LSP972

My Feedback: (13)

Well, I'm about ready to finally assemble this ARF. Still no engine, but the Saito 1.00 is probably the best option for a new engine. Definitely going to fabricate a 1/8" extra firewall like Dean's photos show; I just hope the Saito 1.00 doesn't stick out too far.

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LSP972

My Feedback: (13)

Okay, got side-tracked with an H9 80" Cub; gotta assemble that one first.

But I just plowed through the length of this thread, made notes on the many suggestions, have firmly decided on a new Saito 100... its next.

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KaP2011

My Feedback: (17)

It ought to be an awesome flying plane with the Saito 1.00

deanz406

My Feedback: (28)

Hi- I think ur going to be surprised how fast ur Skybolt will be with a Saito 100. Some of the local guys fly with either a Saito .91 4 stroke, or the OS 91 4S. Both of them are pretty careful with takeoffs, as they can get a bit squirrely on takeoffs if ur not on the rudder, so make sure u have adequate airspeed before u lift off. I have 2 Skybolts, the old original kit built one, and the new GP Arf version. Both of mine are powered with OS 61SF long stroke motors, and fly beautifully. I bought the GP ARF at a swap shop 2 yrs ago, and the guy had an OS91 4S in it, and did precisely that- ground looped it on takeoff. Sent the motor thru the firewall, and the 1st 4 formers. There was no other damage anywhere else on the plane, wings, struts and everything else was perfect. I bought it for $100.00 with 4 new Futaba 3010 servos, and did some mods on it to make it with a lot more structural integrity. http://www.rcuniverse.com/forum/cras...-purchase.html
I will say that it is a beautiful flying plane, and is one of my favorites. Here are a couple pics of my 2. The yellow/black is the kit built. Let us know when u finish, and do the maiden-- Best of luck, Dean

KaP2011

My Feedback: (17)

It will be fast with the 1.00 but with the right prop I think it will be fine, I've seen them powered with 1.20 four strokes and dle 20cc's as well, overpowered of course but still great flyers. Dean, as far as your ground loop issue, did you check the alignment of the main gear? I've had a Saito 82 on mine and now an OS 91 4 stroke and have never had it to ground loop. I tend to get a little carried away when I set up and adjust an airplane and most times going as far as to align the main gear.

deanz406

My Feedback: (28)

KaP- I never had a ground loop issue- i only said that I bought the GP ARF Skybolt from a fellow who ground looped it, and damaged the front end. So far I have had no issues with both of mine, both handle well on the ground, fly superbly, and land with only a click or 2 of power. I did put a little tow in on the orig L/G, on both, and they are very smooth and straight on takeoffs and landings. On my OS 61SF's I'm using a 12/8 APC on the yellow one, and since the GP is a lot lighter, I put a 12/10 APC on it, and it hovers nicely. I'm not a 3D pilot, but I had one of our best 3D pilots in the club wring out the GP, after repairs. and he really put it thru the paces. He really did enjoy flying it, even though it's a lot smaller than most of the stuff he flies. Keep us posted on ur progress-- Dean

LSP972

My Feedback: (13)

Well, now I'm having second thoughts about that Saito. The best way to fit one, using a 90 degree angle exhaust header and a flex pipe (so I don't have to carve up the cowling to clear the standard muffler) would be fine... but those flex pipes just don't last, they start leaking, etc.

OTOH, a big two-stroke with a Pitts muffler would be a lot less hassle to deal with. I would truly love a new OS 61SF, back when those were wonderful engines. They have been long gone, unfortunately. I'm wondering if the current .65AX or .75AX are decent motors. Any body have much experience with either of those motors? I've used a Bisson Pitts muffler on an OS 46SF; those things are pretty much bullet-proof.

Another thing; in the heat/humidity here (south Louisiana), four strokes do better with 30% fuel; particularly Saitos. I've still got a case or two, but that stuff is over $30 a gallon now.

Anyway... I've got a bit before I'm ready to start on the 'Bolt, so I'm up for ideas.

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deanz406

My Feedback: (28)

LSP- Yep, ur right about exhaust & muffler issues if u want to put a pitts muffler for a 4 stroke on it. They are a bit pricey, and like u, I didn't want to chop up the cowl. The OS 65AX would work fine for this plane.
A couple specs for u about these engines. The OS 65AX is rated at 1.73HP(although Tower rates it at 2.0HP),has a power band of 2000-16,000RPM-- The OS 75AX is rated at 2.37HP with a power band of 2500-16,000RPM. Horsepower ratings will vary with prop selection. Now comes something else to look at- Prop selection- The 65AX recommends 12/6-7, 13/6-7, 14/6. I'm sure u can vary that with different pitch props. The OS 75AX recommends 14/6-7-8, 15/6-7. If u fly off grass, u may have to look at ground clearance with the bigger diameter props, as the L/G isn't real high.The prices for these are 209.00/65AX-- 229.00/75AX.
I liked the OS 61SF long stroke pattern motor for it's higher torque, and is rated at 1.9HP @ 16,000RPM. Now looking at that, it will be a little lower with prop. I did some bench testing on mine, and when I did the maiden on it, I started with an APC 12/7, and it turned 13,200RPM-- APC 12/8, 12,500RPM-- APC 12/10, 11,400RPM. All of them flew fine for sport, basic aerobatic flying, and the 12/10 really worked for the 3D that my buddy did. I fly off grass, and don't have any issues with ground clearance, but as noted I did put a little bigger rubber tire on it VS the foam tires that came with it.
Another motor that will work excellently is the OS 61FX, rated at 1.9HP @ 16,000. It runs beautifully with a 12/7-8 prop. If u look around, u should be able to find any one of these motors reasonably priced. If u can't find one, drop a line- I still have a few. If u go back and look at my crash writeup, I think I weighed my bare plane(No motor,elect, tank,servos,rcvr,batt) and the AUW was around 5 1/4 Lbs. I think when finished and RTF, it came in at 7 1/2 lbs. It doesn't take a lot of power to pull a 7 1/2# plane around. That all depends on how u want the plane to perform, and ur flying style.
I thought I might throw around a few specs that I looked up when I was doing the refurb on mine, and how I made my selections. Let us know how u will proceed, and what u decide to use- Good Luck, Dean

LSP972

My Feedback: (13)

Does anyone still MAKE Pitts mufflers for four strokes? I did a lot of looking on the internet, didn't find anything for a Saito 100; or an OS four stroke, for that matter.

Plus, I checked out an OS 95 four stroke a bit ago. If it had a muffler like on the original Surpass four bangers, it would fit nicely under the 'Bolt cowl. I have my old 91 Surpass on the H9 Katana model, and its muffler fits perfectly under the cowl. But now the OS four strokes are coming with mufflers very similar to the Saitos. I have been unable to find any straight stacks (bent the same angle as the original mufflers) these days. Those used to be available for Surpass engines (and Saitos), and would work fine for this set-up.

So now I'm confused. I would rather have a four banger, and I think the current OS 95 would be a perfect engine for the 'Bolt... its 13X7 or 13X8 suitable prop would still have enough ground clearance, and it will run fine on 15% fuel- which I have several cases of. But with those separate, larger mufflers... shucks, I just don't know. Still got plenty of time to figure it out, though. I'm doing some modifications to that H9 Cub; fitting a sixth servo, one for each elevator half, doing different pushrods... doing a different tail wheel set-up so the rudder doesn't get damaged if the tail gets slammed... and not real happy about how the engine is simply clamped to the motor mount. Not satisfied with that one at all.

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LSP972

My Feedback: (13)

Okay, after comparing some original part numbers to Tower's stuff, they actually have a 91 Surpass angled exhaust pipe and a straight 1.20 muffler. I THINK the threads are all the same and will therefore fit on the OS 95V. So I ordered that engine and the exhaust parts; if they all fit properly, that's a win. If not, and the supplied 95V muffler doesn't fit under the cowl, back to Plan B. The stuff should get here early next week, and I'll know one way or the other pretty quick.

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KaP2011

My Feedback: (17)

The 95v and the 91 both have the same thread pitch and size. Not sure about the 1.20, I've got all 3 engines if you want me to compare them.

LSP972

My Feedback: (13)

Okay, good info. That means the 91 Surpass muffler stack will screw into the exhaust port of the 95V. Two questions:

1. Does the 1.20 muffler have the same thread (female) as the male thread on the other end of the muffler stack? I seem to recall that it does, but the 1.20 has a larger exhaust port thread. IOW, the muffler stack of the 1.20 has a larger thread on the end that screws into the engine exhaust port than the end that the muffler screws into?

2. The exhaust port of the 95V… is it at the same place/angle as the one on the 91 Surpass?

If both answers are yes, then that engine is going to work perfectly on the GP 'Bolt in terms of location. Dunno if I would be that lucky...

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MormonMike

My Feedback: (2)

This is incredible !! ten years later and this thread is still going. Both my Skybolts are doing fine with hundreds of safe flights on them.

nmav8r

This is my second GP Sky Bolt. The first one was powered by a Magnum .91 four stroke more than enough power. Lost it when I forgot to extend my antenna remember those days? My new one is powered by a DLE 20 Most flying is done at 1/3 throttle can still do a respectable loop from level flight.

slopoke

My Feedback: (16)

Got disorentied last fall and lost mine. Was in a thicket and couldn't find it for three months. Got another one and it stopped receiving and went nose in on first flight. Now on my third one that still flies great. Magnum 91 FS.

A7Bldr

My Feedback: (40)

I went to order one from Tower and see that they are now Discontinued! I wonder when they did that?
I then checked Ebay and see that there are a few available there, still - at Full price. Managed to get one on order. This will be my 2nd, as I 'lost the first one in the sun'.
Jim

LSP972

My Feedback: (13)

I'm FINALLY getting ready to get started building mine. Been waiting weeks on a few things; first, what engine. I was going to go with the OS 95V, but the several older OS straight mufflers and bent pipes won't work on the 95V, because the thread diameter is a bit different… and the new type of muffler provided with that engine simply is not able to keep most of it from sticking out of the 'Bolt cowl. So I sent that back to Tower, and when they return the $300 bucks that thing costs to my account, I'll buy a .65 two-stroke and a Bisson Pitts muffler and be done with it. Yeah, four strokes are cool and all… but after 25 years of using four strokes, I'd rather stay simple with a regular two stroke and have less grief over the distance.

Another problem… Super SkyBolt kit I bought from Tower over a year ago, and just got around to opening it and checking it out; no manual, no decal set. I called Tower Service, one of those people told me they would send me those two things… and let it slip. I had to call that person back two weeks later, who admitted to the unplanned forgetting about the issue; she told me Tuesday morning that those two items have been found and mailed to me. So hopefully I'll see it in a couple more days and and can start planning the assembly.

Sounds like Tower is out of them now… and won't get any more. Understandable; they've been selling them for many years. All my parts seem to be in the box; I hope I didn't miss anything. I did buy another cowl and pair of wheel pants, but they are about out of them two.

My plan is to simply form another THICK (five ply hardwood) firewall, to attach it directly to the thin, cheap kit firewall. Several folks way back in this thread have covered that. I need a bit more nose weight, anyway, as I keep seeing that the two stroke .60+ engines are lighter enough than the four strokes to cause a balance problem when its all done. We'll see.

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deanz406

My Feedback: (28)

LSP- I know most guys like 4 stroker in a bipe, but, I think u will like the performance with the 65AX, and find that it is more than enough motor to do anything u want with the plane. When u start assembly, do urself a favor, and take a flashlight, and look up inside the frontal area around the firewall, and check the glue joints all around the firewall, and any support pieces attached(ie triangle stock). If u need to add anything, u should be able to get at it fairly easy before u put anything else in the fuselage. If u looked at my repair thread, u can see that i still had to add another 1/4" ply plate to the new 1/4" firewall to get the prop right where it had to be for proper cowl fit. I used an OS #913 alum motor mount and the OS 61SF mounting holes were exact on that mount. If u needed to add any nose weight, a suggestion would be to add it to the open pocket recess at the bottom of the fuse, and make a cover plate like i did on my repair. I don't think u will have a balance problem, after adding the extra ply to the front end, and there should be a minimum of difference between a 4 stroke W/ muffler, and a 65AX W/ a Pitts muffler. Let us know how ur model looks after u unbox it, and what u think of the overall construction. If u need anything in the way of suggestions, or ideas from us, please let us know, and we'll be glad to help. Keep us posted, and good luck. Sorry to hear of the discontinuance of this plane, it is definitely a WINNER. Thank God I bought an extra complete plane, as well as another set of wings and some other spare parts. Dean

nmav8r

I put triangle braces on the inside of the firewall. I'm powered with a DLE 20, balance was right on the money no weights needed. Added 2 clicks down elevator. Probably could got away with adding down thrust.

LSP972

My Feedback: (13)

You, bet, dean, I'll get back to you when I get started on it. Thanks for the info.

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LSP972

My Feedback: (13)

Dean, I thought I was out of the picture; the several new O.S. AX Chinese-made engines I've seen (both .55AX and .65AX) have been crap. So I figured I'd never find a good, NEW older O.S. Engine I wanted.

And then, I stumbled across a NEW, never run, still-in-the-original-box-and-with-everything O.S. 61SF. Talk about lucky. So now I'm back in business; hope to get started on the ARF kit next week.

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deanz406

My Feedback: (28)

Hey- Glad u found the OS 61SF- These are superb long stroke, pattern motors, and i assure u, that u will be amazed how well ur plane will perform. When u start unboxing, check each of the structure components(wing sections, rudder & stab assy), and make sure everything is up to snuff before u permanently epoxy things together. U can still get ur hands inside the fuse cavity, and add any extra support pieces before u start stuffing tank & other parts in there. Check all the glue joints on formers F1-F4 for proper glue, and add more if u find any lacking. If u feel the upper part of the forward fuselage(between canopy & firewall), and press on it lightly, u will see that will feel a little soft- that's because it is only a thin balsa sheet over a foam core. That's where i added the 3 hardwood stringers between the cockpit and the firewall, as u can see in my article. If u nose the plane in hard, or ground loop it, chances are u might "accordian" that frontal area.I was lucky that mine didn't get squashed, and that is why I didn't mind buying a wrecked one. If u mount ur motor sideways, everything will fit under the cowl nicely, and all u will have to do is cut a slot on the bottom of the cowl for ur pitts dual exhaust pipes to clear the cowl.
As u can see on mine, I didn't want to chop up the cowl with the motor installation, so the side mounted way worked best, and i added the fuel filler valves for fueling and exhaust pressure. BTW- if u can't find a Pitts muffler reasonably, drop me a pm- I have several, and can fix u up with one. Let us know what u think of the plane as ur unboxing all the components, and what u find that u like or dislike about the ARF version-- Dean

LSP972

My Feedback: (13)

I'm getting a new Pitts muffler with the engine. Not the Bisson, I recognize the other major brand but cannot recall the maker. Its the better of the two, IMO.

The first thing I'm going to do is make another complete firewall that will screw/glue right over the kit part. Probably three thickness hard plywood (NOT "lite ply"); I was going to make it from five ply for a four stroke, but IMO a good, smooth two stroke doesn't need as much to absorb vibration.

I've got some 3/32" square spruce wood that should be enough to firm up that balsa/foam area; I can get some thicker spruce if that's needed. Fortunately, we have a very well-supplied and complete hobby shop here; their wood supply alone is outstanding.

Once the engine gets here, I'll pretty much have everything else needed; six good Futaba 9252 digital servos (and a 9151 digital for rudder use if I think its needed), a brand new Futaba R6008HS eight channel 2.4 receiver, plenty of varied-length Futaba extension wires, two new EMS battery switch set-ups with battery charging/checking jack next to the switch. I also have a couple of really nice tail wheel units; may replace the kit tail wheel with one of them.

I will buy a new receiver battery; don't have any relatively new ones, no need in taking a chance on that. I just had Tony Stillman build me a new transmitter battery set for my Futaba 9Z. I've had two of them for 15 years, both the latest WC2 versions. I love them; and still think they are better radios than most of the higher-priced models selling these days. I have never had the slightest trouble with either of them. I do have a Futaba 12Z that I use on all the electric planes I have. I have since gotten a 2.4 module for the 9Z, but I still use it on the glow engine models. The wide bought the 12Z for me at Xmas some time back... important to her that she sees me use it still.

Anyway... looking forward to assembling this puppy.

What about the CG? I seem to recall that the two-stroke engines can make the plane tail-heavy if you're not careful placing everything... because they are lighter than four strokes in that size, of course. You have any problems there?

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deanz406

My Feedback: (28)

Hey- You have great electronics going in there, so u won't have any issues there. When i was replacing the firewall on my wrecked one, i used really good 5 ply- 1/4 " aircraft plywood to cut the firewall, and then had to add another 1/4 " X 2 1/2" block behind the aluminum motor mount and that pretty well made the cowl fit perfect, and prop washer location right on location. You can go back to my thread and look at the way my firewall came out. The muffler u have might be the Slimline product- they are excellent mufflers, and i try to snatch them up whenever i see them for sale. I still have had good luck with the Bisson units, so no complaints there.
The CG should be right on according to the instruction manual, so check it with their specs, and recommendation. I don't think u will have a "tail heavy" situation with the mods ur doing with the added wood, as mine came out pretty much perfect, with a little nose drop when i picked it up on the CG. You can always move some of ur electronics, and battery more forward if u do need a little more nose weight.
Let us know how all the parts look when u unbox. Please post some pics when u start. I am lucky enough to have another brand new one in the box. and I'm already seeing "Want Ads" for them. Dean

grh_70

I have a NIB GP Skybot ARF, which I am thinking about selling instead of converting it to electric. I am mentioning it here before listing the ad.
Asking $250 plus 1/2 the shipping from 91214. For more information please send me a PM.

GeneH