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Postby JPXman » Mon May 28, 2007 1:23 am

had the 2-seater up again today for a short hop. i now have the engines running fairly well, the idle started acting funny today. i am finding that i am slowly reverting to the fuel system that shannon recommended i use in 2001.... in tank fuel filters, no primer bulbs, straight line to the fuel pump (in my case) and all uphill on the fuel lines....

by doing all of this i have virtually eliminated all air/fuel vapour bubbles in my fuel lines and it seems that the engine/carb likes it that way. so for anyone having random strange acting engines, attack the fuel system first.

as an aside, i have now theorized that my jets on the dell'orto carb that are modified do not allow full low speed lean adjustment and this is causing my idle to linger at a higher rpm before dropping to tick-over speed. i'll be swapping in original needles and we'll see what we see. if that doesn't do it, then i'm changing the front crank seals on these 2 engines.

Tyler

PS: it could very well be that all of my other engine "seizures" were due to a poorly designed fuel delivery system with bubbles getting to the carb....causing fuel starvation which would look like seizure due to lean gas/air mix....(lack of gas)
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Postby xgary » Mon May 28, 2007 4:04 am

PS: it could very well be that all of my other engine "seizures" were due to a poorly designed fuel delivery system with bubbles getting to the carb....causing fuel starvation which would look like seizure due to lean gas/air mix....(lack of gas)

Tyler, primer bulbs are just dumb. Gettiing rid of them is best thing to do for many. I do not know the dellorta carb that well but I do know the Bing carbs well. Easy to adjustd and to fine tune the high speed mixture it all about the jet and high speed needle ..... EGT's can help but the true tale is from the spark plugs.

You told me once you never got more than 42 to 4300 rpm ? Maybe the max of 4600 could be achived now ?


Shorty
Shorty .............
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Postby JPXman » Mon May 28, 2007 7:11 am

totally peaked out i can get 4400rpm static easily. i back it off a bit to bring down the EGT to about 1100F and i get around 4300rpm. level with full throttle the props unwind and i can see 4500rpm, but i have never seen 4600rpm... i am figuring these engines out as i go along, its hard when you're the only one sometimes :)
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Postby JPXman » Wed Jun 13, 2007 3:34 pm

just a couple of things:

1) I bought a lazair locally for $400! it is an old series II in really bad shape but it came with 4 parts wings, a fuse and two 185's with good bi-props. score :)

2) been thinking about engine tuning - with two strokes, has anyone played with tuning before? I have been reading that if you want to make the engine spin faster, you need to change the main jet - but i guess that is in concert with a higher flow/tuned exhaust? just starting to think about stuff like this.

T.
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Postby xgary » Wed Jun 13, 2007 4:11 pm

good score for sure.

Engines and pipes.

I have not played with the 185 pipes but I would guess you could see 15 to 20 hp outta them at fulll throttle but you would use likley 2 times the gas.
need differnt carbs or at least re jetted.
Alot of trial and error..... possibly including meltdown. ?

more RPM will == a re drive and another prop .


et c et c

oh and dependability might suffer.........
Shorty .............
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Postby JPXman » Fri Jul 06, 2007 10:45 pm

had something interesting happen tonight:

i still don't consider my 2-seater a "daily driver", still testing a lot of crap on it. on my last flight for the first time i experienced tail shake. i had just installed a vertical stabilizer 2 flights earlier with no problems. on this flight though, it felt strange and it just flew strange. when i craned my neck around i could see the tedlar pretty flappy on the tail, and i've never seen that before. and you could see the tail shaking, almost vibrating. drag cables are nice and tight, on the ground though, i don't know about it flight.

tonight was my first time with her since that flight. the tedlar was pretty floppy so i figured i'd tighten it up on the tail. after heating for about 3 minutes around one side of the tail, the tedlar pulled right off the top tube of the tail! i was shocked!

i looked at the rest of the tail and i could see where the tape had slipped off the 1/2" wide stuff and was only clinging to the 2" stuff, which was the white kind and didn't hold i guess.

so now i have to repair my tail with a tedlar fix.

check the tops of your tails for tedlar slippage. i hope once i get this fixed the tail shake goes away.
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Postby JPXman » Mon Jul 23, 2007 3:14 am

bump... see edited post above
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Postby xgary » Mon Jul 23, 2007 5:46 am

you put on a vert Stab?

I saw one like that before -- not sure of purpose really.

I never found the need my self.
Maybe that is causing some deflection of prop wash ?

Who know... V tail works pretty good in flight ..........
You neeed prop wash at sub stall speeds to give it authority though........

Member the early Lazairs had larger ruddervators and they were down size but a good bit later on --- I would venture to guess they were shrunk about 20% or more in size............ Kinda blows the theerory from the talk of larger ruddervators eh from master of nothing Scott perkins. Guy does not even fly anything let alone a Lazair ............ hahahahhahaah
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Postby JPXman » Mon Jul 23, 2007 2:23 pm

yes i'm adding the fin in preparation for float attachment. every conventional aircraft flys better with a ventral fin when on floats, so i figured i'd add a dorsal fin and see how it flies. i'm not looking for one-engine-out-rudder-authority, i'm looking for stability at the tail when i add huge floats on the front of the plane.
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Postby huronflyer » Mon Jul 23, 2007 9:15 pm

TY,

On my first flight at South River last Tueday night I had shaking,

I don't know where it came from. It was not there on my Wednesday flights
Peter Bonnell thinks it may have been cross controls at high power...

My Tedlar is getting a bit slack in a few spots. Considering new covering this
winter.

The dorsel fin for floats is interesting, the Challenger i flew had extra fins for
floats, BTW it was a diff airplane.

Good flying guy.

Daver
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