On Sunday I worked on a project for my son's science fair project:   to test several different fuels, comparing the runs I would get.

I had an O.S. FP 40 on a Nobler.

Brodak 5% nitro, 11.5% synthetic, 11.5% castor               good run, great power in first half of flight, seemed to lag a bit coming out of the outside   loop on the second half of the run. 

Brodak 10% nitro, 11.5% synthetic, 11.5% castor              great run, great power through the whole flight   (needle 2 clicks open from previous run)
                                                                                faster

Fox 10% nitro, 20% castor                   Motor fired but wouldn't start    didn't have time to try with needle further open

Tower  10% nitro,  18% synthetic          Motor wouldn't fire or start

Any ideas as to why the problems with the last two fuels.             Both are old.   The Brodak fuel is fresh

Would all castor cause one to need to open the needle?     I want to try again, especially with the Fox fuel.  Would the Tower fuel be too lean and too dangerous because of the lesser amount of lubricant?

Silly question maybe, but is the plug OK?  It's very strange that it wouldn't even fire.

On Sunday I worked on a project for my son's science fair project:   to test several different fuels, comparing the runs I would get.

I had an O.S. FP 40 on a Nobler.

Brodak 5% nitro, 11.5% synthetic, 11.5% castor               good run, great power in first half of flight, seemed to lag a bit coming out of the outside   loop on the second half of the run. 

Brodak 10% nitro, 11.5% synthetic, 11.5% castor              great run, great power through the whole flight   (needle 2 clicks open from previous run)
                                                                                faster

Fox 10% nitro, 20% castor                   Motor fired but wouldn't start    didn't have time to try with needle further open

Tower  10% nitro,  18% synthetic          Motor wouldn't fire or start

Any ideas as to why the problems with the last two fuels.             Both are old.   The Brodak fuel is fresh

Would all castor cause one to need to open the needle?     I want to try again, especially with the Fox fuel.  Would the Tower fuel be too lean and too dangerous because of the lesser amount of lubricant?

Hmmmm...Sounds like some other problem developed between the 2nd and last tests.  Did you try the Brodak fuel again after the others?

Water in the other fuels or a blocked filter or bad plug or bad starter battery are the most likely suspects!

Randy Cuberly

On Sunday I worked on a project for my son's science fair project:   to test several different fuels, comparing the runs I would get.

I had an O.S. FP 40 on a Nobler.

Brodak 5% nitro, 11.5% synthetic, 11.5% castor               good run, great power in first half of flight, seemed to lag a bit coming out of the outside   loop on the second half of the run. 

Brodak 10% nitro, 11.5% synthetic, 11.5% castor              great run, great power through the whole flight   (needle 2 clicks open from previous run)
                                                                                faster

Fox 10% nitro, 20% castor                   Motor fired but wouldn't start    didn't have time to try with needle further open

Tower  10% nitro,  18% synthetic          Motor wouldn't fire or start

Any ideas as to why the problems with the last two fuels.             Both are old.   The Brodak fuel is fresh

Would all castor cause one to need to open the needle?     I want to try again, especially with the Fox fuel.  Would the Tower fuel be too lean and too dangerous because of the lesser amount of lubricant?

   Castor is much more viscous than most synthetics and will require the needle to be more open to pass the same volume.

   Brett