Just got the Primary Force Model looks good. But was wundering if I should just assemble as is or upgade anything. Thanks John

John, I assembled mine as it came. I'm using a LA .25 and it works very well. Did however have to add 1/2oz weight to the nose for balance. This is probably the best profile plane i have ever had.
JJ

I have a Pathfiner ARF and compared to the Primary Force it is a piece of junk.  The wing is badly warped and the control hardware is useless.  The covering is not fuel proof and the mounts are like balsa.  A new flyer to C/L would have a difficult time making this a useable piece of hardware.  Rich, if you are going to recommend this kind of poor quality junk, you should try it first.
Steve

John, I assembled mine as it came. I'm using a LA .25 and it works very well. Did however have to add 1/2oz weight to the nose for balance. This is probably the best profile plane i have ever had.
JJ

I hope the photos show up <LOL>.

The ARF P-Force shown in the photo belongs to Leonard Rennick of PHX, AZ.  Leonard was kind enough to let me assemble the ARF P-Force model for him.  After about 75 flight the engine started to run erratic (which ran like a Swiss watch at first) and problem was narrowed down to the nose beginning to vibrating.   The simple fix was to add cheek cowl to reinforce the joint between the wing and fuselage.  As can be seen in the photo the cheek cowl was shaped like a Jet intake (sort of Mig-29) and glued to the inboard side of the fuselage.  Make sure the covering is removed from the fuselage and the wing in the required area for good wood to wood contact.  Apply a liberal amount of Epoxy to the wing and fuselage joint and the back of the cheek cowl.  Press the cheek cowl in place and wipe off excess glue with alcohol and a paper towel.

Later,
Mikey

As Mike stated, he added the cheek cowl to fix the vibration problem. The few others things done to it, was to add larger wheels for the grass, and I slid a carbon rod over the existing push rod and added ball link at the control horn. My only complaint would be the white trim tends to come off. When that happens I just replace it with MonoKote. I like the plane so much that I bought a kit from Mike, and I have also built an 80% size one powered by an FP20.

Leonard

Kim,
I was worried at first, but got a chance to ask Mike Pratt about it and he feels it is "bullet proof" if done per the instructions.  My experience so far confirms his analysis.  I tried to estimate the flight time on my original and it is at least 200 hr.  The only problem so far is the departure of some of the white trim.  I have another I plan to assemble this summer.  I will relegate the old one to an engine test bed.  I have a LEO 37 that I want to try along with a JEN 37.  Both fit the existing mounts (OS 25 FSR) and weigh about the same as the 25.  I also want to try a Macs muffler/pipe on the LEO.

Steve

I am using an FP40 run in a moderate 2 stroke setting. I guess I could tack it. Using a real fat setting left the plane without enough to get it over the top on the initial wing overs. This engine can put out more power than needed for the PF, but set as a I use it, it proves a very solid match. With an FP20, I believe the plane would be under powered except in an ideal situation, with a constant breeze that does not change direction. Mike Pratt recommends a 25 as possible power, perhaps on 55 foot lines. Some have recommended similar power for a Twister sized plane. At our club's field, where the air can be tricky and treacherous, I doubt that a 25 would be reliable on either plane. I've seen many underpowered planes plow in when hit with sudden gusts and changeable wind direction. The Primary Force I fly weighs 37 ounces and was built from a kit. It was given to me as a stunt trainer, already assembled, having been flown many times. It is predictable and easy to fly. Nice plane. When equipped with a tongue muffler the FP40 does not create a nose heavy condition.

FWIW, Joe Just has an ARF PF, he flies his with an LA .25. I dont know about others flying conditions, but in Pasco, at 2500 feet on a 90 degree day, that LA did a great job. That being said, there is always room for a bit of margin in power delivery to help in turbulent conditions.

Rick,

Mike flies his with an LA 25 while my arf is powered by a TT36. I wanted something different and wanted to try out a couple building techniques, that is why I went to the 80% size. Right now the FP 20 is a little fast on full 60ft lines.

Thanks Leonard
I know several fellows that swear up and down the FP 20 produces more power than the LA 25. It seems to me this might be a good match, full size P.F. and a FP 20.

Fred K. has been flying his Primary Force Arf with a "Fred 'O Y" Special" modded Magnum 28. It was really flying great. However this engine has balls,  literally, compared to the FP/LA 20-25 stuff.