Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 29-01-2013, 16:05   #16
Senior Cruiser
 
colemj's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Location: Presently on US East Coast
Boat: Manta 40 "Reach"
Posts: 10,049
Images: 12
Re: Mono Transom Extension, Anyone?

Don't compare with catamaran extensions. Catamaran hulls are very easy to extend because the hull form is mostly narrow and uniform and extensions rarely change the prismatic coefficient and catamarans do not heel to any extent that changes the hull shape in the water on different points of sail. You can almost pull the hulls out as long as you like with little change in characteristics.

The examples of mono extensions above are primarily of extensions that exist above the waterline.

If you intend to change the hull below the waterline, you should have more design and engineering information on your particular boat before proceeding. Changing a mono below the waterline has the potential to change almost every carefully designed quality of the boat.

However, it sounds like you are intent on this, so go ahead! We are all waiting for pics and experiences.

Mark
__________________

__________________
www.svreach.com

You do not need a parachute to skydive. You only need a parachute to skydive twice.
colemj is offline   Reply With Quote
Old 29-01-2013, 16:14   #17
Senior Cruiser
 
Sailmonkey's Avatar

Cruisers Forum Supporter

Join Date: Sep 2009
Location: Houston
Boat: '76 Allied Seawind II, 32'
Posts: 5,775
Re: Mono Transom Extension, Anyone?

I crewed on the 72' Bristol "RAJ" that had a stern extension done to lengthen the boat to 83'. The extension caused the boat to steer horribly, the AP was always running shifting the rudder side to side to maintain a course.
It can be done well or poorly, some boats will be more tolerant of this treatment than others.
__________________

__________________
Sailmonkey is offline   Reply With Quote
Old 29-01-2013, 16:24   #18
Registered User

Join Date: Dec 2009
Posts: 3,016
Images: 4
Do it. The ones I've seen were nice. In the 2 to 3 foot range. Only underwater at high speed. All help the water flow when the stern drags at speed. If you are clever it can bolt on with one tidy seam line.

They are often built using the boat as a molding jig. A piece of thin ply bent around the existing hull, extending aft, is a good start on a fair shape.

Great swim step. However the typical cruiser will probably use it as a garden area or Jerry jug storage, ugh!
__________________
daddle is offline   Reply With Quote
Old 29-01-2013, 16:36   #19
Registered User

Join Date: Mar 2008
Location: Akron, Ohio
Boat: Bristol 29(1967)
Posts: 595
Re: Mono Transom Extension, Anyone?

Forget the swim platform.

I'd like to add a raised 2'(or so), poop-deck to my Newport 28, so my cats can sit and watch me work.
__________________
SURV69 is offline   Reply With Quote
Old 29-01-2013, 17:09   #20
Registered User

Join Date: May 2012
Location: Baltimore, MD
Boat: Cal 2-27
Posts: 843
Re: Mono Transom Extension, Anyone?

Found this online

Sovereignty Projects - Sovereignty: A Unique Catalina 27 (hull # 65)
__________________
76% of statistics are made up.
boatsail is offline   Reply With Quote
Old 29-01-2013, 17:35   #21
CF Adviser
 
Bash's Avatar

Cruisers Forum Supporter

Join Date: Dec 2008
Location: sausalito
Boat: 14 meter sloop
Posts: 7,260
Re: Mono Transom Extension, Anyone?

check out this thread for a good look at a professional scoop job: Old Warhorse in the Shop for a Makeover...
__________________
cruising is entirely about showing up--in boat shoes.
Bash is offline   Reply With Quote
Old 29-01-2013, 17:56   #22
Registered User

Join Date: Apr 2008
Location: Cheyenne, WY
Boat: 1981 Ta Tong Cape Horn Cutter
Posts: 323
Images: 2
Send a message via Skype™ to gts1544
Re: Mono Transom Extension, Anyone?

RabidRabbit, Go to the CLASSIFIED section and look up SHARED CORPORATE OWNER MEMBERSHIP. REGGAE is a Beneteau Idylle 11.5M flat transom (originally) until the original owner added a 3.5' sugar scoop swim platform which we love. We can't imagine not having this modification, though I can't speak to any speed increase as we have never been without it.
__________________
gts1544 is offline   Reply With Quote
Old 29-01-2013, 19:28   #23
Writing Full-Time Since 2014
 
thinwater's Avatar

Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 4,337
Re: Mono Transom Extension, Anyone?

Speed/hull speed. Unless the transom is loaded far beyond design this is generally minimal. Sure, you can eliminate some burbles, but unless the lines are quite long, you can actually increase drag. Increased waterline? Moving from 34' to 36' could gain you 0.23 knots... but you have also added weight but no power. Unless you up-rig at the same time I would not expect to find it.

Speed/multihull. Not so clear. Generally somewhere around 10 knots the wake begins to separate from the transom cleanly; unless you modify the entry too, top end speed doesn't change. Weight and wetted surface rise.

Ride. Cats, which can hobby horse in certain conditions, can often greatly benefit from transom mods, particularly for a specific sailing area. This is the real reason for cats. Would this apply to a mono? Perhaps, but certainly less so.

Storage. Sure, you will gain load carrying capacity. Could make sense for certain designs, not for others. And I love my sugar scoops.

Space. Length does not add useable space, as the beam is fixed and the extension will be sealed.

------

Doing a good job--one that will not lower the resale value of the boat--is quite an undertaking. Is it worthwhile? The answer depends on the design, the goals, and the owner. I would focus my design on ride and access, if it were me. The only boats I have personal expereince with are Stiletto cats; the stretched cats are smoother but not faster unless other mod are made. Often as not, the whole rig is changed as part of a refit, so comparing most of the modified boats to stock is apples to oranges.
__________________
Gear Testing--Engineering--Sailing

Writing full-time since 2014.
Bookstore:http://sail-delmarva.blogspot.com/20...ook-store.html
thinwater is offline   Reply With Quote
Old 29-01-2013, 19:57   #24
cruiser

Join Date: Dec 2011
Location: Key West FL - Burlington VT
Boat: O'day 32 CC Ketch
Posts: 493
Re: Mono Transom Extension, Anyone?

So I did mention sugar scoops, because thats what most extension mods are for. I however have no interest in a scoop at all. My transom is huge (7x4) roughly and my thoughts were to extend the lines back 30" and then put a similar but smaller transom on. This area would have a deck access hatch, house a watermaker and be storage for things I never seem to use. Then my current swim platform would go back on. the swim platform is at deck level allmost, when stepping from boat to platform the difference is only 3". This boarding deck has a 2" pole on each side for windgen and future radar, and davits that can lift 600lbs.
__________________
RabidRabbit is offline   Reply With Quote
Old 29-01-2013, 20:29   #25
CF Adviser
 
Bash's Avatar

Cruisers Forum Supporter

Join Date: Dec 2008
Location: sausalito
Boat: 14 meter sloop
Posts: 7,260
Re: Mono Transom Extension, Anyone?

Quote:
Originally Posted by RabidRabbit View Post
So I did mention sugar scoops, because thats what most extension mods are for. I however have no interest in a scoop at all. My transom is huge (7x4) roughly and my thoughts were to extend the lines back 30" and then put a similar but smaller transom on. This area would have a deck access hatch, house a watermaker and be storage for things I never seem to use. Then my current swim platform would go back on. the swim platform is at deck level allmost, when stepping from boat to platform the difference is only 3". This boarding deck has a 2" pole on each side for windgen and future radar, and davits that can lift 600lbs.
On a center-cockpit ketch?

Too radical.

At what point does it become a forward-cockpit ketch?
__________________
cruising is entirely about showing up--in boat shoes.
Bash is offline   Reply With Quote
Old 29-01-2013, 20:46   #26
cruiser

Join Date: Dec 2011
Location: Key West FL - Burlington VT
Boat: O'day 32 CC Ketch
Posts: 493
Re: Mono Transom Extension, Anyone?

Whats too radical? 30" of transom, mostly all above the water line.
__________________

__________________
RabidRabbit is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
40' Required for Circumnavigation owengg Multihull Sailboats 135 23-09-2012 10:49
Mono vs. Multi - Sailing Ability ArtM General Sailing Forum 245 04-07-2012 17:59
Handsome Transom anjou General Sailing Forum 31 27-06-2012 05:01
For Sale: ANTENNA & AMPLIFIER EXTENSION konakoma Classifieds Archive 0 03-02-2012 09:15
GPS Antenna Flush on Reverse Transom ? akio.kanemoto Marine Electronics 29 22-07-2011 20:08



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 00:16.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.