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Was the full size prop damaged from a prop strike which is pretty much the damage model props incur? A little hangar rash repair is one thing; most people trying to save a prop is gluing a full blown break.
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Originally Posted by radfordc
(Post 11757548)
I've repaired wood props for both models and man carrying planes with no failures yet.
Really? I didn't think that was a very good idea. At least for the other guy it wasn't. Are you talking broke right off, or Knicks and scratches? I know a lot can be done to the full scale props, but I usually replace mine if they strike the ground pretty good. I guess that's just me. |
Originally Posted by abufletcher
(Post 11757668)
More break-in/testing of the Saito 82a. This time using the 14x6 APC prop, which is definitely better. At full throttle I was getting around 9,300-9,400rpm. It wouldn't go higher...which is maybe OK. I'm still having trouble getting a stable idle below 3,000.
Mostly, I just ran fuel through the engine with the throttle set in the mid-ranges. Lots of smoke, lots of oil...and the engine cooled down quickly after the run. I also checked the fuel consumption/run time for one full tank at 6,200rpm and that turned out to be just a bit over 5 minutes. The tank I use on the stand is maybe about 1/5 smaller than the tank in the Snipe (which I can't remove without removing the wings and no larger tank would fit anyway). So that gives maybe 6 minutes at 6,000+ if I use the 82...with no safety margin. I should compare the fuel consumption with the 72 with the same setup. The other minor step forward was to repair the loose engine mounting beams with a bit of epoxy and a couple of screws. Did id you say the 82 was still brand new? What plug are you running? |
Originally Posted by [email protected]
(Post 11758252)
Did id you say the 82 was still brand new? What plug are you running?
Type of plug? Um...not really sure. I'm sure it's an OS F-style plug but not sure which brand. |
Yeah, five min. Flights wouldn't suit me fancy either. I wonder if a hotter plug would idle better.
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I think the idle will settle down once I find the right adjustment for the set screw. I can get it running down to 2,400 but it won't stay there.
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How big is the tank?
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I've been trying to figure that out. It's not as simple as reading a number off the side since I can only see the bottom. But I do have another tank that looks the same as the one in the Snipe and it's labeled OK Model 220...so I'm assuming that's 220ml, which would be about 7.5oz. That's definitely too small.
But it would take some serious engineering of the Snipe's interior to make room for a larger tank. Also as things are now, to remove the tank requires that I remove the 3mm music wire running through the wings. And to remove that music wire, I need to remove the wings, which means removing (and replacing a dozen or more rigging wires. Remember that the model was originally designed with a 50-class engine in mind. |
Hmm, sounds like a PITA! I hope you come up with a simple solution that let's you run it for more than five minutes at a clip. I'm interested to see what kind of run times you get with the 72 compared to the 82.
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Sometimes a simple expedient such as new fuel does amazing things!
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The runtime test with the 82 was done with the setting still quite rich, judging the the pools of oil on the stand afterwards. On the next run I'll lean it out a bit and check the time again. Then I'll put the 72 on the stand.
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An oz a minute is about right at full throttle, but at 1/2-3/4 throttle should be more time. Engines run great out of the box today, but broken in is going to be at the 2 gallon of fuel mark. .50 size plane with no details. .70 size with is about right.
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Chris was probably thinking more in terms of an unadorned "sport scale" model. But when the scale outlines are this accurate, it's really hard not to go all the way.
As far as flight times, I'd be perfectly happy with a 10 minutes flight with a 2-3 minute safety margin. |
"OS F-style plug but not sure which brand."
OS F says it all. The brand is "OS", and the type is "F". Les |
What I meant is that it is a "long" type plug. It doesn't look like the other OS plugs I have.
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I used to cram the biggest tank I could and get 30 plus minute flight times untill I lost a throttle linkage in flight and had to fly for over 45 minuts at 1/2 throttle waiting to burn off all my fuel. now I shoot for 15 minutes of fuel with 10 to 12 minute flights. none of my saitos will idle if there still pooling oil. it should be better at a leaner setting.
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I had something similar happen. A bolt came off the carb on a Magnum 2-stroke, the result being it went full-throttle with no control. So I just circled and circled and circled wondering which circle was going to be the last one and where it would be when it went deadstick. It flew for about 20 minutes after that.
On a sport model 15 minutes is nice. With a more serious scale model I'm happy with 10. At 20 minutes flights are almost too long. |
Just because there was room I stuffed a 24 oz tank into my 1/4 scale N 28 (G23 powered) and flew it for about 30 minutes one day for fun. All the guys at the field began to wonder if the throttle link had come off but when I got tired of it I cut the rpm and landed It wasnt empty yet but I had no way to measure what was left. I have since replaced it with a 17 oz tank and it still flies longer than I care to.
Doc |
I've developed a routine where I always count exactly how many turns of the fuel pump it takes to fill each model. Then after a flight, I count how many turns it takes to refill. (counting how many turns to "empty" a tank isn't reliable.) On most of my models filling up takes about 23-25 turns. Usually after an average flight, it'll take about 10-12 turns to refill. So 15 minutes would probably be safe but 20 would be pushing it. Also if I've been flying aggressively or there's a strong wind, I may use a third more fuel.
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I am also a fuel pump "counter".
Brian |
As well! The 1/3 N 28 takes 140 turns, whew!
Doc |
Yeps, fuel pump counter here too. Kind of funny, I thought I was the only crazy one.
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I use a veterinarian syringe. Goes back to CL days (to which I still partake)!
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For some reason I have the urge to build and fly a CL plane. I never have, but I know my kids would love it.
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Originally Posted by [email protected]
(Post 11759138)
Yeps, fuel pump counter here too. Kind of funny, I thought I was the only crazy one.
Some guys like those electric fuel pumps but I like to feel the resistance on the crank as I fill my model. |
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