4*120 Build Thread
 

I've just started building my 4*120.

I am using an Adjust-O-Jig to build my wing panels. I really like this jig for building any type of straight panel that doesn't have any taper too it. You get a perfectly straight wing, everytime. It takes quite a bit of time to actually set it up. You have to measure out all the rib spacing and then lock the jig down, but it's worth the time and effort.

Here are the first pics of the right wing panel. It took me about 2 hours to set up the jig and get all the ribs set and strapped down. But once I got the CA bottle out--I made quick progress. My total time spent glueing on all these sticks you see in the pics was about 15 minutes.

This plane is designed to have an 81" wingspan. But, since all the stringers, and spars are actually 42" long, I've decided to make each panel 41.5" long. When joined together, I will have an 83" wing. This will increase the wing area from 1205sq.in. up to approx. 1235sq.in.

I'm going to use a Ryobi 31cc gas conversion engine on this plane, and they aren't as light as the 120 size glow engines that are spec'd. for this plane, so I don't think an extra 30sq.in. of wing area will hurt things.

You'll have to pardon the messy work bench. When I start building a kit or assembling an ARF--I don't spend the time to clean the workbench before snapping picks. I put a few pieces together--and then snap a few picks. Then I grab the glue and hit it again. If ya don't like messy workbenches, you probably won't like this build thread. Your going to see a lot of pics with my workbench in various stages of messiness. Rarely clean.

RE: 4*120 Build Thread
 

I'm headed off to start the shear web pieces on the main spar and the trailing edge. I'll also begin the center section sheeting.

More pics tomorrow.

RE: 4*120 Build Thread
 

Tell me about this adjust o jig and where to get it,sounds like a neat thing.I like anything to make things easier.I don't mind the mess it is easy to get lost in the build.I am thinking of the 120 for a winter project so I will be following your build actually it will be one of a few winter projects,we get a lot of snow and cold here so I am stocking up on things and I can't do any shoveling anymore so hey more time to build.

RE: 4*120 Build Thread
 

Im right with ya! Is that Peach Brandi in the Mason jar? LOL;) I ran out of CA so Im gorunded till I get to the LHS[:@]

RE: 4*120 Build Thread
 

The Adjust-O-Jig is no available anymore. Collectors item? I bought it about 6y rs. ago and have held onto it. If memory serves me correctly, it was about $125 at the time.

The mason jar is full of rum & coke, but it looks like all the ice was melted by the time I took the pic. Look hard--you'll probably find a pack of Marlboro Lights somewhere in the pics.

Hey, if ya can't drink & fly--you may as well drink & build.[sm=spinnyeyes.gif]

I got the trailing edge sheeting on both the top and the bottom. I got all my shear webs in.

Chris:
The plans don't tell ya to install shear webs in the 2 bays in the center of the wing panles. This is so that the dihedral brace will fit in.

I've made a small change. Most wings will have to install plywood or balsa webs on the front and back side of the spar where the brace goes in. This makes a "pocket" to hold the brace in--and also makes a larger glueing surface for the brace.

Our brace is only 5/32" wide, so you can glue a piece of balsa in between the top and bottm spars. Glue a piece in the front and the back. This makes the dihedral brace pocket smaller and it closes it all up. Now when you install the brace, your glue won't run all over inside the wing panels.

I'm uploading a pic that I drew. This is a top view of the wing panels at the center section. On the left is the LE stock. The dark shaded are in the center is the brace, and you should be able to see the lines that represent the spar and the pocket webs that I've added.

RE: 4*120 Build Thread
 

Im 3/4 through the right wing. Check out the difference in the 81 incher opposed to the 63 inch span of my Alpha 40 trainer. This things gonna be a monster!

bump

RE: 4*120 Build Thread
 

Lookin' good!!

I'll post some more pics of my progress soon. I got a new ARF in the mail today, and I've been busy drooling over it. Haven't touched the 4* in 2 days.[:o]

I'll get busy on it again tomorrow. No point in starting a build thread if I'm not gonna post pics.[:-]

RE: 4*120 Build Thread
 

Alright!! Here's some more pics of the wings. I've got a bit more sheeting to do, but I can't complete it until I pull the wing off the jig.

As you can see, I've added some diagonal braces in between the rib bays. This is the same way that the 4*60 wing is built. These diagonal braces will add a tremendous amount of torsional stiffness to the wing.

Before I put the torsional braces in--the first wing off the jig was VERY flimsy feeling. I was able to hold the tip and root ribs and twist the wing quite a lot. After installation of the torsional braces--I can't budge it unless I twist pretty hard. Lots of strength, for a minimal amount of weight. The torsional braces are made from 3/32" balsa.

At the LE of the root rib bay, I've added a small balsa filler block. This is the area where the wing dowel will be epoxied into the LE of the wing. The plans only have a small lite-ply brace thats glued in between the top and bottom of the first stringer. I don't trust this little piece of lite-ply as my only means of keeping the LE attached to the wing when pulling high G maneuvers. The balsa block will add some additional glueing surface to the dowel and frontal area. Again, a minimal weight gain for a tremendous gain in strength.

Look at the 2nd and 4th pics:

This is the dihedral brace area. The dihedral brace goes into the first 2 rib bays. The brace is only 5/32" wide. But, the main spars are 1/2" wide. According to the instructions and plans, you simply notch out the first 2 ribs for clearance, and then slide the dihedral brace in untill it touches the 3rd rib. Epoxy it.

Thats not going to work for me. The problem is that there is not a "pocket" for the brace to glue into. By just sliding the brace in and glueing it to the top and bottom spars--you will get minimal glueing area. This is because the dihedral brace will only be glued to the spars. Nothing else. Remember, this brace is only 5/32" wide. Just barely over 1/4" in thickness. You have no way to contain the epoxy once you slip the brace into place. The epoxy if free to run all over inside the wing, and get on anything BUT the area where you want it.

My solution:
I've added a simple balsa web--similar to a shear web. There are 2 balsa webs. One in the front of the dihedral brace and one behind it. The front balsa web runs from the top spar to the bottom spar, and is flush with the front of the spars. The rear web is placed so that it is just slightly snug to the dihedral brace when it's inserted.

What I've essentially created is a boxed pocket for the brace to glue into. By putting balsa webs in front of the brace and behind it, there will be no place for the epoxy to run out. All your epoxy will be contained to the area immediately surrounding the dihedral brace. This provides additional glueing area for the brace as well. You will not be relying solely on the glue where the dihedral brace contacts the top and bottom spars. I now have a complete boxed pocket for the brace to glue into. Tremendous glueing area.

I used only 2 or 3 drops of thin CA to install these additional webs. They just need to hold in place. If you flood the area with CA, your likely to end up with a big goober of hardened CA INSIDE the pocket that we're trying to creat. If you get a big goober of glue in there---your dihedral brace is going to hang up and it won't fit anymore. This would be BAD.

Just tack the webs in with enough CA to hold them in place. The epoxy will do the rest when you glue the dihedral brace in.

Again, minimal weight gain for a tremendous gain in strength.

And the pics:

RE: 4*120 Build Thread
 

First time user. Can someone let me know how this works. I would like to talk to RC Pilet
Thanks
Kenj

RE: 4*120 Build Thread
 

Looking to talk to RC Pilet

RE: 4*120 Build Thread
 

Do you see the little icons in the frame below the text box?

Click on the one labeled "PM" and that will let you send the author of that post a Personal Message. Find a post by RCPilet and click on PM in that message.

BobbyG

RE: 4*120 Build Thread
 

I sent you an email. Then I went to my email and found the one you sent me. Good luck.

RE: 4*120 Build Thread
 

I've just hit a snag in th e build process.

I didn't move my firewall back. I just glued it in the stock location. The problem is that the Ryobi is quite a long engine when it's completely assembled. The back of the prop is about 2" in front of the cheeks on the sides of the fuse.

I don't like the way it looks. I think it would look better if the back of the prop was only about 1/2"--3/4" in front of the cheeks.

Another concern is the moment arm of having that much weight sticking out so far. I am planning on installing 3 servos in the tail anyway. 2 elevator servos and 1 rudder servo. The conmbined weight of those 3 servos is about 5oz. That will counter-balance 15oz. in the nose. Give or take a little.

I am mounting the Ryobi 1/8" off center to the left. I'm anticipating needing some right thrust. I'll have to fly it and then make right thrust adjustments with some thin washers behind the left side of the mount.

The wing is almost finished. I have to install some servo mounts in each panel, and then glue the panels together. I usually prefer to cover my wings first, and then join the 2 panels. But, this wing requires some fiberglass on the center joint. I'm not going to use the 2" fiberglass cloth that came with the kit. I've gone to the auto parts store and bought some 4oz cloth. I am going to glue the 4oz cloth just slightly more than 4" wide on the center joint. The fuselage is 4" wide at the wing saddle, and I want just a little bit of fiberglass on the wings where they rest in the wing saddle. So, if I glue the 4oz cloth on about 4.25" wide, it will be just a little wider than the fuse. I want the glass to ride on the saddle, instead of just the balsa sheeting on the wings.

I've sheeted my wings out 1 more bay than called for in the plans. The first 4 ribs on each panel are undersized, so that when you glue the sheeting on, it will be flush with the surface of the rest of the wing. All I did was cut my sheets long enough to go all the way out to the first full sized rib and I just butt glued the sheeting to the side of it. I have 11.25" of sheeting on each panel at the root.

RE: 4*120 Build Thread
 

Pics of the Fuse and the wing sheeting.

I am going to use an HS-77 Low Profile servo for each elevator. They will fit on the sides of the fuse, if I cram them up forward near the 6th former.

You can see that I'll need about 7.5" for my linkage rods to the elevators.

Total wing length turned out almost 83.5" long.

Wing sheeting in the center section is 11.5" on each side.

RE: 4*120 Build Thread
 

Sorry to keep posting. I can only upload 4 pics at one time. My 'puter is running slow on uploads.

Does anybody have an opinion about the engine location? I'm not sure if I should move the firewall back and get the back of the prop closer to the cheeks or not.

If you look closely, you can see the hose clamp on the front of the engine. Thats for the Hall sensor. I'm using a C&H ignition on the Ryobi.

Here are pics of the engine:

RE: 4*120 Build Thread
 

looking good, keep posting!

Im gettin ready to sling about a bottle and a half of POXY !!!!!!!

Im goin in!

:D

RE: 4*120 Build Thread
 

You done yet?:) Let's see some pics of yours.[sm=thumbup.gif]

I'm going to beef up the landing gear mount. I've had one of these planes before, and I know that the gear mount is weak. I plan to add some ply and some tri-stock.

I also plan to add some more meat to the front of the F2D former. this is where the wing dowels will slide into the fuse. It's just 2 pieces of 1/8" lite-ply. I am going to put in some more ply and I'm also wanting to install some brass tubes to keep the dowels from wearing down and getting sloppy.

I'll take detailed pics and post them. Probably won't be untill tomorrow or the next day.

RE: 4*120 Build Thread
 

Im hangin right with ya less the motor. Ill be slow now though, gonna move the cockpit back 3 inches and add Wing tips.

Gonna epoxy the wall in a sec.

Shes big aint she?

Shew weeee

lol

RE: 4*120 Build Thread
 

Put your blind nuts in the tail for your tailwheel assembly. Look at my pics. I got mine mounted. I can take it off for covering and assembly, but if ya don't put the blind nuts in now--it only gets tougher later on.

Lookin' good.

I left my cockpit stock, but I'll be cutting the canopy WAAAY down. I want it to look small and tight. It makes the nose look longer, and I don't like that big bubble look with the stock canopy.

RE: 4*120 Build Thread
 

I've got the holes cut for the tail servos. I had enough room to put the rudder servo in the side. My initial plan was to put it on the bottom. I like it on the side, and I'm glad I had the room to put it there.

HS-77 Low Profile on the elevators and a JR4721 coreless on the rudder.[8D]

Even though the fuse sides are lite-ply--I added another lite-ply brace behind the screws for all the servos. This just adds a little bit more wood for the screws to bite into. I didn't want to chance just screwing the servos to the fuse.;)

RE: 4*120 Build Thread
 

For Roybi engine move firewall back 1 1/2" to 2" install servos in tail under lightening hole cover.

RE: 4*120 Build Thread
 

I just ran out of thin CA.:(

Lucky me, I made an order at Tower on this past Tuesday. Hopefdully, I'll get a little box from the mailman tomorrow. I ordered some CA, and a couple other items.

Can't build the tail feathers without thin CA.

I was going to quit for the night, but as I'm typing this post, it occured to me that I can build my servo mounts in the wings. Then I can glue my wing halves together. I'm pushing hard. I want to get this thing framed up.

Then I can cover it and FLY IT!!:D

RE: 4*120 Build Thread
 

ummmm ut oh, I glued my wings tonight. Havnt done the servos [&o]

that gonna be a problem?

Im not happy with the wing anyway. Didnt line up tp good.

RE: 4*120 Build Thread
 

It shouldn't be a problem. It will just be more work to handle the entire wing while you install the servo mounts.

I got one servo mount finished. I just took a piece of the lite-ply from one of the lightening holes in the kit and glued it between 2 ribs. Couple pieces of tri-stock underneath, and I was ready to hack the hole for my servo.

I'm using JR4721 coreless on the ailerons.

I'll post pics tomorrow

RE: 4*120 Build Thread
 

Here's my idea for a color scheme.

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.

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!

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

RE: 4*120 Build Thread
 

Ok, BIG Milestone here! It now looks like a PLANE !!!!!

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

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

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/

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.

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):D, 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.

RE: 4*120 Build Thread
 

I don't remember asking too many questions. Only asking for opinions about moving the firewall back.

I know that. I'm using a long shaft. Can't you tell by looking at the pics of the engine?

I am using an engine that doesn't have the shroud. I just bolted the conversion parts on.

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?

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.

I saw that. But, I wanted to build the 4*120 kit.

RE: 4*120 Build Thread
 

Word !!!![8D] Goin to sheet the rear of my bird right now~ !

RE: 4*120 Build Thread
 

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.

RE: 4*120 Build Thread
 

Did he ever finish that horizon 2 plane?

Id like to see that

RE: 4*120 Build Thread
 

Ryobi Coyote:

My apologies for getting snippy.[:o] 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.

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!

:)