Reply
 
Thread Tools Display Modes
 
Old 08-16-2014, 01:28 AM   #21
Guru
 
BandB's Avatar
 
City: Fort Lauderdale
Country: USA
Join Date: Jan 2014
Posts: 13,175
Quote:
Originally Posted by Daddyo View Post
Perhaps a bit more info would have helped.
A. There would be no additional weight aft as the fuel weighs less then the water it displaces, ie: the tank full would float if detached.
B. The tank would be only a hundred or so more gallons then the lazerette tanks I am eliminating
C. The two 340 gallon main tanks would be eliminated thereby greatly reducing the total weight of the vessel
D. You have to take into consideration the overall minor weight/issue as we are talking about a 60,000 boat
E. Armstrong makes brackets for small 5-7,000+ fishing boats that carry two, three and sometimes 4 350hp outboards
F. Armstrong advertises the added buoyancy and increase in speed and reduced fuel burn when using their brackets
G. Copying someone like Armstrongs attachment design would be using a well known and proven design.
Helps but doesn't change my opinion.

A. If the tank is then displacing water, you just put tremendous pressure on it and on your platform. The risk to platform and boat is significant. Typically you'd need to reinforce the means by which the platform attaches to the transom. But also you might put too much stress on the transom itself.
B. A few hundred pounds becomes many hundreds if not thousands when now moved beyond the existing water surface. Think of a see-saw.
C. Don't know where the 340 gallon tanks are now but this may add to the problem rather than reduce. You're now adding weight beyond the stern and removing weight forward some distance. So could be impacting the distribution of weight even more.
D. Not as minor as you think. Changes the entire weight distribution. I've seen batteries moved make from behind the engine to in front of it make significant change. Shifting 4000 pounds from somewhere I'm guessing forward of the engine to outside the existing boat is not minor even to a 60,000 pound boat.
E. Yes they do. Doesn't mean those boats work well with that load. Doesn't mean they aren't dangerous. Depends on the boat and what it was designed to accommodate. As to small fishing boat, I don't know any small fishing boats designed or approved for 1400 hp.
F. Advertises. Key Word. They show two examples. I have no doubt it would increase speed just like trimming tabs way out. As to the flotation chamber of the Armstrong, I believe perhaps if the exact right combination. Also the right mounting and transom strengthening if necessary. They also looked at boats that did not have good attitudes before the install so started with bad situations. Easier to look good.
G. Armstrong's design isn't well known and well proven for a boat like you're talking about putting it on. Actually the lightness of the boat makes putting the extra pressure on the transom much less of an issue. Now you're putting 60,000 pounds of weight on an extended surface not originally part of the design.

I think making such a modification as this without a naval architect checking all the factors would be a serious risk. Could it work? Possibly, of course. Would it work? I think a significant possibility of problems. Fact is we can't know for sure what the results will be.

Some boats work well with extensions. Others don't. They all need an architect working to determine what the new boat will be like.
__________________
Advertisement

BandB is online now   Reply With Quote
Old 08-16-2014, 01:53 AM   #22
Guru
 
Daddyo's Avatar


 
City: Cruising East Coast US
Country: USA
Vessel Name: Grace
Vessel Model: DeFever 48
Join Date: Apr 2008
Posts: 2,441
Some more clarification:
I have not purposed doing this without NA approval (don't know how that got started). This does not in anyway involve the swim platform. The current primary tanks 680g are aft of the engines. The secondary tanks 300+ are less than three feet from the transom in the lazerette. The majority of the existing tankage is above the waterline and mounted all the way outboard. The new tank would be centerline and a good 4+ feet lower then the existing tanks. The new tank would add nearly 3' to the hull length.
__________________

__________________
Mark Bowerman
Brokerage owner and cruiser
Esse Quam Videri
http://graceyachting.com/
Daddyo is offline   Reply With Quote
Old 08-16-2014, 01:55 AM   #23
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
Perhaps playing Devil's advocate here a bit. But........

A. I think you are forgetting that as the boat pitches in a sea that the transom goes up in the air and can even be out of the water. Plus it's always been considered a bad thing to put to much extra weight out on either end of a boat.
B. What's that amount of gallons times 7.1?
C. True. But you're removing it from where the original designer intended it to be. That may or may not be a good thing.
D. Maybe. But again an NA may be a better judge of that.
E. - G. I think you might be comparing apples to oranges.

And E. If this is such a good idea why aren't boats designed that way on a regular basis?
Capt.Bill11 is offline   Reply With Quote
Old 08-16-2014, 02:00 AM   #24
Scraping Paint
 
City: -
Country: -
Join Date: Oct 2007
Posts: 13,748
I've seen a few "radical" alterations made to production boats in the years we've been our marina. They all made sense to the owners although most other people wondered what the person was thinking.

The question I would ask with regards to removing stock (I assume) internal tanks and replacing them with a tank mounted on the transom is what this might do to the value of the boat? Not to the person having the mod done, but to potential buyers later down the road. Somebody might like the idea, of course, but it's been my observation that people who want to buy a Grand Banks, for example, want to buy a Grand Banks and not some owner's idea of what a Grand Banks should be.

In fact that was a condition that our broker made sure we put as a qualifier on the offer we made on the boat we have now. The boat had to be what it was supposed to be: a stock Grand Banks 36. No major changes to the interior or exterior configuration of the boat. No moving the galley into the rear cabin or whatever, no matter how much the owner thought it was a great idea.

I don't doubt that if enough money is thrown at the proposed transom fuel tank, and as long as whatever USCG, EPA, etc. requirements are met, if there are any, that the project could be completed in a safe, strong manner. Whether it negatively affects the handling and behavior of the boat itself is anyone's guess at this point. And whether or not a potential buyer down the road will think it's a good idea remains to be seen.
Marin is offline   Reply With Quote
Old 08-16-2014, 02:50 AM   #25
Guru
 
Daddyo's Avatar


 
City: Cruising East Coast US
Country: USA
Vessel Name: Grace
Vessel Model: DeFever 48
Join Date: Apr 2008
Posts: 2,441
I am talking about approximately 300 gallons, so this would be about the same weight when not in the water of two large outboards even though, again when submerged this is added boyancy not weight. This is also a significant lowering of the center of gravity.
__________________
Mark Bowerman
Brokerage owner and cruiser
Esse Quam Videri
http://graceyachting.com/
Daddyo is offline   Reply With Quote
Old 08-16-2014, 07:16 AM   #26
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,920
I think the issues are there...most of us backyard type guys are just "guessing" with just enough knowledge to be "borderline dangerous".

I'm with you Mark in that I don't think it's as bad as many make it out to be but still not something to mess up as major holes/cracks developed in a seaway would be interesting.

The transom on my trawler isn't as thick as the one on my dingy because it doesn't have to be...so even a bolt on bracket for an outboard designed boat will need some transom work on your boat probably beyond even what a 30 foot center console might.

If the mod is going to make your boat $10,000 dollars more usable...then I'd say explore the possibility at least. By the time you pay an NA to do his thing, buy/build a bracket and mod the transom area....I'm guessing $10-$12,000 but a few phone calls might tweak that number to your liking.
psneeld is online now   Reply With Quote
Old 08-16-2014, 09:26 AM   #27
Guru
 
City: Carefree, Arizona
Country: usa
Vessel Name: sunchaser V
Vessel Model: DeFever 48
Join Date: Apr 2008
Posts: 6,372
What problem does the current arrangement present? If you want more storage enclose the area over the aft cabin.

The curved transom of the 48 which adds immensely to sea keeping of the vessel would be a bugger to attach your planned bustle. And then when the tanks are emptying they would float the boat in a nose down attitude or just break right off.

On our DF 48 the laz tanks are about 100 gallons each and protrude no further aft than the aft bunk "insert" leaving lots of room for storage or equipment such as diesel heat.

If you want to make the 48 into a houseboat look on Gibsons for sale and travel to Louisville to pick one up, they are a pretty nice vessel ideally suited for your needs.

And no, Art would not be rolling in his grave. He was buried at sea. For sure though he'd be l
sunchaser is offline   Reply With Quote
Old 08-16-2014, 11:26 AM   #28
Guru
 
BandB's Avatar
 
City: Fort Lauderdale
Country: USA
Join Date: Jan 2014
Posts: 13,175
Quote:
Originally Posted by psneeld View Post
I think the issues are there...most of us backyard type guys are just "guessing" with just enough knowledge to be "borderline dangerous".

I'm with you Mark in that I don't think it's as bad as many make it out to be but still not something to mess up as major holes/cracks developed in a seaway would be interesting.

The transom on my trawler isn't as thick as the one on my dingy because it doesn't have to be...so even a bolt on bracket for an outboard designed boat will need some transom work on your boat probably beyond even what a 30 foot center console might.

If the mod is going to make your boat $10,000 dollars more usable...then I'd say explore the possibility at least. By the time you pay an NA to do his thing, buy/build a bracket and mod the transom area....I'm guessing $10-$12,000 but a few phone calls might tweak that number to your liking.
None of us know what the issues would be. We're just expressing some that might exist. There are probably others we don't even know about. Only a good naval architect can make a good judgement and they may not be right.

Mark's saying now he wouldn't do this without utilizing one. But he did ask us the question and seems to not like the concerns any of us are raising. Sounds like he's pretty determined to do it. I'm guessing by the time you pay an NA to review the ideas and offer a feasibility opinion, then to do an actually design and spec, pay for modifying and strengthening the transom, pay for special tanks of some sort to meet all requirements the $10-$12,000 is on the low side. This isn't a bolt on to an outboard boat. The outboard boat was always designed to accommodate outboard motors, the modification just moves them a bit.
BandB is online now   Reply With Quote
Old 08-16-2014, 11:51 AM   #29
Guru
 
Scary's Avatar
 
City: Walnut Grove Ca
Country: USA
Vessel Name: Cary'D Away
Vessel Model: Hatteras 48 LRC
Join Date: Apr 2012
Posts: 884
Weight and size

300 gallons of fuel plus the tank weight would be around 3000lb. If the boats is a 60,000 lb boat that's about 5%. A 300 gallon tank could be 14' by 5' by 1' and span the width of the transom above the water line and boarding platform it would have little effect on boat handling. Probably work fine. But as Marin states could you sell it to some one else. It would turn me off in a heart beat.
Scary is offline   Reply With Quote
Old 08-16-2014, 11:56 AM   #30
Guru
 
Daddyo's Avatar


 
City: Cruising East Coast US
Country: USA
Vessel Name: Grace
Vessel Model: DeFever 48
Join Date: Apr 2008
Posts: 2,441
Quote:
Originally Posted by BandB View Post

None of us know what the issues would be. We're just expressing some that might exist. There are probably others we don't even know about. Only a good naval architect can make a good judgement and they may not be right.

Mark's saying now he wouldn't do this without utilizing one. But he did ask us the question and seems to not like the concerns any of us are raising. Sounds like he's pretty determined to do it.
I appreciate the comments and have agreed or disagreed with any of them. I have only added details and clarifications. I am not determined at this point at all only as always trying to think outside the box and looking to add value to the mundane like tanks.
__________________
Mark Bowerman
Brokerage owner and cruiser
Esse Quam Videri
http://graceyachting.com/
Daddyo is offline   Reply With Quote
Old 08-16-2014, 12:28 PM   #31
Guru
 
hollywood8118's Avatar
 
City: Port Townsend Washington
Country: USA
Vessel Name: " OTTER "
Vessel Model: Ocean Alexander Europa 40
Join Date: Nov 2009
Posts: 1,482
The big concern is to handling.. most boats that have transom or hull extensions need work done to the steering gear as the change in waterline length effects the rudder and its moment of effort. I believe the Hatteras extensions also move the rudders aft to keep steering effective.

HOLLYWOOD
hollywood8118 is offline   Reply With Quote
Old 08-16-2014, 12:41 PM   #32
Guru
 
Aquabelle's Avatar
 
City: sydney
Country: australia
Vessel Name: Aquabelle
Vessel Model: Ocean Alexander Flushdeck
Join Date: Jun 2012
Posts: 538
Effectively a hull extension. Apart from the recommendations above to involve a NA (I agree with that) you are adding buoyancy. While this is partly balanced by the fuel (but not fully...lower density) as you burn fuel that ballasting effect will be progressively lost, your stern will ride higher and higher & you will become unstable, perhaps dangerously so in a following sea.

If the idea had any merit, NA's would have tried it long ago.
Aquabelle is offline   Reply With Quote
Old 08-16-2014, 01:32 PM   #33
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,920
I can't speak for anyone else....but I do pretty much know what the issues are...just not how much because I haven't run the numbers.

But the issues (all but a few) are pretty clear and people are discussing them.

Many of the issues can be overcome but when all is said and done...is it really worth it for the space gained? Maybe the areas could be used for something else and space traded...but Mark is interested...well see just how much it's worth to HIM.
psneeld is online now   Reply With Quote
Old 08-16-2014, 01:42 PM   #34
Guru
 
BandB's Avatar
 
City: Fort Lauderdale
Country: USA
Join Date: Jan 2014
Posts: 13,175
Quote:
Originally Posted by psneeld View Post
I can't speak for anyone else....but I do pretty much know what the issues are...just not how much because I haven't run the numbers.

But the issues (all but a few) are pretty clear and people are discussing them.

Many of the issues can be overcome but when all is said and done...is it really worth it for the space gained? Maybe the areas could be used for something else and space traded...but Mark is interested...well see just how much it's worth to HIM.
Yes, we know the issues, just not the extent of problems each might cause. My wording was poor. But it's definitely not like popping a unit on the back of a fishing boat for an outboard.
BandB is online now   Reply With Quote
Old 08-16-2014, 03:20 PM   #35
Guru
 
City: Hotel, CA
Country: Fried
Join Date: Sep 2011
Posts: 8,328
That's the great thing about our boats. They can be anything we want them to be. All modifications are not equal or well received by others, but at the end of the day the only person that has to be happy with it is the owner.

Mark seems a prudent owner and unlikely to make a rash call. Definitely thinking outside the box, not all that different from other thinkers.
__________________
Craig

It's easier to fool people than to convince them that they've been fooled - Mark Twain
CPseudonym is offline   Reply With Quote
Old 08-16-2014, 04:22 PM   #36
Guru
 
BandB's Avatar
 
City: Fort Lauderdale
Country: USA
Join Date: Jan 2014
Posts: 13,175
Quote:
Originally Posted by CPseudonym View Post
That's the great thing about our boats. They can be anything we want them to be. All modifications are not equal or well received by others, but at the end of the day the only person that has to be happy with it is the owner.

Mark seems a prudent owner and unlikely to make a rash call. Definitely thinking outside the box, not all that different from other thinkers.
And very opposite from some, like me. I just prefer going with the vanilla, stock as built by manufacturer approach. The proven one. That's why I don't order custom boats either. Don't want to be the first and only, so go semi-custom with proven hulls and equipment. I admit then to being very conservative in this respect and having little risk tolerance.

It's really sort of humorous to find us conservative in respects like this when we're the opposite in other areas of our lives.

I'm sure Mark will figure out what he wants, and how to get it best done. I'd be an anxious wreck waiting for it to be completed and launched and see how it did. Just different people.
BandB is online now   Reply With Quote
Old 08-16-2014, 08:40 PM   #37
Guru
 
HopCar's Avatar


 
City: Miami Florida
Vessel Name: Possum
Vessel Model: Ellis 28
Join Date: Aug 2011
Posts: 3,506
Where is Tad Roberts when we need him?
__________________
Parks Masterson
www.hopkins-carter.com
HopCar is offline   Reply With Quote
Old 08-16-2014, 09:08 PM   #38
Guru
 
Nomad Willy's Avatar
 
City: Concrete Washington State
Country: USA
Vessel Name: Willy
Vessel Model: Willard Nomad 30'
Join Date: Oct 2007
Posts: 13,719
Analysis, conversation and discussion has run it's course and now it may be time for Mark to dump his questionable idea or start a build thread.

Yea a build thread Mark.

How about some preliminary drawings?

Show Hendo how it's done.
__________________
Eric

North Western Washington State USA
Nomad Willy is offline   Reply With Quote
Old 08-16-2014, 11:37 PM   #39
Guru
 
BruceK's Avatar
 
Join Date: Oct 2011
Posts: 7,573
I`m seeing the insurance underwriter clerk read Mark`s disclosure letter of adding an underwater fuel tank bolted outside the transom. " Hey Fred, take a look at this!" "Wow" says Fred, "better show this to the boss", "Hey boss...he got a NA to sign off on it, but sheesh, I dunno...".
On the other hand, how is it different to oil tankers, basically cigar shaped metal buckets filled with crude oil? Two skins required I think.
__________________
BruceK
Island Gypsy 36 Europa "Doriana"
Sydney Australia
BruceK is offline   Reply With Quote
Old 08-17-2014, 03:14 AM   #40
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
Quote:
Originally Posted by hollywood8118 View Post
The big concern is to handling.. most boats that have transom or hull extensions need work done to the steering gear as the change in waterline length effects the rudder and its moment of effort. I believe the Hatteras extensions also move the rudders aft to keep steering effective.

HOLLYWOOD

A lot of boats get extended with no change to the location of the steering gear. Broward's come to mind. I ran a one that started at 85' and ended up 98'. While it's better if the gear is moved aft after the stretch, stretched boats that the steering gear has not been moved do handle a bit differently after there stretched but it's nothing you can't learn to compensate for.
__________________

Capt.Bill11 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 07:40 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