View previous topic :: View next topic |
Author |
Message |
croakz
Joined: 21 Sep 2020 Posts: 104 City/Region: Seattle
State or Province: WA
C-Dory Year: 1997
C-Dory Model: 22 Angler
Vessel Name: Jolly Blue
Photos: Jolly Blue
|
|
Back to top |
|
|
colbysmith
Joined: 02 Oct 2011 Posts: 4657 City/Region: Madison
State or Province: WI
C-Dory Year: 2009
C-Dory Model: 25 Cruiser
Vessel Name: C-Traveler
Photos: C-Traveler and Midnight-Flyer
|
Posted: Mon Aug 09, 2021 7:13 pm Post subject: |
|
|
Both my 22 and 25 were the same way. What's important is to have the motor at the right height on the transom. |
|
Back to top |
|
|
T.R. Bauer
Joined: 17 Nov 2007 Posts: 1786 City/Region: Wasilla
State or Province: AK
C-Dory Year: 1993
C-Dory Model: 22 Cruiser
Vessel Name: C-Whisperer
|
Posted: Mon Aug 09, 2021 7:47 pm Post subject: |
|
|
Yes it is normal. |
|
Back to top |
|
|
DayBreak
Joined: 16 Jul 2017 Posts: 876 City/Region: Monmouth, Or.
State or Province: OR
C-Dory Year: 2018
C-Dory Model: 23 Venture
Vessel Name: DayBreak
Photos: DayBreak
|
Posted: Mon Aug 09, 2021 8:00 pm Post subject: |
|
|
T.R. Bauer wrote: | Yes it is normal. |
Agreed. This may be an indication that consideration was given by the installer for proper height to attain best speed and fuel economy on your given boat. _________________ Gary F
DayBreak, 23 Venture, 2018 - present |
|
Back to top |
|
|
thataway
Joined: 02 Nov 2003 Posts: 20988 City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
|
Posted: Mon Aug 09, 2021 9:05 pm Post subject: |
|
|
Normal, but best practices is to put a compression plate between each set of bolts (Top and Bottom) to spread out the load. Think of the area of a plate 3" x 18" vs the typical fender washer or the amount of structure on the outside of the transom motor mount. _________________ Bob Austin
Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018 to Oct. 2021
Thisaway 2006 22' CDory November 2011 to May 2018
Caracal 18 140 Suzuki 2007 to present
Thataway TomCat 255 150 Suzukis June 2006 thru August 2011
C Pelican; 1992, 22 Cruiser, 2002 thru 2006
Frequent Sea; 2003 C D 25, 2007 thru 2009
KA6PKB
Home port: Pensacola FL |
|
Back to top |
|
|
ssobol
Joined: 27 Oct 2012 Posts: 3446 City/Region: SW Michigan
State or Province: MI
C-Dory Year: 2008
C-Dory Model: 22 Cruiser
Vessel Name: SoBELLE
Photos: SoBelle
|
Posted: Mon Aug 09, 2021 10:57 pm Post subject: |
|
|
My 22 is that way too. Sits about an inch above the transom. |
|
Back to top |
|
|
croakz
Joined: 21 Sep 2020 Posts: 104 City/Region: Seattle
State or Province: WA
C-Dory Year: 1997
C-Dory Model: 22 Angler
Vessel Name: Jolly Blue
Photos: Jolly Blue
|
Posted: Tue Aug 10, 2021 12:08 am Post subject: |
|
|
Thanks all! |
|
Back to top |
|
|
san juanderer
Joined: 12 Aug 2014 Posts: 235 City/Region: Stanwood
State or Province: WA
C-Dory Year: 1990
C-Dory Model: 22 Angler
|
Posted: Tue Aug 10, 2021 2:17 am Post subject: comment from a very wise aluminum boat fabricator ( not me ) |
|
|
As everyone has said " it is normal " !
From the wise guy;
Sitting static, there is very little structural pulling on the fender washers.
Trailering down some bumpy road or down some logging road out in the far north, then there can be some pulling on the transom.
But underway, that motor is pushing on your transom very hard. The fender washers are not part of the equation of your worry, nor the gap. |
|
Back to top |
|
|
T.R. Bauer
Joined: 17 Nov 2007 Posts: 1786 City/Region: Wasilla
State or Province: AK
C-Dory Year: 1993
C-Dory Model: 22 Cruiser
Vessel Name: C-Whisperer
|
Posted: Tue Aug 10, 2021 4:56 pm Post subject: |
|
|
Not that any of it matters in one bit in real application, but doesn't the outboard both push and pull from a vertical axis at the same time while underway? |
|
Back to top |
|
|
ssobol
Joined: 27 Oct 2012 Posts: 3446 City/Region: SW Michigan
State or Province: MI
C-Dory Year: 2008
C-Dory Model: 22 Cruiser
Vessel Name: SoBELLE
Photos: SoBelle
|
Posted: Tue Aug 10, 2021 7:03 pm Post subject: |
|
|
T.R. Bauer wrote: | Not that any of it matters in one bit in real application, but doesn't the outboard both push and pull from a vertical axis at the same time while underway? |
Most of the force an outboard generates when pushing a boat is a torque that is basically trying to peel the transom off the back of the boat. The vertical load on the transom from the weight of the engine is small in comparison. |
|
Back to top |
|
|
thataway
Joined: 02 Nov 2003 Posts: 20988 City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
|
Posted: Tue Aug 10, 2021 7:11 pm Post subject: Re: comment from a very wise aluminum boat fabricator ( not |
|
|
san juanderer wrote: | As everyone has said " it is normal " !
Sitting static, there is very little structural pulling on the fender washers.
Trailering down some bumpy road or down some logging road out in the far north, then there can be some pulling on the transom.
But underway, that motor is pushing on your transom very hard. The fender washers are not part of the equation of your worry, nor the gap. |
Au, if only this were true. In reality there are multiple forces acting on the transom--including torque, downward, and lateral, as well as rearward pull.
Have you seen a transom fail with fender washers crushing into the laminate? I have.
Have you hand held a 25 hp outboard on an inflatable transom which failed? I have.
Have you seen a transom which failed in the center--below the outboard support, and pull ward when under way? I have.
The forces are complex. and the better support one has the better that transom will fair.
I hope that you are not advocating that only fender washers are the best way of mounting an outboard on a transom. |
|
Back to top |
|
|
T.R. Bauer
Joined: 17 Nov 2007 Posts: 1786 City/Region: Wasilla
State or Province: AK
C-Dory Year: 1993
C-Dory Model: 22 Cruiser
Vessel Name: C-Whisperer
|
Posted: Tue Aug 10, 2021 9:45 pm Post subject: |
|
|
I agree with Bob and others - it is complex. The outboard acts as a lever while the boat is propelled forward and the top part of the transom is pulled the other way in order for this to happen. There is also a left to right loading on the transom while underway.....anyways not exactly simple - especially when you toss in sea conditions. The point is, you better have a solid transom:-) |
|
Back to top |
|
|
san juanderer
Joined: 12 Aug 2014 Posts: 235 City/Region: Stanwood
State or Province: WA
C-Dory Year: 1990
C-Dory Model: 22 Angler
|
Posted: Wed Aug 11, 2021 1:59 am Post subject: |
|
|
This "wise guy " boat yard is full of Alaska fishing boats shipped by land down here to WA State for all kinds of construction and modifications. He used to build fiberglass boats then got into the aluminum boat building business.
He has built two outboard pods for me over the years, I had all kinds of questions about the structural aspects, and the 300 hp outboard hanging 30 inches setback from the transom. He assured me with his years of experience.
I will trust the boat builders comments, not the Dr. in the house.
Sorry for being blunt, but the internet is full of " experts ".
Sorry Dr. Bob |
|
Back to top |
|
|
T.R. Bauer
Joined: 17 Nov 2007 Posts: 1786 City/Region: Wasilla
State or Province: AK
C-Dory Year: 1993
C-Dory Model: 22 Cruiser
Vessel Name: C-Whisperer
|
Posted: Wed Aug 11, 2021 2:45 am Post subject: |
|
|
Perhaps we should leave it as a solid transom is very important.....arguing over the forces at play will not bear much fruit. |
|
Back to top |
|
|
thataway
Joined: 02 Nov 2003 Posts: 20988 City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
Photos: Thataway
|
Posted: Wed Aug 11, 2021 10:44 am Post subject: |
|
|
Despite your "expert" I stand by what I said. It is prudent to put a full bar on the inside of the hull rather than fender washers. Especially on the C Dory. We see lots of "Manufactures" consistently make mistakes in the boat building process. Often those who build or modify boats don't have the experience of those who look at the failures. or run boats for many years.
For example best practice would be to put some structural component inside of the transom where the bolts go thru, such as an epoxy plug to seal the core. How many boat builders do this? Hopefully the fellow who made the "pods" for you used best practices. (I have seen some pretty innovative melding of fiberglass boats with aluminum aft sections, as the transom book down in the AK freeze thaw cycles).
Hopefully your "expert" used best practices when he attached a pod to a transom--and that would include a backing plate, and sealing any wood or foam in the transom, especially in boats used in AK.
How about thru hulls in the bottom of the boat? A responsible builder will but a solid glass plate int he way of cleats, thru hulls under the water etc. Why do almost all of the 25's have core issues around the cockpit hatches and steps? It costs more to put a solid structure or seal the core. Same with fasteners into the bottom of the hull. I have been asked to see a number of issues in hulls from migration of water from these, where there was breakdown of the core/laminate.
Actually C Dory does it pretty well. You would not believe how many manufactures handle the hull to deck joint. It is solidly glassed over. Many just put some bedding compound and a U/U channel. Others just pop rivets with bedding compound. Picture the surprise of an offshore sailer, when the entire deck molding starts to come apart hundreds of miles from land!
Ask a couple of these folks who had to recore almost the entire bottom of the boat because where only a few screws had allowed water intrusion?
In fact the fiberglass interior is stronger and better because there are no zinc plated "L" brackets with multiple core penetrations. (They could have been put in with tabs of glass, instead of the cheaper and more easily done way it is done.)
How leaks between the area under the cockpit, which were not adequate tabbed in and the aft bulkhead not sealed, where core material eventually developed rot?.
Yes I worked as an MD. That has little to do with my boating experience. I first worked with fiberglass boats in 1952. Since then I have been interested in the negative structural issues with fiberglass boats. However I have been interested in osmotic issues since college and that lead to my being one of the first nephrologists. The kidney is an osmotic machine...Thus the interest in laminates and osmotic issues.
I saw delimitation in some of the 1960's boats, and then followed osmotic blistering as the problem with laminates appeared. I looked at over 100 boats in Europe which had bad blistering. I had inside information on issues with both Cal Yachts, and Columbia/Coronado Yachts, as to problems. More recently in the mid 2005 era had access to over 20 boats to cut up and analyze cores in both hulls and decks as I helped a friend modify NDT instruments to give a good tool for boat builders and surveyors to actually give a true picture of water intrusion and delimitation. Guess what? The marine surveyors didn't want to pay $2,000 and take a few days to learn how to use the instruments. Only a few high end builders were interested. So we all remain in the dark ages--the NDT for boat laminates never came to fruition. It is pure economics and perhaps some laziness.
My only dog in the fight, is that we as owners and builders should follow best practices rather than save a buck or two. |
|
Back to top |
|
|
|