O.K. Everyone,

I'm building a Twin Otter from plans. The plane was designed for twin speed 480's or .10. I have since decided to go the glow route, and I need some advice. I found some AP engines this past weekend, but I know nothing about them. They were appealing to me as an option because of their relatively compact size and the muffler that rotates which would make fit in the nacelles cleaner etc.

Questions: Can someone tell me about the .15 Yellow Jacket and the .09 Hornet? Would two of them haul around a 3.5 - 4.0 pound twin? How reliable are they?

Should I just go the O.S. .10 route? Would hate to do that cause of the size of the mufflers and don't want blue engines sticking out.

All opinions appreciated. I'm at the point where I need to go ahead and get the engines so that I can make final design mods on the nacelles.

Thanks guys,
John

I would opt for 2 novel .074 engines. Plenty of power and lighter than an os 10. Just a thought. Mike

Mike,
I know there are a lot of opinions out there, but how about reliability of the Norvel's? I thought I read something somewhere about break in and problems.......

Enough with all this Norvel talk...

Just get two Cox .15 Tee Dee's they'll fit nice and clean in the nacelles and it will be almost as loud as the real thing when you get both of those fired up.

No unsightly mufflers to worry about, and you can save weight by cutting out that silly throttle servo.

FULL BLAST ALL THE WAY!!!!!!!!!



that just what I'd do....


-theprole-

I have never had a problem with any norvel engine, I have 5 of them. I break them in as the instuctions say..ie pour motor oil in the cylinder and let stand over night. I then run a few tanks of fuel through them on the ground, then I fly them. Mike

Mike,

I went to the Norvel site. The weight savings is impressive. The website was not clear....Do the mufflers come with the engine, or must they be purchased seperately? Also, could this engine still perform with a three blade prop efficiently assuming I could find some?

Thanks, Anyone else wanna chime in? I'm interested in hearing other opinions.

Yes mufflers come with Norvels, I thought 3 bladed props were less efficient,, someone on here said the AP was the same engine as the Norvel,I dont know but if you like that muffler design go with it,

nothing wrong with ap 15 or 09. had the 15 in a h.o.b. .20 size mustang, it cowled great! ran an 8-3 on it. a freind had the 09, it ran well, but 15 was about the same size/weight. I fly a lot of norvels myself, but from a scale standpoint the ap's are easier to hide with the rear mounted mufflers. I have had really good luck with the phasor motor by hobby lobby, it performs great in my zephyr on a 6-cell car pack. I am mainly a glow guy, but for a scale twin I would go with that! A caribou or twin otter w/ two of those would have plenty power, and be reliable. Hope this helps, wildfred.

Norvel is the only way to go, .074 to be exact.

No problem with break in, if engine is tight, use a heat gun to warm her up and she will then turn easy to start. Break in as normal for a non-ringed engine. Reliability, longevity, and fuel economy are superior with Norvel engines.

Well, you say it's meant for Sp480's, that can mean a lot. I am not familiar with the airplane you are talking about, but the motor recommendation I'd give would change a lot depending on whether it was meant to be flown direct drive or geared.

On direct drive, you'd spin a 5-5" prop and maybe 7 or 8 cells. If it was geared to maybe 3:1, we are talking about and 8-5 or so and carry the weight of 8 to 10 cells. Big difference in airplanes and how they would fly!

Dave

Dave,

You are right, sorry I left out this information:

Specs are as follows:
Wingspan 65"
Length 50"
Weight 3.5 - 4.5 lbs. - I assume as an electric
Wing area 455 sq. in.
Wing Loading 17.7 - 22.8 oz./sqft. - Again assume as electric

The designer used Speed 480's with Master Airscrew 10 x 6 electric props. He also used 2.5:1 gear boxes. Now can you offer a suggestion.....

Anybody else out there got an opinion?

I think you'll find the .074's a bit light on power, a .10 doesn't give enough power to compensate for the weight, so I'd go with .15's.

I vote for Norvel .15's. They are going to be pretty darn fast, but you're talking about a big airplane. Can't beat them for power to weight ratio though!

Dave

Decision Time,

From everyone I have talked with here and back channel, the decision is down to Norvel. Now I just have to decide between the .074 and the .15.

Weight is the key factor from two perspectives: first the weight of the engines...ie thrust to weight ratio, and second the weight of the model as I have built it (not too heavy I hope). All things considered, I think I would be fine with the .15's since the thrust they generate should adequately compensate for their weight and my ability (or lack of ) to build lite. HOWEVER, the .074's would fit much better and in all likelyhood be fine.

Thanks to everyone who has offered their advice and/or opinion in this thread and back channel. I really do appreciate it. I will let everyone know how it turns out.

John

The AP 15 engines are great and what is more, at US$50 they are a great buy. I have been using an AP15 for the last coupkle of years in a MAN Chips by Randy Randolph and it hauls that around a treat. These are schneurle ported, ball bearinged engines!

I have a couple of yellowjackets (.15). They perform reasonably well and are smaller, lighter, and easier to conceal than the OS or the norvel .15s. I love the .061 and .074 norvels they weigh so little and perform so well. For more scale like props and spirited performance I'd go with the AP on that plane.