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4*120 Build Thread

Old 11-26-2005, 02:15 PM
  #26  
Rcpilot
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Default RE: 4*120 Build Thread

Here's a couple pics of the servo mount in the right wing panel.

All I did was take a piece of lite-ply from the kit and sanded it down to fit in between 2 ribs. I glued it in with a couple pieces of 3/4" tri-stock. Hacked a hole in it and then added a couple strips of lite-ply to the back for the screws to grab.
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Old 11-26-2005, 02:45 PM
  #27  
C_Heath
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Default RE: 4*120 Build Thread

Id get high trying to keep up with it in the air. Looks kool!

Uphoric and such, I like it!
Old 11-27-2005, 09:22 AM
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Kenj
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Default RE: 4*120 Build Thread

Hi Chris

This is turning into one quick build. What was outcome of the firewall problem and what did you use for the engine mount? I'm still giving the engine thing some more thought. My experience with wacker engines is there not reliable at all.


Ken
Old 11-27-2005, 03:46 PM
  #29  
C_Heath
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Default RE: 4*120 Build Thread

Ok, BIG Milestone here! It now looks like a PLANE !!!!!
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Old 11-27-2005, 07:55 PM
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Default RE: 4*120 Build Thread

Hello C Heath

What are your plans for a power plant, I've been talkin to RCPILET on this and I'm not sure whether to go gas or stay with the glow engine? Got one on the way if the pony express ever gets here.


Ken
Old 11-27-2005, 10:14 PM
  #31  
Rcpilot
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Default RE: 4*120 Build Thread

Ken:
If you get yourself a new Ryobi--as I did--and buy the conversion parts from www.wackerengines.com you'll have a much more reliable engine than any glow engine on the market. The carb is much easier to adjust. The needles will stay put--no need for tweaking the needles from day too day--as you do on a glow engine.

They are about $200 cheaper than a Saito 150. Thats $200 you can spend on covering, servos, etc... And you'll be able to fly the gasser for pennies compared to a glow engine.

I'm pretty sure C_Heath is going to use a 25cc Toro weedeater for power.

The size and wing area of thisplane just lends itself to a conversion engine
Old 11-27-2005, 10:37 PM
  #32  
C_Heath
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Default RE: 4*120 Build Thread

Saito 150 $369 plus tax

This........ $163.00 Shipped to my door, ready to crank, cheaper to run, to spoogey fuel etc.

http://www.scottellingson.com/
Old 11-27-2005, 10:46 PM
  #33  
C_Heath
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Default RE: 4*120 Build Thread

Sry, I didnt see you were from Canada. So that would be 431.21 plus duties. [X(]

Sheesh, I couldnt live up there. Too cold anyhow.
Old 11-28-2005, 08:15 PM
  #34  
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Default RE: 4*120 Build Thread

Hi Rcpilet,

You raise many questions in your posts and I may be able to provide some additional input.

1. In my experience, the long-shaft Ryobis can be made shorter than the short-shaft versions. Sounds crazy, but it's true.
2. Don't be afraid to remove the integral flywheel shroud; I do it all the time. After awhile you can even get a little "artistic" and do a real neat job! I use a hacksaw first, then finish up with a die grinder equiped with a carbide burr meant just for cutting aluminum. No filing, no emery cloth. Takes me less than a hour; really comes out sharp! Looks like a CNC job! I use the die grinder, because I do alot of conversions. BTW, this is NOT a Dremel Mototool! Of course, many of the fellows use files, etc., and that's OK. Also, I've heard of fellows using a two-piece crankcase with a new jug, so they wouldn't have to grind off the shroud.
3. There are several threads on RCU that relate the successful conversion of the SIG 4S120 to Ryobi 31cc. The only caveat I would raise is to run some ground tests and then some test flights, before you apply full power in the air. You've done a spectacular job with the anti-torsion wing bracing; make certain the tail is also well braced against torsion and vibration effects.
4. Even though I bought a Dodge Aircraft Carrier (aka Caravan), I make most wings "two-piece." Surfboards are cool in CA, but not here in PA! There's an easy technique to do this that has been covered in the model airplane literature. Works every time. It is more work than grinding off a flywheel shroud, but you won't have a surfboard to transport.
5. There's another plane available that was designed especially for the Ryobi 31cc. See my thread: "Got Gas Sport for Ryobi 31cc," in the Giant RC Aircraft Forum. My "Sport" is just about ready for covering. I'm still working on how to up-load the photos. Sure would save me alot of keyboarding.

R.C.
Old 11-28-2005, 09:38 PM
  #35  
Rcpilot
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ORIGINAL: Ryobi Coyote

Hi Rcpilet,

You raise many questions in your posts and I may be able to provide some additional input.
I don't remember asking too many questions. Only asking for opinions about moving the firewall back.

1. In my experience, the long-shaft Ryobis can be made shorter than the short-shaft versions. Sounds crazy, but it's true.
I know that. I'm using a long shaft. Can't you tell by looking at the pics of the engine?

2. Don't be afraid to remove the integral flywheel shroud; I do it all the time. After awhile you can even get a little "artistic" and do a real neat job! I use a hacksaw first, then finish up with a die grinder equiped with a carbide burr meant just for cutting aluminum. No filing, no emery cloth. Takes me less than a hour; really comes out sharp! Looks like a CNC job! I use the die grinder, because I do alot of conversions. BTW, this is NOT a Dremel Mototool! Of course, many of the fellows use files, etc., and that's OK. Also, I've heard of fellows using a two-piece crankcase with a new jug, so they wouldn't have to grind off the shroud.
I am using an engine that doesn't have the shroud. I just bolted the conversion parts on.

3. There are several threads on RCU that relate the successful conversion of the SIG 4S120 to Ryobi 31cc. The only caveat I would raise is to run some ground tests and then some test flights, before you apply full power in the air. You've done a spectacular job with the anti-torsion wing bracing; make certain the tail is also well braced against torsion and vibration effects.
I've done a lot of searching for threads about the 4*120 and conversion engines. Not much luck. You got a link to these threads?

4. Even though I bought a Dodge Aircraft Carrier (aka Caravan), I make most wings "two-piece." Surfboards are cool in CA, but not here in PA! There's an easy technique to do this that has been covered in the model airplane literature. Works every time. It is more work than grinding off a flywheel shroud, but you won't have a surfboard to transport.
I thought about making it a 2-piece wing. But, I opted for the standard wing because I didn't want to spend a lot of time modifying the kit. I know how to turn a 1-piece wing into a 2-piece wing. This ain't my first kit build. I've built about 30--35 kits and assembled more ARFs than I care to count. I just want to get it built and fly it. In order to do that, I kept it as close to stock as possible without getting into a lot of re-engineering. I'm also building this plane right alongside C_Heath. I wanted to help him along with HIS first kit build. Doing a bunch of complicated mods to the wing would have only made it harder on C_Heath.

5. There's another plane available that was designed especially for the Ryobi 31cc. See my thread: "Got Gas Sport for Ryobi 31cc," in the Giant RC Aircraft Forum. My "Sport" is just about ready for covering. I'm still working on how to up-load the photos. Sure would save me alot of keyboarding.
I saw that. But, I wanted to build the 4*120 kit.

Old 11-28-2005, 10:03 PM
  #36  
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Default RE: 4*120 Build Thread

Word !!!![8D] Goin to sheet the rear of my bird right now~ !
Old 11-30-2005, 11:12 AM
  #37  
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Hi Rcpilet,

I started in aeromodelling about 1950. One of my friends started in 1965, and he estimates he's built over 300 airplanes, mostly from plans. I've built somewhere between 100 and 150, mostly from BIY kits. But we both agree that we can still learn "new" ideas. That's why I like this thread and others like it. We all make mistakes and there are misunderstandings, but hey guy, please don't take my comments and opinions personally. I make mistakes and have senior moments. But for an old guy, I quess I do OK!

1. I did not say you asked too many questions, many questions, or any questions. I said you RAISED many questions. Translation: You
increased interest in the 4S120 conversions, by starting this thread, thus "provoking" many questions. I chose to just use "raised,"
instead of "provoked" (or a translation!). I ain't no wordsmith, but I think it's all somewhere in the dictionary.

2. Yep, I did see that you're using a long-shaft engine. Did you see where I kindly suggested that you could probably make it much
shorter? I'm not saying you should make it shorter, because you may prefer to move the firewall back (or have to move it back for
balance).

3. About the shroud comments. I copied that in from my WordPad in error. My error. Sorry.

4. I don't remember the exact threads here on RCU, but try searching for RamboRCU. Also, you'll see Jim's 4S120 on the JAG Engines
website. Jim very kindly answered my questions about his 4S120. Also, Google "Marty Hammersmith's Homepage." Marty also did
a successful conversion, and he used to answer questions. Don't know if he still does. The others were not on RCU, and go back a
couple years or so. Marty and Jim got me onto the Ryobi 4S120.

5. I've seen several examples of structural problems in the Four Stars. Not a reflection, in any way, on Bruce's design. The problems
were mostly related to an over-size engine. I believe Marty's 4S120 developed stress cracks in the deck sheeting, just aft of the
firewall. He suggested 'glassing this area. I've done this on all of my Four Stars since my second 4S40. Cuts down on hangar rash
and holding/lifting fingerdings. The others had to do with failure of the tail group: big engine, lack of bracing, poor glue work. Looks to
me that your building is top-notch, so these comments are for others following this thread. It's always easier to avoid a structural
failure than having to repair one after the crash!!!

Actually, except for the front-end, you've already got your 4S120 conversion going real fine! I like your thread; keep it going.

R.C.
Old 11-30-2005, 12:17 PM
  #38  
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Default RE: 4*120 Build Thread

Did he ever finish that horizon 2 plane?

Id like to see that
Old 11-30-2005, 02:03 PM
  #39  
Rcpilot
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Ryobi Coyote:

My apologies for getting snippy.[] I misunderstood what you were trying to say. It's hard to understand what a guy is saying through the keyboard sometimes. Would be much better if we could all chat in person.

I guess, after 8 years in the hobby, and quite a few kits under my belt--I forget that others might not have the same experience level as myself. I know that building 30 kits is nothing compared to your experience--but compared to the average modeler today, thats about 28 more kits under my belt than the other guy.

So, I do understand where others might have questions that I haven't answered, or maybe I haven't explained something in enough detail to make it clear to everyone.

I encourage ANYONE reading this thread to ask questions. I am willing to help and answer questions from people who have an interest in this project. Or email me. I like to help people, and I am not one of those guys who thinks that my building techniques or ideas are something "top secret". I hate those kinds of guys[:@]

My back is totally screwed up right now. I had 2 microdiscectomy surgeries on my disc at L-5/S-1 in May, and they didn't work. [&o] I have a pinched nerve in my back from a herniated disc, and it's not pleasent. I'm in a lot of pain. I'm kind of out of commision for a little while. I can't walk downstairs to the shop and build. I just need to rest and give it some time to heal up a bit. I went down in the shop a few days ago and built a couple more building tables. Running a powersaw and handling 2x4's and hollow core doors with a herniated disc was a pretty stupid thing to do. It might take me a few more days to recover enough to where I can walk downstairs and stand up to build for any length of time.

I'll get back on this 4* project as soon as I can. Bear with me. It's on hold, but I'll get back on it ASAP.
Old 11-30-2005, 02:55 PM
  #40  
C_Heath
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Default RE: 4*120 Build Thread

Im still pluggin along. Rear is sheeted, I still havnt gotten that "vision" of the cockpit. It has been moved back a full 5 inches. I will roll the top deck when my balsa gets here. Control sufaces are beveled and rounded. I facricated 1.5 inch wing tips and rounded them the ol fashioned way. They will add 3 full inches to the WS and give it a total of almost 85 inches.


I still have a way to go but my parts table is getting real low and thats a good thing.

Get well soon Pilet! Gimme a holler!

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Old 11-30-2005, 02:59 PM
  #41  
C_Heath
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Default RE: 4*120 Build Thread

And for those of you who who noticed my jack stands as risers for my build table, I already have a Patent Pending so STEP OFF [>:]


HAHAHAHAHAHAHAHA !!!!!!!!
Old 11-30-2005, 07:26 PM
  #42  
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Hi Rcpilet

Lumbar disc problems. Ouch![] I hear you, loud and clear. I've been suffering with disc disease for more years than I care to think about; lumbar and cervical spine. I met a guy, some years ago, over in Toledo, at the annual R/C Show. He really made me sad. He had been an avid r/c flier, but had to quit due to pinched nerves in his cervical spine. When he went to look up at his plane, he would get dizzy and/or pass out from all the pain. He had to wear a cervical collar most of the time. The sad part was that he was a young guy. I've experienced similar symptoms, but so far I've managed to keep things in check. I hope you can beat it and get healed.

You know, I owe you an apology as well. One my friends was looking at this thread and said "Hey, you set the guy up." He's right. What I should have said was "Your thread has raised many questions." I should have been more careful with my words. Sorry.

Let's get back to the 4S120.

R.C.




Old 11-30-2005, 08:07 PM
  #43  
Kenj
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Default RE: 4*120 Build Thread


Hello RC Pilot
Sorry to hear about the back, thats a drag. Hope your not down to long this is a great build thread you've got going. A question about the conversion engine. What is the vibration going to be like compared to a 4 stroke glow engine, and do you have to beef up the firewall? Next question is what kind of RPM's willyou get out of it and with what size of prop?



Thanks Ken
Old 11-30-2005, 09:01 PM
  #44  
Rcpilot
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The firewall is plenty strong. Just put tri-stock behind AND in front of it. Then pin it. I like to use bamboo scewers and soak them with thin CA. Rock hard and cheap.

The engine is going to shake like nuts compared to a 4-stroke glow engine. But the airframe will handle it. No problem. This fuselage is solid lite-ply. It's built like a Russian outhouse. Just use plenty of Medium CA on the fuselage and you'll be fine. I have mine glued solidly and there's little fillets of medium CA everywhere I could get them.

My Ryobi engines that I've converted in the past usually will swing an 18-6 just under 7000RPM.

It's generally recommended that you don't exceed about 8000RPM on a Ryobi. If you've ever had one apart--you'll know what I mean. If you haven't had one apart--trust me. The rod is just 2 simple pieces of metal thats stamped together. The crank counterweight is just stamped pieces of metal too.

The engines have plenty of torque, but they are NOT a high RPM engine. I would prop it for 7000RPM on the bench and let it unload in the air. That should keep it under 8000RPM.
Old 11-30-2005, 09:12 PM
  #45  
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Here's a thread in the Tachometer Forum. Some posted RPM numbers with different props. I personally think some of these numbers are too high. I wouldn't crank a Ryobi that hard. Thats why I like the 18-6 prop. Plenty of thrust--good speed, and keeps the engine in the RPM band is was designed for.

http://www.rcuniverse.com/forum/m_32.../tm.htm#328508
Old 11-30-2005, 09:21 PM
  #46  
Rcpilot
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Here's a link to the Ryobi trimmer that I bought at Harbor Freight. They go on sale and off again periodically. It's the 725R engine. Thats the long shaft engine and it's easy to convert.

It's a twin ring. It doesn't have the nasty compression relief slots like some of the Ryboi engine do. Thats a good thing.

http://www.harborfreight.com/cpi/cta...emnumber=51584

Get 'em while they are hot!! I paid $49.99 for mine and got it shipped to my house for $58. This is the same trimmer that I got a couple weeks ago. It says "factory reconditioned" but I couldn't see anything on the trimmer that didn't look brand new. Probably a customer return.

I posted links to places to get the conversion parts in an earlier post in this thread. You can convert it for $140 total investment. Thats the engine and all the parts to convert it.

I spent an extra $120 for the C&H--but it wasn't necessary. More for cool factor and weight loss.
Old 12-01-2005, 05:38 PM
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damifino
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Default RE: 4*120 Build Thread

CHEATH- Have you thought about rounding the corners of your tail feathers? Maybe 1" to 1 1/2" radius. Won't hurt flight performance one bit.......Take some black paper or tape and play around with blacking out what you could cut off the corners.

RCPILET- uh, color scheme is uh, interesting........?

_____________________________
Old 12-01-2005, 05:44 PM
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Damifino,

I sent you an email earlier. Yes, Im rounding EVERYTHING lol.

Old 12-01-2005, 11:12 PM
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Rcpilet, Hope its nice and warm down there in the flat lands [8D] Good to see you decided to build a 4*120. Hope to fly mine at Lost Creek this Sunday if the snow ever quits!!! You'll have to put some skis on it and bring it up this winter. Good luck with the back.

Scott
Old 12-02-2005, 04:26 PM
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Rcpilot
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Hey Scott:
It is exceedingly warm down here. Pueblo is kind of like in a banana belt. I haven't seen any snowflakes yet. Temp is still pretty steady in the 50s and 60s. A bit windy sometimes--but warm. I'll take it.

I had to get out of the mountains. It was straining my sanity. Too cold for too long. It actually snowed the day I left Leadville. I got out just in time.

We bought a house here in Pueblo and just love it. I got a 1200sq/ft shop in an unfinished basement and my wife has a double garage to park her car in.

My back is getting better, but it's a slow and frustrating process.

I sure don't miss that snow. Thanks so much for your hospitality last year. You guys are a great bunch of guy and it was fun flying with you. If you ever get down to Pueblo and want to go flying--I got planes and TX's you can borrow. Just shoot me a PM and I'll give ya my phone number.

Take care and stay warm.


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