Sunday, 17 March 2013

Mast building glues

This is the basis for a thread on a subject that needs discussion from time to time.
There are lots of pictures that I will load in the next day or so but this is the start.

Do it yourself has always appealed to me, just ensure you study the various processes well. Dudley Dix is still designing masts and spars in wood, some of his designs such as the Didi 38 and Didi 26 include the mast design as part of his plans package. He may
be able to do you a design for your own boat?

A story I wrote on mast building can be found in the link below.

Below is the link to a story I did on the subject.

This is a sister ship to the design we are talking about a mast for. The place was the Annapolis Boat Show and in October 1977.

Alajuela 38

Picture by R McBride using a Canon FT film camera.

I will add the brokers name in the morning when I have found his card!

His name was/is Christopher Vaile, broker and of Sarno Associates .Marblehead, Massachusetts, 01945.

Chris told me that the boat was his and bought in as a dealer buy in some time back, he was keen to sell it on and worked hard to ensure it stayed in the perfect condition I saw the boat in. My interest in this boat was the fact that she was a sister ship to the Ingrid 38 I had sailed across the South Atlantic a few months before.

With this boat being in GRP the internal space was a whole lot more than Brer Terrapin, the yacht I had sailed on, built in wood, Sapele Mahogany on Amrican Oak frames, she was smaller inside by as much as 250mm?

I will also post a picture showing the delivery crew after arrival in Portsmouth, it was a 24 hour trip and about 125 miles in all.

The place is the Annapolis Boat Show, October 1977, I was asked by the boats broker to act as a watch captain on the delivery down the Chesapeak Bay and to the boats new owners home port in Portsmouth, just opposite Norfolk in Virgina, USA.

Hi Roy ,

I have read your page on mast building with interest. We have tried to research for our project but have only found yourself, the ‘Pardeys’, a local ship wright and Collars in england who seem to discuss the subject much. We are about to embark on building a 60’ mast for our Alajuela 38, a Colin Archer inspired hull.

We are building it in the states and have been able to source Sitka Spruce. we have not sourced any glue yet but were intending to use resorcinol, aerodux 500 if possible. We’re not sure of whether to trust the american resorcinols such as the Dap product, wondered what suggestions you might have, it also comes in 2 parts, resin and powder.

Also we are getting alot of bemused criticisms from people dumbfounded as to why we’re not using epoxy, hoped you might expand on your reasons, ours so far are the lack of penetration, uv resistance wonder about it’s flexibility? We don’t know how much glue we are likely to use so would really appreciate a pointer for this. We intend to construct the mast as follows: front and back pieces will be 5 1/2 “ wide by 1 7/8 “ deep sides 6 1/4 “ by 1 1/4 “ there will be a small channel protruding from the sides in to the front and back pieces to stop movement on the gluing stage. scarfs will be 1 / 12 so near enough 2 ft long, there will be 4 scarfs on each of the four parts of the mast. Our friends here worry about the staining of the glue, as we intend to varnish the mast, also we worry about the lack of gap filling capability of resorcinol, though we want to use it we’re going to have to make our joints very accurate and clamp it all up quite quickly.

The wood is clear Sitka Spruce, know for its light weight, the sections need to be larger than would be used when using clear Douglas Fir / Oregan Pine due to the latter being stronger.

We’d really appreciate any indications or insights you might have for our project.

We have your phone number and may phone you if that is ok.

Thanks for your attention,

Duncan and Ruth

PS, if you’re interested you can google earth 3911 Liggio st dickinson texas you can see our boat before we started restoring her!

My thanks to Ruth and Duncan for the use of their mast building pictures.


A reply from Dudley Dix on the subject came back by return.

From: Dudley Dix []
Sent: Saturday, March 16, 2013 1:47 PM

To: Roy; 'Ruth Evans, Duncan Fagg'

Subject: Re: CKD_website_enquiry

Read up on the subject of glues and plywoods in Dudleys own blog.
Hi Ruth,

I have intended to write about glues on my amateur boatbuilder tips blog but have not yet had the time to do so. I covered it a bit when discussing plywood at .

I have used Aerodux 500 and the resin/powder varieties. Although I haven't used the DAP version, I don't expect it to be much different from the one that I used in South Africa. Sorry, the name escapes me although I clearly remember the smell and the look of the can. I had equal success with both types and would have no reservations about the DAP version. The Aerodux version uses the same chemicals but the hardener powder is mixed into a resin instead of being in dry form.

I think that the proper curing of the glue is more certain with the resin/powder version than the resin/resin version. I found that the resin hardener separates out no-matter how diligently you stir it up before measuring, with the filler settling to the bottom. The result is that toward the end of the cans you are getting progressively more of the filler in the mix. In balance, the powdered version is more difficulty to quickly measure out quantities like one can with two liquids. Accuracy needs measurement with an electronic scale. Despite that, I have never heard of a resorcinol failure and have myself had numerous epoxy failures.

Resorcinol is described as having low gap-filling properties but I have not found it to be bad. The main difference is that it penetrates into the wood better than epoxy so you must be liberal when applying it, particularly if the joint will be open for awhile. For a mast, apply it thick with a brush. It also starts to develop a skin on the surface, whereas epoxy starts to cure without forming a skin. The skin is not a problem because it will dissolve as you bring the two glue-covered surfaces together but you need to be aware of it and don't let it become more than a very light skin before closing the joint. A mast is the sort of project where it is useful to have a few friends to help with the assembly of the mast, for the primary reason of getting it clamped up fast while the glue is wet on the bonding surfaces. Don't take a shortcut and apply the glue only to one surface, it must be on both surfaces.

As for the dark glue lines showing on your clear-finished mast, I ask so what? It is more important to have a structurally sound mast than to have one built from the wrong glue just to hide the glue lines. You are not trying to make a blemish-free air-brushed faux-wood mast that is actually carbon fibre under the wood look. You are making a wooden mast, with all of the joints that method implies. Embrace the look of the mast and the fact that you can see how it was constructed. It becomes part of the character of your traditional boat and something to show off and talk about. Don't try to hide what it is. I suspect that the friends whose opinions worry you are mostly owners of boats that are much more modern and faceless in their image. Their opinions are not important, you are the ones who need to be happy what you are doing.


Dudley Dix

Dudley Dix Yacht Design
1340-1272 N Great Neck Rd #343
Virginia Beach, VA 23454, USA
Tel (757)962-9273 Fax (888)505-6820


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