Hello Orv,
Thanks very much for posting that. It looks as though it may be my problem too. I too am using 1/16" 1/2A tubing which I think came from Bernie. It will be a few days before I can try the 1/8" tubing in anger as it lousy weather over here. It should be OK tomorrow, but I have a fence to mend ......... At least I can try the 1/8" without flying, to see what the difference is. I will get back to you when I have given it a try!

Thanks,

Andrew.

It is weird -- I use short (1-1/2") lengths of 1/16" ID tubing as a super-flexible clunk line for OS 20FP and OS 25LA engines, and it works just fine.

I wonder if a Medallion carb body on a Tee Dee would help it draw better and still get the same power. I never thought to try that before I found pressure bladders, which ended all of my fuel supply frustrations of Tee Dees. I haven't used a hard tank since.

Rusty

Hi Wayne and Orv.
Hard to believe we've all missed this over the years, something as simple as a wider fuel line. Almost like a no brainer, one of those head slappers.

I do love Tee Dees on a bladder, so simple with the lack of bulk compared to a hard tank and never coughs in a loop. But I have a Tee Dee powered Baby Streak that I can try with a wedgie and a fat fuel line and see how it works. I even built it with the tank hooks but never used them. Guess I better rummage up a stock venturi. I'll report back with my results... if Winter ever gives me a good day to fly. Rain for the past six weekends, and wind this one.

Looking forward to trying this,

Rusty

Hi Ken,
I have not flown a plane with the 1/8th tubing. I have just altered the orientation of the plane and that quite rapidly. Literally waving it around. On 1/8th tubing , the engine runs faultlessly, on 1/16 it certainly doesn't!
  Weather and workload have prevented me from trying the set up for real. I don't know if this is a solution to a longstanding problem or if it is a red herring. All I can say with certainty is there is something different in the two setups. Like you, I find it difficult to believe and cannot for the life of me think of a good reason why there is a difference.
  I will report back when I can actually fly the plane with 1/8th tubing. Despite my scepticism I think that the 1/8th will give me a different result. I will report back when I can get flying.

Andrew.

                  Andrew, I always felt that a rectangular pinched down tank was the solution. Al Rabe does this and it seems to hold the fuel in that corner as intended. I have tried for fun a bit of 1/2A speed. I never ever could get a good run out of a suction tank. But, once I introduced uniflow and used a rectangular tank that was taller than it's width, problems went away. Now, one would think that getting a plane to fly level and fast should be quite easy. I found it to be the most frustrating thing in the entire hobby. I was self taught through this experience and that made things even more frustrating although it gained a lot of knowledge. If you look at any tank used in racing today, they're coffin shaped with the rear being gradually pinched or ramped down to the rear with the far outboard corner sometimes pinched. Recently I did my kit bashed RSM Miss Ashley where I turned it into a Magician like the Brodak version. I have the Perfect wedge installed from the inboard side with the majority of the tank on the inboard and the pickup is only 3/8" sticking out the outboard side of the fuse. Now I experienced extreme problems. The faster the plane goes, the richer the engine runs. No fuel draw problems, just the opposite. The plane is launched screaming lean, the second it gets into level flight it slows, then it rockets through the manuevers and once again slows in level flight. Tank height is not an issue now but the tank in my opinion needs to be shimmed side to side opposed to up and down. Ken

Hi Folks,
I am really pleased with the comments pertaining to my TD observations. I am particularly pleased that Andrew was able to replicate and legitimize my observations.
In order to clarify and address some of Ken's comments, I will give you the complete history.

1. My first setup featured a 1 oz metal Perfect wedge tank as shown in the first attached photo. It was plumbed with small DuBro 1/2A fuel line. The results were not satisfactory at all. The engine was difficult to needle and the run characteristics were all over the map. I could not get an engine run that I was happy with... and I tried! What I didn't try with this setup was a larger fuel line.

2. I will only use Uniflow tanks for my larger stunters because I can always rely on the tank head pressure remaining the same from start to finish thereby giving a reliable contsant-speed run at whatever needle setting. Ah-ha says I, I bet this might also be the solution to my TD problem so I plumbed up a plastic clunk tank for unilow as shown in the second photo (this photo shows the larger fuel line) and hooked it up the engine with the same tubing I used in step #1.
I still couldn't get a reliable run... Now what?

3. This is when, in desperation, I changed the fuel line to the next size up. Well, I was amazed at how well the engine now needled and ran. I was getting beautiful engine runs from start-up to empty with the plane in all attitudes. In fact, the set-up doesn't give me any warning when the tank goes dry and often some of my crashes come as a result of being overhead when the engine stops abruptly.
As I said in my first post, as a test, I switched back to the small fuel line and the problems returned.

4. But as Ken says, good engine runs result from a number of conditions being just right and my resulting good engine runs can be attributed to both uniflow and large fuel line. My existing set-up isn't perfect. My tank is about 1/4" too high so I get a slightly leaner engine rum inverted. But it is still within the stable operating region of the engine. Lowering the tank would mean cutting into the wing and compromising its integrity.

5. Crashes would most always crack or break the TD's carb. body. I don't know how many times I fixed it. I realized that the in a crash, the venturi would be forced backwards and this is why the body would fail. I think I sorted out the problem. As shown in the third photo, I gobbed a bunch of Devcon steel-filled epoxy around the body and I molded a gusset rib between the venturi and the cylinder. So far, it has resisted my crashing.

6 In hindsight, maybe the TD just has a... dare we say ... a finicky female personality and only now works because she likes the sexy purple fuel line fashion accessory .

Orv.

The real fix is to downsize the venturi.  It works great.

Use some wire to keep the spray holes clear.  Epoxy it shut.  Pull out the wires when dry.

Redrill the venturi with a smaller drill.  Trial & error.  Start very small and then run the engine.  You will find a very small loss of power and really great improvement in smoothness.