SrTelemaster150

Generally speaking thrust will not increase with more pitch at a given RPM at a given diameter propeller. Since RPM drops with more pitch, more pitch will achieve less thrust when the propeller diameter remains constant. A larger diameter propeller with less pitch will generate more thrust.

Using this STATIC THRUST CALCULATOR we get the following:
An 18" prop would be "scale" for a 1/4 scale J-3 Cub.

My suggesting would be to use an 18x6 since speed is not what you will be looking for with a J-3 Cub. IF you could turn an 18X8 at near 8.000 RPM, you would be generating 3 HP, but I think that's a bit optimistic for that engine.

ALFIEV

Stated as 0.03 - 0.08 mm

On a 18 x 8 prop you should be getting approx. 7000-7300 rpm going by the performance I have seen in my GF-38's. Other's figures may differ, but it should be somewhere near than.

capnpaul

I am getting 7400 RPM with a 18-6 classic prop. I noticed when i change to a good synthetic oil rpm went up.
One thing i did was add a check valve or PVC valve in the tube going to the manifold and it seems to stop oil form the crankcase entering the engine but still allows fuel to enter the crankcase for lubrication.

SrTelemaster150

You are only making a very slight increase in HP but the 18x10 @ 6200 only makes 11# of thrust while your 18x6 @ 7400 makes nearly 16#!

tyor

when I was testing different props for my black horse fieseler storch I got this numbers.
bmabula 18x8 7300rpm 4.9kg
master 20x10 5700rpm 4.8kg
xoar 20a 3d 5300rpm 4.5kg
20x8 carbon 5900rpm 5.1kg
18x8 carbon 7000rpm 3.2kg

Max thrust with carbon 20x8. And with that prop the plane flies fine. The plane is 2.85m vs. and 7.9 kg

video
https://youtu.be/74Vl5FiWPXQ?t=5m33s

tiger650

My Feedback: (22)

I was also going to use an NGH 38 in the Seagull Spitfire. Was your install making the plane very nose heavy? Also did you have to move the firewall back?
Thanks!
bob

Erwin Z

I advanced the timing all the way, tested with a wooden Turnigy prop 18x8 and got 7300 rpm, didnt had the time to fly but thrust feels good now

Erwin Z

nice plane!!, thanks for the info, I am getting similar RPM with a wooden 18x8 as your results, I guess similar thrust as well. lets see it on flight next weekend

MYHELL99

My Feedback: (47)

So, I jumped on the bandwagon and bought this engine during HK's cyber week sale. Reading this thread helped me get the engine set up right. Thanks to all the previous posts on these tips!!
I've added gaskets on the carb, blue lock tighted almost every bolt, and slid the timing pick up all the way CCW,FLA.
She started right up! Ran it for about 45 minutes now, and I have to say, this engine is running beautifully. It's a bit of a shaker, but hasn't quit on me yet...
I'm using a MA classic 18×6 and just after 45 minutes run time, I'm getting reliable idle down to 1700, and top end is hitting 8300! I'm using Trufuel 4 cycle, with 25:1Sthil synthetic 2 cycle oil.
If anyone is on the fence, BUY IT!

-Richie

robc57

Try running a larger prop, something more like a 19*8. I think this engine is happier at lower revs and vibes will be less of an issue, and going by Tyor's results you will get way more pull running a 19 or 20" prop. I started with a HK beech 18*8, when the weather improves I'll be trying 19*8 and 20*8. I expect to get just as good, or better, performance and less noise.

MYHELL99

My Feedback: (47)

Yes, thanks, that makes sense. The 18x6 was the biggest prop I had. I'm placing an order for more props today.

Daniel Spurlock

My Feedback: (4)

Can someone help me with cam timing? Just a heads up dont remove cam gear cover and turn engine it will push out the cam and jump time.

MYHELL99

My Feedback: (47)

With piston at TDC, the cam dot is pointed down at 6:00.

ALFIEV

1. Post #37 on page 25 shows the correct position of the cam, with the dot at the reinforcing web of the crankcase, approx 6 o'clock at TDC.

tiger650

My Feedback: (22)

Richie,
I have been running this motor in a great planes Waco. I have not made any adjustments or changed any gaskets on the motor and it seems to run fine. What does adjusting the timing do for you? I am running a cf Biela 18x8 and getting about 7900 rpm with a nice idle.
Thanks,
Bob

CH Ignitions

My Feedback: (11)

GUYS, Timing adjustments now I am not sure is need it for the new engines sold I think after September.
But I am not 100% . I know that NGH may use the 40 BTDC CDI insted of the regular 30 and sensor at 40-45BTDC.
No way to know what you may have. Before you do any adjustments mark the sensor position and move it one way or another.


Adrian

robc57

My engine was a nasty biter on starting before I retarded the ignition - maybe it has lost a couple of hundred RPM off the top but it made it a much nicer engine. It was bought earlier in the year though!

MYHELL99

My Feedback: (47)

Adjusting the timing gave me a lower idle and easier starting.
-Richie

SrTelemaster150

By employing the C&H Ignitions module with 40 degrees advance (40 degrees retard at starting/idle RPM) yo can have the best of both worlds. Maximum performance as well as easier starts & general user friendliness.

SrTelemaster150

7900 RPM W/an 18x8 is solidly in the Saito FA-180 glow engine power range & better than the FG-30

ALFIEV

Yes, I am very interested in this module. It does seem that the original module does not operate on a performance curve that would give smooth idle and easy start and then advance to give full rpm. Some of us have sacrificed top-end rpm for a little better idle and start.

ALFIEV

Wow, 7900 rpm is waaay up there for this engine. I guess the Biela is different to the Xoar I'm using. The best I can get from an 18 x 8 is 7100 rpm.

nalby

When will the C&H Ignitions module be available?

SrTelemaster150

As far as I know, it already is.

Try the low tech approach & use a telephone to contact Adrian at C&H Ignitions. If you leave a message he will return your call PRONTO.

tiger650

My Feedback: (22)

Oops rechecked at at the field yesterday and was getting 7600 approx. and the prop is 18x6 not 18x8.
I just bought another one of these motors and can not figure out what to put it in. Any ideas? It's tough because the motor is so long, like 172mm from back of motor to washer.