Tonight the weather was perfect and I got the Funtana up for a short , 8 minute sunset flight. APC 15-6 and she took off very easily and climbed out rock solid. Moving the CG forward a 1/4" really helped. It would do about 50mph full throttle straight and level I'd guess. It would climb very well. I could go straight up for 10-12 seconds until I had a hard time seeing it. It slowed for landing very quickly and has a very predictable sink rate.

With a little larger carb, maybe a 15-7 3 blade prop, and some more tuning it should be a very capable plane. Overall I'm very pleased. After this is a 24cc Echo on the 60-90 size Funtana.

Tomorrow is reported to be the last of the good weather for a while. I'll try to get a bunch of flights in tomorrow.

Doug

It pays to experiment with props, but I don't think a three blade is going to help you any. If you want more low speed performance I would try a 16 x 4. For more speed, I would try a 14 x 8. These gassers don't turn up the rpms like a glow engine, and therefore if you pitch them too low, the speed falls way off. But because of the torque they have, you can use a larger diameter which really helps with the thrust. Three blade props are generally less efficient than two blades. Hopefully you are using APC props, as they really seem to work better by quite a bit than the other brands. I think overall you would like the 14 x 8 unless you are really looking for 3D performance, in which case a 16 x 4 would be worth giving a whirl.

Thanks for the update and keep us posted,
AV8TOR

But not that much. Adding an extra blade is an excellent way to gain more thrust.

a larger two-blade would be better IMO but he might be battling a case of almost non existent ground clearance on this little plane.


dave

After a long delay I finally built a new engine test stand/thrust test stand. Roller-blade bearings running in steel C-channel. VERY stout! I need to do some minor changes before she's finalized. Today I was testing out the "lightened" Echo. I think I took a little too much off of the crank counterweights. It vibrates more that stock.[] Next time I'm going to leave the crank alone.

I just did a search of the last years posts trying to find out what an Echo 21.2cc is turning for rpm. Many hits but not much hard info.

With a APC 15-6 of got 7600 top end and 2000 idle. Does this sound about right for a stock engine(no base gasket) with CDI ignition? Right now I'm using conventional 2-stroke oil at about 32:1. I just ordered a quart of Amsoil 100:1 and will probably mix it about 80-90:1. Do you think this oil mixed with 92 octane will help? How about exhaust goo?[]

Thanks,
Doug

That seems a little low. If I remember correctly, I was getting about those rpms with my last 21cc Kioritz, but with an APC 15x8 and at 4200' altitude and 90+ degrees. I don't remember now, did you gut the exhaust and provide two outlets of about 7/16" i.d., and install a larger carb?? My hopped up 23.6cc Kioritz turns a 16x8 at 8200 rpms here at this altitude. Pulls a 10.5 lb. plane straight up a long ways!

Amsoil is supposed to be good at 100 to 1, though several people have recommended running it at around 40:1. That's what I'm running right now. You probably won't notice any benefit with higher octane fuel, and might notice a decrease. These little engines just don't need it.

Good luck, and keep us posted,
AV8TOR

Thanks av8tor,

I am running the stock(small) carb. I believe it has a throat of 0.300". My 23.6cc has a stock throat of about 0.4375". That's a lot of difference. I think I'll try a slightly larger bore carb. Would it help to take a moto-tool and open up the cast in ring inside the carb throat? That seems to be a restriction point.

Here are some pics of my new stand. I haven't bought the digital fishing scale yet. It is EXTREMELY free rolling. Before I put the stops on the front of the rails, the engine tray would slide out of the rails driving around a corner in the back of my truck.

I'll be in SLC for schooling until the middle of Oct. Then it's time to fly the rest of the fall.

Doug

Hey Dougt I have an old kiortz with points ignition and it had about the same size ventury as what you discribed. I open the ventury with my rotary toll and man did it make a difference. I ended up putting that carb on my 25 cc homelite and got 14lb of thrust with a 18-8 wood prop at 7200 rpms.
So go for it and see what you can get, open it to about 3/8 and try to keep the metal out of the pump section.

You may be a little rich on mix. Echo shows 50:1 in specs for SRM - 2100, 2110
Got a Walbro 167-A 11.11 on mine. w/CH Ign. Zinger 16-8 just about 8500 as I recall.

Finished product: http://www.rcuniverse.com/forum/m_69...anchor/tm.htm#

I would put the larger carb on, and you will definitely notice a difference. You could probably ream that one out, but there is a little tiny orifice hole in that ring you want to ream out, and you will most likely plug it up.

A larger carb and opening up the exhaust are the biggest gains on these little guys, and important to do. If you have not opened the exhaust up, you need to do so. As I mentioned, I find two outlets of 7/16" i.d. and no baffles, etc., to be about optimal. I find my weedies set up like this to be noticeably less noisy than a muffled .61 two stroke glow engine, so don't worry about noise.

Good luck, and keep us posted,
AV8TOR

This was an extremely popular thread. Can't believe i found it on page 22.

That's right 22