Propeller Shroud - Moderated Discussion Areas

  ContinuousWave
  Whaler
  Moderated Discussion Areas
  ContinuousWave: The Whaler GAM or General Area
  Propeller Shroud

search | FAQ | profile | register | author help

Author Topic:   Propeller Shroud

jamesmylesmcp posted 10-30-2013 10:36 AM ET (US)
An interesting gizmo is being added here. It looks as if performance is enhanced with these add-on's.
http://730.mediamasons.com/venturi-say-what/
http://www.mptmfg.com/Home_Page.php
kwik_wurk posted 10-30-2013 12:20 PM ET (US)
[A] Kort nozzle--a common device on low speed, high thrust situations. Very effective in high sea state as well, by reducing the localized turbulence at the prop. -- I use an enlarged prop guard on my kickers (bigger boat, not Montauk), and it will hold grip in amazing conditions.
jimh posted 10-30-2013 12:24 PM ET (US)
Using shrouded propellers is quite common on commercial towing boats.
I don't see any evidence of improved performance. It would be more interesting if the authors of that article waited until they actually tested the device rather than just announcing they were going to use it. There's no results yet.
I think the speed range of the boat is important in determining if a shrouded propeller is effective. I don't see many on boats that go 45-MPH.
jimh posted 10-30-2013 12:46 PM ET (US)
Here is a link to a report on propeller guard testing. In the report the concentric ring propeller guard is tested, and based on some pictures it appears to be the "Thruster" brand. The effectiveness of the concentric ring is rated good at speeds of 5-MPH, but not so good at planing speeds.
At planing speed, an unguarded propeller was judged to be safer than any of the shrouded propellers.
http://www.uscgboating.org/assets/1/AssetManager/ Propeller%20Guard%20Test%20Procedure.pdf
jimh posted 10-30-2013 12:47 PM ET (US)
Also see
http://www.tradeonlytoday.com/home/ 526703-abyc-and-coast-guard-join-on-propeller-guard-test
jimh posted 10-30-2013 12:50 PM ET (US)
By the way, a Kort nozzle is a special type of shrouded propeller. It is the trade name of the company that manufacturers it. See
http://www.kortpropulsion.com/kort_nozzles_and_propellers.htm
There is also a good article on the topic of ducted propeller at Wikipedia:
http://en.wikipedia.org/wiki/Ducted_propeller
pete r posted 10-30-2013 07:47 PM ET (US)
We use the prop shrouds on our rubber duck rescue boats (mandatory) and found they caveated at high revs.
I think they contribute a little towards safety but still need more development.
That carbon fibre one on that previous post looked pretty fancy.
jimh posted 10-31-2013 11:27 AM ET (US)
I wrote to the manufacturer of the THRUSTER to ask for a price quote on the model they would recommend for attachment to my 225-HP Evinrude two-stroke-cycle outboard with the M2 gear case turning a 15.5-inch propeller with 17-pitch. (That's my E-TEC with a MIRAGEplus.) The MSRP of a suitable shroud was $995.

Hop to:

Contact Us | RETURN to ContinuousWave Top Page

Powered by: Ultimate Bulletin Board, Freeware Version 2000
Purchase our Licensed Version- which adds many more features!
© Infopop Corporation (formerly Madrona Park, Inc.), 1998 - 2000.

Author	Topic: Propeller Shroud
jamesmylesmcp	posted 10-30-2013 10:36 AM ET (US) An interesting gizmo is being added here. It looks as if performance is enhanced with these add-on's. http://730.mediamasons.com/venturi-say-what/ http://www.mptmfg.com/Home_Page.php
kwik_wurk	posted 10-30-2013 12:20 PM ET (US) [A] Kort nozzle--a common device on low speed, high thrust situations. Very effective in high sea state as well, by reducing the localized turbulence at the prop. -- I use an enlarged prop guard on my kickers (bigger boat, not Montauk), and it will hold grip in amazing conditions.
jimh	posted 10-30-2013 12:24 PM ET (US) Using shrouded propellers is quite common on commercial towing boats. I don't see any evidence of improved performance. It would be more interesting if the authors of that article waited until they actually tested the device rather than just announcing they were going to use it. There's no results yet. I think the speed range of the boat is important in determining if a shrouded propeller is effective. I don't see many on boats that go 45-MPH.
jimh	posted 10-30-2013 12:46 PM ET (US) Here is a link to a report on propeller guard testing. In the report the concentric ring propeller guard is tested, and based on some pictures it appears to be the "Thruster" brand. The effectiveness of the concentric ring is rated good at speeds of 5-MPH, but not so good at planing speeds. At planing speed, an unguarded propeller was judged to be safer than any of the shrouded propellers. http://www.uscgboating.org/assets/1/AssetManager/ Propeller%20Guard%20Test%20Procedure.pdf
jimh	posted 10-30-2013 12:47 PM ET (US) Also see http://www.tradeonlytoday.com/home/ 526703-abyc-and-coast-guard-join-on-propeller-guard-test
jimh	posted 10-30-2013 12:50 PM ET (US) By the way, a Kort nozzle is a special type of shrouded propeller. It is the trade name of the company that manufacturers it. See http://www.kortpropulsion.com/kort_nozzles_and_propellers.htm There is also a good article on the topic of ducted propeller at Wikipedia: http://en.wikipedia.org/wiki/Ducted_propeller
pete r	posted 10-30-2013 07:47 PM ET (US) We use the prop shrouds on our rubber duck rescue boats (mandatory) and found they caveated at high revs. I think they contribute a little towards safety but still need more development. That carbon fibre one on that previous post looked pretty fancy.
jimh	posted 10-31-2013 11:27 AM ET (US) I wrote to the manufacturer of the THRUSTER to ask for a price quote on the model they would recommend for attachment to my 225-HP Evinrude two-stroke-cycle outboard with the M2 gear case turning a 15.5-inch propeller with 17-pitch. (That's my E-TEC with a MIRAGEplus.) The MSRP of a suitable shroud was $995.