Upnet

My Feedback: (8)

I inherited a partially assembled GP Shoestring. I plan on putting a Supre Tiger .61 up front. I don't have the manual. What's the CG?

Thanks...

masonman

30% back from the leading edge. At the root.............You will enjoy that string alot more with a .91. A .61 would not give your model the respect it deserves......My 2 cents

Mr. Mugen

Our club president has a shoestring with a 61 and it rips. I bet it hits 80-90mph....not terribly fast but it rips in my book. Just my observation,
Kevin

da Rock

Get out a yardstick and make 9 simple measurements. Plug them into this online application and you'll have a reliable, safe CG. http://www.geistware.com/rcmodeling/cg_super_calc.htm

If you want a CG range, then choose 20% as the Static Margin for the front of the range, then run the app. with 10% for the aft of the range.

That app. uses the same formulas the aeronautical industry uses. They work for 747s, MD-80s, Cessnas, and our models.

krproton

I have a Soestring instruction manual at work.

If you can wait a day, I'll look at it Monday and post the answer then (if somebody doesn't find it before me).

pdansalvish

My Feedback: (23)

Here is the link to the manual from Great Planes web site.

http://manuals.hobbico.com/gpm/gpma1325-manual.pdf

Iflyglow

My Feedback: (79)

I bought mine back from my friend. He never did anything with it. Tower .75 and 12-8 prop make for some awesome speed. It is by far my favorite plane ever.

Upnet

My Feedback: (8)

I looked on the GP website..but could not find the .pdf for the manual. Jeez....maybe I need to get the old eyeballs checked. Especially when I get this plane finished....and BEFORE I maiden her.
Wow....putting a .91 on it?? Hmmmmmmmmm........????? Maybe that would be suicidal....wonder if the airframe would hold up?

What do you all think? .61.....or.. .91?

Thanks for the link to the geistware.com

Thanks to all. I just love this site. So many people willing to help. You folks ARE the best!

da Rock

The link a couple of posts up this thread points into the manual itself. You can do a "Save As...." if you want to download it onto your own pc.
Here it is again:
http://manuals.hobbico.com/gpm/gpma1325-manual.pdf

da Rock

The mfg says it'll be a 7lb airplane when it's ready to fuel. That's light for a 91. A 61 will pull this decently, very decently. Can't see any reason for a 91.

Upnet

My Feedback: (8)

Thanks for your help. I think a .91 may be overkill.

However...maybe a .75?????

Iflyglow

My Feedback: (79)

The .75 is just perfect. A .61 would be under powered in my book. I plan on installing one of my YS 1.10's

russm

the 61 is a dog in this plane. most guys are puting 4-strokes in theirs, from what i have read. have a ys 110 in mine. nice combo.

Yak18

My Feedback: (11)

Do NOT put a .91 in this airplane. You will have to add a bunch of lead to the tail to get the CG. It has a long nose! Mine has the recommended OS.61 and it hauls A**! The airframe will come apart if you go any faster. I've flown mine for over 200 flights and it's still my favorite. Too bad it's discontinued.

NM2K

My Feedback: (14)

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The .91's sold by OS, ST and any other manufacturer that simply bored out a .61, are not as powerful as the true .90's and .91's that came out in their own original crankcases. Not to worry. A contemporary .91 built in a .61 crankcase would give you a tad more in vertical flight and barely anything noticable in level flight. The difference in displacement/power production is not as great as when one designs an engine to be a .91 in the first place.


Ed Cregger

krproton

I assume you've uploaded the manual and found the C.G.

But if not...

Mark the C.G. on the bottom of the wings 3-3/16" back from the leading edge where it contacts both sides of the fuselage. You can go 7/16" forward and back from there. The model is balanced upright (supporting it by the bottom of the wings where you marked the C.G.).

Upnet

My Feedback: (8)

Yes...thanks to pdansalvish and da Rock I got it covered.

OH..... DUH! I went back to the Great Planes website...and scrolled ALL THE WAY DOWN. Which initially I did not do....to the DISCONTINUED planes.


Thanks Guy's!

pdansalvish

My Feedback: (23)

UPnet,

Glad to help. I had a Shoestring for 4 seasons with an OS 61 in it. The plane flew so well I bought a second one which is still in the box. As for engines, I had to add 1 ounce of lead to the tail to get mine to balance. If you put to big of engine in it you will need more weight to the tail to balance. One question you need to ask your self is how do I intend to fly it. With a 61 or 75 it will be great sport flying plane. I would only use a 91 or larger if you intend to race it.

Dave

masonman

I have a Little Toni, which handles alot like a shoestring. It weighs 7.5lb. I agree you should power your model with the intent of how you plan on flying in mind. With a .61 its fun to fly. But thats about it. Everyone at the field knows what a Shoestring an toni are for. I have had a .91 on board for awhile now an I have to say I have enjoyed it alot more than a .61. Unlimited vertical. I have no clue how fast it goes with a zoar 13x9 at 10,600. But its way better than the 9000 with a 12x7 on a .61

I have found with an airplane like what you have its better to have a little to much, rather than not quiet enough. Just my thoghts on it

Cyclic Hardover

My Feedback: (3)

I run a G90 sideways in mine. The corners of the head do hit the cowl. I really did not want to cut a hole for it, so I just dremeled out the area it was touching at and made a hole for the plug and it all just blends right in