Like Tree0Likes

Rough sandpaper-like hull???

Reply
Old 04-29-2008, 10:46 PM
  #1
Gold Member
Gold Member
Thread Starter
 
Ona-Mission's Avatar
 
Join Date: Apr 2008
Location: Tampa, Fl.
My Boats: boatless
Posts: 739
Default Rough sandpaper-like hull???

I just looked at a 41 Apache for sale that had a rough sandpaper-like bottom. I was told it is used to make the hull faster. I could be wrong, but it seems to me like that as rough as it was it would scrub speed off. Anyone have any input on this?
Ona-Mission is offline  
Reply With Quote
Old 04-29-2008, 10:48 PM
  #2
Registered
 
Join Date: Jun 2005
Posts: 9,587
Default

Sure it wasn't bottom paint?
Jupiter Sunsation is offline  
Reply With Quote
Old 04-29-2008, 10:50 PM
  #3
Registered User
 
Join Date: Oct 2003
Posts: 9,495
Default

Wet-sanding to break the shine off helps to un-stick the hull from the water. Can get you an MPH or so.

Rough? Dunno.
Chris Sunkin is offline  
Reply With Quote
Old 04-30-2008, 01:55 AM
  #4
Registered User
 
Join Date: Feb 2008
Location: West edge of the Pacific
My Boats: Beat up ole Sleekcraft
Posts: 610
The blow boaters were doing it first. A slightly rough hull reduces for lack of a better word "suction"
29Firefox is offline  
Reply With Quote
Old 04-30-2008, 02:54 AM
  #5
Registered
 
Join Date: Oct 2004
Location: Newbury Park, CA
Posts: 1,425
Default

I was over at the harbor the other day, and saw a blow boat with more than a sanded bottom. It looked like non-skid texture below the waterline, and perfectly smooth gel coat above.

Michael
Michael1 is offline  
Reply With Quote
Old 04-30-2008, 09:08 AM
  #6
Who Me?
Platinum Member
 
FeverMike's Avatar
 
Join Date: Jan 2001
Location: Tampa
My Boats: 2006 38TE Fountain
Posts: 6,656
Default

wasn't someone doing a gold ball like texture on a racing sail boat to break adhesion to the water? I wonder if it ever worked out?
FeverMike is offline  
Reply With Quote
Old 04-30-2008, 09:23 AM
  #7
Registered
 
Join Date: Apr 2008
Location: Milwaukee Wi
My Boats: 98 Ultimate Warlock 28SXT
Posts: 90
Default

Quote:
Originally Posted by Chris Sunkin View Post
Wet-sanding to break the shine off helps to un-stick the hull from the water. Can get you an MPH or so.

Rough? Dunno.
The rough bottom helps to break the surface tension of the water, yes giving a little more speed like Chris S stated. After a few high speed runs, the bottom will smooth back out form the friction of the water.
Warlock28SXT is offline  
Reply With Quote
Old 04-30-2008, 09:25 AM
  #8
Registered
 
Join Date: Aug 2006
Posts: 68
Default

It is not a simple subject, but yes, some kinds of surface roughness can delay the transition from smooth (laminar) to turbulent flow over a surface. That can significantly reduce drag. The roughness of shark skin is believed to cause such passive boundary layer manipulation, and thus aid their swimming speed.
Njawb is offline  
Reply With Quote
Old 04-30-2008, 09:25 AM
  #9
Registered
 
Sean's Avatar
 
Join Date: Oct 2000
Location: Darien, CT
My Boats: Donzi Sweet 16
Posts: 3,161
Default

funny...when i bought my 30 Shadow Cat back in 96 it had what i would best describe as a bad case of orange peel over the entire running surface. I sanded it all down, compound, wax... the whole nine yards...probably spent an entire week doing it...only to find out it was that way on purpose...

it was supposed to create air bubbles and release the surface tension on the hull...freeing it up and making it faster...
Sean is offline  
Reply With Quote
Old 04-30-2008, 09:36 AM
  #10
Registered
 
Join Date: Aug 2006
Posts: 68
Default

Not air bubbles. The surface roughness can add energy to what would otherwise be a more stagnant boundary layer. That can delay the onset of turbulent flow.
Njawb is offline  
Reply With Quote
Reply

Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
boca7667
General Boating Discussion
49
07-23-2007 03:15 PM
sandcraft
General Boating Discussion
53
03-29-2006 09:31 AM
BryanTuvell
Cigarette
4
03-04-2003 12:17 PM
Bayley
General Boating Discussion
16
01-18-2002 11:54 PM



Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 11:18 AM.


Copyright 2011 OffShoreOnly. All rights reserved.