A good rule of thumb guide for 3 blade props versus 2 blades is an inch down in both diameter and pitch as a good starting point.

I have had good results with the Master Airscrew 16-8 three blade props. Depending on a number of variables, getting 7,000 to 7,500 RPM with this prop. Besides that, they look good and give up very little performance to a two Blade.

Lovely looking models

RBean,

Can you give some details on your models?

The Corsair is a Koyosho ARF, 71" wingspan. DLE 20 with compact pitts muffler from J-Tec. Turns about 7,100 rpm. The Tony (KI-61) is a Flite Models ARF, 71" wingspan.Carb cooling was a real problem but finally got it sorted out. Took some careful baffling, air ducts and cowl flap. The plane flies great but I believe no longer available. From Hobby King. The P-40 is Top Flite 60 size ARF. Unfortunately no long available. The plane flies good with no bad problems. This DLE 20 has a "Bowman Ring" (he is now retired). and Bowman treatment re the reed valves. This involves honing the surface of the reed valve block to get a better seal. The engine starts easy, idles good and runs great. I think I'm getting about 7,500 rpm. This on also has a compact pitts muffler.

Is the Kyosho Corsair still available?

With the Tony, because of the tight cowl, I was getting vapor lock in the carb causing all kind of problems, engine out, lean running etc. because of the carb setting right above the muffler can of the pitts muffler. Finally put in the "blast tubes" ducting cooling air to just above the carb and the cowl flap to help remove the cooling air. Seems to work as I have had no problems since.

On the P-40 I also ducted air back to the carb. This was easier because of the top scoop. Notice I opened up the cowl flaps. Not sure if all this was necessary on the P-40, but certainly didn't hurt.

Yes the Kyosho is still available, go to their website. The ARF goes together will and has some nice flaps already installed. It also has gear doors, but I had to redo the operating mechanism. It comes with metal rotating air retracts which have obtained mixed reviews. I couldn't keep mine working and replaced them with Robart air retracts. Others have reported no problems with the kit retracts.

Thanks for the details!

I love the blast tubes mod, excellent work sir!

This may have been asked already but this is such a LONG thread I could not find it.
My DLE 20 takes a long time to come down to a slow idle. It idles fast for about 20 sec.
and then settles down to a good idle. Any ideas? Tks

Yes, that's a pretty common issue that's easy to tune out. The low speed is just a hair lean. Richen a tiny bit (screw driver blade width) at a time until it comes down to an idle reliably.

ahicks relayed the correct response. Follow his advice regardless of what some might say to the contrary. The earlier ignition modules had a timing curve that amplified this problem. You can tune it out, as referenced by ahicks or buy a new module with a CM-6 sparkplug cap.

Thanks for the reply! Except for the hesitation to come down to normal idle, everything is Great. Idle is good after about 20 seconds and at anytime the transition is flawless...no midrange gurgle whatsoever..smooth as can be! Maybe I should live with setup I have,. I am 80 years young and can really get those needle valves screwed up and have to go back to factory settings. I ALWAYS discard the spark plug that comes with the engine and install a CM6 plug. Thanks again.

That burble, and the "high idle hang" are your 2 options here. If the engine is rich enough to come down to an idle reliably, it's very likely rich enough to have that burble in mid range.

Honestly, with that high idle hang doing it's thing anywhere on final, most guys will go for the burble rather than face the uncertainty of the idle thing, especially with it's habit of doing that on final. For that reason, in my mind anyway, burble is the lesser of the 2 evils. Burble can often be minimized noticeably by opening the plug up to .025". For whatever reason that wider gap will burn the rich mixture more efficiently.

What club do you fly with? I spend the winters flying with Tri County over by Dunnellon. -Al

On Top of the World (OTOW Flyers)- Bob

I know your question has been answered, but I figure I'd just let you know how I got rid of the "hanging rpm". My DLE20 did the same thing and it annoyed the hell out of me. It made landing a pain. After a crash damaged the spark plug cap I decided to just get a new ignition. I went with a DLE30 unit. SInce it doesn't have the timing step, the hanging rpm was gone! You can richen the tune like has been mentioned, but I hate the burbly sound of a rich engine.

Oh, and FYI, I too always use the NGK CM6 plugs.

good day,
Jeremy

Bob, Jeremy is talking about the ign. modules shipped with the earliest generation 20's. It drove many nuts. Could go into detail regarding them, but there's not many around still making owners crazy.

You can tell if you have one easily by looking at the max input voltage for the module. If it's 8.4v, you have the newer one that does not have the issue Jeremy describes.

If you have an older one, be happy to go into it. -Al

All my module's have 4.8v to 6.0v on them. I must have the older type. I can live with the "idle hang" as I like a smooth transition.

If you switch to something like a DLE 30 CDI you can have both a smooth transition and not have that pesky hanging idle! :-)

The current replacement Ignition for the 20 doesn't have the strange timing curve either. In fact, you can use the ignition from any size DLE single without problem. They all use a CM-6 plug.

HK has their brand for about $30. Those work fine as well.

I wouldn't trust hobby king, but that's just me. I'll try their stuff on my SC truck and buggy, but I won't trust their stuff in anything that flies. I kinda think of them like Harbor Freight tools. If they break or don't work I won't mind too much and I'll throw it in the trash. If it works, then I saved a couple bucks.

Anyway places like Valley View sell ignitions that'll work well too. Most of them are made from the same company anyway.

My DLE 30 module is identical to my DLE 20's but I purchased all my DLE's a few years ago, right after Jody's first post on this thread.
All my 20's (I have three in service) run the same, either I have the idle hang or the mid range "gurgle". I opt for the smooth transition and
put up with the "idle hang" I have other larger DLE but they are still new in the box. I am 80 yrs old and slowing down on my RC so I do not
know how they will perform. Thanks to all for the info!

3 things being discussed here.
1. Transition (idle to wide open transition)
2. High idle hang
3. Burbling

That #1 smooth transition (idle to wide open throttle response) is not hard to achieve with any of the modules, and has little to do with whether or not your engine is susceptible to the #2 high idle hang or #3 burbling

The tuning option I was mentioning earlier, is regarding the #2 high idle hang and #3 the degree of burbling you experience. You can have pretty decent transition through that entire range. It's not really an issue.

You can minimize/eliminate the #2 high idle hang by running the low speed screw a hair richer from where it is now, WITHOUT affecting your transition. If you have the older module (#2?) you can further minimize the idle hang by setting your idle speed as low as possible (something under about 1800rpm or so). Because of the single step timing curve that occurs around 2200 rpm or so, there may (will!) be some difficulty if your idle is set closer to 2000rpm.

Yes, you may notice a little more #3 burbling with the richer mixture, but that can be minimized by increasing the spark plug gap to .025"

All of the above works. I made these adjustments several years ago and there has not been an issue since. I went one step further; The plane is one of the older H-9 Corsairs, .60-size. I installed a 3-blade Master Airscrew 16x8x3. The additional mass of the 3-blade prop completely eliminated all of the three issues discussed after setting up the three steps outline in ahicks post.