Go Back  Offshoreonly.com > Technical > General Q & A
Bottom Blueprinting >

Bottom Blueprinting

Notices

Bottom Blueprinting

Thread Tools
 
Old 01-06-2010 | 07:32 PM
  #31  
Registered
 
Joined: Apr 2005
Posts: 2,957
Likes: 1
From: www.bajaboatowners.com
Default

Originally Posted by crayolacrazy
what I would do is find the center of gravity ,move as much weight to the back you need bow lift ,it looks to flat .after you find your CG you would want to shorten the lower two lifting strakes Think of it like a lever with the CG being the pivit point the ferther back the CG the less wetted surface,the boats being pushed always to the surface .I hope this helps ,easy way to prove this is put 2 80lb sandbags beside the engines what kind of power do you have and what else are doing,WE had my 33ol with ac porcelin head, microwave 20 inch flat screen sink and fridge 75 mph to78 with stock 496 ho,s spinning 30 labbed turning in and its 1.5 mph faster with people in the back seat
Problem is there's not much I can move without taking out the galley pack and the porta potty. I have 3 batteries under rear bench and 2 in the engine compartment otherwise thats it...And of course normal gear for a weekend away, but I know clothes don't weigh that much. Thats how the boat has always ran no matter what..

I'm putting 500efi's in it and Imco boxes and shorties. Drive height is 7.25" right now. I know nothing about the bottom and won't claim to, so it's definately not something I'm willing to take on.
Irishtornado is offline  
Reply
Old 01-06-2010 | 09:24 PM
  #32  
Platinum Member
 
Joined: Dec 2002
Posts: 2,195
Likes: 2
From: Dallas, TX
Default

Blue,
In your video, it looks like you are running out of bottom (strake support). Can you stop your video (side view) and pick a reference point where the spray leaves the bottom? If you are porpoising, the spray will appear to be moving forward and aft. With our boat. the inner stake was way short (designed for 60-70 MPH) and at 85-90+ MPH you are losing stability and scrubbing speed. You can test by lengthening the strakes by screwing and glueing (gel coat paste) short pieces of oak to the existing inner strakes until you get control. We started by picking a strake length that was 1/2 way between the forward and aft spray points. You can see the spray points best by starting and stopping your video and splitting the difference. After the final testing, we had the strakes permanently lengthened almost 5' from the length out of Wellcraft mold. Another method is to just put your oak test strakes at about 12" behind the CG...you will be close.
If you want to pursue this, we have two 12" pieces of oak that we have on the shelf that match the factory strake you could borrow to get some wood cut locally.
Ben
BenPerfected is offline  
Reply
Old 01-06-2010 | 10:54 PM
  #33  
Banned
 
Joined: Sep 2009
Posts: 289
Likes: 0
From: SOME WHERE IN TIME AND STILL LOST
Default

Dave , you really need to post some pics of the areas where the shingles are that you want removed and to tell you the truth it just might be a good idea to hold off on the bottom until you test the boat with the new boxes and motors just to see where you are at, and go from there .

Last edited by SUE C Q; 01-07-2010 at 07:08 AM.
SUE C Q is offline  
Reply
Old 01-07-2010 | 04:04 PM
  #34  
blue thunder's Avatar
Registered
20 Year Member
 
Joined: Nov 2001
Posts: 3,393
Likes: 6
From: IBX
Default

Thats a good thought Ben. If you look at this vid it looks like the spray is exiting maybe 6-12" from the transom. The boat is almost completely out of the water. The blue strip is the end of the side of the boat. I'll study this some more. I guess you are suggesting I need to lengthen the strake to fix the walk as opposed to eliminate the hook?

PS Allicat38 - sorry for the HJ. If its a problem I will take my discussion off line or to a new thread. Just say the word.

http://www.youtube.com/watch?v=XHkTn7YeZuU
blue thunder is offline  
Reply
Old 01-07-2010 | 07:55 PM
  #35  
crayolacrazy's Avatar
Registered
 
Joined: Jan 2003
Posts: 853
Likes: 0
From: Pgh. Pa.
Default

Originally Posted by Irishtornado
Problem is there's not much I can move without taking out the galley pack and the porta potty. I have 3 batteries under rear bench and 2 in the engine compartment otherwise thats it...And of course normal gear for a weekend away, but I know clothes don't weigh that much. Thats how the boat has always ran no matter what..

I'm putting 500efi's in it and Imco boxes and shorties. Drive height is 7.25" right now. I know nothing about the bottom and won't claim to, so it's definately not something I'm willing to take on.
why in the world do you have 5 batterys, yachts dont have that many ,maybe 3 anyways after you make your changes you can meet me at the lake maybe near put in bay I have a place in Marblehead will dial her in I have lots of props ,just adding the power will change the additude of the boat My 302 ran 74 with454 mags only 2 batterys HA HA, with the new hp you should need to go up about 3 to4 inches
crayolacrazy is offline  
Reply
Old 01-08-2010 | 02:00 AM
  #36  
Registered
 
Joined: Apr 2005
Posts: 2,957
Likes: 1
From: www.bajaboatowners.com
Default

Originally Posted by crayolacrazy
why in the world do you have 5 batterys, yachts dont have that many ,maybe 3 anyways after you make your changes you can meet me at the lake maybe near put in bay I have a place in Marblehead will dial her in I have lots of props ,just adding the power will change the additude of the boat My 302 ran 74 with454 mags only 2 batterys HA HA, with the new hp you should need to go up about 3 to4 inches
3000 watts of stereo is why I need 5 batteries...I could probably ditch 1, but the 2 main ones in the engine compartment I have to have for the stereo or all I hear is CLICK CLICK when I go to start it. I'm guessing you mean 3-4 inches in prop height not pitch. I had 496HO's before the 500efi's I have a set of 30's labbed by Bblades that I was spinning 4700rpm's with the HO's. I'm guessing it's going to be close and need a little tweeking, but of course I don't know jackchit...I do know there is what I would call a "rocker" about 5-6ft from the transom a hump in the bottom from gunwale to V rises about 1/2" off the bottom and then there are the built in hooks in front of the tabs. Thats all I can find with a 6' straight edge while its on the trailer. Boat has always had a hardtime getting on plane as well. Usually I have to use tabs full down to make it easy on drives. 280 Kplanes
Irishtornado is offline  
Reply
Old 01-08-2010 | 02:03 AM
  #37  
Registered
 
Joined: Apr 2005
Posts: 2,957
Likes: 1
From: www.bajaboatowners.com
Default

I also have a BAD bounce when running trimmed up as this video shows..

http://www.youtube.com/watch?v=zyP5c...eature=related

http://www.youtube.com/user/nightlif.../4/fURqm-UVloY

Keep in mind that my boat is loaded down for a weekend on the water, but it almost always rides like this...I call it the "BAJA BOUNCE" I'm guessing it's something to do with the bottom, but again I know nothing about bottom blueprinting reason for this thread I guess.

Last edited by Irishtornado; 01-08-2010 at 02:17 AM.
Irishtornado is offline  
Reply
Old 01-08-2010 | 04:33 PM
  #38  
blue thunder's Avatar
Registered
20 Year Member
 
Joined: Nov 2001
Posts: 3,393
Likes: 6
From: IBX
Default

Rocker will cause pospoising like you have. Hook will cause the bow to stay low bow steer if bad enough.
blue thunder is offline  
Reply
Old 01-08-2010 | 04:53 PM
  #39  
Panther's Avatar
Frank's Marine Service
20 Year Member
Gold Member
 
Joined: Sep 2002
Posts: 11,959
Likes: 142
From: Elkton, MD
Default

Originally Posted by BenPerfected
Blue,
In your video, it looks like you are running out of bottom (strake support). Can you stop your video (side view) and pick a reference point where the spray leaves the bottom? If you are porpoising, the spray will appear to be moving forward and aft. With our boat. the inner stake was way short (designed for 60-70 MPH) and at 85-90+ MPH you are losing stability and scrubbing speed. You can test by lengthening the strakes by screwing and glueing (gel coat paste) short pieces of oak to the existing inner strakes until you get control. We started by picking a strake length that was 1/2 way between the forward and aft spray points. You can see the spray points best by starting and stopping your video and splitting the difference. After the final testing, we had the strakes permanently lengthened almost 5' from the length out of Wellcraft mold. Another method is to just put your oak test strakes at about 12" behind the CG...you will be close.
If you want to pursue this, we have two 12" pieces of oak that we have on the shelf that match the factory strake you could borrow to get some wood cut locally.
Ben
Now that's some valuable info dude!!!!!!!

I blueprinted the bottom on my last Scarab back in 99' timeframe and picked up a little. I had healthy hook across most of the stern... I ground it all out flat, deep enough that I hit the cheese cloth (had to fill that in..) and sharpened all the strakes... It's been a good 10 years but I think I gained 3-4 mph from doing it!
Panther is offline  
Reply
Old 01-08-2010 | 05:38 PM
  #40  
crayolacrazy's Avatar
Registered
 
Joined: Jan 2003
Posts: 853
Likes: 0
From: Pgh. Pa.
Default

[QUOTE=Irishtornado;3019740]3000 watts of stereo is why I need 5 batteries...I could probably ditch 1, but the 2 main ones in the engine compartment I have to have for the stereo or all I hear is CLICK CLICK when I go to start it. I'm guessing you mean 3-4 inches in prop height not pitch. I had 496HO's before the 500efi's I have a set of 30's labbed by Bblades that I was spinning 4700rpm's with the HO's. I'm guessing it's going to be close and need a little tweeking, but of course I don't know jackchit...I do know there is what I would call a "rocker" about 5-6ft from the transom a hump in the bottom from gunwale to V rises about 1/2" off the bottom and then there are the built in hooks in front of the tabs. Thats all I can find with a 6' straight edge while its on the trailer. Boat has always had a hardtime getting on plane as well. Usually I have to use tabs full down to make it easy on drives. 280 Kplanes[/QUO ********************************** I have never herd of any 302 haveing to use tabs like that .you should have had 28s labbed with all that weight and I would of bet it would have went faster 4700 is lugged down the motors .dont make to many changes at once ,its hard to tell what worked and what didnt.if the boxes raise you x and the shorty raise it moreyou wont even get on plain with a 4 blade When you put the new motors in out all four batterys behind the seat .My swim platform sits 6 inches lower then any other 33 ol I found that the boat went faster with 3 more people I move everthing back added strainers ,sshatch mirrors Diamound plate on the back of my seat 55 lb dumbells ,one on each side as counter weight for my ac ,porcein head 20 inch flat screen ,microwave fridge some other **** it does have a long porpois in the70,s in flat water only, when I approch 80 mph the boat gets real light 97 its like an arrow real smooth then I have to work for a few more last day out I saw 99.8 she will go right to 96 /97 with a fuel tank and 3 adults Man its a rush my harts beating just talking about it

Last edited by crayolacrazy; 01-08-2010 at 05:48 PM.
crayolacrazy is offline  
Reply


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.