Too Much?

Stuka Stunt Main Forum · 6 of 6 known posts recovered

SteveD · Jan 19, 2003 10:04 PM

With a stock OS LA-S .25 w/muffler weighing 241 grams. And a stock Brodak .40 w/muffler weighing 240 grams.
The plane in question is a Primary Force. (designed for the stock .25) Why not go with the B-40? Thanks for any input, SteveD.

Steve Helmick · Jan 19, 2003 10:07 PM

#1 source

Add in the weight of the bigger prop, tank and fuel, longer landing gear required for the bigger prop, too. Or try both, through use of New Mexico-style engine mounting pads. Let us know which is better. Steve

Steve http://www.nwskyraiders.com/index.html

Crist_Rigotti · Jan 19, 2003 10:56 PM

#2 source

LAST EDITED ON Jan-19-03 AT 10:57 PM (CDT)

Steve,
Last year I flew a Jamison Special with an OS 25FP with a blocked boost port and swung an APC 11 x 4 and did very well with it. I also flew Mike Pratts PF with an OS 25 LA. I think a B-40 would be a great choice. He has some CF landing gear to accomodate a longer prop. My 25FP burned 4 oz of fuel to do a full pattern and reports are that the B-40 will do it in about 3 1/2. So the it looks like the fuel issue isn't an issue at all. I've seen some PF with a Fox 35 on them too!

Crist Rigotti
"A driver trying to be a pilot"

JTH · Jan 20, 2003 12:53 AM

#3 source

Stock OS muffler weights typically about 60 g. There you can save weight, if that was your concern.
regs, Jyrki

SteveD · Jan 20, 2003 07:16 AM

#4 source

The weight of the stock LA muffler isn't a worry. I was just thinking I could remove the extra weight of the larger prop by going to one of Mr. Pratt's cf landing gear. Those two swaps would give me awfully close to the same weight. ? Thanks SteveD.

Mikey · Jan 20, 2003 10:46 AM

#5 source

Steve,
The B-40 has more power than the OS .25 and should be a great match. You can swing a little bigger prop with the B-40 so a good place to start would be the APC 11-1/2” X 4” or something similar. The line length will have to be increased to 62” from eyelet to eyelet to slow the lap times to 5.1 to 5.2 and you may have to add an extra head shim along with a green Bru-Line airfilter.

The Primary Force can and will handle a wide range of engine from 25 to .40 but the reason that I choose the OS .25 FP & LA was they were cheap, available at the time, and would run quite well right out of the box. I recently installed a Magnum .36 on my Primary Force and have only flown a few flights with it so far. I would not say the Magnum is better than the OS .25 FP & LA at this time, but it has more power and I am sure with a little more tweaking I can get it to run just fine.

Mike

Mike Pratt