Reply
 
Thread Tools Search this Thread
 
Old 12 October 2013, 19:18   #101
Member
 
Projectile's Avatar
 
Country: Canada
Boat name: WB465
Make: Zodiac
Length: 4m +
Engine: 2013 ETEC 30
Join Date: Dec 2012
Posts: 254
Here's the same view (still from below the boat looking up) from a different angle:
Attached Thumbnails
Click image for larger version

Name:	2013-10-12 13.39.07.jpg
Views:	103
Size:	109.7 KB
ID:	86320  
__________________

__________________
Projectile is offline   Reply With Quote
Old 12 October 2013, 19:20   #102
Member
 
Projectile's Avatar
 
Country: Canada
Boat name: WB465
Make: Zodiac
Length: 4m +
Engine: 2013 ETEC 30
Join Date: Dec 2012
Posts: 254
This is a pic from the side. With my friend's help, we raised the boat with some blocks under the buoyancy tubes. This let us get a pic of the hook from the side as the hull was raised above the trailer bunks. There is a straight edge, the right side of which is contacting the hull along the center line, in place. The hook at the back of the hull is clearly shown and it's wide enough for my to slip my fingers in between.
Attached Thumbnails
Click image for larger version

Name:	2013-10-12 13.46.20.jpg
Views:	87
Size:	86.1 KB
ID:	86321  
__________________

__________________
Projectile is offline   Reply With Quote
Old 12 October 2013, 19:22   #103
Member
 
Projectile's Avatar
 
Country: Canada
Boat name: WB465
Make: Zodiac
Length: 4m +
Engine: 2013 ETEC 30
Join Date: Dec 2012
Posts: 254
This is a similar pic from the side with the straight edge in place but a little more close up.
Attached Thumbnails
Click image for larger version

Name:	2013-10-12 13.47.30.jpg
Views:	86
Size:	105.2 KB
ID:	86322  
__________________
Projectile is offline   Reply With Quote
Old 12 October 2013, 19:23   #104
Member
 
Projectile's Avatar
 
Country: Canada
Boat name: WB465
Make: Zodiac
Length: 4m +
Engine: 2013 ETEC 30
Join Date: Dec 2012
Posts: 254
This is a pretty good photo of the hook in the hull:
Attached Thumbnails
Click image for larger version

Name:	2013-10-12 13.52.00.jpg
Views:	90
Size:	99.7 KB
ID:	86323  
__________________
Projectile is offline   Reply With Quote
Old 12 October 2013, 19:25   #105
Member
 
Projectile's Avatar
 
Country: Canada
Boat name: WB465
Make: Zodiac
Length: 4m +
Engine: 2013 ETEC 30
Join Date: Dec 2012
Posts: 254
Because frankc mentioned that the hook can become more pronounced under power, this last pic shows what a little gentle push in that region can do.

I think that this is very likely to be the cause of my problems. When this is the cause, the more one accelerates, the more the bow gets pushed down, which is exactly what I experience.

Now, what is the solution? Whatever it is, it'll have to wait for spring ...
Attached Thumbnails
Click image for larger version

Name:	2013-10-12 13.53.58.jpg
Views:	91
Size:	110.1 KB
ID:	86324  
__________________
Projectile is offline   Reply With Quote
Old 12 October 2013, 19:57   #106
Member
 
Country: USA
Town: Seattle
Boat name: Water Dog
Make: Polaris
Length: 4m +
Engine: Yamaha 60hp
Join Date: Apr 2007
Posts: 1,152
Quote:
Originally Posted by Projectile View Post
Because frankc mentioned that the hook can become more pronounced under power, this last pic shows what a little gentle push in that region can do.

I think that this is very likely to be the cause of my problems. When this is the cause, the more one accelerates, the more the bow gets pushed down, which is exactly what I experience.

Now, what is the solution? Whatever it is, it'll have to wait for spring ...
You can't really diagnose a cupped hull on an inflatable out of the water. And you can't see the shape of the hull underway. But your cup seems pretty pronounced, to the point where its obvious just sitting still - although its hard to know if the trailer bunks are doing on the dry what water does underway.

There are 2 solutions:
1) make the floor boards longer to take up the slack in the fabric and uncup the hull. Some sort of spacer might work, but only if the tubes are long enough that the extra floor board length can actually stretch the hull fabric enough to remove the cup at the transom.

2) return this brand new boat to the dealer. Its defective from the get go and you shouldn't need to be modifying it to make it ride right without bow steering.

I would not waste your money on a different prop, that will not cure the bow steering which is due to the defective hull.
__________________
captnjack is offline   Reply With Quote
Old 12 October 2013, 21:13   #107
Member
 
Country: USA
Town: Pooler, Georgia
Boat name: not applicable
Make: Avon
Length: 3m +
Engine: Outboard
Join Date: Aug 2011
Posts: 156
Looks like the bunks support the transom itself which is proper. The photos show what we suspected was the case.

When a boat is being driven through the water, the water under the boat develops pressure, and that hook will be more pronounced with the boat in use. No wonder he has a bow steering problem.
__________________
frankc is offline   Reply With Quote
Old 14 October 2013, 11:41   #108
Member
 
Projectile's Avatar
 
Country: Canada
Boat name: WB465
Make: Zodiac
Length: 4m +
Engine: 2013 ETEC 30
Join Date: Dec 2012
Posts: 254
Here are a couple more pics I found on the web related to hooked hulls.

Looks exactly like what I've found with my hull.

Would appreciate it if anybody might be able to take some similar pics of the junction of their hull with transom ...
Attached Thumbnails
Click image for larger version

Name:	Hookcopy.jpg
Views:	81
Size:	61.5 KB
ID:	86375   Click image for larger version

Name:	Hook.jpg
Views:	80
Size:	136.1 KB
ID:	86376  
__________________
Projectile is offline   Reply With Quote
Old 14 October 2013, 11:51   #109
Member
 
Country: USA
Town: Portland, OR
Make: Zodiac F470
Length: 4m +
Engine: Suzuki DF25EL
Join Date: Jun 2013
Posts: 229
Mine looks very similar.


I'd like to see perfect shaped keel. Especially at very end where it wraps on itself.

Cavitation happens where pressure change is severe when there is sudden changes in flow direction. Pressure differential in front and back of prop is what propels boat forward. Smaller prop diameter necessitates higher pressure differential. As boat accelerates higher speed requires higher pressure because of higher drag. Pressure depens on flow. Higher flow higher pressure. Impeller type pump flow depends on propeller pitch and RPM. Lower pitch has to spin faster. Lower pitch means higher angel of attack. Higher angle of attach means flow direction is changed more rapidly. Hence higher likelihood of cavitation. Cavitation may also create positive feed back loop. As cavitation bubble develops resistance load applied to prop drops. Therefor at constant throttle you engine will speed up higher possibly over-revving. Over-revving at speeds significantly below theoretical means likely cavitation.
And/or ventilation. The later can also be a factor with smaller pitch prop as it creates more turbulence at given speed.
Really important to match prop with load/speed.
__________________
SIBRider is offline   Reply With Quote
Old 14 October 2013, 12:07   #110
Member
 
Country: USA
Town: Portland, OR
Make: Zodiac F470
Length: 4m +
Engine: Suzuki DF25EL
Join Date: Jun 2013
Posts: 229
What you/we see is somewhat different from the hook. In case of hook if you continue keel in strait line it drops down at the stern. Effectively acts as trim tab. Ours turn up a bit with a small cup. It would be darn impossible to make perfect hull shape with so many loosely fit inflatable and fabric pieces. Unfortunate imprecision of type of boat we have I think.
__________________

__________________
SIBRider 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





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 01:56.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.