Prop for a .12 engine - Page 2 - RC Groups
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Oct 06, 2012, 09:03 AM
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It is timed fairly tame. It will likely unwind a bit with the 7-5 in the air with the small plane.
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Oct 07, 2012, 01:21 PM
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Yes it has a rather tame timing but I donīt want to push it too hard as it has seen itīs best days. I actually have a pipe that might work on this engine with some minor tweaks on the timing, but I think itīs best to let it die slowly.

If the plane outlives the engine I might go to something stronger, maybe a Enya Ultra 11 CX...
Oct 18, 2012, 11:30 AM
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Well, I finally got to do some more testing, with two smaller prop.
It didn't respond as well as I had thought it should do.

APC 7X5 16600rpm -Peak
APC 7X6W 14400rpm -Peak

Iīm beginning to think that this engine has seen all of itīs good days...
Idle is something that it doesn't like at all, hand-starting is completely out of the question.
But it runs great in the mid-range with good response!

Any suggestions on a good engine in this size?
Oct 18, 2012, 01:19 PM
jeffie8696's Avatar
I am not a huge fan of ASP but my .12 works really well, it will be going on the front of my SIG Little Extra. It was on the front of my first one but a radio failure rekitted it, permanently.
Oct 18, 2012, 01:49 PM
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Iīm not a huge fan of those either, but at that price I might have to think about becoming one.
The thing is that I made the engine mount as a part of the wood structure to save some weight, so.. now Iīm somewhat limited to what I can use without to much hassle.
The engines I have found so far that share the exact mounting dimensions is;
O.S. 10LA, 15CV-A

But minor adjustments is not a problem, so a SANYE-made .12 or .15 would work.

I will do a test with increased compression to see if that will help, but when itīs worn out itīs probably not going to help a lot.
Oct 18, 2012, 02:37 PM
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16,600 is better than an LA .15, which is 16,200 with muffler. That is pretty good for a smaller motor. I checked with a MA 7-5, but they are very similar. If it is leaking past the piston faster than maybe 4 seconds it may be tired. I think if it runs that good and idles ok you would be wasting time and money on something else. It is much stronger than a .10 LA and most other motors. Maybe not Novarossi and the CV-A though.
Oct 18, 2012, 04:14 PM
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I might have "a bit" to high expectations...

Iīm going to try a different fuel and see if that will seal up the engine a little better.
Most likely it will unload in the air to.
Oct 18, 2012, 04:29 PM
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surfer_kris's Avatar
The ASP .12 will do about 16600rpm on a 7x4 prop and the stock muffler, more on a pipe or no muffler. So I would say that your numbers are fairly normal for a .12 engine. Since it is a car engine it may have an advantage at higher revs though. When you change the prop you also need to retune the pipe, if you are using a tuned pipe.

If you want to get another engine I think the ASP .15XLS with the blue head is very good value for the money. Should give you around 18500rpm on a 7x5 prop.
Last edited by surfer_kris; Oct 18, 2012 at 04:46 PM.
Oct 18, 2012, 06:40 PM
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Itīs running a muffler right now, but I have a pipe for a HB .21-PDP thatīs right in size. But I donīt have a manifold for this engine or to that pipe, so I leave it "as is" for now.

I just mixed a small batch of fuel with an increased viscosity of the oil package, will see if that seals the engine a little better.
Itīs sometimes the little things that makes the difference, as I just noticed that I had the Expo at a + setting instead of - for this plane... Might be a little less nervous now.
Oct 18, 2012, 07:37 PM
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My blue head ASP .15 does 17,600 rpm with no muffler on 10 %. Most worn out motors run good with a little more castor in to help seal things up. The old Fox's and ringed motors loved that stuff after they were worn out. 25% oil is good. Smaller motors like a bit of nitro too, 15 to 30%. (80%) 16,600 rpm will give about 80 mph on a fairly clean plane. I don't know what it is going into.
Last edited by aspeed; Oct 18, 2012 at 07:44 PM.
Oct 18, 2012, 09:08 PM
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I always run some castor in all my fuels, but then I always run synthetics also.
The fuel I've been using I think was about 16.5% oil at 15-16cts/100c, the fuel I mixed today is 17% oil at 18.7cts/100c.
Both has 20% nitro.

The airplane is something like a SIG Wonder, but with my own little twist (as I didn't have the original plans).
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Oct 18, 2012, 11:13 PM
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Should be good.
Oct 19, 2012, 10:52 AM
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As has been mentioned earlier, & your experiments show, the engine "wants" a smaller prop. Just adding my two cents worth here. I don't have an OS CZ model, but I have several Enya .11 cx models, a MVVS 12, & a couple of converted OS CVRs. The largest prop I use on any of these is a 7x4. Have a fair amt. of flying time with the OS, & Enya in a Lil' Extra. Both engines move the plane around quite nicely, & both are "happy with the 7x4 prop, BUT, both would really like a smaller prop. The Enya is stronger on the bench than the CVR; 18,600 vs 17,100, but the CVR appears to unload more in the air, and give slightly better overall performance. With a 6.5x5 The CVR runs 'bout 21,000 on the bench, & really gets "mean" in the air. The "problem" (if you can really call it that) with all of these small, hi-strung engines is that you need a rather small, slippery airframe to accomidate them. I really don't have a such plane, but have been using a loose copy of a Simple 400 fuse & tail feathers with a MSS wing. I'm sure that the wing is not up to what the CVR can dish out, so I have to be careful with the G-forces. Really need a whole new airframe. Probably end up with something small enough to be able to run a 5.5" diameter prop. ...... Once you get into the "BIG" 15 size sport engines, with somewhat more tame timing, the "correct" prop selection opens up a bunch. ...... George K.
Oct 19, 2012, 11:31 AM
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Thank you George K!

They had 6.5" propīs at the LHS, might look in to that and also see if they can order some 7x4.
I guess it will take some trial and error to find out whatīs the best combination. At this point I donīt want to give up to much static trust as Iīm new to hand launching.

Well I got to run one tank of fuel before the rain came here and there was no difference in power with the change of fuel. So I remixed the fuel with more and thicker oil and gave it 25% of nitro, itīs easy on the fuel anyway.
Oct 19, 2012, 12:29 PM
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Yeah, hand-launching is a bit of an art, sometimes rather challenging. But, as BRUTUS stated, static thrust generally is not the problem. If you've got a lo-thrust engine/prop combo, then just wind up like Bob Feller getting ready to launch a 92 mph fast-ball, & let loose. !!! Most of our flying models are at flying speed with just a brisk, well released, launch. The problems show up with screaming RPMs, & a prop running near, or at stall. This generally occurs with a hi-perf engine & a prop having a hi pitch/dia raito. Things really get strange when the prop starts to grab some air. Do a video search on the 'net for hand launching models. Some pretty wild shows.!!! I don't know how some of those guys were able to save the plane. I know that I would not have. On a much calmer note, I haven't had problems with the 6.5x5 prop at 21K. I launch at 'bout 3/4 throttle, let the plane get some extra air speed, & ease into the throttle. ..................... George K.

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