syd
Well-Known Member
Anyone had their props cupped? Did it make a difference?
Syd
Syd
Prop Cupping
- Thread starter syd
- Start date
oldgit
Well-Known Member
.......but my boat is not a fast planing craft.
BartW
Well-Known Member
What drive type ?
on my first boat with merc Alpha One drive,
when I bought her, there was an old non cupped prop,
the third season I damaged the prop and put a new one on
I bought a brand new merc. cupped prop, that was in stock at a local shop
I didn't know about cupped props when I boaght the new one, I could just see there was a small diffrence in shape between the old and new prop
this prop made a very noticable difference,
faster on plane,
higher max speed
less prone to ventilation,
the boat behaved better then ever before.
I believe that all props for merc or Volvo outdrives are cupped now aday's
so yes I can recommand a cupped prop
I am not sure if this can be done on an existing prop,
you could asc "Steel developements" for shure they can give a good advice
on my first boat with merc Alpha One drive,
when I bought her, there was an old non cupped prop,
the third season I damaged the prop and put a new one on
I bought a brand new merc. cupped prop, that was in stock at a local shop
I didn't know about cupped props when I boaght the new one, I could just see there was a small diffrence in shape between the old and new prop
this prop made a very noticable difference,
faster on plane,
higher max speed
less prone to ventilation,
the boat behaved better then ever before.
I believe that all props for merc or Volvo outdrives are cupped now aday's
so yes I can recommand a cupped prop
I am not sure if this can be done on an existing prop,
you could asc "Steel developements" for shure they can give a good advice
tico
Well-Known Member
Second Barts advice, ask Julie at Steel Developments.
When i fitted the 2 diesels in place of the petrols, i needed to increase the pitch on the props and add cupping to load the engines properly without changing the gear ratios.
worked perfectly!
When i fitted the 2 diesels in place of the petrols, i needed to increase the pitch on the props and add cupping to load the engines properly without changing the gear ratios.
worked perfectly!
Latestarter1
Well-Known Member
Prop cupping
Cupped propellers have concave faces. There are many ways to achieve this but the most common is ito introduce cup at the trailing edge, sometimes cupping is worked around into part of the tip area as well. As cupping strenghens the blade this often means a thinner section can be used which improves effiiciency
The effect of cupping is is to increase the true or virtual pitch, a good rule of thumb is that moderate cupping is worth about 1 inch of pitch. As cupped blades help to delay and reduce the onset of cavitation in high speed, highly loaded propellers, for such craft cupping can produce speed a increase of between 6 to 12%. Therefore on a 40 knot vessel this would be in the region, of 3.6 knots.
Now the bad news, cupping serves NO useful function under 30 knots and only really starts to work its magic over 35 knots.
Cupped propellers have concave faces. There are many ways to achieve this but the most common is ito introduce cup at the trailing edge, sometimes cupping is worked around into part of the tip area as well. As cupping strenghens the blade this often means a thinner section can be used which improves effiiciency
The effect of cupping is is to increase the true or virtual pitch, a good rule of thumb is that moderate cupping is worth about 1 inch of pitch. As cupped blades help to delay and reduce the onset of cavitation in high speed, highly loaded propellers, for such craft cupping can produce speed a increase of between 6 to 12%. Therefore on a 40 knot vessel this would be in the region, of 3.6 knots.
Now the bad news, cupping serves NO useful function under 30 knots and only really starts to work its magic over 35 knots.
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