My Shoestring Stunter - bit by TLAR

**RknRusty** Sun Jan 27, 2013 5:54 pm

This is a continuation of the thread I started when I was invited out to fly a Goldberg Shoestring Stunter back in early December. As y'all all know, up until now I've only flown 1/2A planes and so I was excited to have a chance to fly a bigger model. Unfortunately the owner wrecked it before I got the chance to hold the handle, but he gave the airframe to me to take home and repair. The rear fuse is busted in half and a wingtip needs rebuilding. Not a problem. But he had covered it with some really heavy fabric about 30 years ago; heavy enough to cause him to use an OS 40 on it. It seemed to fly well until he dropped the handle. Affraid or WOW!

I posted the following questions on RCG too, but since I value the members' input at both forums, I'll cross-post here too.

When I rebuild it, unless I can think of a way to re-attach the fuse, I'll probably cut the wing out of it and re-make the rest. I will try to lighten it and will probably use Ultracote for the wing and paint on the rest. I don't know what the airframe should weigh. I'd be curious to know that if someone can tell me. Assuming I get it back to its original intended kit weight, or close, what engine would be best for me to use? The original kit said .19 to .35 engines, but that was then and this is now, with modern more powerful engines. Brodak recommends a .25 with their kit. I'm not going to use a Brodak engine though.

I want to start looking for an engine soon, so what's the popular opinion on what size power plant I should fly on this old bird? I've never flown a 4-2-4 break before, so I want to get one that runs well that way. Since I only use pressure bladders on my 1/2A planes, I'll need to know what sort of tank configuration I will need to get the break right. I know my bladders won't work for that. Mike, the previous owner and builder had a plain looking wedgie. He had trouble on his only two flights getting the break to work consistently, but swore it usually did. In Mike's defense, he was very out of practice and hadn't thought of flying CL until I joined the club.

Thanks for any help,
Rusty

Ken Cook Sun Jan 27, 2013 6:35 pm

Rusty, here is my findings. What model 40 did the original builder have on the Shoestring? A modern Fox weighs in at 7 oz's without muffler. The Shoestring flies well but can be tail heavy with a Fox. Most modern OS .40's weigh close to 10 oz's. This wouldn't be a good choice. The other problem I see is the beam spacing due to the wider case of the .40. The Shoestring can be a problematic plane although it flies very well. I say problematic due to vibration issues. This I believe can be traced to the 1/16' ribs under the fuse. THis is my theory and I make a solid 1/2" rib under the fuse. I'm using Fox's which are typically shakers. The nose of the Shoestring doesn't lend itself to many tank options. I would say that the OS LA .25 would be a good choice, but in no way do I feel it will fly a Carl Goldberg original plane like the Fox.35 will. Seeing that your flying at a club is there muffler requirements? I would assume yes.

In my honest opinion, given the weight of a Goldberg kit, I would suggest a engine like the Enya SS .30 which has a lot of power even when muffled. I would go with a tongue muffler to reduce weight and give back some performance and I certainly wouldn't recommend a 4-2-4 break. Modern engines run a wet 2 stroke rarely breaking into a 4 and they run with low pitch props to keep the rpm's up and the drive steady. Typically like all of my Shoestrings, they're all powered with Fox .35's due to Foxberg racing. I enjoy the Fox's but I run them hard and I run them with almost no break running 9x6's flat out.

If you decide to run a Fox .35, I have some good suggestions. The Fox .35 and the Mccoy work fine on the Shoestring provided you don't experience the dreaded vibes. I certainly would check you beam to beam spacing to see what you can accomodate. I would recommend a Master Airscrew 9.5x6 prop with the Fox. The nose to the leading edge of the Shoestring is quite short. Certain tanks are required here. Ken

WingingIt74 Sun Jan 27, 2013 6:38 pm

Rusty, I may have a McCoy red head for you. I just picked it up for $25, figured someone may need it. Supposedly, it's never been ran, I'll get it some time this week and let you know.

**RknRusty** Sun Jan 27, 2013 7:14 pm

Ken I'll get some measurements on the beam. I was hoping to be able to fix this plane without cutting the whole fuse away and starting with just a wing. Though I know that would be ideal and I could then put the 1/2" rib in place as you recommend, but I would rather do a quicker fix if the plane will still be a quality flyer. I was thinking of splinting the fuse back together, stripping the old covering(which seems to come off clean so far) and re-covering the repaired wing with Ultracote.

Travis, if the dimensions are right and the engine size is right, I'll take the Read head off your hands. Is it a .29 or .35? Either of those might do. Just let me know what you want for it.

Thanks,
Rusty

**Cribbs74** Sun Jan 27, 2013 7:17 pm

Rusty,

I have that kit headed my way soon. It's a real beauty. It flies really well too. I saw one in action last weekend. It had a Fox .35 on the nose. I also saw a cool mod that you can do to the intake cowling to help cool the engine if interested. For engine choice I would do what Ken says..... Very Happy

Ken Cook Sun Jan 27, 2013 8:44 pm

Rusty, the best thing to do is to get an engine in that plane and go fly it. In the event you ever decide to build one, the 1/2" rib like I said helps. I can't explain as to why it happens, (the bad vibes) it just does. I've owned 4 Shoestrings all shakers and I have a 5th on the building table currently. I lost one of my best Foxberg Shoestrings last year. My son is the pilot and I'm the pit guy. The plane was coming in for the last pit in the end of the race when the tail wheel wire collapsed on a hard landing. The objective is to get the plane quickly to the pit guy. He did, and when this happened the control horn caught the ground breaking the clevis. I now had a terrific land speeder. Unfortunately, the plane headed in a upward 45 deg angle only to come down the same way. This is bad enough on grass you should see what happens on asphalt. It just shattered the crankcase.

I like the Mccoy's except for their durability problems. They don't like mufflers at all if you decide to use one with a strap. Parts are pretty much nonexistent other than some gaskets I've seen currently available. They have a good run however. I'm a Fox fan and I know many don't like them. The OS MAX-S.35 is also a terrific choice which works extremely well with slightly more power than a Fox. There is also the Enya .35 5224 which is a real powerhouse but heavier. Ken

duke.johnson Sun Jan 27, 2013 11:24 pm

Rusty
I have a Cosmic Wind, which if I remember right is almost the same plane. The wing is the same and the fuse different. Mine had a Fox .35 originally and then I put a Fox .25 in it. The Fox engines run the 4-2-4 break very well, I love how the engine sounds when it breaks in and out. But the Fox is the only engines I've run well this way. If the OS .25 FP or Enya .25 SS would have dropped in they would have been my chose, though. My comic wind does have the vibration, but not bad enough to effect any thing. I really like flying mine. If you cover with Ultracote and want to save weight, I'd go with the Ultracote Parklite (1/2 the weight). You'll enjoy flying it I'm sure.

**RknRusty** Mon Jan 28, 2013 10:32 am

Thanks for all the input. I'll have to think about the engine while I work on it. That project will begin in a couple of weeks when I finish fixing up the T-28. Also I forgot to reply about the noise restrictions, as far as I know we don't have any out at Fort Jackson. The Army makes a racket too, tanks, artillery and machine gun fire are common background noises.

**RknRusty** Tue Jan 29, 2013 8:18 am

Here are some pictures of the wreckage. I have new pieces for the wingtip, so that's an easy fix. The fuse, not so sure. I think I'll get it aligned and epoxy it with either fiberglass cloth or balsa splints on the outside. I'll look around the builders forum and the crash analysis forums at RCG and see if there is a similar repair.

Also the beam appears never to have been widened. I measured the cutout and it fits a crankcase that is 1-1/4" wide, and the holes for each mounting tab are 11/16" apart. Does that sound like a Fox 35 measurement?

microflitedude Tue Jan 29, 2013 9:23 am

I had that happen once - a friend was going to let me fly his .40 J-3 on floats, but he dunked it so many times it got too heavy to fly. Very Happy

pkrankow Tue Jan 29, 2013 9:29 am

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXUHU7&P=7

The dimensions are here.

That's doesn't look too bad, You could just pin the fuse with some 1/8 inch dowel and CA or epoxy.

Phil

**RknRusty** Tue Jan 29, 2013 11:29 am

I checked the measurements and it looks good for a Fox 35. I think I'll have this thing flying fairly soon. It does need a new elevator, I didn't see that until just now. So I either have two projects going or one will take a back burner. Rolling Eyes

For the fuse, I'm thinking of some bamboo pins and epoxy. It's not a good fit, so I may glass the side too. Gotta watch the weight though.

WingingIt74 Tue Jan 29, 2013 1:30 pm

I'll have that red head McCoy in my hands this week, you still interested?

**RknRusty** Tue Jan 29, 2013 2:09 pm

I don't know, Travis. That Read Head is tempting because it's new and it's a really cool engine. But I have to admit I'm leaning toward the Fox, due to plentiful parts and also what I'm hearing about dependability and durability. It makes it seem like the logical choice for me. I'll keep thinking it over while I do the repairs, but if you have another buyer that wants it, don't hold it on account of me. Thanks.

duke.johnson Tue Jan 29, 2013 4:08 pm

[quote="RknRusty"] But I have to admit I'm leaning toward the Fox, due to plentiful parts and also what I'm hearing about dependability and durability.[quote]

Rusty
If you haven't run a Fox before, you might watch out for the "Fox Burp". I have several Fox engines and they all do it. When you enter an outside or inverted, they burp. But they keep going and they run that 4-2-4 break you are looking for. As for as the "plentiful parts" I think O.S. is easier to get (at least in our area). As I mentioned before, I have an OS .25 on mine and it never misses a beat and always starts. The Fox engines seem to be a little picky and like a big gulp prime. Of course just another opinion.
Duke

**RknRusty** Tue Jan 29, 2013 6:14 pm

I ripped the covering all off tonight. I don't know what the hell it is, but it weighs 130 grams, 4.5 ounces! I think I can beat that.

WingingIt74 Tue Jan 29, 2013 6:17 pm

I got it today, looks to be in good but used shape.

**RknRusty** Tue Jan 29, 2013 6:22 pm

Okay Travis, if you let me have a day or two to look around first, then I'll let you know. Is it a .35?

**Cribbs74** Tue Jan 29, 2013 7:42 pm

Rusty,

That break is pretty clean so it should come together well. The bamboo is a good idea or carbon fibre if you got it.

Epoxy for sure. Looks like all profiles fuses love to snap after the wing. What is wrong with the elevator? Looks ok in the pics. Hinges tear out?

Ron

pkrankow Tue Jan 29, 2013 8:07 pm

Looks like cotton broadcloth, like a dress shirt, with a mountain of paint on it.

Phil

**RknRusty** Tue Jan 29, 2013 8:22 pm

The break is actually kind of ugly up close. It will fit together straight but not without some nasty gaps. I can fill them in with some pine sawdust and it should be okay. The elevator is broken in half right at the narrow part where it passes through the rudder. I'll have to either cut the rudder or make a whole new one to mount a new elevator. Maybe i can bridge it but it has been previously repaired where the break is, so a new one is the best, but not easiest fix. The stabilizer is not broken.

Yeah, Phil, it does look like cotton cloth.

Mark Boesen Tue Jan 29, 2013 8:38 pm

hi Rusty,

Looks like a nice well built plane. That fuselage break should be a no-brainer. Some old school Monokote (c. 1969) and you're in business!

Like Ken sez, slap a engine on'er and go fly. But, if you're gonna fly at a R/C field i'd think they have muffer regulations?

What you need is a modern .25 ball bearing engine that you can set the needle and go!

Hmmm, maybe...something like a Thunder Tiger Pro .25 ABC with Super Tigre needle? PM me if interested.

**RknRusty** Tue Jan 29, 2013 9:02 pm

Hi Mark, I just dropped in, taking a break from scouring the web for Fox 35s. I was going to ask what the difference was between a Fox 35 and a 35X.
Sooo, that's a pretty engine you have there. PM sent.

EDIT: or a 36X for that matter. I don't know what the differences are between these variations. So far I'm seeing Fox 35, 35x and 36x. If I got an RC version, I could just lock the throttle wide open, right?

Mark Boesen Tue Jan 29, 2013 9:41 pm

A 'modern' .25 will has as much or more power then a Fox. If you want to tinker with the 2-4-2 break they're a blast, theres nothing like it...as long as it doesn't burp and die on outsides, lol!
If you want to go fly (with a muffler and standard r/c fuel) get a nice .25-.40 R/C engine, prop it accordingly and go fly.

**Cribbs74** Tue Jan 29, 2013 10:57 pm

Rusty, from what I can gather the "X" is a performance designation however it never amounted to a whole lot. A Fox .36X is a combat designed engine. From what Ken has told me it's a real bruiser.

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