borer prop

[M1]

I have a few questions about the borer props that I was hoping some of you that have flown the borer for a while can answer.

I have a 8241 on a PA18-150. Starting to think that its pitched to fine. I just changed from floats to skis, and am still getting the same speed on cruise. About 76 knots. Used to get 92 knots with the stock prop and just wheels. If I get the prop repitched, any suggestions as to what pitch. I would like to get a bit more cruise, without loosing too much on takeoff.

When I first put this prop on, I was really happy with how smooth it seemed compared to the stock prop. But now after 6 months of flying, it seems a bit rough again. Do these props change pitch a bit when they first get used? The prop was checked before I started using it.

 

[cubunltd]

I've flown Borer props on all the 150's and the 8241 is best for climb. Repitching the prop to a higher pitch won't do a lot for cruise, maybe a couple mph, but it will have more effect on takeoff performance. As far as the roughness goes, I'd check it over real good for tracking.


John

 

[aktailwheel]

When I bought my cub (PA-18-150) it was 8241, and was running really rough. I had the prop overhauled. It turned out that one blade was 42 and the other something less than 41 - so they were out of whack. Plus, the prop was wrong all the way throughout the length of the blade. So, we started from scratch, repitched it all along the blade to the right dimensions and changed to 42. I picked up a few mph cruise and dropped just a little rpm on take off, but it did seem to climb faster. I don't have any details on how much it changed, I was new to the cub world at the time and didn't pay too close attention to the minutia. I also had the prop dynamically balanced on the plane. By the end, it felt like a different plane, smooooooth, quiet, and it felt like I had more power. I think a lot of energy went into vibration, and when that got cleaned up I think it made up a little for pitching to 42. Plus, my engine is newly overhauled and running really strong, so it was really winding up on the 41 pitch. Just my two cents worth. Nothing scientific here, except that having a prop properly pitched and dynamically balanced makes for a much smoother and quieter ride.

 

[cubunltd]

Most of the Borer props I've used were good. Every once in a while you get one that's like aktailwheel discribes. If it was good initially and now it's rough, I would make sure it's tracking properly. Check your spinner also.

 

[Dave Calkins]

Most of the new ones I've had were rough out-of-the-box.

I take 'em to the prop shop to have them checked every time nowadays. I've had one blade at 47 and one blade at 41 on a factory new 82-41.

For the 150HP I'd stay with 41 or maybe go to 42. If takeoff performance is ones primary concern, keep it at 41. Understand that your engine's static RPM (tail tied down/ aircraft not moving) is likely somewhere around 2350RPM. Check your airplane out so you know.

Note that your engine makes 150 HP at something like 2700 RPM....thus, you don't have all 150 HP until the aircraft is moving, probably not until the thing is in the air......

If you pitch your prop higher, you'll lose even more RPM and HP "out of the hole".

>...My two cents.

If everyone could have a lightweight controllable prop, we'd have what we really need.