Home Hull Construction - SailNet Community
LinkBack Thread Tools
post #1 of 5 Old 06-13-2005 Thread Starter
Join Date: Sep 2004
Posts: 54
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 13
Home Hull Construction

I''m curious, if one is making a small sailboat hull (20-25 ft)... I''m thinking of using 3 layers cross-overlapped 1/4 inch laminated ply (end thickness 3/4 inches) with 2 layers of cross-overlapped dynel/resin outer layer.

Am I way off base? What changes, if any, would be appropriate?
Vastbinder is offline  
Quote Quick Reply Share with Facebook
Sponsored Links
post #2 of 5 Old 06-13-2005
Senior Member
catamount's Avatar
Join Date: Sep 2002
Location: Gulf of Maine
Posts: 599
Thanks: 0
Thanked 1 Time in 1 Post
Rep Power: 15
Home Hull Construction

You might want to read a book like "The Gougeon Brothers on Boat Construction" -- I expect that it would answer your questions, as they were pioneers in the development of cold-molded construction (which is essentially what you are talking about).


catamount is offline  
Quote Quick Reply Share with Facebook
post #3 of 5 Old 06-13-2005
Jeff_H's Avatar
Join Date: Feb 2000
Location: Annapolis, Md
Posts: 7,507
Thanks: 12
Thanked 248 Times in 198 Posts
Rep Power: 10
Home Hull Construction

Three layers of 1/4" plywood would produce a pretty heavy hull for a 20-25 footer (and in and of itself, weight does nothing good for a boat). You probably could get by with a single layer of 1/2" plywood for the hull or even less depending on the quality and species of the plywood and the proposed use for the boat.

To give you an example of scantlings for a pretty ruggedly built 25 footer, attached is a part of the scantlings for the Thunderbird One Design class. <http://www.thunderbirdsailing.org/bbook/TOC.html>

3.2 Wood Hull and Deck

3.2.1 Planking, bulkheads and inner transom are to be 1/2" (12.7 mm.) plywood as specified in the official plans.

3.2.2 Cabin sole, cockpit floor and decks are to be 3/8" (9.53 mm.) plywood or equivalent suitable material.

3.2.3 Cabin top is to be constructed with two (2) layers of 1/4" (6.35 mm.) plywood as specified in the official plans.

3.2.4 Cabin sides and cabin face are to be not less than 3/4" (19.0 mm.) thick.

3.2.7 The chine shall be shaped from wood of the dimensions shown in the official plans and shall not be less than 3"(76.2 mm.) in width inside the planking after shaping.

3.2.8 Floor timbers are to be not less than 2" (50.8 mm.) in thickness

There have been many good boats built from plywood and perhaps even more bad ones. Designing a good plywood boat takes a lot more skill than designing a good boat in many other materials. Properly designed plywood can produce a reasonably strong boat for the weight but proper design takes a lot of care. Plywood boats can be quick to build, but not all that quick if you are going to glass it anyway. At that point there are other, nearly equal build time techniques that can produce lighter stronger boats for a similar cost.

Good luck,
Jeff_H is online now  
Quote Quick Reply Share with Facebook
post #4 of 5 Old 06-17-2005
Join Date: Oct 2004
Posts: 92
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 13
Home Hull Construction

I used exactly that schedule to repair the ruined deck of a 45 foot ketch.

Truth? It was INCREDIBLY strong, and VERY heavy. The big ketch could handle it like nothing. I''m not quite as sure about a little daysailor, but then, I once had a little 19 foot Cape Dory that was as heavy as a rock and sailed like a dream. I could easily handle weather that sent all other little daysailors scampering for shelter.

Double the lamination thickness in the belly of the hull to about 1 1/2" in the shape of a surfboard, with the buildup being inside, so you will have a super strong mounting pad for a keel, then search out the salvage yards for the cast iron keel off a Tartan 22.
FalconEddie is offline  
Quote Quick Reply Share with Facebook
post #5 of 5 Old 06-27-2005
Senior Member
paulk's Avatar
Join Date: Jun 2000
Location: CT/ Long Island Sound
Posts: 2,845
Thanks: 4
Thanked 45 Times in 44 Posts
Rep Power: 18
Home Hull Construction

You may also want to check out Ruel Parker''s books on plywood boatbuilding, and the Woodenboat website. If you''re going to build in plywood, one thing to watch out for is voids. Much of the plywood available has voids in interior plies, and this WILL create problems if you use it; problems building AND problems later on. Paying extra for plywood without voids is worth it if you want anything more than a one-season punt.
paulk is offline  
Quote Quick Reply Share with Facebook

Quick Reply

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now

In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page

Similar Threads
Thread Thread Starter Forum Replies Last Post
Glassing hull GreenEarth General Discussion (sailing related) 18 06-19-2009 11:52 PM
High Tech vs traditional-Comments? Pangaea General Discussion (sailing related) 38 08-07-2007 01:07 AM
Hull speed and wide sterns Jeff_H Boat Review and Purchase Forum 24 11-21-2006 11:58 PM
Thru Hull Replacement Stormer_2003 Gear & Maintenance 1 09-13-2004 11:22 AM
Thru Hull Replacement Stormer Gear & Maintenance 4 08-03-2004 08:21 AM

Posting Rules  
You may post new threads
You may 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 On
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome