Author Topic: Symptoms of Too Large a Prop (Read 2012 times)

Peter in Fairfax, VA · « **on:** August 15, 2022, 10:19:46 AM »

If the prop has too great of a load, what symptoms are expected?

Mike Alimov · « **Reply #1 on:** August 15, 2022, 10:45:45 AM »

If combustion stunt engine is overloaded:
- It runs hotter than optimal;
- Increased fuel consumption;
- Very sensitive needle setting (say, 1/8 to 1/4 turn instead of the more normal 1/2-3/4 turn or even more;
- (Assuming a 4-2 break style engine) very little or no break from 2-cycle to 4-cycle.

Motorman · « **Reply #2 on:** August 15, 2022, 10:57:41 PM »

404 error

Brett Buck · « **Reply #3 on:** August 15, 2022, 11:39:49 PM »

Quote from: Peter in Fairfax, VA on August 15, 2022, 10:19:46 AM

If the prop has too great of a load, what symptoms are expected?

Depends on which engine. Most 4-2 break engines will just lose performance before anything interesting happens to the engine itself. Piped engines, and modern ABC/AAC engines, most of them, particularly the big ones, almost can't be overloaded because they can swing massive props and the turn performance stops you from making them any bigger long before you get near the limits of the engine. I tried as much as a 14-6 on an ST46, that was clearly too much and I think I launched it at around 6800 rpm. But a 13-6 was not completely unreasonable.

Al Rabe told me he used as much as a 16-6 2-blade on his Jett 76 or 88, and I have no doubt that even the relatively wimpy RO-Jett 61 would have no problem with a 14-4 3-blade (and I have run a 13.5-4) if you set up for it. Of course, that kills the turn and provides no real advantage in propulsion, so I use a 12.5-3.75.

I have even seen people using am 11-4 3-blade on a *20FP*, and while it sounded like it was going to melt, it didn't, and pulled the airplane (a Flite Streak or something like it) marginally OK. That is rather beyond the pale, because we used the same prop on a piped 40VF! A APC 9-4 works a lot better!

Point being, the performance will go away somehow long before you cause any real engine problems.
Brett

Peter in Fairfax, VA · « **Reply #4 on:** August 16, 2022, 10:09:25 AM »

Symptoms:

1. Bogs down in maneuvers. Fine in level flight.
2. Does not bog down due to being set lean. Gets worse if set richer.
3. Runs pretty hot.
4. Difficult to set needle.
5. Very little break.

I'm trying a smaller load next. Likely go from Zinger Pro 12x6 to Rev-Up 12-5 cut to 11-1/4.

thanks a million for weighing in,

Peter

George Fruhling · « **Reply #5 on:** August 16, 2022, 07:22:02 PM »

Quote from: Mike Alimov on August 15, 2022, 10:45:45 AM

If combustion stunt engine is overloaded:
- It runs hotter than optimal;
- Increased fuel consumption;
- Very sensitive needle setting (say, 1/8 to 1/4 turn instead of the more normal 1/2-3/4 turn or even more;
- (Assuming a 4-2 break style engine) very little or no break from 2-cycle to 4-cycle.

What about too small a prop. I have a half dozen 10-6 props laying around I bought for Fox stunt.35 powered models. Would that size hurt on a ST G21 .46 motor?

Brett Buck · « **Reply #6 on:** August 16, 2022, 08:01:07 PM »

Quote from: George Fruhling on August 16, 2022, 07:22:02 PM

What about too small a prop. I have a half dozen 10-6 props laying around I bought for Fox stunt.35 powered models. Would that size hurt on a ST G21 .46 motor?

It loves that sort of prop, the ring will be very happy with you, that's a prop RC guys would have used on it. Unfortunately on a typical 46-sized airplane (610-650 square inches and 44=52 ounces) will be get very mediocre vertical performance. Put it on a 35-sized airplane and will work pretty well.

Always remember that none of these engines were designed to be run in a 4-stroke like we always want. Mr Garofali was trying to build the most powerful RC engines he could, running as fast as they knew how to make it go - not chugging around wasting 1/2 the fuel at 7500 RPM.

You are not going to destroy it either way- too little prop, or too much prop, the engine is OK but the performance will suffer. Too slow and too rich, maybe, the ring doesn't want to seal, but if it was ever any good it will come back if you run it at normal revs and settings with typical RC props like a 10-6.

Brett

Steve Helmick · « **Reply #7 on:** August 17, 2022, 10:41:37 AM »

Quote from: Peter in Fairfax, VA on August 16, 2022, 10:09:25 AM

Symptoms:

1. Bogs down in maneuvers. Fine in level flight.
2. Does not bog down due to being set lean. Gets worse if set richer.
3. Runs pretty hot.
4. Difficult to set needle.
5. Very little break.

I'm trying a smaller load next. Likely go from Zinger Pro 12x6 to Rev-Up 12-5 cut to 11-1/4.

Was this an OS .46LA? The chopped RU might work ok. I still like an APC 11.5 x 4. Some will whine and say they're ugly or some such rot, but they work and they're often available at the LHS. Oh, they're heavy, but I have never had a problem that I thought that was the cause. I've seen guys use the 12.25 x 3.75 APC and THAT looked like it was too much load. I'm sure it COULD work if the muffler exit was opened up, and/or more nitro was applied at the NV.
Steve

thanks a million for weighing in,

Peter

Peter in Fairfax, VA · « **Reply #8 on:** August 17, 2022, 11:31:27 AM »

G21/.46

Air Ministry . · « **Reply #9 on:** August 17, 2022, 08:51:20 PM »

" I have a half dozen 10-6 props laying around I bought for Fox stunt.35 powered models. Would that size hurt on a ST G21 .46 motor? "

Could put TWO of them , on it . In Tandem . Cant find a picture today , but seen WW1 era shots .

Intresting if you put them at 90 Deg. , blades in trail , or blades 90 Deg. to trail . Might get some intresting noises .

Youd have to get your finger out quick . !

George Fruhling · « **Reply #10 on:** August 18, 2022, 02:27:03 PM »

Quote from: Steve Helmick on August 17, 2022, 10:41:37 AM

Who is Robert Heinlin and does he fly C/L Stunt?

George Fruhling · « **Reply #11 on:** August 21, 2022, 10:33:24 PM »

Quote from: Steve Helmick on August 17, 2022, 10:41:37 AM

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death. In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

In 2015, Americans were still fighting and dying in Afghanistan. There were no "safe zones" in that country.

Roy Johnson · « **Reply #12 on:** August 22, 2022, 11:21:13 AM »

Quote from: Air Ministry . on August 17, 2022, 08:51:20 PM

" I have a half dozen 10-6 props laying around I bought for Fox stunt.35 powered models. Would that size hurt on a ST G21 .46 motor? "

Could put TWO of them , on it . In Tandem . Cant find a picture today , but seen WW1 era shots .
Intresting if you put them at 90 Deg. , blades in trail , or blades 90 Deg. to trail . Might get some intresting noises .

Did that with a RC Kadet in the 80's. Was looking at severe noise restrictions at my flying site and got a set up from Duke Fox on using 2 props mounted 90deg and a 4 oz sullivan plastic tank as an after muffler. With 6 ea. 3/16:" holes drilled in the bottom. This was a G21/46 RC. At flight altitude you could not hear the engine. It was spooky. I would keep having to rev it up to make sure it was still running.

Youd have to get your finger out quick . !

Brett Buck · « **Reply #13 on:** August 22, 2022, 08:56:53 PM »

Quote from: George Fruhling on August 21, 2022, 10:33:24 PM

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death. In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

In 2015, Americans were still fighting and dying in Afghanistan. There were no "safe zones" in that country.

No offense, I generally agree with your sentiments - but what is it that you are responding to? You quotes are blank.

Brett

George Fruhling · « **Reply #14 on:** August 22, 2022, 09:43:47 PM »

Quote from: Brett Buck on August 22, 2022, 08:56:53 PM

No offense, I generally agree with your sentiments - but what is it that you are responding to? You quotes are blank.

Brett

I was responding to "In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death. In 2015 18-20 year old's need safe zones so people don't hurt their feelings." In 2015 we had young men and women fighting and dying in Afghanistan.

Steve Helmick · « **Reply #15 on:** August 25, 2022, 01:29:46 PM »

Quote from: George Fruhling on August 18, 2022, 02:27:03 PM

Who is Robert Heinlin and does he fly C/L Stunt?

https://duckduckgo.com/?q=robert+heinlein+wiki&t=h_&ia=web

To answer your question, it doesn't appear like he even flew CL at all. But then, if you read his bio on Wikipedia, it does sound like a weird thing he might have done as a ute (sic)!

Steve

George Fruhling · « **Reply #16 on:** August 28, 2022, 12:12:34 PM »

Quote from: Brett Buck on August 22, 2022, 08:56:53 PM

No offense, I generally agree with your sentiments - but what is it that you are responding to? You quotes are blank.

Brett

I was responding to the quote... In 2015 18-20 year old's need safe zones so people don't hurt their feelings."

Steve Helmick · « **Reply #17 on:** August 29, 2022, 08:27:01 PM »

Quote from: George Fruhling on August 28, 2022, 12:12:34 PM

I was responding to the quote... In 2015 18-20 year old's need safe zones so people don't hurt their feelings."

Yep. In 2022, those young adults want US taxpayers to pay off their college loan commitments, which is total BS. I would be impressed if they'd use the GI Bill.

Steve

Colin McRae · « **Reply #18 on:** October 13, 2022, 04:52:18 PM »

Any issues w/ a 12-4 prop on an OS 40LA (on a Vector 40)?

Dan McEntee · « **Reply #19 on:** October 13, 2022, 08:53:42 PM »

Quote from: Colin McRae on October 13, 2022, 04:52:18 PM

Any issues w/ a 12-4 prop on an OS 40LA (on a Vector 40)?

The 12" diameter is just a bit much for a LA.40. You may get away with a 12" cut down to 11.5" APC makes a 11.5" by 4" that I have used successfully on Brodak and FP-.40s. The problem there is getting the hub tucked into the spinner. It's worth experimenting with some wood 11-4 and 11-5 props, mainly because the Vector seems to finish out a bit heavy and you need a good pulling prop and the 5" pitch may get you there. The only way to tell is to just fly and test pros once you are pretty sure you have the model pretty much where you want it in trim. The APC props just seem to be the magic prop in a lot of different scenarios with different size engines and planes. The big knock on the APC is weight and the big hub and blade roots, but the results in the air are pretty good. Some don't want to or can't spend a lot of money for the extra props to test, but keep in mind that if you don't use it on this airplane, it may work on another. Even if you cut it down, and it's not exactly what you want and need, at least you have some more experience with props and what they do and how they work. Take a bunch of different brand props, hold them side by side and look down the blade from the tip to the hub. Notice how the blade changes angle and twist, and how the airfoils and thicknesses are very different. Blade shape, in my opinion, is secondary to the airfoil in how well a prop works or doesn't work.
Type at you later,
Dan McEntee

Colin McRae · « **Reply #20 on:** October 14, 2022, 08:48:09 AM »

Thanks Dan.

My Vector 40 is new to me (acquired it from a guy). I did not build it. It comes in at 64 oz, so pretty heavy as you say. I have 11-4 thru 12-4 props available and will experiment. I also have a 11.5-4.

My main question is if a 12-4 might overload the 40LA? The OS manual mentions 11-5 and 11-6 props for the 40LA. I would think the load on the engine would be similar for a 11-6 vs 12-4.

And yes, the larger APC's don't fit my available spinners, but I have some wood XOAR's and BYO's (smaller hubs) that do fit.

My Vector is also very tail heavy. Had to add a bunch of nose weight to balance. So, a heavier APC is not a bad thing!

Dan McEntee · « **Reply #21 on:** October 14, 2022, 09:25:39 AM »

Quote from: Colin McRae on October 14, 2022, 08:48:09 AM

Thanks Dan.

My Vector 40 is new to me (acquired it from a guy). I did not build it. It comes in at 64 oz, so pretty heavy as you say. I have 11-4 thru 12-4 props available and will experiment. I also have a 11.5-4.

My main question is if a 12-4 might overload the 40LA? The OS manual mentions 11-5 and 11-6 props for the 40LA. I would think the load on the engine would be similar for a 11-6 vs 12-4.

And yes, the larger APC's don't fit my available spinners, but I have some wood XOAR's and BYO's (smaller hubs) that do fit.

My Vector is also very tail heavy. Had to add a bunch of nose weight to balance. So, a heavier APC is not a bad thing!

At that weight, I would shop around for a LA.46 for a drop in upgrade in power. I have a 60+ ounce Legacy40 that I fly for sport with a LA.46 in it and a APC 12.25 by 3,75 in it and have to really wick it up to do a decent pattern. I have my doubts that the .40 would be up to the task with any prop. I know that is not what you wanted to hear (or read) but that's the deal. A test flight with anything in the 11-5 range, and just to get the experience, try some 12-4 props and see how it handles it, but be careful in any maneuvers. If the engine just starts to sag whenever the nose goes up, wave it off and try a bigger engine.

Type at you later,
Dan McEntee

Colin McRae · « **Reply #22 on:** October 14, 2022, 09:56:08 AM »

Thx Dan

My Vector (bought from a guy) had a 40LA on it, but I did not purchase the engine as I already had a new 40 LA awaiting a model. Due to needed nose weight anyway, I was going to try the heavier 40LA. But I do have a new 46LA just in case.

The 46 being, a bored out 40, is a bit lighter. But then will need a bit more nose weight to balance.

So, as you say I will experiment w/ the 40 LA. I typically use 5% nitro. But can also try 10% for more power if needed. My 40 LA also has a 6mm venturi (stock venturi that comes w/ a OS 25LA). I can also try a larger 7mm venturi (stock one for the 40LA) for more power. So, lots of fun experimental stuff to play with.

I have also read that some have used a 40 LA successfully on the Vector. But don't know the specifics.