Bob Paris

My Feedback: (13)

I am installing an RCG 20cc gas engine into a new model, and I need to know what the prop shaft dia. and thread size is. I need to know, so I can order a spinner adapter for my new model.

The instructions state to use 25~40/1 oil mixture. From what I read...it looks like I'll be using 25 to 1 ratio for my oil/gas mixture. I've been told to use outboard moter two cycle oil...any suggestions ?

I would like to replace the carb on this engine...any suggestions ?

What replacement spark plug should I use ?

This is my first gas model, all my other models have been glow fueled. I built a 60~90 size Big Stick and mounted a RCG 20cc engine to the nose.

Thanks for the help,
Soft Landings Always,
Bobby of Maui

w8ye

My Feedback: (16)

More than likely is 8 X 1 metric..

ahicks

My Feedback: (2)

25/1 should be plenty safe! I was thinking that 32/1 (4oz/gal) was the suggested though? I've been running that in everything for quite a while, but went to it (from 40-50/1) because of the suggested for this engine. Now, I don't remember where I got that info though! Maybe for the DLE 20? I'm not real picky on oil brand, but I do insist that it say "for use in air cooled engines" on it somewhere! Outboard oil not a real good plan. They run MUCH cooler than these little guys run.

Just curious, what's the thought behind replacing the carb?

NGK CM-6 is the plug most are using, gapped at .024 for more consistent mid range. Available at auto supply for 4.00 or less. Some outfits are raping buyers....

Nice idea on the exhaust!

karolh

To the best of my knowledge the RCG 20 is supplied with a Walbro carb which is just about the best there is for our small engines. This model and engine combination is very good first choice for a gasser and should provide you with lots of enjoyment so enjoy.

Karol

capnduane

Flew my 1/4 scale 16lb Clip wing cub today, It has the RCG 20 with 17/6 prop. Bone stock. Always runs great, flys great, enjoy!

Bob Paris

My Feedback: (13)

Thanks for the information...I'm still not sure about the prop nut size, but I'll try to get a 8x1 adapter for my metal spinner. The kit came with a plastic spinner...but after having a plastic spinner expoled on me...I will use them no more.

I read that the carb on the RCG 20cc engines was not reliable...just what I've read is some forums. I wouldn't know a Walbro carb from any other brand carb...but thought I might as well find out where I can buy replacement carbs incase my carb turned out to be a problem. How can I find out if its a Walbro carb..and where do you go to buy replacements?

I installed a DoBro vibration mount (90~120 size). I hope this helps with any vibration issues I may have. Several of the guys in our club have had issues with servo's going bad on their 2 stroke gas models. I did balance my wood prop, as I do with all my wood props and I only fly wood props.

I'll try and find a good 2 cycle engine oil for air cooled engines...any recomendations ?

I'm hooking up the DLE rpm sensor, as well as a battery voltage meter for the ignition...all put on top of the fuel tank cover I built. So when the battery voltage meter is showing a green light, you will know the engine is hot. No light, no fire.

I ended up going with a 500cc fuel tank, installed over the CG. The throttle servo is up forward in the forward bay, with the electroic unit for ignition, and both batteries will be set way aft in the tail, for balance (I'll make a hatch aft for this-and still to do).

Thanks again for all the help,
Bobby of Maui

ahicks

My Feedback: (2)

Regarding carb reliability, I haven't experienced any trouble, and haven't even read about anything serious? Generally, worst case is you need a carb kit, commonly available at most shops servicing chain saws, etc.

Regarding servos, gas engines are hard on them. Most will recommend metal gears (not cabonite!) on the flying surfaces for reliability.

Favorite oil brand? As mentioned, I look for "for use in air cooled engines" on the bottle. If it says that I'm good to go. Don't have a favorite. My thought there is if I'm running something that says that, doesn't matter to me if it'd dino or synthetic based, the engine is not likely going to suffer from an oil related issue (not at 32/1 anyway!), and it's very likely going to out last me....

Nice plane! Have fun! -Al

karolh

All around very good advice. To check if your carb is a Walbro, it should have the name embossed on the carb cover with the single centre bolt.

Just for the heck of it re your oil question, any good mineral or synthetic oil designed for 2 stroke air cooled engines and mixed at 32:1 will work just fine such as, Pennzoil, Stihl Ultra, Red Line, Royal Purple or Castrol to name a few.

Karol

capnduane

Prop nut is 8x1.25 on the RCG 20. Ahicks advice is spot on.

Bob Paris

My Feedback: (13)

Hi Guys,
I finished my new model and found out that an 8mm x 1.0 does not fit a RCG 20...the thread is to fine, so I ordered a 8mm x 1.25 nut and adapter for my model. The model came out to 9 lbs. even, with two 2000 ma. batteries mounted aft near the tail, on the bottom of the model. The balance came out spot on and no lead was added to balance the model...the two aft mounted batteries did the trick. I'm going to use a 15 x 6 prop on the model and I ordered 5" DuBro ballon airfilled tires for more prop to ground clearence-and yet to receivce from Tower Hobbies. The carb on my model is a Walbro and I am going to use Royal Purple 2 cycel oil for my 25/1 oil fuel mix.

I mounted my servo's aft and installed a solid tail wheel assembly for the model.

I ended up with four "Y" connectors in my model...I wish someone made short "Y" connectors, like the ones that cme with my DLE RPM sensor. All my servo connetors, as well as inline connections, have safety clips installed.

I used metal control rods to connect the engine to the servo (I used a Airtronics 94322 servo) to contrl the engine. I also used a metal control rod to connect a choke rod to the engine for start up...any proplems with this set up ? I'm using a Airtronics 2.4 10G system.

It was my first Gas model build and was surprised at all the goodies that go into a gas model. This model is almost to small to install all the requirements needed to support a gas engine...but feel it should do the deed just fine.

Thanks for all your support,
Soft Landings Always,
Bobby of Maui

ahicks

My Feedback: (2)

Bobby, a 15x6 is too small! You're after something closer to a 17x6. Check out the note from the guy with the Cub above. That would duplicate my experience with this engine as well? -Al

acerc

I have two 20cc's and so far theprop I like bestis an 17x6. Those are on a Profile and a Stearman.

raydar

If you are going to run a 15 6 prop then you will miss all the fun you can have with this engine, it will rev its t*ts off and give poor performance, 17 6 and it will drag that plane about like you would not believe.

3136

Hey Bob, looking at your 3rd and 4th pics it looks like you are using a metal rod for the throttle servo.
Do those rods screw into a plastic connecting rod inside that sleeve or is it metal all the way through?

acerc

Good catch 3136. That is a definite no-no. Just those two point's being metal, throttle arm to metal control arm, will cause RF. And wear really quick from vibration also.

3136

Hey Bob, the dubro ball links are great, I also put a washer between the nut and link for extra safety.
Use a nylon pushrod in a sleeve and that will give you extra protection from the dreaded rf.

bcchi

I do not no if your ignitions is all set the way the pictures show?
But your spark plug cap is not all the way down on the CM 6 spark plug.When the cap is on all the way It should cover the hex of the spark plug.Push hard with the heel of your hand,They go on hard and come off harder.
Good Luck
BCCHI

Bob Paris

My Feedback: (13)

Hi Guys,
God Bless...thank you for all your advice. I will need to change out my choke pull and engine servo connection to the engine. I will hook up DuBro ball links like 3136 advised. My control rod for the engine and choke is metal...all the way through. I was led to believe that 2.4 radio's are not effected with RF nose from metal to metal contact. I stand corrected and will make the changes stated.

I will double check my spark plug connection to make sure its seats properly.

I will need to by 5" DuBro balloon tires and go with a smaller tail wheel. My prop to ground clearence with a 17" prop would almost hit the ground with my current set up...bummer. Ok...changes coming.

By the way, up front next to the RPM indicator is a voltage check...when the lights on...mags are hot and this is connected to the ignition battery. The voltage check, below the radio switch, is for the receiver.

Thanks again for all your help guys...
Soft Landings Always,
Bobby of Maui

ahicks

My Feedback: (2)

Didn't understand you were faced with a ground clearance problem! A 15" 3 bladed prop might be an option for you?

Bob Paris

My Feedback: (13)

Ok Guys, here is today's mods,
I took your advise and placed ball links into my choke and throttle linkage. I did have a bag of 2/56 ball links, and hardware, so got busy and changed them. Next I ordered 5" DuBro balloon tires, and a .60/90 size tail wheel assembly, and will remove my 120 size I now have installed. I have only 2" of prop clearence with the model sitting on its tail...and 1" with the tail in the level placement. No where near enough clearence and the new tail wheel assenbly and larger tires should allow 17" props with no clearence problems.

I mixed my gas up with Royal Purple, 25/1-2 cycle oil, with "0" E-92% unleaded gas. I pulled the choke, hit the starter until I saw the gas make it to the carb, then went choke off, 1/3 throttle, and hit the mag switch. The engine fired right up and ran... : ) It ran for 10 minutes then I shut if off. The first run almost used up all the fuel my 240cc fuel tank. I let if cool off, then filled the tank and ran it again, this time it ran for more then 15 minutes and much smoother. So it looks like a 240cc fuel tank will be large enough for the model. I will run it for at least one hour...maybe two hours before I fly her.

I did notice that the tail shook like crazy...infact the whole model shook a good bit, even with a balanced 15x6 prop and a DuBro vibration dampening engine mount. At higher rpms, it seemed to smooth out, but at lower rpm's...it did vibrate a bit. So I made a second tail brace for the model, to stop the forward tail shake and called it a day.

I'm not sure how to read the RPM indicator...but at full throttle it showed 970 to 985 on the meter, with a 15x6 prop (my 17x6 props are inbound from Tower and Hobby King). Finding 17x6 props is not easy and since we don't have a real hobby shop on the island...its all mail order.

I bought and used 15x6 props, because the instructions I received with the engine stated to use this prop size. I will go to 17x6 like you guys suggested, as soon as they arrive. Prior to my first engine run, I put an allen head bolt through my muffler extension...a buddy of mine told me that there is a possiblity it could melt off the silver solder I used, at extended full power runs.

By the way...no clean up and no oil all over the place !

Thanks again for all your help,
Soft Landings Always,
Bobby of maui

3136

Hey Bob, 2 cycle gas engines are not like glow, just set it a little rich and fly it, otherwise you may overheat it and ruin it.
The gas engines run a lot hotter and the centre of the prop will not cool it enough, it needs air flow.

The rpm needs to be multiplied by 10 so it looks like you are revving it too hard and need a bigger prop.

I have tried anti vibration mounts and found that they make it actually worse, but I have not used the one you have.
When you run the engine on the ground for tweaking, make sure you have the wings on, as they dampen it a little.

Have fun

ahicks

My Feedback: (2)

I was going to mention having the wings on when running too. They dampen a lot of the motion that's concerning you. More will go away as you get some time on the engine and carb settings are closer to what you'll actually be running long term. The extra tail brace wires won't hurt a thing though!

I agree also that time spent ground tuning/running (beyond what is required for a basic tune) is generally not necessary. The best ground tune available will still very likely need to be tweaked when it's actually flown. I get it though if this step is more of a confidence builder!

Regarding your ground clearance issue, you could narrow your gear up a bit to gain some, and look around to see if you can find a tail gear with a little lower profile?

DaleD

Bob,

I am building this very same Stick for a friend, however, we are installing the 15cc RCGF. I have found the 15cc RCGF engineon 15x7 propto be more than sufficient for my H9 Ultra Stick 60 providing unlimited vertical performance, hence, we are using the same set up. Your Stick with the 20cc will be an absolute blast once you get past the prop clearance issues.

Can you provide details on the hardware you use to connect the vertical fin to the horizontal stab? What length and size push rods are you using and what type of ends and fastners?

Thanks

DaleD

karolh

A 15x6 prop is too small for your 20cc engine and would suggest you use at least a 16x6.

Karol

Bob Paris

My Feedback: (13)

Hi Guys,
I have a RCGF 15cc gas engine...but since I had two RCG 20cc engines and the physical size and weight is almost the same, decided to go with the 20cc gas engine. I believe this model will have a nice vertical presintation... : ) ... nothing like cubic inches to add climb rate to any model. I just wonder how the torque will effect the model with a 17x6 prop. When I broke in my ST G90 on a .40 size ultra stick...the vertical acceleration was outragious...but the torque was something to care for when adding power. Ugly sticks have powerful rudders and I just got used to using my rudder thumb when I had the G90 on board.

My 5" wheels, 17x6 props and new smaller tail wheel assembly are inbound and should be here by months end. I could have gotten them here sooner...but paying more for shipping then the flippen things costs is a bit to much for my budget. Shipping is always an issue here...and patience. It will arrive soon enough and until then, I'll run the engine a bit more...this time with the wing attached. I've other models that need my attention and will get busy until the new parts make it here. I'm not in a rush to fly it...but do look forward to the day. My Airtronics 10G Tx was sent in for an update and I will not fly anyway until it gets back to me.

I used plain old 4/40 wire rods (cut from 36" long rods-12" 4/40 rods are not long enough), for the tail brace wires. I went to Radio Shack and bought pre-tinned connectors, the one with no plastic covering-with the screw hole in the middle-w/a wire connetion tab. I fit the wire into the slot/tab and just silver soldered the wire to them. I made the top rudder connector first-screwed into place, for flight, then moved the wire to where I wonted to place the outboard stab connection, and cut the wire. Then I marked how the tab was to be set on the wire...then just soldered the tab to the wire-after removing it from the model. You will need to bend the tabs a bit to fit the angles of the wires to the stab, from the rudder...but Its really quite simple to do...and make sure you have the proper screws and hardware on hand for the five attachment points. I've done this on my models for years and it works. It gives you something to hold on to and also beefs up the tail feathers a bit. I used 4/40 cap head screws, washers, lock washers and fiber lock nuts...double saftied. I have a good collection of hardware on hand...so I just go to the cap head screw length that works best and attach the goodies. 3/4" long cap head screw for the top of the rudder and 1/2" for the stab connections. #2 washers, lock washers and 4/40 fiber lock nuts.

As soon as I get this model ready for flight, I'll let send you more pictures of the model.

I used different main landing gear then came with the kit. This gear is a bit heavyer then the kit supplied main gear and not easy to bend or reshape. I did add my rubberband mod to my landing gear and it does help with your less then perfect landings and helps keep the ground from sneeking up and causing prop damage on your model. I started this up in Alaska, and works wonders with rough landing fields. Even though I fly off of pavement, our field is note worthy for gusty and windy conditions. It can go from dead calm to 15 kts wind in a heart beat...the tropical trade winds can be tricky here. We also fly next to old WWII Corsair reventments and the revetments play hell with the winds. So strong landing gear sure helps in gusty cross wind days. Landing gear issues are a common problem at our field...guys are always messing with their landing gear, landing gear attachments and wheels. I also like to do touch and goes...so I beef up all my landing gear and have at it. I wore out three sets of wheels on my ultra stick .40...and two engines...before a big bush up and grabbed my model...may it rest in peace.

Soft Landings Always,
Bobby of Maui