Four Star 40 with Saito 56 (Full Version)

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Andrewmc -> Four Star 40 with Saito 56 (2/12/2008 9:31:50 AM)

I am currently putting together a Four Star 40 kit. While this is not my first kit build, it will probably be the first kit I finish and fly. I have a nearly completed 1/6 scale J3 Cub that is ready for covering, but I wanted to get experience with a low wing plane after my Hanger 9 Alpha before flying the scale model. (I also have a 1/4 scale tiger moth waiting paitently to be started!!).

I have the wings framed and the leading edges shaped, I decided to sheet the leading edges - more for aesthetics than anything else, and the fuselage is built, with a sheeted turtledeck. I am in the process of installing the servos and now have a few questions:

The first photo is of the servo layout. I have used Sullivan Gold n Rods instead of the supplied nylon pushrods following advice from RCU members regarding thermal expansion of the nylon rods. Is this layout ok? I don't know why it wouldn't be but I have no experience with servo layout other than the ARF I am currently flying. The pushrods do not cross between the servo and the fuselage exit, someone has told me that they should cross to provide slight resistance but surely the less resistance the better?

The second two photos are of the engine mounted on the firewall and the throttle linkage. I have removed the cheeks with the intention of building a balsa cowl. I have lowered the fuel tank by 20mm to allow for the side mounted motor. Does anyone have any suggestions as to how to connect the throttle to the servo? I seems very close to the edge of the firewall.

Andrew



DavidAgar -> RE: Four Star 40 with Saito 56 (2/12/2008 12:53:31 PM)

I am not seeing any issues with your push rods as long as they are secure the full lenght of them. As for the engine it can be done a couple of ways. Dubro makes a 4 stroke kit that mounts right of the edge of the motor mount. It is for all intensive purposes half of a bell crank. Your rod comes from your servo to the bell crank which is mounted on the engine mount about even with the center of your crankcase and then you make a rod that goes to your throttle arm from the bell crank. Another way of doing it is to have your push rod come out low on the carb and it then gets bent 180 degrees going back to the throttle arm. I prefer the bell crank method as it a little more presice, but they both work. Good Luck, Dave



submikester -> RE: Four Star 40 with Saito 56 (2/12/2008 2:42:56 PM)

I believe the throttle arm on the carb can be moved, either that screw in the center or a set screw along the side allows this. Turn it 180 degress and you'll be away from the edge of the firewall and more towards the inside.



Acs_guitars -> RE: Four Star 40 with Saito 56 (2/12/2008 2:59:39 PM)

I too am building a 4* with the Saito 56 side mounted... I have already used a Dubro 4-stroke throttle linkage kit to set mine up; It works very smooth.



frenchie79 -> RE: Four Star 40 with Saito 56 (2/12/2008 3:45:45 PM)

You may need room behind your servos for the battery for balance. Is everything glued down and cut? Do a prelim check on your balance before any more glue is laid down.

Looks like you have room to drill the firewall and mount the throttle-be tight to the side, conect to the middle hole on control arm of carb? just a idea! Servo placement looks good but keep checking the balance part to leave room for moving radio gear. I always glue down servo tray ectt. after I complete the build and sometimes after I cover so no LEAD is added-good luck.



Acs_guitars -> RE: Four Star 40 with Saito 56 (2/12/2008 4:55:26 PM)

quote:

ORIGINAL: frenchie79
Looks like you have room to drill the firewall and mount the throttle-be tight to the side, conect to the middle hole on control arm of carb? just a idea!



That looks like it could work on this one; my engine sits closer to the firewall... My carb is also set to have the needle pointing up thru the cowl for easy adjustments.



Test005 -> RE: Four Star 40 with Saito 56 (2/12/2008 5:34:45 PM)

quote:

Does anyone have any suggestions as to how to connect the throttle to the servo? I seems very close to the edge of the firewall.


This is how I do it, works perfectly and no bellcranks or extra items needed... Keep it simple.




hrrcflyer -> RE: Four Star 40 with Saito 56 (2/12/2008 5:48:03 PM)

Carrot,

Your servo layout looks fine to me too, as long as there is no way the two servo arms can touch. I have also used the 180 degree bend method for connecting to the throttle and it works great. You can relocate the servo arm to the bottom to give you more room by loosening the set screw on the side of the throttle arm , not the screw in the center of the throttle. That screw is your low end needle valve adjustment. Please don't ask me how I know that [;)]

Good luck with your plane. Can't wait to hear a flight report.



Andrewmc -> RE: Four Star 40 with Saito 56 (2/12/2008 7:10:22 PM)

Acs Guitars - the needle valve on your Saito points up, did you change it around? If so how did you do it? I checked through the engine manual but did not find any info in this regard.

Frenchie79 - I have already glued the servo tray into the rails. I only though about moving it for balance afterwards. I could try and de bond it (tightbond) or put it down to experience and remember next time.

Thanks everyone for the great ideas and photos.

One other point I noticed. I have used the Dave Brown 4045L mount. This is the mount recommended for the Saito 56, however the engine mounting lugs are slightly wider than the mount beams so that the screw holes are not in the beam centre and in fact the front ones "blister the side of the mount close to the bottom edge. Has anyone else experienced this. I do notice that the beams on this mount are slightly narrower than the 2 stroke version, is it possible this is just a mount from a bad batch and another unit may be ok?



Acs_guitars -> RE: Four Star 40 with Saito 56 (2/12/2008 7:28:00 PM)

As for rotating the carb, you simply un-bolt it and turn it around. I used the same motor mount and found the same issue in the past but it has yet to pose a problem (The 4* is the Saito's 2nd home). You can tray a Dave Brown FS60 mount if you feel uneasy with using it as-is.

Personally I would try to "pop" the glued in tray free, but it really depends on how much glue coverage you have. My servos will be on a remavable tray right on the CG that also locks in the fuel tank (ARF inspired idea). With the weight I am adding in Balsa to the rear balancing will be no problem with the everything close to the CG and the battery can go Fore or Aft to make up any difference. It is always a good idea to leave the electronics until last.... Lead doesn't fly so why add it to your airframe [&:]



Andrewmc -> RE: Four Star 40 with Saito 56 (2/12/2008 7:39:29 PM)

Sorry must be nearly time to sleep. Two allen cap screws at the back of the carb and the whole unit pivots on the intake manifold.



frenchie79 -> RE: Four Star 40 with Saito 56 (2/12/2008 7:42:26 PM)

Before you debond or cut or whatever, finish the plane and check your balance, you may be right on.



sqeakalong -> RE: Four Star 40 with Saito 56 (2/12/2008 7:50:17 PM)

Hi, Carrot! Have built and flown the Four Star 40 (and the Mid Star 40) and can tell you they both flew real nice. No problems. Had O.S. 45's on them. Another flier did have a 4S on his and it flew nice too. Have fun and take your time setting everything straight. You'll be rewarded with a great flying model. Happy building!



Acs_guitars -> RE: Four Star 40 with Saito 56 (2/12/2008 7:57:13 PM)

Yes, you simply pull it off, turn it around and re-install... nothing to it.



bpoates25 -> RE: Four Star 40 with Saito 56 (2/12/2008 8:20:18 PM)

I have a 4 * 40 with the Saito 56 on it, and I used the 4 stroke throttle kit. It works great.

Ben



CustomPC -> RE: Four Star 40 with Saito 56 (2/13/2008 12:40:37 AM)

This is how i did it with a Saito .62 on a Four Star .40 ARF.

I used the Dubro 4-Stroke linkage and also an extra set of ball joints.

This setup worked very well and the .62 was a perfect match. The .56 will propably be an excellent match too.



Andrewmc -> RE: Four Star 40 with Saito 56 (2/13/2008 10:38:08 AM)

Is it better to mount the engine using the supplied sheet metal screws (Dave brown Mount), or to drill and tap for 6-32 allen cap bolts.

I notice that most of the photos show allen cap bolts!




Acs_guitars -> RE: Four Star 40 with Saito 56 (2/13/2008 1:50:26 PM)

I perfer the allen cap-head screws. Being a finer thread gives them a stronger, longer hold in a vibrating engine mount.

I also Used all ball links on my 4-stroke throttle linkage, but I use Sullivan #508 cable instad of the nylon SIG junk. In fact I am using the #508 cable for every thing except the Flapperons.



428CJ -> RE: Four Star 40 with Saito 56 (2/13/2008 6:40:20 PM)

Hey Carrot,

Add me to the list of those working on a 4 star with a Saito 56 4-stroke.

I decided two nights ago to sheet the turtle deck for looks and ease of covering.

I bought one sheet of 1/16" x 3" wide x 36" long balsa and made a left and right side sheet to minimize the seams. I'm amazed how easily you can manipulate balsa when it is damp from water. The pieces kept their overall form even after they dried.

Last night, I simply clamped the sheeting on, tacked it in place with thin CA, then went over the entire seam with Medium CA. I already sanded down the balsa and the first coat of filler.



Andrewmc -> RE: Four Star 40 with Saito 56 (2/14/2008 5:16:55 AM)

Yeah I really prefer the planes appearance withthe sheeted turtledeck and I was also surprised at how easily it moulded. I did it slightly dfferently though. I joined three sheets of 1/16" balsa and made a template with cartridge paper from the model. Then cut out around the template placed the cut balsa sheet over the plane and applied water from a spray bottle. With the pressure of holding the sheeting onto the plane the balsa formed around the stringers - just like that. I added some rubber bands and let everything dry overnight and the next day did a final sand to fit and glued.

Next some rounded wingtips and the balsa cowl...

I alligned the wing with the fuselage yesterday. The wing was square in the saddle from first fit, but one wing tip was 15mm higher than the other. The corresponding wing saddle had a thin layer of expoxy (from the joining of the doublers) once I sanded this down and checked the fit of the wing again 1mm difference. I double checked with some trigonometry calculations that a 0.5mm high spot on the wing saddle will throw out the wing tip by 10mm. So it doesn't take much to to offset the wing. I should have taken some photos before and after but got too caught up in the build.



428CJ -> RE: Four Star 40 with Saito 56 (2/14/2008 1:57:51 PM)

I can't wait to see your photos, please post some when you make some progress!

I would love a cowl on my 4* but I'm getting a bit impatient and want to start covering.

Last night I tested the skiis on my Nexstar. The snow is all powder and the plane sinks a bit into the snow. Perhaps I can find a plowed but snow-covered parking lot to use.

dave



Andrewmc -> RE: Four Star 40 with Saito 56 (2/18/2008 4:50:23 AM)

I had set up the wings for drilling the hold down bolts and was happy with the setup. However after drilling the wings were out by 2mm. The drill, I assume, had been deflected by the glue joint of the bass wood tip and the trailing edge. Trying to slot the holes and fill the gaps with micro balloons was an option - but not very elegant. I plugged the holes in the wings with dowel and sanded flush and then removed the wing mounting blocks from the fuselage and made new ones from spruce and remounted everything including the tri-stock re-inforcements. It took 5 hours to get back to the point were I was before miss drilling!!!

I am now ready to drill the wing mounting holes again. How can I hold the wing firmly in position relative to the fuselage to make these holes accurately?



428CJ -> RE: Four Star 40 with Saito 56 (2/18/2008 6:27:31 PM)

Luckily for me, I had a little interference (between the servo-end of the wing and the fuselage) so my wing was quite tight when I drilled the holes.

In your case, I'm thinking that a pair of nylon clamps would do the trick provided you have a flat spot to securely clamp down onto. If you can't use these, perhaps a helper can secure the wing while you drill.

If it makes you feel any better, my wing dowel is crooked because the drill bit jumped to one side of the ribs. It turned out okay in the end but it isn't that pretty.

Different topic, last night I plumbed in the throttle cable for my Saito 56. I ended up putting a hole through the nylon engine mount and used the metal clevis on the engine end. This setup works rather well and the clevis clears the hole (in the engine mount) rather well. I'll post a photo this week.

dave



frenchie79 -> RE: Four Star 40 with Saito 56 (2/18/2008 7:12:51 PM)

Two things you can use-drill a small hole into one of the blocks and run a 2-56 cap screw and also a clamp. Drill a piolet hole first. Harry Higleys makes a tool just for drilling wings straight, Look at a picture of one and maybe you can fabricate something like it. I believe tower carrys it.

http://www3.towerhobbies.com/cgi-bin/wti0001p?&P=SM&I=LXL780

Just a thought



Acs_guitars -> RE: Four Star 40 with Saito 56 (2/18/2008 7:20:29 PM)

I just thought I'd show the cowled 56 on my 4 star bash.... Still needs a little refinement into it's final form, but you get the idea.



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