Mettler1

From my experience a 12x6 is way to small for a 91 four stroke. I'm running an APC 13x9 and I wouldn't go any smaller than a 13x8. Saito and OS 91 four strokes should not be run over 10,000 rpm. My OS 91 is turning the 13x9 at 9800 rpm. I can't imagine what kind of revs your're turning with a 12x6. Put a bigger prop on the Saito. At least a 13x8 or a 14x6. If you must run a 12" prop go with either a 12x10 or a 12x12. APC makes those sizes as do other mfg's. And get a tachometer. They always come in handy for tuning an engine

Mettler1

Nice pic's! I wish we had weather like that. But we seldom get over 90 degrees in the summer. We have snow coming tonight. Not much but still a bummer.

Primodus

My Feedback: (56)

It's a balmy 65 today with sunshine projected for the remainder of the week[sm=sunsmiley.gif] I will be trying both an 11x7 and a 13x8 on my 61FX to see how they change versus the 12x8 I am swinging now. Of course the 11x7 will bring higher speed in the top end, and the 13x8 will pull more in the vertical. I just want to see it happen first hand.

See ya in the air!
Luke[8D]

BasinBum

My Feedback: (2)

.61 FX
11x8-10, 12x7-11, 12.5x6-7

Primodus, I looked it up for you and the 11x7 seems like it might be under-proping that engine. The 13x8 might be over, check your manual and do experiment to see how it makes the plane feel differant. You will see a differance in how it feels in the air.

crashland 73

My Feedback: (24)

OOPS! I do believe I have a 13x8 or 7 on it instead. I gues I have HUB syndrome LOL! (head up butt)

Primodus

My Feedback: (56)

I have ordered the following prop sizes to try... 11x10, 12x8, 13x6

I think it will be interesting to see how the model flies with these props. Note the lower the diameter the higher the pitch. I figure it will be very fast on the 11x10 and pull like mad (maybe hover) on the 13x6, the 12x8 seems to be an average performing prop for this engine/plane combo. I will tach them all and get readings next time I am able to fly. (work stinks)

Luke[8D]

BasinBum

My Feedback: (2)

That's a good start. Don't forget to readjust the high end needle for each prop. You'll definately see changes in the sound, idle, top end and fly charecteristics of the differant props. A good learning experiance. I've tried to get my stuborn brother to try differant props but he insists on using the same one until he dings it and pulls something else out of the drawer. I think he was adopted.

MormonMike

My Feedback: (2)

Were at 4500 feet useing a ST.91 with a 12-9 APC, results, 111 mph on the level here in Logan Utah. Darn this alttitude.[&o]

Primodus

My Feedback: (56)

I am located at 364ft. elevation. How will that affect me?

CDignition

My Feedback: (9)

Im going to run a 15x6 on my Shoestring with Saito 100...I also have a 14x8 and a 15x8....will be fun to try

Cogburn

Has any anyone tried using crossed controls(coming in in a crab-then straightening out for touchdown) for slowing the Shoestring for landing? Or flaperon mixing?
I am in the process of completing my Shoestring and my radio has the ability for flaperon mixing.
I usually have to use crossed controls for landing my p-40(also very slippery).
Our field has some obstructions(trees,powerlines) in the glide path so a long low approach is not feasable.
Also what is the best method for strengthening the landing gear block? I was thinking of gluing a ply block on top of the landing gear and bolting through it.
Futaba 6exa,Magnum pro61(perry carb,slimline pitts).
Any help is greatly appreciated!

crashland 73

My Feedback: (24)

On my shoestring, I tried the typical flap settup. Down aileron (flaperon) and it would shoot almost straight down. Totally oposit of what I thought would happen. So I made them go up instead, that worked. Maybee not as good but it made the plane flare up like the usual flap action would do. I have no idea why this done that. I use a JR 8103 radio. Maybee I had too much throw on the down flap and that made it do that. I dont know, does anyone have any idea or had this happen?

Primodus

My Feedback: (56)

I haven't tried my flap setup yet. Only had 3 flights on it so far and the first two were limited to pattern rounds for trim and balance. I had to fix my gear after the first two flights also. The gear don;t budge now though (hardwood planking and triangle bracing extensively). My next flight plan will test maneuvers at dual rates, and the flaperons also. Based on what crashland said I will take it VERY high to test the flaps. I am also using the Futaba 6EXA. Unfortunately I won't be able to test it for another week[] Oh well, my field equipment is in route this week from Tower Hobbies. I will use the extra time for building the flight box.

Luke[8D]

CheezeyPoof

I don't want to insult your intelligience here but the reason it went straight down is you did not mix any "up" elevator with it. I don't use them on my Shoestring. I use flaperons on my Midget Mustang and they work fine. You need to try a little at a time. Try dropping them down 1/8 inch to see how the plane handles. You should have enough elevator without mixing to compensate. If you just drop them down a 1/2 inch or so, your going to be in trouble.

DrDeath

My Feedback: (3)

What I found on my Shoe and magic was that flaperons actually does the opposite of what you think. This is common from what I have been told. With the 8103 mix in a little up elevator and put the whole thing on the landing switch. This will allow you to have everything on one switch. You can also mix in a little elevator using the mix function. Many ways to skin this cat. I actually took off flaperons because you really don't need them. The plan will fly and land well without them.

Lee

BasinBum

My Feedback: (2)

I agree that you don't need flaperons with this plane. It is not going to do funfly manuvers and landing should not be that difficult anyway. If anything spoilerons may aid landing as it will effectively give you washout making the plane more stable at slow speed but at the cost of reduced lift.

Most planes will pitch down when flaps are deployed and as was mentioned mixing in up elevator is common. What is happening is the back of the wing has more lift and is raising up while pitching the nose down. Also if you are going to experiement with flaperons only deploy them at low throttle settings or you will really have your hands full.

AirIck

i have the shoestring also and love it. have not seen any of the stall problems or any bad habits at all. had a saito 100 on it with a 13x10 apc and several other props but didnt have the umph im wanting to feel.(very fast just the same) switched to os.91fx, and am now going thru a pile of props to find the most top end speed. note on fx.91.. i dont know what the problem is with some peoples .91`s.. i read very bad stories about them but have had not one problem. its mounted inverted, no pump,and just moved needle valve 90º. runs like a champ on 10 or 15% nitro. someone here said there shoestring with saito 100 went 128? must have been a 25 mph tail wind which is good you will get compliment after compliment on this plane. it looks VERY realistic flying. super stable. perfect flyer. ive listened to several stories from the uhh easy now.. older gentlemen at my club. they all speak with a tone in their voice that says nothing but love for this plane, and i know why.
Erik

Jeff396

My Feedback: (1)

AirIck,

Please let me know what prop you end up with on that .91FX. I'm running a 13x8 apc as suggested on the OS website but am looking for something with a bit more zip. I bought a 14x8 apc to try but have yet to make my first flight of the year. My final flight last year ended with a dead stick with over half a tank left so I want to figure that out before changing props....foaming fuel maybe.

I am one of the people who had to add a pump to my .91. The reason is that I am using an aftermarket Pitt's muffler which did not supply enough tank pressure causing it to run too lean and overheat. It was so bad that I was unable to get the engine to die no matter how much I richened the needle. The engine would keep running even to the point where the needle was completely off the threads. Oh well, should have went with a 1.20!!!

Jeff

JAkridge

I've been watching this thread for some time now. I got interested after seeing the post from "Chevelle" about him haveing the U-Control Version of this plane years ago. I read it and it's exactly what I would write, only it was me and my brother-in-law, we both had one. I would say around 1967-1970. We also flew them tell they fell apart at the good "Old Whitter Narrows Field". Things have really changes since then.
I have to say, It's time for another Shoestring. I started back flying after a 20 year gap 3 years ago, started with a Zagi then to a Ultra Stick and went to WarBirds.
I said I never wanted a Pattern / Pylon Flyer..... "Well".... I saw a Shoestring at my LHS last week, and as soon as it open's I'll be there, guess I found a place for this extra Saito 91 I have......... I'll Keep every body posted how I like the New RC version.

Damm..... I already fill 13 years old again.

autoguns

you won't regret buying one .....You will love flying it with the 91.....JW

crashland 73

My Feedback: (24)

I agree on really not needing flaperons. I love this plane. It lands great. As for the mixin you are probly right. What confused me was I am used to the ultra stick planes and on flaps on them I have them as far as the flaps will go and it will nose up, making me mix in down elevator. The total oposite. Odd but I dont claim to know much to begin with, I am from the Ozarks LOL! I do love this plane though.

RickVB

My Feedback: (24)

I picked up a used plane recently, and in going over it based on the advise here on RCU, I'm glassing the landing gear mount and probably the wing center section too. I'm going to use the Sig wheel pant mounts as also mentioned before (those are really cool!), and strengthen the bottom edges of the pants, and rebuild the cowl mounts.

But I haven't noticed many of you mentioning what servos you're using - mine came with standard Futabas. Given the size of the plane, I'd think that's OK, but since I've been reading of your tales of 110-120mph potential for this plane and I have to wonder if that's adequate.

Also, a quick estimated CG seems to show that the plane is really nose heavy as it is. Looking at my setup (it has a TT .91 fs), I figure I could quickly get closer to balanced by moving the engine back on the mount. Eyeballing it, it looks like I could move it 1/4-1/2" back before either the carb runs into the firewall or the back edge of the cowl hits the L.E. of the wing. But, as it is, the prop hub is almost exactly the specified 5 15/16" from the firewall. Has anyone else tried this, and is there anything I'm missing here before it start drilling?

AirIck

could anybody tell me about how much props unload in the air? i just put an 11x14 apc on and was getting a slightly rich 10200 static rpm. is this too much for a .91 fx?
thanks
Erik

nitrous pete

My Feedback: (40)

Wow, you all love this plane , Well so do I , I have put a ys 110 in mine and holly ****t . Not to change the subjsct but I also have a Thunderbolt . 60 , I put a ys 110 in It also, This is also close to the speed of the shoe string , Ahah Not realy but ... !!
The thunder bolt is fast and stable , I use a 14x10 on the TB,,, And a 14x10 on the SS
As far as landing its slows down fine , No need for flaperons on this plane , I come in hot 1/3 throtel 80 ft from touch down lower throtel to just off idle and 10tf till tch down cut it back , peace nitrous pete [8D]

AirIck

never mind.. i found i was only getting 3/4 throttle