GizmoMadMax

HELP!!

I have some Q&A on my FIRST pusher...

My first nitro Bobcat/Jet and this is my first plane over a 46 size endine.
I haven't flown any Jet shape object except for my cool YardBird F22 foamy pusher delta wing, but being foam with NO airfoil, should never really fly...Doh!

So for flying expierence, my 30 yrs on and off, has been Cox planes way back, then gliders with Cox then .15 OS, then trianer 25 then 40's and now 46 Hanger 9 Tribute profile 3D, and a 40 size P-51 Mustang that lands like a stickin brick....
Then my long list of electrics, Ikarus nemesis, Ikarus F11A 3D, hand made monster foamy, war bird, mini tiger,

BUT, now this Bobcat has me scared and on edge...
As some of you know, I have a Bobcat 50 with a Super Tigre G-61 ABC and fuel tank line supply about 13" long....


NOTE: I have NOT flown this bobcat yet, just tuned on the ground so far. I want to maiden this week, but want to verify I will NOT have a fuel system issue once in the air????


QUESTIONs
=========
> Do you all fly your Pusher Bobcats & other aircraft with a perry pump or a header tank when the fuel line is over a certain length or with pushers?
Some say I need it, others say a header tank because pumps are a nightmare and others say just fly it, confused once again...

My supply silicon line from the brass elbow back to the carb is about 13"
My brass elbow I bent myself, so that there is a solid connection pointing to the rear for the silicon carb supply tube.
The brass elbow comes out the front of the tank, and is bent in a radius 180 degrees so that the there is a straig line for the silicon fuel tube back to the carb

For a header tank, yuk, there is no way to mount one that I can see, unless I cut out a window in the bottom read and then mount it, then seal it back up for strength with gorilla glue or expoxy, by expoxy is brittle???



Then, yesterday out at our flying field and guess what...
1. I was checking out a heli, and he has a 2oz header tank and NO pump...

2. He has this COOL device called "Carb Check"!!!! this is a little electronic gizmo that has a sensor that you RTV between one of your cylinder fins and it monitors the head temp and then automatically richens the fuel mixture if the engine is getting hot, so how cool is this!!!!

> Has anyone here tried this out? I can NOT find a carb check online???

> HELP, I can't seem to find a tiny to small header tank, only a 3" one, hmmm, I was hoping for a smaller one??
Any thoughts?


Thanks in advance for the tech help!

combatpigg

My Feedback: (3)

I'm no real help here, I've never attempted to run a pusher with a throttle on muffler pressure. The little I do know is that some set ups are more sensitive to tank position than others. I would do things to make the "head pressure" of the system less critical.
A uniflow plumbed tank is supposed to iron things out. There was an article about this in the last couple years in Model Aviation.
Personally, I'd run crankcase pressure with the throttle wired wide open and use the throttle as a flood off. The high pressure system will give the engine a much more even run. Some guys have used checkvalves on the muffler tap with similar results.
Maybe the YS engines solve this problem altogether with their built in timed fuel injection pumps??

freakingfast

My Feedback: (3)

I had a OS 55 AX on a Bobcat clone and had no problems at all after I leaned it out after the first flight. I went fat because the tank was elevated at take off so don't richen the engine, peak it more than a normal plane.
It had a huge tank, it was set up with a OS bubble-less clunk toward the rear of the plane and a long large size fuel line.

It ran amazingly well from start to finish with every thing I could throw at it. Dang I wish I didn't kill that plane in a low altitude flat spin, just not enough time to save it.

Don't over think this thing, just go fly it. Adding gadgets that you don't need may cause more problems....like that exhaust extension. Let the stinger go into the airstream, yes it will make a mess of the muffler...oh well, it'll run!
Fly it high and down wind on the first flights, test the engine's throttle range where it's safe if it dead sticks and you'll make the runway.

GizmoMadMax

ok, good to know others made out with long fuel lines.
Now you mentioned large fuel lines? mine are the standard size for the 2 runs, is that too small?
thanks

still4given

I didn't have problems with the fuel delivery on mine. Just make sure the tank is installed with the outlets toward the front of the plane so the clunk is at the back of the tank. As for the exhaust, I ran mine through the wing and out the bottom of the plane. Worked slick. I'll add a pic of it for you.

Blessings, Terry

freakingfast

My Feedback: (3)

I used Dubro large on the fuel run only, stretch a short 3/16" length of fuel line around the outside to hold it tight on the ends.

Most of the time exhaust deflectors hurt performance or make it run bad in spots. Just trying to keep it simple.
In one case where the use of a deflector gained 300 rpm. Webra 55, red Jett muffler, 9X10 APC, and 10%.

GizmoMadMax

Well, Fuel problem showed up...
My fellow club member who flies 5 different jet types (from ducted to .91 nitro) took the first attempted maiden flight of my Bobcat....
BUT, about 20 feet off the ground during maiden take off, and the engine shutoff, crap.... so she came in for a fairly good hard landing at a high AOA landing and bent the landing gear and broke one of those cheap THIN china plastic screws. So, I am frustrated that it shut down, what the heck????

> So I guess I will order a perry pump tomorrow??? I do not want to play games and have the engine shut off again due to a 13" fuel line, plus the tank elbow, plus the clunk line of 4 or so inches, so I suspect the 18" to 20" from clunk to engine is a problem???

> would a header tank solve this, of just stick with the perry pump or some other brand pump?

Any thoughts

Help

combatpigg

My Feedback: (3)

I guess my reply in post 2 was a waste of time. Sometimes the best way takes some effort.

freakingfast

My Feedback: (3)

Yeah, CP. Don't feel bad, it looks like he didn't heed my warning about going rich on take off (post #3). Mine almost died on take off on the maiden flight too.
Oh a Perry pump on a stock carb, this'll be interesting. Betcha he used that real long exhaust extension too.


Start simple and basic, make one change at a time. What one guy's setup or engine can do, yours may not.

blindfaithnogod

i would think a bladder tank would be the best way to go. from jett engineering or a tetra from perfomance speacalties.

bob27s

My Feedback: (19)

A pump might solve the fuel delivery problem, but it will also create other types of problems for you. It is not an autoamtic fix for a poor running engine.

Try to get it right without the pump first...... do not be affraid to lean out the top end a bit, and be CERTAIN you have the low speed mixture set perfectly.

still4given

The only thing I noticed on mine was that it would tend to go rich when I first stabbed the throttle on take off. It took a couple of tries of leaning the needle a couple clicks at a time until it would not load up on roll out. Fortunately I discovered it while it was still on the ground and I was able to shut it down and taxi back.

These planes don't glide very well. On my first flight I got a little metal filing in the carb and had to fly it out of fuel. Even though I stayed high, I still barely made it back to the runway. Don't try to slow these Bobcats down too much on landing if you care about your gear.

GizmoMadMax

I tuned this and ran it for a week or so every other day and it was tuned to idle, slam the throttle with no hesitation, and come down fine, run at all throttle positions and no issues, UNITL it was 20 feet off the ground at maiden, and just shut off, crap.....

any thoughts...
I guess all those that said I needed a pump or header tank are right .....

We messed up the landing gear with a helicopter type hard but flat landing.... bent landing gear and broke that tiny junk boom plastic screw... but at least it is still in great shape...
so once again, I am NOT going to fly it until I get a header tank or pump

any thoughts...

thanks in advance!

blindfaithnogod

try adjusting the needle nose up... then you can see how the climb out will affect tuning.

freakingfast

My Feedback: (3)

A valid point.

freakingfast

My Feedback: (3)

Some points:
Header tanks are great for keeping air out of the line (Heli acrobatics), but wont improve fuel delivery.

A long exhaust diverter will add a bit of back pressure and could overly richen the mid range or ruin transition.

A Perry pump on a Super Tiger carb will overly richen the mid range or ruin transition to the point the the engine will quickly die at part throttle.
You can dial down the pressure with the low and high speed needles but you can't reduce the mid, your a the mercy of the carb's fixed metering.
Adjusting the pump pressure down will help, but that defeats the purpose of the pump in the first place.

A blader tank will keep out air in the fuel line, but wont improve fuel delivery.

A 11X6P APC will reduce the load on the engine and keep it cooler. That's what I ran on the OS 55AX, the ST is about the same power. The 11X7p ran hot.

Run the engine nose up and see what happens in a few moments, does it respond to leaning? How is it when back to level?

A Uniflow tank layout works in some cases, but in this long fuel run I think it will be a detriment.

There is the Cline on demand regulator,and I know you want a gizmo to fix all your woes, but you haven't exhausted other avenues as you can see.

Keep it simple. Besides the Cline is ugly hanging in the breeze right next to the carb.