OMP 47" PRO YAK at altitude

[tomatocan]

Anybody flying one of these at about 7000 feet of elevation. What engines are being used for solid 3d performance? Things are a lot different here, so most sea level recommendations don't really apply. I wanted to use a Saito 82, but am not really sure. Would like to go smaller if it would be sufficient. I'm coming from electrics, so I don't have much reference for glow engines at this elevation....and the other guys that fly around here don't fly 3d...with glow, anyway. I do know that the glow guys here run quite a bit more engine than the sea level guys....just for plain flyin! I'm guessing that power is down at least 15% here....maybe more.

Any help would be appreciated.

[rc4stroker]

I know you said that you were coming from electrics and were looking for a glow engine, but?
I converted to electric and like it.
Here the Edge version of the OMP 47" airplane.

[tomatocan]

I like it too....just getting tired of charging batteries for an 8 minute flight. Even with 10 battery packs, there is still a large amount of pre-planning and time required to fly for an hour and a half. I'm building a large version of my favorite indoor plane....the Clik. It will be a 50cc profile gasser, and I'm looking very forward to it. I would also like to have a smaller nitro 3d profile on hand as well. I fly electric indoor all winter, so the wide open spaces and the blue skies of summer seem more appropriate to me with something noisy. I love Colorado, but it sure isn't the best place to fly....given the lack of air volume and all.

[flygilmore]

Saito .82 would do very nicely-for the weight, it will be your best bet especially with 20%-30% Nitro. A Saito .91 would of course be heavier and have only a VERY slight power increase-many would not even notice it over the .82. IMHO, that is what I would choose. If going two stroke (which I love too) an OS .55AX, if you needed more, you could add a Macs header and MCP.

[tomatocan]

Thanks for the reply....what elevation are you flying at? I saw Virginia by your username......and I can't remember anything there over 1500' or so.

[mjws00]

It's tough to really make anything ballistic at altitude. Watch every gram. Run 30%. I'm kinda partial to the os 50sxh heli engine on slabs here. The .55AX is close. Saito .82 is about the only 4-stroke option that will keep the wing loading nice. A good MCP or a muffler that REALLY flows well is critical. Tried some of the 1/4 wave pipes, and an irvine, but they were really hard to 3d with as they just hit too hard. They did put a smile on my face for the vertical lines.

We're at '3700 here and it's bad enough. That said I have a reasonably light Fusion (~4.25 lbs), and it does well on 30% and the .50. A 50cc gasser will have to be well under 15# to be in the same ball park. My Edge is 14# 6oz and pulls strong but not mind blowing. Big Electrics have a huge advantage up high, but gas is just so convenient and cheap.

Good Luck, you have your work cut out. Read some of the threads by the guy from Mexico city that did XFC last year. He came up with some really interesting stuff.

Mike

[tomatocan]

Ya, the elevation is not too friendly on power. I'm not too worried about the gasser....weight is only going to be between 12 to 13 pounds dry with a DL-55. It should move alright. I just can't seem to find any thrust figures for the glow stuff. I noticed with the electrics that a larger diameter prop made a huge difference in the 3d performance....so I have been reluctant to use a 2 stroke. It just seemed like a 4 stroke would be better suited for the task....but maybe that's just a mental hurdle for me since I haven't tried either one. I was hoping to avoid 30% fuel, but that seems inevitable from what I have heard from everyone flying at this altitude....those engines are thirsty enough without adding more nitro. I have flown a few electrics with about a 1.5 to 1 thrust to weight ratio, and I definitely wasn't happy with them, so I would assume I'll feel the same about glow planes for 3d if they perform similarly. I don't know....maybe I'll just finish the gasser and keep a few electrics. I have given thought to a GP Reactor 1.60 with a BME 58. Should come in under 14 lbs, too.

[flygilmore]

I fly @ 2100ft. The Saito .82 w/ an APC 14x4W is crazy power on 30% in a 4-4.5lb profile

The DL50 I have also has all the power I'll ever need on my 17lb+ Yak

[katman]

	Quote: Originally Posted by tomatocan
	.........I noticed with the electrics that a larger diameter prop made a huge difference in the 3d performance....so I have been reluctant to use a 2 stroke............

So use a large diameter prop on a lighter 2-stroke. Whats the down side? On a .40 size plane how much of a diameter increase does running a 4-stroke net you? One inch? I guess it depends on what motor you are using. If you were to go from a .46AX to a .90 size 4-stroke i suppose there would be a big difference. I have never flown higher than 100 feet above sea level so I have no experience but I would try the .55. It has much more power over the .46. It seems like it would be better to sacrifice a little power (smaller prop on 2-stroke) to get a lower total weight than to add a heavier motor just to bump the power up (larger prop on 4-stroke). Somewhere, that power to weight/in relation to elevation curve has a peak and thats the motor you need.

Good luck. Glow goes