greekmath

Hello all. I saw this thread and it interested me because I have been looking at the same issues of weight and power. My approach/issue was a bit different I think in that I was looking for the best 2 stroke versus 4 stroke to power my profiles which are multiplying faster than my budget for expensive 4 strokes!

I was interested in seeing if I could find a less expensive way to power my typical 48 inch span 5 pound profile planes than the superlative and superlatively expensive YS 63's and 70's I have been using.

I have done a lot of weighing and measuring and in the final analysis I can really only judge by the way the planes perform. In other words in spite of trying hard to document with stats and predict the outcomes it still boiled down to observation and personal experience.

These are my conclusions; if you can afford them nothing beats a great 4 stroke for profile planes. I have used Saito 72's 82's and ys 63 and the 63 is the clear winner on power. The Saitos are great but the difference is measurable in actual flight performance. The 82 is a great engine light weight and powerful but I would tell you the YS 63 has it beat no question.

Of the 2 cycles; I have had predictable results. Used a cheap magnum 52 XL and burned out the bearings with an APC 13x4W prop. Just too much prop for this engine. The Evo 60 NX spins that prop fine and performs well enough but no where near any of the 4 strokes. The tuned pipe option really doesn't fit here because more rpms are not needed, more torque is. Still in the correct application, a 40 sized plane the evo 60 is clearly far more powerful than the typical 40-46 and the Jett muffler puts it into the 16+K range with a 10x6.

The biggest difference in the 2 strokes is in vertical and throttle response. To hover my planes I need to keep the 2 cycle throttled up in the ¾ range and there is a slow spool up from there to pull out of the vertical with not much leeway for a mistake. Hence I save the low altitude hovers for the 4 strokes which have a much more positive and instantaneous throttle and vertical pull out response.

I have had great results with the OS 55 AX in my profiles and remarkably it comes close to the ys with the same prop in overall power, in flight performance. Its also very reliable has great throttle transition and is a fuel miser. Compared to the Evo 60nx it is a far better choice for a profile plane and one that rivals the 4 strokes in applicable performance at a much lower price. I realize the more sensible of you would have already figured out that 4 strokes are generally superior to 2 strokes in profile applications; still it was a fun experiment and in the future might save me some money. Really love the AX 55 as a reasonable substitute for the more expensive 4 strokes (which incidentally all weigh close to 18 ounces in this 70-80 displacement). I have some cheap Chinese 72’s and 80’s from ASP via Nitro On the bench they seem quite strong but are 4 ounces heavier than the engines above so I doubt I will put them in small profile ships!

I also have a new Rossi .57 which is supposedly designed for profiles so I will post on that result at some point when its warm again!