier today. It has a Saito 125 on board. I never got much over half throttle and this plane will do anything I ask. After reading the threads regarding this plane, I could not wait to get it built. I was not disappointed. I highly recommend this plane to anyone looking for their first biplane. MinnFlyer thanks for the informative review.

You bet it was.

It's the easiest way to have the top aileron move exactly in sync with the lower aileron. The hardware provided by the ARF mfg, and the rigging it provides will result in the top aileron moving a different amount than the lower. It moves somewhat less going up, and even less going down when you use their hookup.

Truth is, the airplane flies great with the provided hardware. I figured my would fly "greater".

I originally used my concept on the little 40size Ultimate. A couple of them that I've seen fly with the "unequal" setup were supposed to be sensitive to tip stall. And you had to watch out to keep the speed up on landings or they might drop a wing. Mine does neither. Matter of fact, I've never had mine drop a wing yet and I'm flying the heck out of it. I frankly don't know why the wings are still on it. I figured it's worth the effort for any of them since it actually takes less effort to do it.

Big biplanes with 4 servos will have all 4 ailerons working in sync. I've seen instructions that emphasized that the builder needed to take care that all 4 ailerons moved exactly the same. I figured it didn't make sense to have my little ones work any other way. And I knew how to do that. I'm surprised nobody else has ever made any noise about it.

BTW, mine is sweet..... VERY sweet, and getting sweeter. I've yet to have her do anything other than follow my sticks exactly.

Will do snaps every direction like a whipcrack but is steady as a rock when you want. Jeez what a fun airplane. I was going to get a 60 or 90 size Ultimate, but decided I already got an Ultimate. Am I glad I got this Skybolt.

BTW, the OS61 is getting stronger and stronger. And the 13x6 still seems right for her.

Only problem is last time I flew her, our field maintenance got her. The field was recently plugged and after two flights, the underside of the stab was chopped up in two places. Fixing that checkerboard can be a pain. So after fixing those holes, I'll have to go to my "other" club to fly her until the plugs get gone. Of course, that ain't too bad a deal. I got a P40 with retracts that I have to fly at the other field, so I got two reasons to drive to the other field. Flew that P40 today. Dang they look nice doing knife edge passes. Sun going down behind my back..... clear blue sky getting darker blue..... BIG TEETH and growling engine and wings cocked up to get the last sunlight.....

Jeez, this stuff is fun....................

Hey Spanky,
What size prop is the Saito swinging? And how do you get it to clear?

Must be taking off on pavement? At H.park?

Easy Darock. After reading your descriptive message regarding the P-40 I got so excited I needed a cigarette. The Saito is turning a 15X8. I took off on pavement and grass. Obviously the pavement is not a problem, and the grass is trimmed close. I have about two inches clearance when the tail comes up. You are correct...it was at Hobby Park. What part of NC are you in?

Like I said in the review (or at least implied anyway) the original Skybolt was one of my all-time favorties, and it was my #1 favorite aerobatic Bipe.

The ARF flies every bit as good, and it's about two pounds lighter. What's not to like???

I LOVE IT!!!

BTW, this winter's plans include stepping it up to the YS91AC that I had in my original, and adding smoke

I'm flying off a mostly Fescue grass field. We cut it as short as possible but almost everything smaller than a 1.20 engined model winds up with props that are green on the tips.

The 13x6 on my Skybolt started it's service life with some white and red paint strips on the tips. They now show a hint of green.

I measured the clearance of the 13x6 on my cement garage floor and it's about 3". I figure any grass field (other than Bermuda) is going to be about 2" tall. I really can't figure out how anyone can prop much bigger than 15" diameter and hope to fly the Skybolt off grass.

Pavement... no worries.... but grass and a big engine in a Skybolt???????

Did my ARF mfg short me on the gear????

The sucker looks sorta like a Daschund anyway......

My Skybolt with a 1.20 swinging a 15 x 8 has not mowed our grass runway...yet. Still has a two inch clearence on a two point landing.

Some guy at the field has one with a Saito 125, it's insane... the guy flies it like a trainer tho [&o]

OK, people, take a look at the two pictures above. The one in post #15 by 150flyer shows the Skybolt ARF. The one in post #16 by joesabido shows a very different Skybolt.

The "different" Skybolt has polished metal gear that looks to be quite a bit longer than the Great Planes Skybolt ARF's gear. That 2nd Skybolt also has bent wire cabane struts that are soldered together, and the interplane struts do not have the ARF's screw connections.

We're obviously talking about two different airplanes when the topic is ground clearance.

It's usual to measure clearance for a taildragger with the fuselage parallel to the ground. When I measured my Skybolt ARF on the cement garage floor, it was parallel. Like it'd be in a two point landing.

Maybe a picture would easier to understand.

There you go. Note the tail wheel is 3 inches off the ground. I use a spring and piano wire set up on the landing gear to make sure the gear does not splay out in the event of a hard landing.

The included pictures show the clearance a 13x6 prop has when the GP Skybolt ARF is parallel to the ground as it would be when touching down in a 2point landing or as it would be after rotating on takeoff. Please note the stack of books that were used to "level" the airplane. I carefully selected each one in order to more accurately elevate the model and the level of this thread.

The steel right angle ruler was used to show that the prop was perpendicular. The measurement actually will err on the long side, since the ruler pressed into the carpet more than the tires of the airplane did.

As the pictures show, a 13" prop on the ARF Skybolt would have about 2 1/4" clearance. A 15" prop would have about 1 1/4" clearance. Those distances would be accurate off paved runways and would suggest how your prop would clear relative to the depth of the grass on your field.

We've been discussing the Skybolt prop clearance. Obviously there are a few details that affect clearance. The landing gear is certainly one of those details. Look closely at your gear and the gear in the pictures of an unaltered ARF. I've seen 4 of the ARFs so far and every one of them sported the gear as shown in the pictures of the unaltered ARF.

It's clear that you fitted your landing gear with spring/piano wire, but it also looks very much like either you bent it as well, or your ARF came with taller gear. No wonder there is confusion over the clearance.

Thanks for your picture. It fills in the details about your advice. BTW, your first picture of that Skybolt in the grass seems to show a Skybolt with wheel pants and the stock gear legs. Your last picture shows the modified gear without the pants.

I wish one of us had had the time to include pictures early on in this thread and it would have been a shorter, better thread.

Folks,
We need to take the advice on prop lengths with a grain of salt. There are a number of details that should be noted beyond just their prop size.

It really appears that the ARF comes with shorter gear than the BIY kit aircraft comes with. And when someone suggests they're using a longer prop, it'd be worth asking if they're using the stock gear with the stock wheels.

Engine size dictates prop size. Prop size affects prop clearance. Prop clearance can be increased by bending your stock gear taller or retrofitting longer gear or using something that will pull the gear legs in or using larger wheels.

There is a BIY Skybolt. It appears to come with taller gear than the ARF. The ARF appears to come with gear that when unmodified will only give a 13" prop about 2 1/2" clearance to pavement.

When considering the engine size for your Skybolt, it'd be sensible to ask yourself, "How deep is the grass at the field?" and "do I want to rebuild the gear?"

It can all be made to work with very little effort. The gear as shown with the plane in the grass and the plane on the carpet have been in the same configuration since day one. The wheel pants were removed since the first picture to repair some cracks that developed from always landing on grass. I do have three inch wheels from the normal 2 3/4 inch that come with the ARF.

Good deal, we now have two pictures that illustrate why little details make or break advice.

The attached picture shows a Skybolt that's completely stock, right out of the ARF box. It's been jacked up in the rear so that the prop is square to the floor. It's got the suggested propeller on it for one of the suggested engines. The prop is a 13" prop and the engine is an OS61 and the spinner is the one that came in the ARF box. (Pay no attention to the person behind the curtain holding the tape measure.)

One magazine always reports a special measurement when they do ARF reviews. They report the prop shaft to floor distance. That gives readers a feel for how big a prop the airplane can swing without cutting grass or chipping off on the pavement. If you look at the attached picture the tape shows that measurement would be just a bit over 8-1/2" for that ARF as it was assembled with the components that came in it's box. If you look, you can also see the angle of the unmodified stock gear legs as they come from the mfg. Keep in mind that gear flexes on landings and usually flexes a bit less on takeoffs, depending on how bumpy the runway is.

That setup gives that prop about 2" of clearance to a tile floor.

I've got a couple of airplanes with that prop clearance over the pavement runway at one field. When I fly them at the grass field, they start to turn green. The last few days, they've also been turning the color of red clay. They've been shattering dirt plugs that're scattered around in the grassless places that're all over that field. You always need to take your flying conditions into consideration when deciding on prop clearance. And a LOT of other small details.

Hope all the pictures and discussion have covered most of the important details and this was helpful.....

So how simple is it?

If you already have the airplane, you just slap on the bigger prop and go cut grass or not.

But if you haven't bought the airplane yet and you're looking for info on what size engine can be slapped into the ARF Skybolt you can't slap on the prop and tip up the tail and look. But now you got enough info to figure what'd work with the stock parts that come with that ARF.

(If you had figured you'd make any diameter prop work, you also have the info now on how much modifying you might need to do.)