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Sharpening edges of prop blades?

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  • Sharpening edges of prop blades?

    This might seem like a stupid question, but what harm or good might come from sharpening the leading edges of the blades?

    thanks
    Verne


  • #2
    Re: Sharpening edges of prop blades?

    I've seen racing boats with sharpened prop leading edges but for most normal boating I doubt there would be much to gain...I run a Stainless Steel Ballistic prop on my Yamaha 90HP and the edges are pretty darn sharp enough as they are....at least for my usage...

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    • #3
      Re: Sharpening edges of prop blades?

      If its just you at home with a file,its more important that you keep the leading and trailing edges clean and smooth, taking out nicks when you get them.

      There is a thinning/reshaping process called labbing. When done properly it can really wake up the performance of a boat. Expensive at around $100/blade, hard on toes if you're swimming and thinning weakens the blades so service life drops.

      Comment



      • #4
        Re: Sharpening edges of prop blades?

        Try cutting meat with a dull knife and then with a sharp one. The principle is the same. Sure, sharpening will ease the blade entry through the water but: A sharpened edge is not the whole story, blade thickness and design count too .A knife can be as sharp as possible but if it is not hollow ground, it will not slice through meat easily. And, that is why there are different blade designs for different cutting jobs. Similarly, there are different prop blade designs for different expected uses.

        But back to your question: If done judiciously, no harm can be done by sharpening the leading edges of your prop blades. However, any performance gain from just that will be so slight that you will probably not notice it.

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        • #5
          Re: Sharpening edges of prop blades?



          10.00 sharp as you want to get it..Be careful
          Stickly a opinion your milage may vary.

          Speed is how fast you hit the wall
          Torque is how far you move the wall"

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          • #6
            Re: Sharpening edges of prop blades?

            First off W_Guy there is nothing as a stupid question....the only question that is stupid is the one not asked.

            If you are looking for performance gains by sharpening the answer is simply this....NO....you wont notice anything unless you have a fast ultra light boat setup for racing and then it is better off to let the prop experts get there hands on it. BUT it is a good practice to keep the leading edges of your prop true and in good shape. This will help to keep the prop performing as it should and also help to eliminate any further problems but keep in mind that any file work done should be VERY minimal for fear of getting one out of balance which aint good.

            Comment



            • #7
              Re: Sharpening edges of prop blades?

              I'm thinking that a sharp leading edge on the propeller will hamper the performance and give you greater tendency for cavitation under load conditions. Probably something that is advantageous only for surface drives.

              A slightly rounded leading edge might be the best. Take a look at airplane wings & propellers, hydrofoils, etc. - rounded leading edge, thin trailing edge.
              Best regards,
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              • #8
                Re: Sharpening edges of prop blades?

                Originally posted by robert graham View Post
                I've seen racing boats with sharpened prop leading edges but for most normal boating I doubt there would be much to gain...I run a Stainless Steel Ballistic prop on my Yamaha 90HP and the edges are pretty darn sharp enough as they are....at least for my usage...
                I'm running the Ballistic 13 1/4 x 24 XP SS on my 90 Merc.. A real performer. For you folks out there, blade thickness is important and SS prop ads. stress the point. As Frank A. said, slice the water with a baseball bat and a machette and see which one takes the most force. I realize that sharpening your blades isn't like a SS blade, but it doesn't hurt. Nicks don't really hurt either other than cutting yourself with them when around your engine for whatever reason. I used to sharpen mine when I ran alum. props.

                Mark
                If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

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                • #9
                  Re: Sharpening edges of prop blades?

                  Originally posted by 1FASTLASER View Post
                  First off W_Guy there is nothing as a stupid question....the only question that is stupid is the one not asked.

                  If you are looking for performance gains by sharpening the answer is simply this....NO....you wont notice anything unless you have a fast ultra light boat setup for racing and then it is better off to let the prop experts get there hands on it. BUT it is a good practice to keep the leading edges of your prop true and in good shape. This will help to keep the prop performing as it should and also help to eliminate any further problems but keep in mind that any file work done should be VERY minimal for fear of getting one out of balance which aint good.
                  ^^^^+1

                  Comment



                  • #10
                    Re: Sharpening edges of prop blades?

                    Just to clarify a couple of things....

                    Labbing isn't just for racing, nor do you need to be running the prop near the surface. Most boats will see a benefit if its done properly (of course some more than others).

                    Nicks are where cracks tend to start. Its always a good idea to keep them cleaned up, but as has been pointed out, remove as little material as possible.

                    Comment



                    • #11
                      Re: Sharpening edges of prop blades?

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                      Here is an example of a cleaver prop with sharp leading edges and somewhere around 15 hours running time. Even though it is stainless, note the relative blunting of the leading edge due to normal running, not damage from running through sand or mud. Note also the pattern of paint wear from ventilation/cavitation before the prop "Locks-up."

                      Note the damage at the tip of one blade that was incurred in shipping. UPS treated the shipping box like a football. The sharp blade punctured through the factory original shipping carton, an outer corrugated carton, AND a layer of packing in between both. You can NOT take a prop with thinned blades and sharp leading edges like this one and bang it against anything. Hit anything while running and the prop would probably be beyond repair.

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                      • #12
                        Re: Sharpening edges of prop blades?

                        I recently had a pair of stainless props reconditioned to remove some relatively minor nicks and dents along the leading edges. It was approximately $400 for both but the props came back like new. When the pros do it they weld a little material here, grind down a burr there, and make sure the prop is perfectly balanced and re-shaped to original specification. I guess the point I'm trying to make is that there is a lot that goes into fixing a prop correctly not just simply filing it down. Be careful, it's not as simple as it looks.

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                        • #13
                          Re: Sharpening edges of prop blades?

                          Originally posted by Frank Acampora View Post
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                          Here is an example of a cleaver prop with sharp leading edges and somewhere around 15 hours running time. Even though it is stainless, note the relative blunting of the leading edge due to normal running, not damage from running through sand or mud. Note also the pattern of paint wear from ventilation/cavitation before the prop "Locks-up."

                          Note the damage at the tip of one blade that was incurred in shipping. UPS treated the shipping box like a football. The sharp blade punctured through the factory original shipping carton, an outer corrugated carton, AND a layer of packing in between both. You can NOT take a prop with thinned blades and sharp leading edges like this one and bang it against anything. Hit anything while running and the prop would probably be beyond repair.
                          Frank, we usually get along pretty well, but I am going to offer a different view. Back when OMC decided to come out with their first SS prop; the SST (Stainless Steel Teflon) of which I purchased one and used for many years, they used Teflon for the coating, not paint. Having run alum rebuilt props for a lot of years, I had the paint peel in a similar fashion.

                          My opinion is that you can't paint something as slick as SS put it under pressure like happens to a prop and expect it to stay. That's the way I see it.

                          I have been running SS props since 1973 (when this prop first came out) and never painted them, nor ever had any deterioriation to the extent you mention.

                          So sir, my take on what is happening to your prop is not due to thin blades PER SE. I'll go and find a picture of my Ballistic prop which is on my boat and has been since 2005 which I used to run regularly right at 50 mph (see Avatar) with no burning or blade tip damage and add it either to this answer, or if I can't will quote this thread.

                          Mark
                          Attached Files
                          If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

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                          • #14
                            Re: Sharpening edges of prop blades?

                            Added pics. Can't find the closeup I wanted. May have to go out to the shop and take another.
                            Attached Files
                            If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

                            Comment



                            • #15
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                              Re: Sharpening edges of prop blades?

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                              Well, Mark: I don't know if Chrysler ever had Michigan teflon coat their props but it does stand to reason that they might. When I had this prop repaired, the fellow who did the repairs remarked that where he removed the coating, the stainless underneath was not polished but rather it appeared to be sandblasted. Additionally, the parts of the blades where the coating has worn or peeled or otherwise failed to adhere, the surface looks the same. Logically, if I were going to apply a coating such as teflon or even a powder coat, I would ensure a good surface with a lot of "grab." This particular coating is glossy like powder coat but I don't think they had powder coating technology in the early 1980s (The approximate year of this prop).

                              These two photos hopefully show the glossiness of the coating. One also shows where an aluminum tag with "Chrysler" silkscreened in red was applied. This tag blew off the first run.

                              As for the leading edge, I can offer no explanation. The prop was initially sharper. It was always run in clean water and never touched bottom of any type.

                              This prop has probably 15 hours running time at about 3000 prop RPM and 60 MPH. I never noticed any loss of performance.

                              Unfortunately, My Ballistic 21 pitch runs about 600-1000 engine RPM less (I forget the exact number) and still delivers the same top speed so this prop rarely gets used anymore. Personally, I am a big fan of Ballistic props however, the lower unit thrust washer needs to be replaced with a split shaft collar on Chrysler/Force engines in order to get the necessary exhaust snout clearance to use these props.

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