Continuing flights & videos of the Shoestring

Double Ditto with Ron's post!!! Coolo !!!! And what's the point of doing any of this if you don't "push"it a bit ???!!!! GOT to get back after the Ringmaster...and one of the days...SOME of us GOT to get together and REALLY scatter some balsa !!!

Sorry...Spring Fever, I suppose....

Scatter some balsa, yeah! I came closer than I intended to liberating some toothpicks at the bottom of a loop today.

My movie is crunching as I write this. When it it finishes I'll shoot it up to the tube. But first I have to watch an episode of Battlestar Galactica on Netflix. So it'll probably be about 2 or 3 hours before you can see the SS.

Bummer.......

Uploading now, about 75 minutes from the time of this post.

https://www.youtube.com/watch?v=39j3jdKMDe4&feature=youtu.be

Good vid Rusty,

I especially like the fuel bottle launch. I have done that myself, good thing the lid was on!

So, have you had that tank apart yet? Also can you take a real close up pic of your tank setup?

Something is up with fuel delivery for sure. I don't feel it's the prop or needle setting as it runs better using standard vent configuration.

Ron

cribbs74 wrote:Good vid Rusty,

So, have you had that tank apart yet? Also can you take a real close up pic of your tank setup?

Haven't opened it, but I plan to pressure check it again tomorrow. I have the bolts padded with silicon grommets made from thick fuel tube and a splayed open piece of tube under the strap at the edge of the wedge. There are three tubes padding it against the fuse. I'm going to change that to foam. I found a piece of gray porous packing foam that came in a box with some king of fragile cargo. I'll layer it up and put a square behind the tank. I'm pretty sure foaming is not the problem. Ken has made some suggestions re: the venturi I'm looking into. He doesn't seem to think the bore is excessive at .172".

Here's the picture of the tank mounted up:

Thanks for the pic Rusty, I use foam on mine as well and it may help although the way you have it mounted seems fine.

I was looking for a side shot so I could see your pickup level.

Here is mine, it's too high although it works. I am going to move it though as both Ken and Zuriel Armstrong says it's wrong. Sometimes you get lucky I guess.....

Mine is actually a little low.

RknRusty wrote:Mine is actually a little low.

Ken told me 1/4" above the NV is about right. Maybe it's too low and is trying too hard to pull fuel in level flight and when stunting. I suspect when inverted you richen up?

Ron

Yep, contrary to what you read, tank height center should be a little above venturi. I think you might try muffler pressure to increase fuel flow, can't hurt.

Then again, watching the video again, the last flight she sounded pretty nice, maybe raise tank, open it up just a tad, maybe a click or two tad and go!

[quote="cribbs74"]

RknRusty wrote:...Ken told me 1/4" above the NV is about right. Maybe it's too low and is trying too hard to pull fuel in level flight and when stunting. I suspect when inverted you richen up?

No change in the engine run when it's inverted. That's why I had almost forgotten that item of interest. I'll shim it up and see what happens. It wont draw the tank empty on the ground unless I hold the plane pointed up at the sky. Maybe it's as simple as that.

I repositioned the tank. It was lower than the nv and now it's higher. I also added a pad behind it. I hope it's not too thick, about 1/4". I'll crank it tomorrow and check for bubbles. They went away when I put silicone grommets on the mounting screws. If I see any, I'll put them back on. I'll take it out to fly this weekend and see if it performs any better. I'll also use some stocking screen on the venturi. I'll only start with a thin piece for dirt protection. If the engine stumbles I'll add more. If it's totally uncooperative, I'll open the tank and have a look. I've posted over at SSW about it too.
Here's what it looks like now. I hope it's not too high.
I need to plug that old screw hole.

Ken, I'll add that to my list of tips, thanks. BTW, before I started relocating the tank I pressure tested it and it's tight as a drum. It wouldn't leak with all the strength I could apply to the 60cc plunger.
This morning's ground test is very encouraging. I used the same 10% nitro I've been using and filled the tank. With the bottom vent capped and the uniflow open I drew some fuel back out of the feed line. A few small bubbles would pass now and then, depending on how I tilted it but not too much. I then pulled fuel back out of the uniflow vent and got a steady stream of bubbles. So that tells me the lines don't end right in the same place. That's a good thing.

So I proceeded with cranking. Before, with the tank at the lower position, cranking was a real argument, even hot. The first good sign is that after choking and turning the prop over to prime it, It blasted off on the first couple of flips. It does have to be really wet to crank, but maybe that's just me being used to tiny engines. The second good sign is the needle settings were definitive, like it was back when it was on the test stand, before the plane was built. On the plane, the needle was all over the place and never made a lot of sense.

Now for the third good sign. With the nose pointed level and the outboard wing tilted down, I adjusted it rich enough so that a quick pinch would increase the RPMs, and I even added a little more, so that it sounded wet. This one doesn't really like to 4-stroke, and I don't know if it would take off that rich anyway. Then when I pointed the nose up, it ran smooth and fast. It never would do that before(if I was actually treating it right; forgive the noobness). And it would quickly switch back and forth between rich and lean every time I tilted it between up and level.

I could see a bubble now and then as I tilted to different positions, but that's probably always going to happen with the uni vent open. Besides the 3-hole sprinkler should smooth that out. I had the stopwatch running and it ran exactly six minutes and cut off like a switch. The tank was bone dry. I'll take it out to the field this weekend and see what it'll do in the air. Six Minutes is longer than I've ever had one in the air before. At two minutes per ounce, I think I'll start with four minutes of fuel when I first try it out.

If you read my previous post, above, you'll understand my optimism. Today I took it to the proving grounds.

Dang Rusty,

I am real sorry to see you are having a rough go at something that should be so fun.

I have so little experience that I don't have much to offer in the way of help. As you know I use a Fox .35 and a standard vent tank on my Ringmaster. It worked really well for me. So much so I am using the same setup on my Super Clown.

Perhaps it's just time to crack the tank open.

Ron

After re-reading my post of last Thursday, 5-16, I got to thinking. That day I made the final needle adjustment with the outboard wingtip pointed at the ground, and the nv was definitive. Today, it was back to being all over the place. Maybe I should hold the plane like that to needle it. Then pinch it off, hook it to the stooge, top off the fuel and fly... assuming it'll take off with however it runs once it's back on the ground. I'll try that next time. Either Thursday or this weekend. It's hard to pack the time for a flight into either of my two "free" weekdays, and it's hard not to be rushed. Plus I burn over an hour just getting to and from the field. Had today been a Saturday or Sunday, I would have taken a break, tinkered, and tried harder, maybe gotten a half decent run. I know I've gotten somewhat better runs by switching to normally vented, and I could have cleaned it up, glued on the rudder and tried again.

On another note; for the second flight I used up the last of the 10% nitro fuel, so I had half 10% and half 15% in the tank. Next time it flies it will be on 15%. Maybe it'll like that better. And even though it has a new glow plug, an OS #8, I'll put another new one in. Sometimes it sags when I remove the glow driver. If I let it warm all the way up, it doesn't do that. I could try letting it run lean longer on the ground before I rich it up. But then I'll be flying on 3/4 tank of fuel.

Pardon me, I'm just kicking myself, going back over the chances I missed by quitting today. It sure would be nice to have a flying buddy. But as it turns out I would have gotten caught in a thunder storm if I had stayed another hour.

Still postponing surgery on the tank. Ron suggested it looked like it might be too high above the venturi. I had aligned it using the TLAR method, so I checked and it was more than 1/4" above the hole. So to hell with aesthetics, I cut the strap and rubber banded it on. Still too high but now I can adjust it. I might take it out to fly again tomorrow.

Off to check the weather forecast.

I lowered mine as well. I think I went too low on the Super Clown.
If you look on the first page of this thread you can see how high it was.

Ron

Hi Rusty,

Not sure what to make of it...not being there its tuff, heres some thoughts:

Your last video from April 35th ( https://www.youtube.com/watch?v=39j3jdKMDe4 ) the third flight looked pretty solid, but still seemed just a little lean. Remember with that setup you're gonna take off rich and once it gets airborne and engine unloads its gonna go lean, almost like its got a tuned pipe.

I think you're setting your needle for how it sounds on the ground and not what it sounds like in the air?

At this point i'd go back to you needle setting you had and launch appx. 500 rpm less. Are you using a tach to keep tabs on your launch RPM?

I also think the heck with CG, slap the muffler on there and go to muffler pressure.

Tank height is not that critical with the higher revving engines, they'll draw the fuel. Appx. 1/4" to slightly higher than venturi center is about right.

What did the guys on stuka stunt say?

Also, is the flight speed ok, not too fast? Remember once you get the needle set and lap times are less than 5 seconds, you might go back to a 10x4 prop, BUT FIRST get the fuel draw issue solved.

Mark, the Stuka guys, including Jim Thomerson, think I need to open up the tank and probably reposition the uniflow vent. Other things like stiffen the nose, but I don't think that's the problem because foam in the fuel has never been the issue. It's sucking air from the uniflow line right across into the feed line. Big single bubbles all in a neat row, 1/2" apart. I tried breaking them up with a filter and thought I had it stopped, but it comes back. I also choked the venturi, as they suggested, with some nylon stocking material, but not a lot. The consensus, and Ken Cook agrees, is that my venturi width is fine, not too big.

I'll give re-positioning one last try before I perform tank surgery, and tomorrow, or whenever I fly next I'm going to run it normally vented. There are no bubbles that way, and the needle is actually workable. But with the uni vent open, the needle is completely senseless. I turn and turn in either direction and nothing happens for ten seconds. If I set it wet rich, by the time I run out to pick up the handle it either cuts off or leans out. I see Ron is flying his Fox normally vented and it apparently runs great. I'll do that and try setting it really wet and see what happens. I might have been a little spooked by having it fly in over center one day when I tried to take off really rich. That's when I broke my 10x4 prop. I'll try not to be to shy about riching it up. I glued my tail fin back on today too. Knocked some of the pretty off. That was what aggravated me as much as anything yesterday.

Ron, in that picture on the first page, your tank is where mine was yesterday, almost exactly that height.

Yep,

And it actually worked well that way. The only reason I lowered it was because I was told it was wrong by Zuriel Armstong, Ken and a couple other guys.

It shouldn't have worked well. Like I mentioned Ken reworked the internals of that tank so that may have been my saving grace. On my Baby Clown I am running a Perfect wedge that hasn't been reworked and it runs great as well. The line is too long, I don't have vent caps and it's not padded. So by all rights it shouldn't work either.

Don't know what to tell you there. Try it like you have it now and the next step is replumb time. If working the needle causes no change in RPM then something is not right.

Ron