Bow Lift>>Stern Lift PROPs ????

[Boilermaker]

Could someone please explain the differances in Bow lifting/stern lifting/ all around lifting props??<br />I would like to know what the design differences are, and if it is something that is evident by sight??? such as a lot of rake, or differant shyaped blades to the screw??? I always thought that props just gave thrust inline with their axis???<br /><br />Thanks for helping in my continuing education

 

[Winger Ed.]

Re: Bow Lift>>Stern Lift PROPs ????

opps double post.

 

[Winger Ed.]

Re: Bow Lift>>Stern Lift PROPs ????

Originally posted by Winger Ed.:<br /> The real obvious ones are the 'choppers' and 'cleavers'. Within the groups, some are made to run under water, some along the surface only partially submerged.<br /><br />And they are some big bucks too, both to buy and have tuned properly. Plus a Prop Doc. often has to play around with thinning and tweaking on them to get one perfect for the application. <br /><br />You'll see them on racing boats. I forget which does what, but one tends to lift the bow, the other the stern.<br /><br />If you see a prop that looks like it came out of some sort of commercial food processing machine- its probably one of them.<br /><br />Some of the 'big eared' props like the Mercury Tempest series tend to lift a boat's stern a little. It is supposed to try and sort of climb up on the denser water under it towards the less dense/bubbly water above it. At least that's what I've heard.<br /><br />Go over to the Scream & Fly high performance boat site and dig around a bit. They'll have various pictures and discussions about them in their forums.

 

[Boilermaker]

Re: Bow Lift>>Stern Lift PROPs ????

Thanks WINGER Ed.>>>I have seen those props on hi performance boats here>>>but I was more interested in the "everyday" type props such as TURBO-STILLETO, OMC's SST, QUICK SILVER, BALLISTIC, VIPERS ect...<br />Some of these advertise that they are "bow lifters" some say they help the stern out of the water to plane faster & some adds just say they are overall lifters???<br />I was just curious about the designs & if it was evident by appearance>>>such as "elephant ears" or more pointed blades./ Or maybe more or less rake to the blades??? Just curious.

 

[Dhadley]

Re: Bow Lift>>Stern Lift PROPs ????

Sometimes its hard to tell visually. The obvious ones are the cleaver style. They have a straight trailing edge and sharp tip vs a round, curved tip. Cleavers are usually associated with being stern lifting. We use them as surfacing props on air entrapment hulls and/or some pad bottom hulls that dont require bow lift.<br /><br />Cleavers, in general, tend to vent on hard acceleration although there are exceptions. <br /><br />Rakers have good bow lift but still dont let the stern "squat". In the V6 line the 24 Raker tends to have more lift than the rest. <br /><br />Stilettos seem to have more overall lift than a Raker and good bow lift. Turbos, especially those with larger diameter, seem to lift more than Stilettos and therefore have more "bite".<br /><br />Normally, positive rake is associated with bow lifting capabilities. There are also other factors like length (not ammount) of cup. IE -- how far it comes from the trailing edge around the blade tip and down the leading edge.

 

[Winger Ed.]

Re: Bow Lift>>Stern Lift PROPs ????

Originally posted by Boilermaker:<br /> I was more interested in the "everyday" type props

Like most of us hanging out here, I'm glad to help.<br /><br />If you're seriously interested in a maximizing the performance of your boat-keep in mind there is about as much science and technology in different boat propellers than there is in the Space Shuttle, most of which will take you years to learn. <br /><br /><br />But, to shortcut the system,,,,,<br /><br />Go to a 'Prop Doc'. One of the propeller shops where the owner is a grizzeled old guy, who has worked on boat propellers, and run the shop all his life. Show him your boat & engine, then ask for what he recomends to get it to do what you want it to do.<br /><br />Listen carefully, write check, take prop from counter, then go home. <br /><br />I have found this works real, real well.