Reply
 
Thread Tools Search this Thread
 
Old 12 October 2009, 09:22   #1
Member
 
Country: Ireland
Town: Ireland
Length: 10m +
Join Date: Aug 2009
Posts: 169
Chine walking Searider 5.4

Does anyone have problems with their SR chine walking? Mine has a Mercury 90hp 2 stroke.
In calm water I can go full ahead (about 40/41kn) without any problems, the engine needs to be well trimmed up to achieve this speed & it appears that the only contact with the water is the engine leg & the aft 2 feet of the hull. Any disturbance on the water will induce chine walking which gets worse with each roll, I guess it is similar to parametric rolling on ships.
The chine walking can be stopped by reducing the rpm & not adjusting the trim or by trimming the engine down & leaving the rpm unadjusted. Obviously both have the effect of reducing the top speed (to about 35 kn).
Is there a solution to this problem while still maintaining full rpm?
The cavitation plate on the engine is just in line with the bottom of the keel.
__________________

__________________
Zubenelgenubi is offline   Reply With Quote
Old 12 October 2009, 10:26   #2
Member
 
Country: Canada
Town: Tobermory, Canada eh
Boat name: Verius
Make: Zodiac Hurricane 590
Length: 5m +
Engine: Yamaha F150
Join Date: Oct 2006
Posts: 1,365
Send a message via MSN to Stoo
Zub, you might want to have a look at this thread...

http://rib.net/forum/showthread.php?t=32415
__________________

__________________
Pump it up and RIDE!

www.wetspotimages.com
Stoo is offline   Reply With Quote
Old 12 October 2009, 15:27   #3
Member
 
Country: UK - England
Town: Looe
Make: Delta
Length: 4m +
Engine: Mercury
Join Date: Apr 2004
Posts: 1,380
They all do it with 90's on the back!!
__________________
Turbodiesel is offline   Reply With Quote
Old 12 October 2009, 15:32   #4
Member
 
Country: Ireland
Town: Ireland
Length: 10m +
Join Date: Aug 2009
Posts: 169
So do you reckon there is any point in lifting the engine up a notch or two then or do SR's with 90's have a "critical speed" above which they will chine walk due to hull design?
__________________
Zubenelgenubi is offline   Reply With Quote
Old 12 October 2009, 16:09   #5
RIBnet admin team
 
Nos4r2's Avatar
 
Country: UK - England
Town: The wilds of Wiltshire
Boat name: Dominator
Make: SR5.4
Length: 7m +
Engine: Yam 85
MMSI: 235055163
Join Date: Jul 2005
Posts: 12,898
RIBase
I reckon they all do it once you trim them out too far in search of 40 knots
__________________
Need spares,consoles,consumables,hire,training or even a new boat?

Please click HERE and HERE and support our Trade Members.

Join up as a Trade member or Supporter HERE
Nos4r2 is offline   Reply With Quote
Old 13 October 2009, 02:39   #6
Member
 
Country: UK - England
Town: Bristol
Make: Ribcraft
Length: 5m +
Engine: Yamaha
Join Date: May 2006
Posts: 4,283
if you can hit 41kts then you have achieved what the hull was designed for!! leave it at that.
__________________
matt h is offline   Reply With Quote
Old 13 October 2009, 04:49   #7
Member
 
HUMBER P4VWL's Avatar
 
Country: UK - Wales
Town: N Wales Chester
Boat name: Mr Smith
Make: Humber
Length: 6m +
Join Date: Feb 2009
Posts: 5,238
Quote:
Originally Posted by matt h View Post
if you can hit 41kts then you have achieved what the hull was designed for!! leave it at that.
I'd agree, if you want more speed than that in a boat that size, get a different boat! Our 5.4 with a 90 opti did the same. Pushing an SR any faster would be madness. Ribs are mainly for seaworthiness, if you want flat out speed on calm water, perhaps the rib isn't the boat for you? Personally, 41 knots is plenty for all but racing circumstances.
__________________
HUMBER P4VWL is offline   Reply With Quote
Old 13 October 2009, 05:10   #8
JSP
Member
 
Country: UK - England
Town: Southport
Boat name: Qudos
Make: 5.4 Searider
Length: 5m +
Engine: Yam 115 V4
MMSI: 235068784
Join Date: Sep 2008
Posts: 3,930
My SR4 chine walked like nothing else. Not had the 5.4 do it yet.
__________________
JSP is offline   Reply With Quote
Old 13 October 2009, 05:35   #9
Member
 
Country: UK - England
Town: PORTSMOUTH
Make: Avon 5.4
Length: 5m +
Engine: Yamaha 60FE -
Join Date: Sep 2003
Posts: 1,880
Quote:
Originally Posted by matt h View Post
if you can hit 41kts then you have achieved what the hull was designed for!! leave it at that.
I'd be happy with that
__________________
ollyit is offline   Reply With Quote
Old 13 October 2009, 08:43   #10
Member
 
Country: Ireland
Town: Ireland
Length: 10m +
Join Date: Aug 2009
Posts: 169
Im more than happy with the speed & am not looking for it to go any faster,38-40kn is more than enough in the SR.
The issue is not being able to maintain the speed even in a slight chop without the boat chine walking, it seems strange that a boat designed to carry a 90 hp 2 stroke engine & fitted with a 90hp 2 stroke engine (engine weighs 135kg) chine walks & from what I can gather it seems to be a characteristic of this boat??
__________________
Zubenelgenubi is offline   Reply With Quote
Old 13 October 2009, 20:30   #11
Member
 
Country: Canada
Join Date: Jan 2003
Posts: 15
Zubenelgenubi - chine walk is pretty common on performance hulls like yours.

As the hull accelerates, lift increases and the wetted running surfaces that are required to support the hull are reduced (more Speed = more Lift = less Surface). As the speed increases throughout the velocity range, the hull often gets to a point where the lifting surfaces become very much reduced and the hull is now "balancing" on a small area of the vee-portion or the "vee-pad" of the hull. When that surface becomes sufficiently small, it becomes very tricky to "balance" the hull on its vee or pad. The result is a rocking of the hull from side-to-side. This rocking can tend to get a little more extreme with each motion, and so the "balancing" must then be provided by additional driver (steering/throttle/trim) input in order to maintain the hull in a balanced state.

With some driver input, the condition can be stabilized. With changes to hull setup and/or changes to the driving technique the condition can be alleviated.

Chine walking is predominantly characteristic of vee-hulls with deep Vees (more deadrise), hulls with deep or narrow running pads and hulls, with a Veed pad or no pad (straight vee). These bottom designs are just more inherently difficult to balance at higher speeds. Another contribution to chine walking can be seen at higher speeds from "propeller slap" (usually seen more with props of fewer blades). As the prop turns, each blade enters the water and another exits the water. This irregular in/out of every blade, changes the dynamic forces at the location of the propshaft, repeatedly putting an imbalance on a hull that is trying desperately to balance on it's vee or pad, and ultimately initiates chine walking.
Setup of your hull and driver "seat-time" are the best solutions to the problem. Usually an alteration to the hull, or hull setup and/or modification to your driving methods (read seat-time) will improve the problem.

Some established steps toward minimizing chine walking include:
1. Check & adjust steering
2. Use solid mounts
3. Clean Hull Lines
4. Weight balance of hull
5. Motor height
6. Propeller selection
7. Seat time (experience)
8. Minimize Trim Angle

Summary: Optimize Hull Setup and Driver "seat-time"!

check out article on chine walk for more details.
Jimboat is offline   Reply With Quote
Old 14 October 2009, 05:40   #12
mdt
Member
 
Country: UK - Scotland
Town: fife
Make: Humber / searider
Length: 5m +
MMSI: ... - - - ...
Join Date: Sep 2005
Posts: 720
Ah Jimboat, that all makes a lot of sense. On the 5.4SR the chines on the hull run out to nothing towards the stern and there is next to no “planning pad” so there is not a lot of hull to balance the boat on.
__________________
“The only difference between men and boys, is the price and size of their toys”
mdt is offline   Reply With Quote
Old 14 October 2009, 06:46   #13
Member
 
Country: UK - Wales
Town: ANGLESEY
Boat name: MAGGIE B
Make: AVON
Length: 5m +
Engine: OUTBOARD
MMSI: MMSI 235071331
Join Date: Oct 2008
Posts: 23
Chine walking Searider 5.4

Hi,try a set of Nauticus Smart Trim Tabs (www.nauticusinc.com) gas ram non metalic components automatic adjustment with the gas rams.Better hole shot,eliminates chine walking and reduces planning speed.It did it for me.
__________________
AVONMON is offline   Reply With Quote
Old 14 October 2009, 10:00   #14
Member
 
Country: Ireland
Town: Ireland
Length: 10m +
Join Date: Aug 2009
Posts: 169
Thanks for all the information, the explanation is completely logical!
Isnt it a wonder that on the SR hull which has been around for years & years that Avon have not tried to solve the inherent chine walking problem with some type of fixed tabs / extension aft of the transom to improve high speed stability?
Ill have to experiment further to find a happy medium between trim v's speed v's chine walking.
__________________
Zubenelgenubi is offline   Reply With Quote
Old 14 October 2009, 13:18   #15
RIBnet admin team
 
Poly's Avatar
 
Country: UK - Scotland
Boat name: imposter
Make: FunYak
Length: 3m +
Engine: Tohatsu 30HP
MMSI: 235089819
Join Date: Sep 2005
Posts: 11,118
Quote:
Originally Posted by Zubenelgenubi View Post
Isnt it a wonder that on the SR hull which has been around for years & years that Avon have not tried to solve the inherent chine walking problem with some type of fixed tabs / extension aft of the transom to improve high speed stability?
I doubt that the typical new buyer of a SR is using it at maximum speed very often. Its not sold for its performance - but rather its commercial attributes.
__________________
Poly is offline   Reply With Quote
Old 22 October 2009, 14:32   #16
Member
 
Country: Ireland
Town: Ireland
Length: 10m +
Join Date: Aug 2009
Posts: 169
Nauticus Smart Trim Tabs on a SR

Quote:
Originally Posted by AVONMON View Post
Hi,try a set of Nauticus Smart Trim Tabs (www.nauticusinc.com) gas ram non metalic components automatic adjustment with the gas rams.Better hole shot,eliminates chine walking and reduces planning speed.It did it for me.
Looked at nauticusinc.com website. The tabs are something of a passive damping system.
Has anyone installed trim tabs on their SR?
As far as I can see, the trim tabs have the effect of increasing the water plane area of the hull beyond the transom, however if they are installed at the trailing edge of the hull, they will just increase the hull length, ie the WPA but will be at the same angle as the hull & I cant see how they prevent chine walking. If they are trimmed down to angle X they will have the effect of lifting the stern & lowering the bow & consequently increasing the WPA of the hull proper, the same effect as just trimming the engine down?
Thoughts / experiences?
__________________

__________________
Zubenelgenubi is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

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 20:54.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.