Guys, I met a fellow this past weekend who says he has had great success converting weedies to glow. He said he makes a glow plug adapter, hub for the prop, replaces the o-rings/seals with some that are compatible to glow fuel, removes the flywheel & mag, and may or may not replace the stock carb. I'd like to try this on my next big plane, and I'm thinking of a 31-36cc ryobi or mccullough engine. It seems that although the fuel would cost more, it would save a lot of weight without the stock or even an electronic ignition, not to mention the savings over buying a large glow engine. Anyone have any success doing this? Sound stupid? I'd love to hear some qualified opinions!

This has been done before, - however you will probably not need the huge amount of oil as used in a normal glow engine because of the needle roller bearings used in a "weedie".
I believe that alcohol fuel still may be necessary, but you may benefit from higher compression when using alcohol.

One person who has a lot of experience in this area is RCIGN1, - he has described it in some threads, but I just can't find them at the moment, ( maybe somewhere in "scratch built ignition"),
I do know that it is in the forum somewhere.

Thanks, Will. I'll do a search of his posts.

We run glow fuel in our race engines all the time.. We raise the compression and do some port work for higher rpm....No problems with seals or carb parts, just replace the diaphragms when the carb quits working like it should..The fuel passages in the carb need to be enlarged to twice the area, not the diameter......We ran the same glow plugs for 2 years in a 289cc race engine, using up to 22% nitro...
You WILL need to run glow fuel..
A stock G26 runs 600 rpm faster on glow fuel, using either stock ignition or a glow plug...
You can run 50-1 oil ratio with the methanol....

Thanks, RC. From your current and previous posts, I gather I can take (for example) a Ryobi 31cc, remove the flywheel, magneto & spark plug, make a glow plug from a spark plug or buy an adapter, buy a WT-499 glow carb from Zenoah, buy or make a prop hub and muffler, and use 0-5% glow. I should end up with a weight of around 2 lbs., which is the purpose of the exercise. Am I oversimplifying it, or leaving something major out?

Should work fine, you could also do some of the other performance mods found here on the Ryobi threads....

Wow, I'm amazed this isn't more common. I just saw a 20cc Weedeater @ Wal-Mart for $55. This is a 1.20 2-stroke engine, which retails for $200 for a GMS! I guess the catch is the weight, and possibly the power. We'll see.

What would the oil content be? Since alcohol is less viscous than gas I would assume that 100:1 oil ratios are out. Maybe 5 to 9%?

Why not mod or replace the carb and use the ignition system with glow fuel?

Weight...
We run 8% oil in our raceplanes, more than enough.....

I've done several weedie to glow conversions. To me as a sport flyer, about the only viable application is to give a 25-33cc weedie a fighting chance of powering a 1.20-1.50 size aerobat with good authority. With some careful selection, you can have a glow weedie come out weighing 40-45Oz with power close to OS 1.60FX territory at about half the price - all the while burning fuel that cost half as much as regular glow fuel, and producing 1/4 as much slime on your airplane.

BUT!!... The main problem is that weedies usually have very low CR and so don't make too much power on 0% nitro. Adding nitro back in increases the cost of the fuel and the rate of burn - kinda defeating the primary purpose of being frugal. Yes, you can run 4-5% oil if you use straight castor, but the weedies I played with (ryobi 31cc being one example) seem to make a bit more power with more oil content - possibly because it helps compression seal?

If you are willing to spend a little time tweaking these weedies for glow conversion, they'll make pretty decent sport engines.

A glow G23 weighs under 2 lbs, turns an 18-6 Mejzlik about 8200 rpm....Been there..Twice...A glow G26 weighs a little more, turns the 18-6 Mejzlik 9600 rpm.. Been there also....

RCIGN 1 So we do not have to assume nothing.....how much nitro (percent) are you adding to get those RPM figures on the 23 cc and 26cc engines? Thanks Capt,n

The G23 I have now came originaly as a glow version when I bought it brand new right about the time Horizon discontinued it. Add any muffler to it, least of which the heavy steel stock muffler, and the thing weighs quite a bit more than 2lbs.

Cap John..Don't know about the nitro, it was some very old glow fuel I had..The first glow 23s were made from old broken engines with the rear cases milled off because one of the corners was missing due to a crash...I also milled the extra casting bosses off the front half...The G26 is not sold as a glow engine. The 26 was made the same way, the case was milled flush on the back...The rear crank extension that held the mag rotor was cut off...The G23 was mounted on a profile plane with 2 aluminum angle pieces using the 4 bolts that hold the case together...The old spool hub from the 23 was used on the 26, it's lighter than the new style hub and 8mm stud. A 6mm threaded rod with locknuts holds the prop on...I could probably get the 26 lighter by turning the fins down....

RCIGN 1 Thanks for the reply. I was thinking of trying a profile plane. Your way of mounting sounds good. Also milling off any metal not needed saves more weight. Take care....Capt,n P.S. How is the weather...cold and rainy here in Mich

The weather here is great, about 75....the plane the glow 23 WAS on weighed between 8 and 9 lbs, flew like a TOC plane, taking off straight up from a handhold...It was the victim of a midair with a trainer...

RCIGN,
Say is it worth converting 18 cc weedeater on glow fuel and run 0 nitro in it?Will it haul .90 size plane?If i will be able to burn 0% nitro and say 10% castor the fuel will be somewhat more affordable ....You think??