jaka

Hi!
I thought that the pressure nipple was clogged as the engine ran fine without pressure...and that putting the fuel line back on the pressure nipple created vacuum in the tank. -Have you checked that?

Can't see why a big spinner could create the problem your are talking about.... using pressure or not.
But why use a such a big spinner in the first place?? Steals lots of power! And why that Master A prop? Worst prop you can use performance wise.
A RAM or Graupner Cam-prop (or Sonic) is much better.

blw

My Feedback: (3)

A spinner is going to give a decrease on drag from the root area of the prop, as well as some reduction in profile drag.

huck1199

I thought the FP should have 20% oil with a dose of castor.

handyman

My Feedback: (2)

turn the ext tube on the mur so it faces down

edh13

My Feedback: (9)

Lightning you need to edit your first post with big red letters that tell these people that don't read all the posts that the problem has been solved.

Now we need to figure out why the spinner caused the problem. My vote is heat also. I have had old worn out engines that would run fine in the winter but do the exact same thing as yours in the summer (Arizona); just quit suckin fuel when it got too hot. I think the reason you were able to get it to complete a tank without press was you had to run it fat from the begining keeping it cool enough to finish the tank.
Eric

flybyjohn

My Feedback: (2)

I don't think it was heat, because you said it would only run till it hit the top of the stopper and then stop. It is fuel level mixed with the airflow over the carb. I never heard of this before, but after what you have said I can imagine it. If you wanted to truly test this to eliminate overheating then you would have to put the spinner back on and fill the tank full start up and tune with pressure attached and then stop engine, pour half the fuel out, start up and see if it runs cold with half a tank. if it doesn't then with the carb leaned to the flying setting and full head of fuel it has just enough pressure in the fuel tank to run but anything less than a full tank and it dies. I guess a 3 line tank setup (two clunks on the bottom of tank) would test this theory also being the tank would have the same pressure from full to empty.

Ernie Misner

Yeah, fun test here and we don't want to put it to rest any time soon.....

Could it be that you re-set the needles after removing the pressure system and it would run the tank out with that different setting?

Thanks,

Ernie Misner

Lightning Fan

My Feedback: (17)

OK, so the following comments were raised, and I'm paraphrasing some of them, after the correct answer came through on:

1. The problem isn't fixed, and its heat, and you need to fix it.
2. The oil content is too low
3. The prop might be too big and if the engineisn't ABC then the oil is wrong. The OSengine needs 20% oil. It might be worn out and it is going to repeat the problem when it gets hot again.
4. The big spinner overloads the engine.
5.I am an idiot for running a Master Airscrew prop

I'm going to be in big trouble after I respond to these comments.

1. The problem ISfixed, and I do not need help. I tried to convey that in the problem statement, but obviously failed. When the spinner was removed, the engine ran to empty with no changes to anything other than replacing the pressure line. It flew fine this way four more times, full to empty tank. Please also remember how repeatable the problem was it did it on the ground and in the air. It isn't getting too hot, and seizing. Itdoes get starved for fuel in the last fifteen seconds or so of the run, and obviously starts getting hot, but it is fuel starvation that is killing it. It isn't running lean the whole run. When you start the engine cold at half tank, it will start only if you richen it up a lot, and it will still stop. Take the spinner off and all that stops. I forgot to mention that the successful test happened on aday where we hit 97 degrees F.

2. Excerpt from Byron's site:

These fuels feature a wide range of nitromethane and oil percentages and are available in your choice of synthetic/castor blends or straight synthetic lubrication. Generally, a 16% total oil content is more than adequate for optimum performance and minimal parts wear. For those who feel more comfortable with higher oil percentages, we manufacture our Aero Traditional Blends with 20% total oil content and our Aero Premium 18 Blends with a total oil content of 18%.
Our entire club runs this stuff, 25 active fliers, in every engine you can think of. We use the Aero Gen 2 version, which has a blend of synthetic and castor oils. I'm not going to debate castor with you guys .. I believe in the higher breakdown temperature feature, and I know I'm old school in that belief. To each his own - I've run this for over fifteen years with no issues, and I tear down a lot of engines to see how they are doing.

3. Excerpt from the OSsite on the 25FP:

25FP

12331

ABC

0.248

0.708

0.63

0.6 @ 15,000

2,500 - 16,000

1.42

0.55

2.62

1.77

2.93

1.83

1.14

1.56

2.36

UNF 1/4-28

6.52

E-2030

2A

9x5

9x5, 9x6, 10x5

The 9x5 I'm running is on the low end of what it can turn. It is an ABC.
Excerpt from the OS manual for the FP series is included as an attachment, and it does call for 20% castor. I think that is excessive ... my opinion. Also, the only manual I could find had the iron piston ... not the ABC like I have.

4. The big spinner overloads the engine. No, this is a misconception. This is the one commentthat made me have to respond. Once the spinner is up to speed, it takes virtually no energy to keep it spinning. The air friction it experiences is negligible, and therefore there is very little work done by the spinner. Overcoming the inertia to get it spun up ... ok, that might be a bit more than a smaller spinner, but guys, this is in the noise! The spinner actually acts as a ducting device to direct cool air to the right places on engines when set up right and reduces air drag on the airframe, making the engine load less. It is why spinners are there on full scales ... it isn't because they look nice. As another poster said, it also covers the root area of the prop where a lot of drag is produced. F=ma rules here ... it takes force to accelerate the spinner to speed, but once there, it actually stores energy like a flywheel in its rotation. Unless there is a decelerating force on the spinner, which there isn't, it does not load the engine except during throttle changes. I pretty much ran full throttle the whole time. The problem with THISspinner was how it lined up with the mouth of the carb intake.

5. Master Airscrew. Everyone knows that the MAprops have had issues at one time or another. One magazine that is out of print beat that prop up in every issue, saying that the pitch was wrong and changed under load. We all have heard these things. Combat guys in the USare required by the rules in some classes to use MAprops in the 8x3 size on .15's to limit the speed. They do not break as easily as an APC prop when you skid in (I broke the two APC's I had in the first landings and this MA prop is still on there after many flights). I had the prop ina junk drawer, and the Draco is the fastest plane on the field with it, now that the engine is reliable.

Thanks for all the inputs, I recommend we let this thread die.

jaka

Hi!
Get rid of that plastic spinner! Belive me...It steals power! It's way too large.
Use an aluminium prop nut instead!

And replace the MA prop with a RAM or APC 9x5 (don't know if RAM makes that size ) and you will see what I mean.
Also, either use a Uni-Flow tank (two clunks) or use Tetta "Bubble less tank".These tanks gives a more even tank pressure than a ordinary 2-line tank.

By the way...Have you checked the pressure nipple?

koastrc

Fun quiz. Have a 46 with the same sort of problem. Not sure it will be the spinner. Sitting in the shop studying the set up on the engine. You know it could just be the spinner. We some time take things like spinners for granted. They could and maybe they do rob power. I feel and this is a feeling, a spinner of low quality may just cause more problems than we might think.
Would like to say a bit about Master Air Screw. Like most folks in this racket. I do not care for MAS props, but they have a use. I use them on trainers because as the OP pointed out. They don't break as easy as others. I would like to thank the OP for the thread. Never so smart I can't learn something.

sljensen

My Feedback: (6)

I know I haven't and don't post very much. I go along time between posting, but I had to throw my two cents out there. Instead of asking what he as checked, perhaps I might add HAVE YOU CHECKED YOUR GLASSES?, or perhaps you need some.
Thanks for letting me add my two cents.