unclecrash

How big a prop can an AP .09 handle.

KidEpoxy

are you talking regular,
or by adding shims and dropping the nitro to make it Texaco'y ?

unclecrash

Its a stock AP.09 on 15% nitro.

foresterxt

My Feedback: (35)

I run an APC 7x4 on mine. Turns it just fine. I've also tried a MAS 8x3 which also worked well but I can't remember the RPM numbers.

Mr. Mugen

How much does this .09 weigh? I can't find it anywhere.

unclecrash

I just pulled the prop off it and checked to see the size. But i culdn't see it. []I had to get the magnifer out its an 8x4. It will hold it in a hover in my hand at full throttle. I think its heating up too much with the tight cowl on it. Then I found a 7X4 and it rrr's up nice but can't hold it up in a hover in my hand. I think I will try the 8x4 on maiden set a little rich.

unclecrash

Wondering whats the best glow plug to run in it.

JohnAV8R

I do not have an AP, but run Cox .09's , APC 7x4; 10% gives 16K rpm using a glow head adapter.
Using the Cox plugs will add 500 to 1000 rpm.
Running rich with an 8 x4 works well with a glider type model.
The Cox .09 is doing well in a small 300 sq in Wild Thing, full size radio gear, 30 oz.
In fact, the Cox does as well as an MVVS 2cc (.12) in a similar plane which is much heavier.

MJD

My Feedback: (1)

IMHO:

I am not surprised it is heating up with the 8-4, 2-stroke + large load = lotsa heat. For the hovering more disc area is always better, but for an .09 you need to lower the pitch. 8-4 is what I deem maximum load for a .15 (well, unless you want a fraction of it's potential performance). For the .09, and if you need 8" diameter, then try an 8-3. You might also try a 7-3 and let it spin up a bit more with finer pitch, you will be producing a bit more horsepower and should also see increased thrust at low airspeeds, including static.

I doubt a 7-4 will ever be your choice for hovering type flying. For small engines it is a "cruise" prop versus a "climb" prop in full scale lingo. With .09's to .15's, 3"-4" pitch is the "normal" sport flying range. 7-5 and 7-6 are also sometimes used on a .15, but those are only appropriate for small, clean and thus faster aircraft. You gotta let these little guys spin up. 13-14k is low rpm for small engines. It's okay for a lot of sport applications, but for hovering you want lots of pull at low speed, and lots of power from the engine - so I would prop it for at least 16k with finer pitch.

Does anyone know where the hp peak is on this engine?

MJD

unclecrash

Thanks MJD That was my thought on the prop was a bit much. The only 2 I had to try 8x4 and 7x4. I didn't get to try the 7x4. I believe It is supose to spool up 16.000rpm not sure though. I doubt it will ever see it.

MJD

My Feedback: (1)

Do you mean the 7-4 should turn 16k, or the engine is "rated" for that like they do in ads and instructions etc.? The mfg lists top rpm as 18,000, a figure which I take with only partial seriousness, although in general there is no reason to run it higher I think. I doubt it is set up for peak power above that, my guess is 17-18k. But it won't turn a 7-4 there of course. I believe it might hit 13k or so with that prop from the data I've found in a quick Google. I dunno if this is practical for where you hail from, but I'd at least test run it on a 7-3 and see where it turns and how the static thrust feels to you in relation to your other prop choices.

I found this:

"Measured performance using 10-percent nitro fuel:

Propeller Rpm

APC 7x4 13,000

APC 7x3 13,500

Graupner 7x3 . . 4,000

Idle speed . .. 4,700"

at [link=http://findarticles.com/p/articles/mi_qa3819/is_199908/ai_n8852836]AP .09 test[/link]

How representative this is I do not know. He says it turns a 7-4 at 13k, but a 6-4 at 19k - that indicates quite a jump in hp through that rev range, although I do realize the blade cross sections etc. of 6" versus 7" props may play a significant role. But a 7-3 at 13,500k doesn't exactly knock my socks off. Someone claimed a Gilbert .11 would turn one at 16k.

I guess all you can do is experiment. Myself, I'd probably try an MAS 8-3 and an APC 7-3 stock first, and paying attention to the cooling issues, if any, on the 8" prop. Then, I might try clipping the 8-3 as well, a bit at a time.

There is a bit of a limit to the available prop choices, but after all the market for .10 size 3D props is so small now that it just isn't wirth tooling for.

MJD

unclecrash

Ya I thought I had read in the instructions that it was 16,000 I could be wrong. Like you say Im sure its grossly over rated. And that I think was with a 7x4. I tried it with the 8x3 today and it didn't like it it would lean out after a short run. I then put on the 7x3 and I wish I would have barrowed one of the guys tachs. It spooled up a hole lot better and seemed to like it. Oh and I was running it on 35% sig. But after the 7th or 8th flight i lost the plane due to aileron flutter. My own fault I told myself that i should rehinge them and add stiffer wire the stock push rods were wimpy. I think a bit thinner than the debro micro ones[:-] You can see it fly on utube if you want. Its a CG shock 3d I converted from Electric to glow it. Just punch in unclecrash in the search and you will find it. It was flying very nice till this happened. It was pretty zippy. I guess a bit too zippy for a 3d plane the dive probably put it over the edge.

MJD

My Feedback: (1)

Oops!

The sound of ailerons trying to disintegrate!

But the engine sounded happy..

MJD

unclecrash

Yup she was singing a nice tune.