My Shoestring Stunter is RTF

I got my engine today, posted about it in an engine thread. I test ran it and it runs really nice, but it's a serious gas guzzler. Now I know what gallon jugs are for. I gotta find a fuel tank for it. Hopefully my LHS can get a 3 oz wedge for me, that should be about right. Until then I can use a makeshift tank. I need to go back and re-read what our experts have advised me to do regarding the engine settings that pattern flyers use. I'll need a proper tank for all that. That's something I want to learn to fly if the SS will do it well enough in its repaired form. Until then I'll probably just fly freestyle like I do with the little ones. I might see if a bladder will work for freestyling. The needle is pretty fine, not as fine as the others, but it might work.

My progress comes in spurts and it ain't looking like it's gonna be flying this weekend. I still need to make a stooge for rolling launches. Repairs need sanding, filling, painting. Covering the wings. Slowly but surely. If I get free Sunday I'll take the babies out to fly. They're all good to pick up and go with no fiddling. I've had good luck that way lately, all except for the Re-Fried Bean. I still feel bad about that.

Not me, but a similar engine. He's turning about 4-1/2 second laps as best as I can tell. His plane looks pretty snappy. I hope mine will be too.

https://www.youtube.com/watch?v=riedp-eOuj8






It's raining so freakin' hard I can't even go out to the shop tonight!

I just remembered I need a prop spinner. What size should I get, about 2"? Would the same spinner fit all of my 9 and 10" props? I slam forgot about that when I was at the HS the other day.

Spinner are nice, especialy if you need some extra nose weight or use an electric starter (if so then avoid plastic spinners) or just go aluminum hub (Higley?) or one piece aluminum sinners (Dubro?) or leave as-is with nut, but yes 1.75"-2" would be fine for Cosmic and 9-10" props.

I ordered a cheap plastic 1.75" one on eBay for a couple of bucks, and some Sig 10% fuel.

Since I didn't have my new engine to divert my attention... blown plug, I got some work done on the Shoestring tonight. I started removing the broken parts and removing the old glue. Man the old glue is SUPER brittle. I can see this thing crumbling with one good smack. I better fly it right.

It's old wood glue. I was able to wet an emery board with acetone and get some of the old stuff to dissolve, and I smoothed everything out. Tacked the new pieces in place with CA and it looks good. But for the wood that's already glue soaked with the old stuff, I don't know what to use. If I use Titebond, I don't know if it will do anything but stick to the surface of the old brittle glue. I could use epoxy, but it won't soak in any better than the Titebond. So I'll probably make tiny gussets and blocks with scrap balsa to hold everything in place and Titebond it. It's not that much that has to be glued so it won't be that much weight. I still have to make two pieces that aren't going to be easy to shape.

The wing has one problem that can't be fixed. Some of the ribs on one wing aren't fully seated in their slots in the LE. At first I thought maybe they pulled loose in the crash, but they're glued firmly in place. It must've been a building accident. You can see that the ribs were once seated, and then where the glue dried after they shifted. They are only pulled out less that 1/16" but there is a gap in front of several of them. I will fill the gaps with fresh glue for whatever it's worth. This guy didn't believe in doing much sanding either, so I will smooth out everything a little better so the covering looks nice. His old fabric would have hidden a dead rat, but Monokote will show up the rough rib edges.

Rusty,

If you read my Ringmaster resto thread Ken gives a real good synopsis on what to do with old glue and re-adhering.

Basically mine was built with ambroid so I used the modern day equivalent Sigment to rebond the joints. It worked well and really strengthened the wing.

Shoot, I thought it was in there, maybe it was in an email. Anyway, the jist of it was reglue with whatever was originally used.....

Okay thanks. I wonder if that applies to wood glue like Titebond as well. It beats adding balsa beside the joints.

Almost finished the wingtip. I had to stop to let the Titebond dry. Not all of the wingtip parts he gave me were the right ones, so I had to make a few. It's a three piece curve plus a short section of LE and three gussets, two of which are installed so far. You can see the LE section I carved on the table in the picture. I wanted to make sure the joints between the curve sections were strong so I put a patch of fiberglass on each one, over and under.

Good quality fix Rusty, I like the way you slotted the LE piece. Should be a nice strong splice. From the looks of the wood Rusty it appears it wasn't built too awfully long ago.

Ron

cribbs74 wrote:Good quality fix Rusty, I like the way you slotted the LE piece. Should be a nice strong splice. From the looks of the wood Rusty it appears it wasn't built too awfully long ago.

Ron

I intended for the tab to extend further down the slot, but after I add last gusset I think it'll be strong enough.

The way he talked about how long it's been since he last flew CL, I was under the impression it's 2 or 3 decades old. I'll ask him about that. It sure looks better than your Ringmaster did when you got it.

2-3 decades means 80's or 90's. The S-1 was kitted in 1950 so it could be pretty darn old. Who knows.

I wonder when the Shoestring came out? I am thinking late 50's

I think '50s too.

Okay, here's the question of the day; if you wanted to buy a fuel tank for the Shoestring, which one would you get from the following list. It looks like the fuel feed comes out of the bottom of #2. Could that just be a reversed picture? I don't know if the uniflow setup of #3 is any advantage over either of the others. #1 is the simplest, always with the feed tube even with the venturi... not that gravity isn't constantly attacking from different directions.

Read up on uniflow. I would probably go with #3. Uniflow us an interesting arrangement inside. The pickup and vent are both in the outside corner. The overflow has to be capped for flight.

The advantage is the fuel remains at the same effective feed pressure for the entire flight, till the uniflow vent becomes exposed. It is sorta like a glass full of water held full upside down in a sink.

You can also strap a plastic tank on with clunks if you want. It is a legitimate option even if it lacks appearance.

Phil

+1 for the uniflow. Is 2oz going to be enough? I was told 3.5oz for my Fox .35. Mabke the TT .25 is more efficient?

Once again I recall Ken doing a lengthy writeup on fuel tanks and once again I cannot find it........

I'd go 3 oz., uniflo and muffler pressure.

Bottom most item on the page
http://www.aeromaniacs.com/Tips.html

http://www.bjm-home.com/BJMEnterprises/page59.html

http://www.fraserker.com/heli/uniflow/how_uniflow_works.htm

3 to 7 minutes of run time should be quite nice. Not enough is no fun and too much means you get tired.

Phil

Rusty,

Not the exact info I was after, but here is what Ken said about uniflow,bladders and chicken hoppers.

Ron

https://www.coxengineforum.com/t2697-uniflow-and-bladder?highlight=Uniflow

It all really depends on how you want your engine to run. Personally for me on these planes I prefer standard venting. This will yield the fastest run out of the engine. The engine will have to be launched rich enough so that through the course of the flight the engine doesn't go overlean. Some find this unacceptable, running a sport plane for me is just for fun and I don't use a Shoestring for maneuverability although it's much more capable of smoother maneuvers than a Ringmaster for example. Uniflow can be problematic and it's not always going to work. When you hook muffler pressure to the uniflow line, the tank is no longer on uniflow. Profiles can be problematic for uniflow to work correctly due to the turbulent air coming over the cylinder and into the uniflow pipe. Sometimes the 1/8" uniflow pipe is just too large and needs to be necked down to 3/32" or less. There are times the uniflow pipe needs to be routed to the inboard side of the fuse to get the uniflow into clean air. The engine launch setting has to be much richer due to the second the plane is released the engine will go lean as well. All this takes experimenting. In my opinion, I personally would just run standard vent or muffler pressure due to the simplicity of the mechanics.

I'm not opposed to uniflow, I can just say I've seen and witnessed a lot of problems as a result of it being used. I also see many that just run perfect. This sounds contradictory however it just comes down to trying and using what works. The fact is regardless of what you chose, a uniflow tank it can be used in 3 different modes of your choice. Standard vent, muffler pressure, or uniflow. On uniflow the uniflow pipe is open to the atmosphere and the fill and overflow is capped. If you decide to use muffler pressure, you could hook the muffler pressure line to the uniflow as this appears to be what Mark is suggesting and have your vents capped. You could also pressurize one of the vent pipes, either or and cap the opposing vent and uniflow. These are 2 muffler pressure options and it certainly could make a difference in the engine run. Or you could run standard venting with both vents open or just one of them being capped.

My point is, all of these examples sometimes need to be tried to achieve the best run so that purchasing a tank with a uniflow pipe gives you the options to do so. Once again, I will harp on the fact that not all tanks are created equally and they all need to be pressure tested and should be opened up for inspection. When running uniflow, the height of the tank is dictated by the uniflow height and not by the pickup. Tank height on a standard vent tank is dictated by the pickup. I find that many of my Uniflow tanks like to be slightly above the needle valve rather than dead center. You will know for sure if you go inverted and the engine runs drastically change from lean upright to rich inverted. The tank will have to be raised. I would lean towards the 3 oz tank. Ken

I am going to the HS in the morning to get a glow plug. I'll run it again and time it. I was guessing 2oz was getting 3 or 4 minutes the other day, but that was on the stand. It probably gets a shorter run in flight. Thanks for the tank answers. I know I was asking for info that has been written and re-written. I'm on my way out to the shop now, so I'll digest it all before I make a tank purchase. Brodak has a lot to choose from. I'm pretty sure the HS only has big clunk tanks.

I'll be back later tonight.
Rusty

I finished fixing the wing, so on to the broken elevator. I cut out new tail feathers and will sew up the hinges tomorrow. I checked my Monokote supply and need more, so the HS will be happy to see me tomorrow. Unfortunately I have to get the fuel tank online. Y'all are right, it would be dumb to put too small of a tank on it. I can get a 3oz tank from Brodak, but shipping costs the same as the $9.00 tank. I'll see if the HS will order one for me. This is the one: http://brodak.com/oval-profile-standard-vent-fuel-tank-3-oz.html

A uniflo on muffler pressure (attached to uniflo tube and all vents capped) is still a uniflow, only under pressure. The problem with standard venting is if you set it too lean, your going to be screaming toward the end, great for racing, not so great for stunt, a uniflo on pressure will not change as dramatically. Surf Stuka Stunt on uniflow and muffler pressure, there's more info there than you'd want to know, lol. You could also try muffler pressure on a standard tank, which as i'm typing I'm thinking might be just fine!!!

also, before you order your tank make sure it will fit length wise....don't ask.