I'm trying to pick an engine for my new Imagine 50 beginner pattern ship. I'm just learning aerobatics at the sportsman level, and up until now I've only flown two-stroke engines. Would I be better off getting a .60 sized two-stroke for this plane, or is it worth the extra money to get an O.S. Max Surpass .70 II four-stroke? Will the four-stroke be harder to fly straight because of the extra torque?
The ARF is rated for a .46 to .60 sized two-stroke or a .54 to .70 sized four-stroke, so both options are within the recommended power range. Thanks in advance for the advice.
I think what you need to aim for is utter reliability across a wide range of power settings.
That has more to do with the individual engine than whether its a 2 or 4 cycle.
Many people are now choosing electric for the simple reason that its a more reliable and progressive form of power..if very expensive at the sort of 800W level of a decent 60 two stroke..
Just my opinion, but I would go for the four stroke. They use the extra torque (not really true) to swing larger props which are more efficient at producing thrust. Pattern requires very good vertical performance and parger diameter props help with that. They also help control down leg speed with their larger disc diameter.
Rather than the OS 70, I would go with a YS or Saito in the same size range. The OS is rather older technology so you pay the price with a little more weight for the power.
Why go so far overboard for a pattern plane? That really makes no sense especially for someone wanting to learn pattern. Besides, you probably couldn't fit the appropriate size prop and still have ground clearance.
Hi Ed, After having spent a major portion of my modeling years (60+ off and on ) listening to the beautiful sound of a 2C in full song I have gravitated to the soft (comparatively), mellifluous, more realistic sound of the 4C. :) If I were you I'd go for the Saito FA82a. It has the exact dimensions of the FA 72 but it's 8g lighter (not much) but markedly more powerful (1.2 vs.
1.6HP) I don't place any great importance on manufacturers HP ratings but the SAITO numbers are a good indication of the comparative power. While the OS61FX 2C would develop more HP (1.9) it would have to swing a smaller prop at 16,000 RPM to do so. For pattern the 4C is the only way to go. Good Luck -
Is there a successful pattern pilot at your field? Ask him.
If not, change fields. You'll need a successful pattern pilot to teach you how to fly, to help you un-learn all the bad habits the local "experts" have taught you.
The two two-stroke engines that I would consider are the Webra .50 GT and the Irvine .53. No tuned pipes, just mufflers.
The only four-strokes that I would consider would be the Saito .82a, if you can afford it and the OS FL-70 if dollars are a problem. Other four-stroke engines in this class are expensive or too heavy.
I have the Webra .50 GT and am looking to obtain an Irvine .53 with the old carburetor. Not that OS's carbs are bad, but the Irvine carb is reputed to be a jewel.
I also have the Saito .82a and the OS FL-70, but both are NIB, so I can't comment on how they run. From what I have read, they are superb.
Four-strokes are easy to run, but not so easy to tune for some folks. Those that find the tuning by hearing technique have successfully used a tachometer to dial in their four-strokes. Valve adjustments are a piece of cake and they are not all that critical. Just don't over tighten them.
The Webra and Irvine engines I suggested will run fine on 5% nitro fuel. The four-strokes can truly benefit from 15% to 20% nitro. However, the four-strokes burn less of the expensive juice, so it isn't really a problem.
I would stay away from the sixty two-strokes. They are heavy and not that powerful these days. Any more power/weight than necessary is a disadvantage in a pattern ship. You want an overall lightweight model that is true and adequately powered.
Good luck. Let us know what you do and how you fare.
The most important thing in pattern is a reliable engine. You must also be comfortable with how to operate the engine. Since you have been running 2-strokes for a long time, I would stay with them. Weight may be a consideration also. Both types of engines will work well if sized and propped properly. A lot of .90 sized engines are about the same size and weight as the .60s. You can always throttle back. Pattern is not fun if you don't have enough horses. You need to be able to make nice big graceful maneuvers.
What part of the world are you located? Definitely try to find some pattern guys to help you learn. A couple of days with some guys who know what they are doing is worth more than a summer's worth of practice on your own.
The older pattern planes would be a good start. Planes such as a .60 Kaos or Choas, the World Model Intruder, and the Daddy Rabbit would be good starter planes. The SPA guys fly them with OS. .91 Surpass's, but that is because their rules limit them to .61 two strokes or .91 four strokes. Of course the larger dispacement is stronger these days. If not flying SPA I would opt for a .75 or .90 sized two stroke, though they will make them nose heavy.
On second thought, I forgot that you were using a .50 sized plane. If using a two stroke engine on this I would consider the Supertigre .51 with pipe. Why? Because with the 98 Db rulling you will need to turn a large prop slowly and this is the best choice I can think of, the pipe of course would be tuned for lower speeds no more than 11,000 I would think. The pipe would help regain power you would have had at higher revs. You may also have to use a three bladed prop to keep prop noise down.
Fox always wanted to be different and he managed that successfully.
While I have some different Fox carb equipped Fox engines in my possession now, I haven't ran them yet.
My entire Fox carb experience was with the seventies era carb that had the cast in fuel nipple. I could make them run very well. How? I followed the instructions, which were completely backwards from conventional engines of the day. After filing a groove around the cast carb nipple and fitting it with its own lock washer, the only short coming of that carb was over come (spitting off the fuel line).
The Mk. X was supposed to be a conventional two needle design, but, alas, the execution was iffy.
I haven't used their airbleed (new version) as yet, but I am looking forward to trying it.
It is rumored that Duke had a dislike for R/C and favored C/L. I often wondered if this is why his carbs always seemed as though his heart wasn't in them. Just my speculation, mind you. Nothing from his lips.
When I spoke to him, he said that his engines were designed to rev up, not be lugged down. As a consequence, and from his lips, his carbs only worked well with lots of air flowing through them. The kind you get when you let her wind up.
So a Fox .50 which will turn a 11-6 in the upper 12's is a lower reving engine than a ST .51 which will turn the same prop in the low 12's? Or is my recollection wrong about the ST. Not the Fox because I am currently running one.
I have heard many others say the same thing about that carb. Duke was always out to save/make a buck. Most of the time it worked. But you had to follow the instructions, which, obviously, you did.
What I like about the Fox .50, and other Fox engines, is the distinctive snarl they make at the field. Even my old Eagle .60 crossflow engine was identifiable by its sound and how it lugged large props. This must be one of the few engines by Fox that I have owned that did not rev up real high, but it certainly did snarl. My old Eagle .60 wouldn't get above 10.5k rpm even with an 11x7 on it, but you couldn't slow it down substantially even with a
13x6. I now have acquired two more of these old long stroke sixties used.
Talk about forgetting things. I forgot that Tower sold a rebadged Fox .60 Eagle as their housebrand engine for a while in the Seventies. I saw a sample of this for sale on eBay last week or two ago.
Instructions? Never had any stinking instuctions! I can't see how the Mk-X works any differant than any other carb. Have an old Eagle I myself, but I seem to get more revs out of it than you. Over 12 K with an 11-7 prop, I think it was an APC and with 15% nitro. I like Perry carbs, I bought this one partly because it had a Perry carb. Never could get it to idle right. Bought a nearly worn out Fox .50 with a spare Mk. X carb. Tried the Fox carb on the Eagle I and it ran fine.
The Mark X was allegedly a clone of the Super Tigre carb, whether it was intentional or not is another matter. Clone in operating principle, not looks.
My old Fox Eagle was kind of like a combination of a four-stroke and a Diesel. It didn't rev real high, but when you pointed the nose up, it didn't slow down and sag out like many other two-strokes of the day. I used to do huge loops with my 7.5 lb. Kaos. It came out so heavy because it was my first attempt at a K&B Superpoxy finish. Plus I used Super Coverite on the wings. Talk about a tank.
I have often thought that even with all of the flights that my Eagle had on it, plus considerable bench time, it was nowhere near being broken-in when it met its demise. And I had to have at least a couple of hundred flights on it, plus two hours on the bench. Those two piston rings took a while to seat. I sent the remains back to Fox and he popped off the carb and head and put another engine under them.
The Tower .60 came with a Perry carb on it. I don't think they bothered rebadging the castings in those days. It said Fox on it, if I recall correctly.
I think your recollection may be a bit fuzzy. I ran a .51 with a Macs Quiet Pipe and APC 11X7 at around 13-14K (after it was broken in). It was as strong as just about any 60 out there.
I would never fault their designs. Their biggest downfall was back-woods machining! Even their instructions told you how to modify the needles to make the engines run right. After you did that, you found that the threads were so crude that it would never hold a constant setting.
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