Thanks Cap. Hopefully that will help.

Tstotts

I was playing with my gas/glow us 25cc that is going on a Sig 1/4 scale j-3 cup. 109" span. what would be a good prop for this engine on this plane... I was testing the engine with a 16x8 and I was going to go out and get a 18x6 to see if I like it. but before I put out the money I though I would ask you all what you thing about it.

Paul

Is the plane to fast with a 16 x 8 ?

What RPM can you reach?

The 18 x 6 uses almost the same power as the 16 x 8, about 10% more.

If you could live with a slower plane, I say go for it.

I use a 16 x 8 almost exclusively on this size engine, because most of my planes are faster, aerobatic planes. An exception for example, is my Fokker Triplane, on which I use an 18 x 6. The Cub might very well like an 18 x 6, but you will only know after trying both for yourself. Within reason, pitch determines speed, so it will also depend on how powerful your engine is whether a 6 inch pitch will give you the speed you desire.

AV8TOR

I found that my Poulan does not have enough torque to unload 18x6 on the ground. My test prop MA 16x8 Classic has more rpm (7400) than NX 18x6 (6200). The best prop for maximum performance for my Poulan 25cc was APC 17x6.

As for quarter scale Piper, both combinations should work well. It is a big high-lift wing and does not need much speed to fly. With 18x6 I guess you will not be able to fly faster than 40 mph (about 1.5 of stall speed) - not much reserve for wind gusts. With 16x8 you should still have enough thrust (over 9 lb of static thrust) to take-off and fly the plane with reasonable performance and you may actually be able to fly faster (about 2 times of stall speed). You may also consider 17x6 as alternative to 18x6 (it should give better transition).

Either way I would expect such combo to fly like a real thing - smooth and slow.

Actually I'm building CoroCap 96 inch span as a "test plane" for my engine. I'm going to use MA 16x8 Classic for the look and speed (coroplast is a little heavier than balsa).

I have been flying an 88 inch, 1/4 scale clipped wing cub with a ST-90.
Plenty of power and speed with a 13 x 8.
I just put a Brillelli Toro on it and am planning on using a 16 x 8.

I 'm thinking a 6 pitch prop may be to slow, and APC doesn't list a 7 pitch prop in 16, 17 or 18 inches.
Of course it is a Cub and a 6 prop may be very scale.

Well I did some playing to day and my us25cc will spin my 18x8 at 7600. on gas/glow..
It is nice to see that lol.. that is what my 35 will do on strate gas

I have a new plan here with a 3w 42. The ingnition modual quit. So I was going to try gas/glow on it.. but this engine has one of the small spark plugs on it.. Any one have a idea on how I can convert this one?

Paul

These guys might have one to fit on this page: http://www.aero-sports.com/airhobbies/access.html

Or you could just make one yourself from aluminum.

AV8TOR

CH-Ignitions has them.
http://www.ch-ignitions.com/

Just tell them what plug you have now so there will be no doubt on the correct size.

TELEPHONE ORDERS:
Call 307 857 6897. Telephone hours are 9 a.m. until 5 p.m. Mountain
Time, Monday through Friday. (During the summer we might be out flying
all day Friday.) 24-HOUR FAX: 307 857 6900.

Ralphbf
Thanks for the info.. I know I can get one from CH but going to gas/glow is alot cheeper and there is so much more power out of it.. I have 2 good CH ingitions that I will keep that way but the rest of all my gassers are going gas/glow.. (I am hooked lol)

av8tor1977

Your right it looks as if I will have to make one.. that was not my plan lol..

Paul

NO NO NO

They have the adapters for the 10mm plugs so you can use glow plugs.

The reason you give them the plug number is so they send you the right adapter.

ooops sorry lol.. I will give them a call...

Who's on first? No, What's on second

I'm so confused....



AV8TOR

Let have some fun with this post......

Lets here from the ppl on the post, and post what engines you have on gas/glow. What kind of plane is it on, and what is your likes and not likes.


Why am I asking this..

From what I see in gas/glow, I think it will be a big thing and it is one of the best ways to go..

Paul

For those who are wanting to try Gas/Glowand not wanting to but a whole gallon of fuel to start with
Tower Hobbies sells quarts of 10/12.

http://www2.towerhobbies.com/cgi-bin...8&I=LXUU70&P=K

For $8.99 and no hazmat fee, added to another order this is about as cheap as you will find.

That is just what I needed to see.. Thanks Ralphbf

Paul

I had an interesting occurrence. My Twist 60 with the Super Tiger .90 running Gas/Glow was continually being finicky to adjust. When I got a good idle adjustment, it would hesitate on acceleration. When I got it rich enough to transition, the idle was crappy. Finally, since it really was acting like a "too large a carb" problem, I checked the size of the carb I had put on it. I was shocked to see it was a 12.7mm!! WAY big for a 15cc engine!

When I first ran the engine on Gas/Glow, I had problems with the Zama carb diaphragms. Aggravated and in a hurry, I just grabbed a Walbro out of my box of carbs. They are all in plastic bags, marked by the seller with the size. The bag said 11mm, and that's the size of the Zama that was on it, so I mounted it up and adjusted it without double checking the size. It ran better on the test stand because I wasn't slamming the throttle open as fast as the radio (servo) does in the plane.

So realizing my mistake, and the problem, I prepared an 11mm carb to put on it, but I decided to first check the max rpms with the big carb just to see if it would lose any power in the carb swap. I got well over 12000 rpms on an APC 13 x 6. I remembered it was around 11600 with the Zama 11mm carb before the diaphragm gave me trouble. I hated to lose that power, so just for the hell of it I put the glow heat back on. I was easily able to adjust it for max rpms, a nice slow smooth reliable idle, AND a perfect transition. At that point I decided to stay with the huge carb and just install onboard glow heat, which I just finished doing. A 3800 mah battery weighs 2.24 ounces and will fly it for well over an hour with the glow heat on full time, and it runs perfectly.

So, the lesson is, if you are having transition problems that you can't tune out, go to a smaller carb, or try full time, (or even part time; below 1/3 throttle) glow heat. I'm not going to run glow heat on my other Gas/Glow planes as it's not necessary, but it works well in this particular case.

BTW -- The Twist 60 is a rocket with this engine, and a blast to fly!!

AV8TOR

I am trying to convert my last gat to gas/glow. but I am not having the luck with this one as I was with the last..

What it is doing is I can get the top end up to about 7400 rpm. but when I get the low end set to a good seting then If I let it idle for little bit and I give it gas it will bog down and some times quit.. So I will tern the low end richer to get it out and then it will not idle very well.. I need some help with this one..

Paul

If you can, try another carb, preferably a touch smaller. Another trick is to add exponential to the throttle channel in the radio so that it doesn't slam the throttle open so quickly.

AV8TOR

That's exactly the same I had with my Poulan 25cc. I setup the engine for nice transition and good idle with clean top end. If I let it idle for minute or so then it hesitates when I open the throttle fast. Sometimes it just dies. Kind of like a lean low end on glow engine.
I figured that it is a glow plug getting to cold . When I kept glow plug powered on idle the engine could idle "the whole day" and be responsive to the throttle any time.

I left the glow plug powred and it stoped doing it.. so I think that is what It is.. I need to look in to finding my 10/10 fuel and stop trying to make what I got work..
Paul

What fuel are you using now?

If the RPM drops when you disconnect the glow starter a little more nitro may be in order.

I am running 15/17 2:1 gas

Ki8fr
A smaller carb will fix that problem. I have a mac 28cc that will not run on a "28" 11.1 mm carb. Adjust high or low end but never both.
Droped down to a "26" carb and runs like a top and the Max Rpm is still the same. your motor just can't handle the larger airflow and bogs..

Yeah, the first thing is to get the right fuel. The extra percentage of nitro and oil is taking the place of needed methanol, and could be a factor.

AV8TOR