Reply
 
Thread Tools Display Modes
 
Old 02-19-2015, 07:13 PM   #1
Newbie
 
City: Caribbean
Country: Caribbean
Join Date: Feb 2015
Posts: 4
chine walk

Hello everyone ,

I am a new member. I live in the Caribbean and most time of the year the sea is rough. I have bought a Mainship Trawler 34 from 1979 repowered with a 250 cummins 6BTA. The shaft is 1 1/5 and the prop is 22x18 (three blades) . They have put fins under the boat almost but not on the egdes at the back. The boat leans on the left side if you're standing from behind of it. I was thinking that maybe because the former owner have removed the generator and that's why it leans on one side. I have put weight on the other side so it will stay straight and other parts of the boat. I 've put more weight, because I thought that it would help prevent the 'chine walk' .When I go with the waves I have to deal with the 'chine walk', although this is what I think it is what it's doing and it can be really scary. This happens only when I go with the waves and it doesn't happen when I go against the waves.

I'm not sure maybe I have to much weight and my prop is to small?
Should I remove all the extra weight? Should I change my prop to the original size?

Please help
__________________
Advertisement

littlejack is offline   Reply With Quote
Old 02-19-2015, 07:39 PM   #2
Enigma
 
RT Firefly's Avatar
 
City: Slicker?
Country: Bumpkin?
Join Date: Oct 2007
Posts: 9,994
Greetings,
Welcome aboard. Sorry, Mr. lj. Can't help you out. There are better minds than mine reading this...
__________________

__________________
RTF
RT Firefly is offline   Reply With Quote
Old 02-19-2015, 07:43 PM   #3
Hospitality Officer
 
Andy G's Avatar
 
City: Pittwater
Country: Australia
Vessel Name: Sarawana
Vessel Model: IG 36 Quad Cabin
Join Date: Sep 2010
Posts: 1,557
Sorry, what actually happens to the boat when you are in a running sea, ie going in the same direction as the waves?
Andy G is offline   Reply With Quote
Old 02-19-2015, 07:48 PM   #4
Newbie
 
City: Caribbean
Country: Caribbean
Join Date: Feb 2015
Posts: 4
chine walk

It will turn first to the right and than go left. It seems like the wave does what it wants with the boat.
littlejack is offline   Reply With Quote
Old 02-19-2015, 07:55 PM   #5
Guru
 
High Wire's Avatar
 
City: Cape May, NJ and Englewood, FL
Country: USA
Vessel Name: Irish Lady
Join Date: Dec 2007
Posts: 1,596
This is an example of "chine walking" that I'm used to:


...They have put fins under the boat almost but not on the edges at the back. ...

WHY did they do that? Was it to correct this condition or did this condition occur after the fins were mounted?
__________________
Archie
1984 Monk 36 Hull #46
Englewood, FL and Cape May, NJ
High Wire is offline   Reply With Quote
Old 02-19-2015, 08:03 PM   #6
Newbie
 
City: Caribbean
Country: Caribbean
Join Date: Feb 2015
Posts: 4
Ok so what I am dealing with is something else, my mistake sorry. I thought it was chine walk. I bought the boat with the fins. The problem is that the former owner is sick and do not remember anything. I think that they wanted the boat to go faster and I think also that this is why they have changed the prop to 3 blades . These Mainships come originally with a 4 blade prop 20x20
littlejack is offline   Reply With Quote
Old 02-19-2015, 08:04 PM   #7
Guru
 
tpbrady's Avatar
 
City: Anchorage/Wrangell
Country: USA
Vessel Name: Silver Bay
Vessel Model: Nordic Tug 42-002
Join Date: Sep 2012
Posts: 505
If you are traveling slower than the seas (the waves are passing under you from the stern), what you are experiencing is what happens to a square stern boat presenting a flat surface to the wave front. It doesn't put equal force across the stern so the boat tends to want to go right or left and sometimes both on the same wave. A full displacement boat with a full keel will do this a little less than a semidisplacement hull. Trim tabs if they are down make it a lot worse. I would say the fins are probably not helping any as it gives more surface area for the forces of the wave to act on just like trim tabs. The first time you go at hull speed with a 5 foot following sea in a 22 foot C-dory and forget to bring the trim tabs up, you'll know what I am talking about. Running faster generally makes things a lot better.

Tom
tpbrady is offline   Reply With Quote
Old 02-19-2015, 08:09 PM   #8
GFC
Guru
 
GFC's Avatar
 
City: Tri Cities, WA
Country: USA
Vessel Name: Beachcomber
Vessel Model: Sea Ray 550 Sedan Bridge
Join Date: Nov 2012
Posts: 2,684
Littlejack, I think what you are describing isn't chine walk, but more the typical action that happens when running in following seas. The wave picks up the boat's stern, the boat picks up speed as this happens, and you start to lose steering. When this happens to an extreme the boat broaches and if the following wave is large enough it will roll the boat over.

I think the solution to this is to maintain your boat speed so you can ride on the back of the wave and not let a wave push on the stern, lift it and cause you to lose steering.

If you're always climbing the back of the wave and traveling at about the same speed of that wave it won't be pushing on your stern.

Oops, tpbrady and I had the same thoughts, he just typed a lot faster than I did.
__________________
Mike and Tina
Beachcomber 1995 Sea Ray 550 Sedan Bridge
GFC is offline   Reply With Quote
Old 02-19-2015, 08:10 PM   #9
Guru
 
tpbrady's Avatar
 
City: Anchorage/Wrangell
Country: USA
Vessel Name: Silver Bay
Vessel Model: Nordic Tug 42-002
Join Date: Sep 2012
Posts: 505
The fins might to reduce the tendency of the stern to get deeper in the water as the boat tries to climb the bow wave after hull speed is exceeded. The same thing you would do with trim tabs in a planing hull. They might also have some positive effect on rolling in the beam sea.

Tom
tpbrady is offline   Reply With Quote
Old 02-19-2015, 08:24 PM   #10
Newbie
 
City: Caribbean
Country: Caribbean
Join Date: Feb 2015
Posts: 4
I want to go faster and I think that my prop is getting worse because when I bought the boat this prop was in really bad shape and it had to be cut. And he guy told me that it was cut from 19 to 18 but this is not correct. It is like 17.8. My engine is not reaching his rpm. I can hear the engine working but the prop cannot handle it. I think my problem is the prop.
littlejack is offline   Reply With Quote
Old 02-19-2015, 08:51 PM   #11
Guru
 
tpbrady's Avatar
 
City: Anchorage/Wrangell
Country: USA
Vessel Name: Silver Bay
Vessel Model: Nordic Tug 42-002
Join Date: Sep 2012
Posts: 505
Littlejack,

There are a lot of things in play here. Things you need to know are:

a. What is the wide open throttle (WOT) RPM for your engine? You need to be able to reach this RPM when your boat has its typical load on board. ( I do fully loaded with fuel, water, food, and a month's supply of wine, whiskey, and beer).
b. What is the maximum continuous RPM for the engine (Typically a couple hundred RPM below WOT)

Once you have determined what prop meets the criteria of "a" then "b" tells you how fast fast is. Trim tabs and things that can change the trim of the boat can affect "fast" a little but not a lot for a given prop. What they might allow you to do is reach the proper WOT with slightly higher pitch prop so you should be going a little faster when you drop back to cruise RPM.

Tom
tpbrady is offline   Reply With Quote
Old 02-19-2015, 09:15 PM   #12
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
Got any pictures of these "fins"?
Capt.Bill11 is offline   Reply With Quote
Old 02-19-2015, 09:44 PM   #13
Guru
 
O C Diver's Avatar
 
City: Fort Myers, FL... Summers in Crisfield, MD
Country: USA
Vessel Name: Slow Hand
Vessel Model: Cherubini Independence 45
Join Date: Dec 2010
Posts: 4,803
Also, speed will greatly be effected by marine growth on the bottom and on the running gear (prop, shaft, and rudder).

Ted
__________________
Blog: mvslowhand.com
I'm tired of fast moves, I've got a slow groove, on my mind.....
I want to spend some time, Not come and go in a heated rush.....
"Slow Hand" by The Pointer Sisters
O C Diver is offline   Reply With Quote
Old 02-20-2015, 03:30 PM   #14
Guru
 
jleonard's Avatar
 
Join Date: Jun 2008
Posts: 2,735
Was the previous owner's name "Monty"?(Monty Lewis I think)
I owned a model 1 for 14 years and repowered it. I also installed trim tabs.

Sounds to me like you are describing "surfing" and the "fins" are trim tabs.
In a following sea the tabs need to be full UP with that boat.
These boats are set up to return fuel to the port tank. If that set up still remains, then that could explain the port list. The generator should have been directly centered.
These boats will indeed "chine walk" but only when they get to 16 knots or more. That is very predictable in my experience and in talking with many others who have repowered with more than about 220 hp.

I repowered with a 270 hp Cummins and a 1.5:1 tranny. With that set up I was able to keep the 20 x 21 4 blade prop and could make over the 2600 rpm at WOT.
I don't know how the 3 blade relates to a 4 blade, but it sounds like it is "over propped" assuming a clean bottom and assuming you have calibrated the boat's tachometers with a handheld tach.
With that power you should also fair the keel if it has not been done. That will get more clean water to the prop and increase your rpm, at least it did when I faired my keel. (I gained almost 250 rpm).


Oh yes almost forgot, you need trim tabs fully UP to do a valid WOT run or you will be plowing the bow and not be able to get to WOT.
__________________
Jay Leonard
Attitude Adjustment
40 Albin
Mystic,Ct
jleonard is offline   Reply With Quote
Old 02-20-2015, 04:19 PM   #15
Guru
 
Moonstruck's Avatar
 
City: Hailing Port: Charleston, SC
Country: USA
Vessel Name: Moonstruck
Vessel Model: Sabre 42 Hardtop Express
Join Date: Nov 2008
Posts: 7,848
Jleonard is spot on about the tabs. If you have them, trim them all the way up. That will sink the stern a little, and get the forefoot out of the water or at least with less resistance. What you are experiencing (I think) is bow steer from sheering off to one side. When you over correct it will sheer to the other direction. This is a common problem with boats with fairly flat runs aft as there is a lot of buoyancy to make the stern rise and bury the bow.

Unfortunately, on a boat like yours there is no way to eliminate the tendency altogether. You just have to mitigate it, and get the feel for how your boat handles.
__________________
Don on Moonstruck
Sabre 42 Hardtop Express & Blackfin 25 CC
When cruising life is simpler, but on a grander scale (author unknown)
http://moonstruckblog.wordpress.com/
Moonstruck is offline   Reply With Quote
Old 02-20-2015, 04:26 PM   #16
TF Site Team
 
Baker's Avatar
 
City: League City, Tx
Country: Texas
Vessel Model: Carver 356
Join Date: Oct 2007
Posts: 5,630
What you are experiencing is "bow steering". Everyone above has pretty much explained it. You have a wide wquare flat transom that allows a lot of buoyancy to be produced and acted upon by a wave. The forward portion of your hull is very fine and sharp with not a lot of buoyancy. So the wave pushed on the stern and buries the bow until it has to come up. If it keeps sinking then the stern will come around and cause a "broach". And that is the scary part. Like has been mentioned, go the same speed of the wave train for safety purposes. If you want to go faster, then you just have to be quick on the wheel and make sure you are not falling off the front of any waves. You would have to pick your path thru the waves. Which requires experience and a lot of work on the wheel.
__________________
Prairie 29...Perkins 4236...Sold
Mainship Pilot 30...Yanmar 4LHA-STP...Sold
Carver 356...T-Cummins 330B
Baker is offline   Reply With Quote
Old 02-20-2015, 04:37 PM   #17
TF Site Team
 
Larry M's Avatar
 
City: JAX, FL
Country: USA
Vessel Name: Hobo
Vessel Model: Krogen 42-120
Join Date: Nov 2008
Posts: 5,721
I believe the 34 Mainship was originally powered with 165 hp? Going up to 250 hp, I can see where it could get a little scary.
Larry M is online now   Reply With Quote
Old 02-20-2015, 05:38 PM   #18
TF Site Team
 
Baker's Avatar
 
City: League City, Tx
Country: Texas
Vessel Model: Carver 356
Join Date: Oct 2007
Posts: 5,630
Quote:
Originally Posted by Larry M View Post
I believe the 34 Mainship was originally powered with 165 hp? Going up to 250 hp, I can see where it could get a little scary.
2 engine options. Both Perkins 6-354s....one is the 165hp you mentioned and the other the 200hp version of the same engine. Although a small difference, that little bit of extra HP is what got you over the hump and gave you a realistic chance of cruising at 12 or so knots.
__________________
Prairie 29...Perkins 4236...Sold
Mainship Pilot 30...Yanmar 4LHA-STP...Sold
Carver 356...T-Cummins 330B
Baker is offline   Reply With Quote
Old 02-20-2015, 05:47 PM   #19
TF Site Team
 
Larry M's Avatar
 
City: JAX, FL
Country: USA
Vessel Name: Hobo
Vessel Model: Krogen 42-120
Join Date: Nov 2008
Posts: 5,721
Quote:
Originally Posted by Baker View Post
2 engine options. Both Perkins 6-354s....one is the 165hp you mentioned and the other the 200hp version of the same engine. Although a small difference, that little bit of extra HP is what got you over the hump and gave you a realistic chance of cruising at 12 or so knots.
I wasn't aware that it was an option in the early Mainships. We had an 1981 with the 165. A friend repowered with 200 hp and the boat got up and moved. Yahoo! After driving with the 165 the extra hp made a definite difference in handling.
Larry M is online now   Reply With Quote
Old 02-20-2015, 05:55 PM   #20
Guru
 
Moonstruck's Avatar
 
City: Hailing Port: Charleston, SC
Country: USA
Vessel Name: Moonstruck
Vessel Model: Sabre 42 Hardtop Express
Join Date: Nov 2008
Posts: 7,848
This may have been mentioned before, but there is another way to correct bow steer. Crank the wheel over hard the opposite way, and apply power briefly. This will "kick" the stern to correct the situation. You will just have to practice it, but it works.
__________________

__________________
Don on Moonstruck
Sabre 42 Hardtop Express & Blackfin 25 CC
When cruising life is simpler, but on a grander scale (author unknown)
http://moonstruckblog.wordpress.com/
Moonstruck is offline   Reply With Quote
Reply

Thread Tools
Display Modes

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 Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 02:26 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012