Merlin Man

Hi,
Just hoping that you guys that fly witha Moki 1.8 might tell me what prop sizes you have tried and like best.

I have a 18"x10" on my 23lb. ,82" Platt Mustang and it is ok but wonder if there are better sizes to use. The prop I am using is a glass fibre" Bolly" brand and cost $50 (Australian ) At this price, I don't feel like buying a few to see what they are like !!

My Moki has a custom made exhaust with the same internal capacity as the commercial Bisson unit and the same pipe outlet areas.I mention this to establish that the muffler , while not a tuned pipe, will allow the motor to run reasonably well.

I find the engine difficult to fine tune at the top end. I had a flight today with a rich setting .( only discovered after seeing the thick smoke trail after takeoff ) I can't pick the top end tune by sound as is normal. Performance was marginal. I think I will need to taco the engine before each flight to avoid this happening again.

This is why I am asking about the prop. Any help would be appreciated.
Cheers
MerlinMan

ekir

My Feedback: (1)

I am not sure that my information will be helpful, but here goes. I fly am Extra 260, 80" wingspan that is 14.5 pounds with a Moki 1.8 and Bisson Pitts Style muffler. I use pressure off the muffler. I fly the extra with a Zinger or Zinger Pro Wood Prop 18 x 8. I know it is not the most efficient prop, but easy to find and works for my type of general flying.

I have a glass prop that is a better performer than the Zinger. It is a Mejzlik 18 x 10. More expensive, but has more performance.

Ed

BOLTMAN

My Feedback: (1)

MerlinMan

Try a Bolly 20x8. I have used this prop for about 10 years on a few warbirds varying from 80" to 96" span & from 19lbs to 26lbs, with 3 different Moki 1.8's.

I too have & still do use a home made muffler, have tried a few different styles & outlet sizes. It seems the Moki is a bit sensitive to outlet sizes.

The top end needle I have found to be not very responsive, must be a very fine needle. I tend to make adjustments in 1/4 turn increments rather than a couple of clicks on most motors.

I run mine on 15% coolpower oil & 5% nitro, all three have done alot of work.

That P-51 looks great, good work. I have a Pica 89" P-51 part built, hopefully I will get back onto it next year. I am planning to use a Moki 2.1 in it.

Cheers

Merlin Man

Hi,
Thanks for your replies Ed and Sportstar.

Do you have any tacho figures for what sort of RPM to look for ?? I do not have a tachometer but could get the use of one and it would help if I had some figures to use as a reference .

Many Thanks
Cheers
MM>

BOLTMAN

My Feedback: (1)

Merlinman

Sorry I don't have a tacho either. Unfortunately it will be a few weeks before I get to the field to be able to borrow one get some numbers.

Cheers

JGrc

My Feedback: (29)

Merlin man,

After several trials, I fly my BT Spit (18 lbs) with a 1.8 / 18-10 Power Point. Muffler is JTec. This seems to give the best combo.

JG

eddiegersh

hi guys just to change the subject a moment i am trying to get my moki 180 to run inverted and am having a hard time getting it started i have it installed in a wm p51. i had it side mounted in a midwest extra 300 and never had a problem i would apprecate any help you guys can give me thanks eddie

Merlin Man

Hi,
Yes, I would like ideas on this too !!!

I have difficulty most of the time ,especially on a first start.I think getting the priming right is the real difficulty. With my invertsd set up, it is difficult to get the fuel up into the upper crankcase and often, I revert to turning the plane onto it's back to start .

Cheers,
MM

BobH

My Feedback: (2)

Mine seems to start ok inverted. You need to get the Moki wet or it doesn't start easy. I use a large starter and a Md Daniels glow driver and an F plug. All this seems to help.

BOLTMAN

My Feedback: (1)

Guys

I have used a Cline pressure regulator with good results. This involves using crankcase pressure to pressurize the tank alot more than muffler pressure. The Cline regulator is a demand regulator & seems to stop any flooding tendencies with the Moki mounted inverted. I believe Iron Bay makes a similar regulator. I would not try to run a Moki inverted again without one of these.

Good Luck

gary9648

My Feedback: (1)

When you say marginal, what do you mean? If the plane is flying to slow, then try a 18/12 prop. I have used the Menz ultras, and the Zinger-pros. The 12" pitch will not get you off the ground faster, but you will have much better flight performance. If your Moki is turning this prop in the high 7,000 RPM range you should have very good performance. If in the low 8,00RPM range it will realy goooo. You have not said what weight the plane is. Also the Pica Mustang was designed around a G62 gas engine if memory serves me. That is a very large plane to fly with a Moki 1.8 in it to my thinking, unless the weight is in the 20-22 pound area. just my thoughts. I fly a converted TF ARF Mustang, that I changed form a D to a C. I first flew it with a US41. The plane weighs 21 pounds. I had a 18/12 prop on it and it turned the prop at 7400 RPM. The plane was marginal on real hot days. Had to fly around at full throttle most of the time. I now have installed a Fuji 50EI in the nose and can fly at half throttle. Tremendous more power. I use a Menz 20/12 prop on this engine, and it turns it at 7500 RPM.
Good luck with your Mustang down under.
Gary Webb

Merlin Man

Hi,

I got some tacho figures for my Moki 1.8. today but not much joy really! Both the Bolly 18x10 and the Topflight 18x10x6 peaked at about 7,500rpm. I will have to wait until I try other props before I can decide on what's best.

A mate has a 1.8 with a bisson muffler and got 9,000 with a 17"( cut down 18")x8" He uses 15% Castor while I use 10%castor and 10% synthetic ( Coolpower) He is flying a lighter model (14.5lbs Extra ) and is happy with the performance . Of course, This prop would hardly be "enough " for the P51 .

Gary, my P51 is the David Platt one ( 82" , 23lbs.) and by "marginal" I mean that the take off climb out is slow and a go around last flight had the model barely flying before I was able to retract the gear. The flight performance is good , with decent sized loops etc. I don't think the engine would get near 7,500 with a 18"x !2" in it's present fuel and muffler setup ? but have not tried this combo yet.

I think the 2.1 Moki might be a better motor for my plane ,but costs prevent this ( at the moment )

BTW, I found today that I was able to start the moki much more easily. I simply lifted the tail to the level position ( put it on a small box ) and fuelled up as usual. Without priming, I had enough fuel in the motor to flood it! but after removing the plug to empty the fuel, I was able to hand start immediately. And I repeated this 6 times with out any problems. So, this starting problem may be resolved!!

BOLTMAN

My Feedback: (1)

Merlinman

20% oil is way too much for this motor, if you really want to run some castor, go to 10% coolpower & 5% castor. My Moki's have done a heap of work on 15% coolpower with no problems.

My father used to fly a Model Design 96" span Spitfire which weighed 26 1/2 lbs on the Moki 1.8 using a Bolly 20x8. He flew at Canberra, which is reasonably high altitude by Aussie standards. It flew fine, as long as the motor was tuned OK, although if it was slightly off it was a struggle. This model was one of the most realistically powered WW2 fighters I have seen.

Cheers.