A friend recently suggested that Ilook into the AMR&D prop tip mod. www.pipermods.com/proptip.html
They don't actually explain what they do to the prop, but (of course!) it sounds like the neatest thing since sliced bread. Anyone have any experience with this mod?
There was a prop mod sorta popular years ago for 170's called the California twist, I believe it was done by Aero Propeller in Hemet. Don't know if they're still around or not, don't know what that mod was either. Same question re: experience.

Eric

I have heard that the AMRD prop mod is simply filing, sanding, grinding etc. the blade "face" (which is the bottom of the airfoil) to the shape of the Hoerner wingtip. The Hoerner wingtip in turn is the design used by Met-Co-Aire that sells a lot of fiberglass wingtips.

The Hoerner design means an up-sweep of the bottom at about 45 degrees until it meets the top surface.

I don't know the details of the AMRD prop tip mod and have never seen one.

Anyone wanting to become an expert in propeller design, and have the key to the mysteries of propellers... should get Jack Norris' strange but totally brilliant book on the subject. Go to www.propellersexplained.com .

Bill

Back in April, I ended up buying a new Sensenich 74DM6S5-56 prop from AMR&D with their STC'd tip mod. Indeed, the mod involves undercutting the tip similar to a Hoerner wingtip-- it's supposed to give you the higher cruise speed at a given rpm of the prop pitch, but allow the engine to turn up like it was pitched 2" flatter. Sort of a free lunch deal, and you know what they say about those. I don't think it turns up any more than a regular 56" pitch would, although since I had a 52 on there I couldn't say for sure. The main reason I bought it is that Art Matson of AMR&D sells these props at only about a $30 premium over the lowest price (from Spruce) I could find on a stock prop, with a shorter lead time to boot. I figured I could take a chance & I'm only out $30 if it's not all it's cracked up to be. I had paperwork issues with the prop that was on the airplane when I bought it, and a new prop was the quickest easiest way to make it all legal.
So the moral of the story is that it's true what they say -- there's no free lunch. And if you wanna buy a new Sensenich prop, call AMR&D for a price.

Eric