6 meter sailboat

by Fred

I have an old classic boat built in 1947.

This is a wooden boat and at some point someone covered the boat with fiberglass.

I am stripping the fiberglass because of moisture and replacing part of the stem.

As I have removed some of the planks I noticed there is no cotton caulking, only putty.

I do not plan to replace the fiberglass but rather paint and seal.

My question is, if there is no cotton between the planks is the putty alone going to keep the water out?

It seems either I have to remove the putty and caulk with cotton and putty or I have to replace the fiberglass?

Do I have to caulk only below the water line or the whole boat?


Comments for 6 meter sailboat

Click here to add your own comments

6 meter 12/30/17
by: Ned L

Yes, cotton would be correct.

Oakum is for planking thicker than about 2" or so, and even then you start with cotton. (Start with cotton in the bottom of the caulking seam, then as the seam widens toward the surface you change to oakum for the big part of the seam.)

It is possible that this boat was built "tight seamed", and therefore would have nothing but a bit of seam compound.

Tight seam construction is typically more European and requires more care in fitting the planking.

I would suggest learning more about your boat’s construction before doing to much.

by: Anonymous

Thanks for your recommendations.

cotton caulking
by: Anonymous

Sorry Hugo, but you are way of the mark suggesting that he does not use cotton.

Hemp is only really useable in thicker planks.

On a smaller hull like this the only option is cotton.

If you have experienced discoloured cotton it is because of the cotton being contaminated some other way.

Currently working on a twenty four foot wooden yacht with seams which are definitely thirty plus years old and the cotton is pure white.

Anything thicker than a one eighth seam I would consider hemp, anything less absolutely not.

by: Anonymous

Thank you again for sharing your knowledge about the care of these boats


cotton caulking
by: Anonymous

The cotton serves another very important purpose other than keeping out water.

It serves to stiffen the planking and prevent sawing, the action where the planks move against one another when the boat heels.

Cotton and putty or sikkaflex and cotton, but either way don't be tempted to leave out the cotton.

A sheathe of fibreglass would have stiffened to an extent but doing such a thing shows a grave contempt for the boat and a lack of understanding of timber.

by: Anonymous

Thank you for your feedback . I will follow your advice .

by: Dr Hugo

Hi Fred,

Proper caulking below the waterline is essential.

It is much better to use hemp/jute/oakum than cotton that rots, turns black and stinks in time if there is seepage.

Hemp or jute is easier to work with, twisting and tightening and paying into the seams strongly with a caulking iron leaving an adequate groove for the sealant.

For sealant, marine Sikaflex is very good, the black one being easier to sand when dry than the white one.

Once applied, it can be smoothed while still soft by rubbing over gently with your finger with a little kerosene for an even finish with little or no sanding needed.

The 3M caulking compound, also in a tube to be used with a caulking gun is also good but more expensive.

Later when dry, just wipe down with thinners or acetone before painting with primer and top coat.

Caulking above the waterline is usually not necessary but clean all seams thoroughly by scraping, vacuuming and brushing with thinners or acetone to ensure good adhesion for the sealant.

Hope this helps.

Click here to add your own comments

Join in and write your own page! It's easy to do. How? Simply click here to return to Wooden Boat Projects...

Want to add more photos?

If you are having problems uploading Photos or would like to add more click on this link for the Upload Form.

You can upload as many as you like and there is no need to resize them.

You might like these

  • Boats and Bits, Free Advertising.

    The Boats and Bits Exchange is a FREE advertising space for anyone wishing to sell, buy or exchange Wooden Boats, Boat Bits or other items of Chandlery.

  • Project Boats by Proud Wooden Boat Lovers.

    A showcase for Wooden Project Boats that enthusiasts are working on building and restoring.

  • Readers Tips for Your Wood Boat.

    Readers Tips advice on how to maintain and improve your Wooden Boat and save time and money

  • Wooden Boat Women

    Wooden Boat Women, come on girls, you can do it just as well as the guys, show off your skills, your boats and encourage other environmentally friendly female boat builders.

Recent Articles

  1. We absolutely need this brand-new 1930s wooden speedboat from Fitzke Boatworks

    Sep 17, 19 03:32 AM

    This mahogany and oak wonder looks like it came straight out of the 1930s, but it was built in 2019. Fitzke Boatworks

    The boat is called Bugbite, is based on plans from a 1930s boating magazine and is staggeringly pretty.

    Read more by Kyle Hyatt at Cnet.com

    Read More


    Sep 17, 19 03:32 AM

    Reedville hosts the best little boat show in September. Photos by Eric Eichenmuller

    Reedville hosts the best little boat show in September.

    Read more by Ann Eichenmuller at Chesapeake Bay Magazine

    Read More

  3. Margin/Cover Boards, How to, Tips, Please.

    Sep 16, 19 04:28 AM

    Hi there, I am about to work on my Margin boards on my 12'runabout. I am wondering what the best way to scribe the shape is? And what's the best/easiest

    Read More