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Seagull Yak?

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Old 01-17-2012, 07:01 PM
  #1376
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ORIGINAL: rowdyjoe

Well, she's all in one piece. I mounted the cowl about an hour ago after a bit of trial and error. It fits fine and looks good and all the stuff that heats up should get plenty of cooling.

Assembled everything and attempted to balance her at the factory CG ....7 to 8 CM back from the leading edge at the wing tip. OOOPS ! Waaaaaay nose heavy. Guess that little 20cc gasser is heavier than it looks. Haven't weighed it yet but, that's next.

I've searched this thread for CG advice and find that most folks are recommending 5.5 inches back from the leading edge at the root. I'll try that next but, wanted to look around a bit first to see if there is a consensus about the CG location.

I'm still hoping for first flight tomorrow but, I'm getting pretty tired. I've been working on this bird since about 11 AM. Ran the engine for a while and found that I'm getting 7700 RPM with a 16x8 Xoar prop and velocity stack installed. I removed the stack to make the cowl fit better and I discovered that it cost me 500 RPM. Lesson learned ....velocity stacks work well.

More later.

RJ





Definately balance it at 5.5" back from the leading edge next to the fuse.....mine balanced spot on with a Saito 180 (31oz) by simply positioning the RX battery to rear of the fuse under the canopy area. Not sure what your gasser wieghs, but it may take more than that to balance it correctly.
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Old 01-17-2012, 07:07 PM
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Sourkraut,
Thanks for the advice. I just weighed and balanced her and she came in at 10 lbs even. Balance at 5.5" back from LEat the root was just a tad nose heavy. MUCH better. I like my birds to fly neutral so, I may add an ounce or two to get the sweet spot. When Iturn them inverted, I like little to no forward stick at mid throttle. After Ifly her tomorrow I'll have a better idea of how she balances in flight.

I'm happy with the set-up so far. Wish me luck on the first flight.

RJ
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Old 01-17-2012, 07:41 PM
  #1378
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ORIGINAL: rowdyjoe

Sourkraut,
Thanks for the advice. I just weighed and balanced her and she came in at 10 lbs even. Balance at 5.5'' back from LE at the root was just a tad nose heavy. MUCH better. I like my birds to fly neutral so, I may add an ounce or two to get the sweet spot. When I turn them inverted, I like little to no forward stick at mid throttle. After I fly her tomorrow I'll have a better idea of how she balances in flight.

I'm happy with the set-up so far. Wish me luck on the first flight.

RJ

Mine came in at 9lbs 12oz without cutting the bottom out of the canopy and using the stock landing gear. (just like she came out of the box)

Balance her at 5.25-5.5" and the maiden will be a success.

Good luck with the maiden

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Old 01-17-2012, 08:26 PM
  #1379
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Default RE: Seagull Yak?

Yep, same here. Box stock with a 20cc RCGF gasser.

A fellow club member has this bird with a 20cc DLEand it flies great with plenty of power. Hope mine flies as well. I'm a bit concerned about the 500 RPMloss without the velocity stack and am considering going to a smaller prop to get more RPM. I think mine should turn between 8 and 9K so, I'm down on RPM by a bunch. We'll see tomorrow.

RJ
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Old 01-17-2012, 08:40 PM
  #1380
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Here's a few pics.


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Old 01-18-2012, 04:31 AM
  #1381
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The only problem that I have had with mine was the Pilots dash popped off and was rattling around inside the canopy. Hardly had any glue on it, so I had to cut the section out below the dash, and glue it all back in. Any more trouble to that area and I will remove the entire bottom of the canopy.
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Old 01-18-2012, 07:52 PM
  #1382
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Well, Murphy's snake bit me again. The engine ran for me at the field for approx. 3 min. during a pre-flight check of all systems and then quit. After that, it would start but, not run. We pulled the carb and took it apart checking everything we could thing of and then put it all back together. Same thing ....start and run for about 5 sec. and then quit.
This thing is driving me nuts. It ran fine at home yesterday but, no soap today at the field. Must be something in the air out there that causes this problem because this is the second engine I've had do this to me. The first one is a 26cc gas and the problem turned out to be a lousy cheap stock carb ...so, Iordered a new one and will see how well it works when it gets here. So, two birds down due to carb problems.
To be honest ....I think I may have stripped the threads in the adapter block that fits between the engine and carb and created an air leak. Dang thing is plastic. Any how, I've ordered a new adapter and should have it by Monday or Tuesday (I hope).

RJ

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Old 01-20-2012, 09:41 PM
  #1383
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The continuing Yak saga ....

I worked all afternoon and into the evening on the engine in the Yak and finally got it to start and run. I can't explain what I did to make it do that but, Idid use an electric starter to get it going after fiddling with the needle valves ....starting from scratch. The starter saved wear and tear on my sore arm from the day before.
It starts by hand and runs fine now but, won't idle below 2200 rpm without dieing. When I drop the rpm down to around 2k it will idle very sweetly and then die without warning. Don't know what's up with that but, Ithink I need to pull the plug after it dies and see if it will give me a clue as to whether it's flooding or starving ...or neither.
I hand started with the cowling on and it ran just fine. Starts from dead cold are good after choking it 'til the carb is wet and it warms up easily. Transition is smooth but, I still have a bit of 4 stroking to eliminate as the engine breaks in a bit more.
Oh, almost forgot. I bought a velocity stack from TBMand installed that yesterday. Don't know if it helped the problem or not but, it does increase high end RPMsignificantly. RPM drops about 500 without the stack.
The winds were a bit high today for a first flight so, Istayed home and worked on another engine issue. I bought a new carb for my GPro 26cc engine and installed it today. It's mounted on my new Seagull Spacewalker II 120. The stock carb is junk but, the RCGF carb I ordered from BPHobbies fit perfectly and runs great. Itook this opportunity to rework the throttle linkage and servo and change the choke from servo to manual. I like this arrangement better and Ihave eliminated the weight of one servo.

.....and so it goes.

RJ
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Old 01-21-2012, 09:48 PM
  #1384
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Yak saga cont'd ....

The weather was great and timing was good but, the we couldn't get the idle speed down low enough without it dieing. It would idle at 2200 to 2300 rpm but, would die when set below that. So, discretion being the better part of valor, Icancelled the first flight attempt.
I've decided to wait until my new adapter plate arrives Monday. I'm hoping it will eleminate what I believe to be an air leak and make the engine run and idle as it's supposed to. We'll see.

I had better luck with my Spacewalker II 120. The 26cc gas engine on it ran well enough to get two flights in. The first flight was OK but, very twitchy in pitch and inverted flight indicated she was tail heavy. So, Ilanded after about 5 min.. and removed approx. 2 oz. of the weight Iadded to get her to balance. The second flight was much better ....more stable and predictable in pitch and inverted flight required just the slightest touch of fwd stick. More about this bird on the appropriate thread.

RJ
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Old 01-22-2012, 02:00 AM
  #1385
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Default RE: Seagull Yak?

Rowdyjoe, What thread do use to discuss your Spacewalker?
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Old 01-22-2012, 02:07 AM
  #1386
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ORIGINAL: RCplanman

Rowdyjoe, What thread do use to discuss your Spacewalker?

This one ....

http://www.rcuniverse.com/forum/m_81...tm.htm#8190668

Lots of great info there.

RJ
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Old 01-23-2012, 09:58 PM
  #1387
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Yak saga cont'd ....

The carb adapter arrived today as advertised and Iinstalled it this evening. Everything fits nice and tight now but, it didn't make it run any better. In fact, it wouldn't even start. Inoticed that gas was dripping from somewhere under and in the middle of the carb body. I never did find the exact location of the leak, let alone the cause. Ipulled it off the engine and replaced it with one I had on-hand.

I installed the carb that came off my Spacewalker 26cc engine. The one I thougt was defective. It was a tight fit (due to small design differences), but, it's on there and the engine is starting by hand and running steadily. This is the carb I thought was junk because it would take forever to drop down to idle speed.
As it turns out, that "defective" carb is the same bolt pattern as the carb adapter on the 20cc Yak engine. So far, it's doing a nice job on the 20cc engine but, I have a bit of adjusting and clean-up to do on the installation. The throttle linkage is binding a bit and Ineed to rig the choke.

Even though the carbs appear to be very similar there are variations that make a difference on installation. They look to be the same physical size but, since the replacement carb came off a 26cc engine I expected it to be a bit larger. It doesn't appear to be larger unless the difference is internal (slightly larger venturi?). One external difference is the direction the gas inlet tube points. It points at the engine making it difficult to route and attach the fuel line.

WX forecast says chilly with rain for the next couple days so, I'll have time to tweak and fiddle with my birds to get them all airworthy.

RJ
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Old 01-24-2012, 10:31 PM
  #1388
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cont'd ....

As it turns out, the "defective" carb is. So, Ipulled it off and installed the original one and messed around with the dang thing for a couple of hours before Icould get it to run right. Isuspect it needs a rebuild as the diaphram doesn't seem to draw fuel as it should. I think this engine sat on a shelf for quite a while and the diaprhram and valves dried out and got stiff. It's a V1 and it was new in-the-box when Igot it but, the latest version is V3. So, this carb was obviously NOS.

The original carb is a Walbro but, I'm having difficulty identifying the correct model no. It has 2 sets of no.s on it ... WT 942 and below that is the number 743A. I've been searching the web for about 2 hours now and can't find any reference to a WT 942 but, did find a 743-1. I'm confused and a little frustrated right now but, I've sent a question to one of the sellers who carries the rebuild kits to ask which one Ineed. Ihope to hear from them tomorrow and have a kit on the way soon.

I finally got the engine to start and run but, it's tough to start when it's cold. Warm starts are one or two flips. Cold starts will wear your arm out.

Forgot to mention; the new adapter block didn't seem to make much difference but, that eliminates on possible problem. I'm focused on a rebuild kit for the carb now.

RJ
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Old 01-25-2012, 03:29 AM
  #1389
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Default RE: Seagull Yak?

Joe, if your using the China spark plugs, get rid of them & change to NGK.... China plugs are hit & miss. Gap with #11 Exacto blade, and check timming, approx 27 deg. BTDC
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Old 01-25-2012, 03:53 AM
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Default RE: Seagull Yak?

On a cowled engine, priming the carb when cold requires either of three methods. A finger over the ventura, soldering the hole in the choke plate closed, or an injection tube aimed into the ventura. The easier choice by far is soldering the choke hole closed.

Remember, these carbs require crankcase pressure impulses for the pump... if the insulator mount only has the port on one side, the carb can only be mounted one direction. Sometimes the carb will be rotated to provide better linkage hookup without noticing the pulse port issue. Some engines once primed will draw enough fuel to run without the pulse port to the pump but they won't run properly or be able to be tuned.

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Old 01-25-2012, 04:10 AM
  #1391
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Default RE: Seagull Yak?

On my schedule this rainy day are two task. The storage hanger is made for the Spacewalker for the garage ceiling but it needs mounting. Unfortunately it requires moving a hanger for another plane slightly... but neither is much of a deal. The bigger deal is a wing rack... I'm running out of room and have two choices... get rid of something or get more creative... and I like the latter choice better. Probably what will be needed is a rack that has dowels for the wing tube holes where the wings mount perpendicular to the wall.

I also want to put an incidence gauge on the Spacewalker to see if it will detect any variance between wing and stab.
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Old 01-25-2012, 05:09 AM
  #1392
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Incidence checked... 0-0

Oops... sorry for my mental failure... wrong thread.
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Old 01-25-2012, 11:29 AM
  #1393
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Quote:
ORIGINAL: SkyPilot101

Joe, if your using the China spark plugs, get rid of them & change to NGK.... China plugs are hit & miss. Gap with #11 Exacto blade, and check timming, approx 27 deg. BTDC
Thanks for the tip but, it came with CM6 and I just changed to a new one to be sure it was working well. Static test shows it's firing everytime.
I checked the timing and it's right on 28 deg. BTDC.

I found a tip on one of the other forums here and learned that the carb on the 20cc DLE may fit my engine. It's reported to be a very good carb and Tower sells them for a reasonable price. So, if this one doesn't work out Ihave an alternative.

RJ

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Old 01-25-2012, 11:55 AM
  #1394
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Quote:
ORIGINAL: AA5BY

On a cowled engine, priming the carb when cold requires either of three methods. A finger over the ventura, soldering the hole in the choke plate closed, or an injection tube aimed into the ventura. The easier choice by far is soldering the choke hole closed.

Remember, these carbs require crankcase pressure impulses for the pump... if the insulator mount only has the port on one side, the carb can only be mounted one direction. Sometimes the carb will be rotated to provide better linkage hookup without noticing the pulse port issue. Some engines once primed will draw enough fuel to run without the pulse port to the pump but they won't run properly or be able to be tuned.

Fortunately, my carb can be mounted either way and Iturned it over to simplify the throttle linkage. I can also reach the needle adjustments without removing the cowl or drilling a hole.
I've considered the pulse tube and replaced the original tubing from the crankcase to the carb and secured both ends with small zip ties.
My next effort will be soldering a brass tube to the vent hole in the diaphram cover and running tubing into the fuselage.
I don't have a choke system rigged up at the moment and have been choking it by putting my hand over the velocity stack opening. To save weight and complexity I'm considering using a "cork" to temporarily plug the velcity stack opening instead of using my hand, which is awkward, while trying to turn the prop. I need to visit the hardware store and look around.

Looks like your shims have done the job on your SW wing incidence. Hope she flies better for you next time out.

Our WX is bad for flying but, good for everything else. We need the rain so, I'm not complaining.

I need to replace the gear on my MX2 and reassemble it. I need to get my favorite bird back in the air. She's rested long enough.

RJ
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Old 01-25-2012, 01:28 PM
  #1395
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Default RE: Seagull Yak?

RowryJoe, I have a early V1 ? & it's a bear to start cold but after you get the carb wet & running it'll restart very easy. I pull the plug & give the cly.a shot of starter fluidbingo it'll start. You may have to repeat it but it works. Good luck.
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Old 01-25-2012, 03:11 PM
  #1396
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Quote:
ORIGINAL: RCplanman

RowryJoe, I have a early V1 ? & it's a bear to start cold but after you get the carb wet & running it'll restart very easy. I pull the plug & give the cly.a shot of starter fluidbingo it'll start. You may have to repeat it but it works. Good luck.

Thanks for the tip. The thought of using starter fluid has crossed my mind with this engine only I was thinking of something more like blackpowder or dynamite.

RJ

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Old 01-25-2012, 03:17 PM
  #1397
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[/quote]

Fortunately, my carb can be mounted either way and Iturned it over to simplify the throttle linkage. I can also reach the needle adjustments without removing the cowl or drilling a hole.
I've considered the pulse tube and replaced the original tubing from the crankcase to the carb and secured both ends with small zip ties.
My next effort will be soldering a brass tube to the vent hole in the diaphram cover and running tubing into the fuselage.
I don't have a choke system rigged up at the moment and have been choking it by putting my hand over the velocity stack opening. To save weight and complexity I'm considering using a "cork" to temporarily plug the velcity stack opening instead of using my hand, which is awkward, while trying to turn the prop. I need to visit the hardware store and look around.

Looks like your shims have done the job on your SW wing incidence. Hope she flies better for you next time out.

Our WX is bad for flying but, good for everything else. We need the rain so, I'm not complaining.

I need to replace the gear on my MX2 and reassemble it. I need to get my favorite bird back in the air. She's rested long enough.

RJ

[/quote]

I have researched this thoroughly and while a standard wine cork needs to be tapered to get a good fit, a champagne cork is "just right". Trying out the various corks was tough challenging work, but I am happy to share the results. Also, to prime, instead of flipping the prop through compression repeatedly, just grasp the spinner and rock it back and forth 8 or 10 times to get the fuel to the carb. A 2 stroke engine is a pump, after all.

Happy flying.

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Old 01-25-2012, 03:41 PM
  #1398
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RCVFR,
Thanks for the info. I was looking forward to finding just the right cork but, hadn't planned on going to the expense of testing champaign corks. I was thinking more along the line of a cork from a bottle of Ripple or Boons Farm.

RJ
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Old 01-26-2012, 06:04 AM
  #1399
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I really don.t know this but..... they don't have corks
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Old 01-26-2012, 08:24 AM
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Default RE: Seagull Yak?

RowdyJoe, What I did once on a G-23 was use a short piece maybe [I don't remember the size ] 3/4 " plastic hose on a short stck.
Same idea only the cork could crumble a bit===not good for the carb.
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