A Dory for Gazela Primeiro and at the end tips on glass application

A while ago I received a nice email from Tony Souza regarding construction issues with a new dory he intended building for the old Portuguese barkentine Gazela Primeiro.

Hello Ross,
Thanks for your recent article "Stems and Trailers".  In that article you discuss natural timber vs plywood construction and show the merits of plywood glued lapstrake for boats that are dry stored.
Im trying to choose a construction technique to use for a reproduction dory that will be "dry sailed".  The dory is a Grand Banks dory of 17 feet overall, 13 feet on the floor. The new dory has to resemble closely the last of the three dozen Portuguese grand banks dories that sat on the deck of Gazela Primeiro, the 100+ year old Portuguese barkentine on which I am one of the all volunteer crew.  Last winter we patched and repaired the last dory, and this year Id like to build a dory to be used often for the teaching of boat handling, rowing, and dory sailing.  the boat handling includes launching and retrieving over the side using hand operated boatfalls. The new dory will spend most of its time stacked inside the old dory, the two as deck displays of what was used in long line fishing of the early 20th century.
As a matter of resemblance the new dory will have four frame sisters overlapped, removable thwarts, 5/8" cedar planking, solid gunwales, a mast step on the floor and two sets of oarlocks.
For ease of construction and in keeping with the dry storage idea I plan on using modern materials where I can.  The flat bottom will be Meranti plywood already on hand, no need to soak the floor seams closed before putting boat into the water.  The frames are already built from laminated ash. Tree crotch and buttress sections are too difficult to find.  I plan to epoxy the garboard plank to the bottom, glass tape and epoxy the inside seam.  After planking I plan to turn the boat over and glass the bottom and garboard with cloth.
After that long prologue we come to my uncertainty area, the clinker planking joints.  Its tempting to use lap-stitch aka ship lap joints, easily cut with a router and epoxy fastened.  On natural, i.e. not plywood, timber that may lead to splitting along the grain at the join.  Likewise dory lapped (rolling bevel) joints likewise glued might suffer splitting.  I should have said earlier that using modern glues and eliminating metal fastners is a goal.  The old dory is a pincushion of steel nails on the planking joints which has resulted in rusty streaks and rotten wood.  (Of course dories were not supposed to last more than a couple years in ocean service. Old dory is probably 40+ years old.) 
Would it be better to caulk the planking seams with Boat Life, a polysulfide, rather than epoxy fasten?  The frames are there to give cross grain strength.  With your expeience you might see that Im headed for problems not yet envisioned.
Any suggestions will be very welcome and gratefully accepted.
Gazela can be seen at www.gazela.org.
A picture of the old dory is attached. 

Here is part of the text of my reply: -

I agree totally with your concerns regarding "hard" gluing of either "lapstitch" or dory-lap joints when using natural timber rather than plywood - I believe that they would definitely crack at the point where the planking thickness returned to single-plank. Harry Bryan wrote about the matter when he did a couple of articles for WoodebBoat Magazine about the building of his Daisy design. She had either double-planked cedar (glued with epoxy) for the bottom, or a single sheet of plywood. The topsides were planked with lapstrake cedar planks in the normal manner (I think using copper clench nailing from memory). The important thing in our context is that he expected her to be dry-sailed, and after completing the planking in the normal way, he dragged a sharp, flat-blade screw driver along the underside of the lap on the outer side of the planking. This produced a sort of square-shaped groove of about 1/8" x 1/8" in the underside of the lap. He then filled the groove with a bead of polyurethane (I would use 3M 5200 or Sikaflex 292, using a polyurethane-specific primer)

Having said all that, I wonder whether you could just glue the entire lap with polyurethane (I dont know enough about polysulfide to say anything about its adhesive qualities where no fastenings are used). The polyurethane is strong enough, but I dont know whether a fully-glued lap would allow enough movement to overcome the cracking problem, even given the flexibility of the compound - but my guess is that it would be ok, especially if the glue-line was thick.

If I was doing it, Id go the copper-fastened route, with the polyurethane (or polysulphide) run into the groove under the lap.

I think that the garboard arrangement you propose would be fine. The glass on the outer face should supply cross-grain reinforcement, and the tape on the inside will extend some distance beyond the vulnerable line of intersection between the inside faces of the bottom and the garboard.

On two boats I built (one of which ended up in the Jody Foster film, Nims Island - see the recent comment made on Duckworks http://www.duckworksmagazine.com/10/reports/may/index.htm ), I made the bottom from Western Red Cedar glued strip, continuing around the turn of bilge, after which I continued the planking as plywood glued lapstrake. I cut the bevel on the bottom planking to accept the first lapstrake plank before glassing the bottom. When glassing the bottom, I continued the glass right around and onto the bevelled face. This meant that when the first plywood plank was glued on, the glass was sandwiched between the WRC strip planking and the inner face of the plywood - the aim being to prevent splitting in the WRC.  This explanation is a bit clumsy, but I havent got time right now to do a sketch. In your case this will not be necessary, as you will have the glass on the outside of the cedar planking anyway.

??

Western Red Cedar bottom planking

???

Bottom covered with 400gsm (12oz) double-bias glass and the first two planks of plywood lapstrake attached - the first plank going over the glass, which itself had been laid over the bevelled edge of the cedar bottom planking.

???Here is Tonys latest up-date: -

Hiya Ross,
Here are three pix of the dory project to date.  This boat is a copy of the last original belonging to Portuguese fishing barkentine Gazela Primeiro.  You can see more pictures on www.Gazela.org and my facebook page. My version of the dory has a meranti plywood bottom and white cedar planking over laminated ash frames.  The gunwale and cap are white oak. The dory will essentially be dry sailed i.e. living on Gazelas deck most of the time and occasionally be used for crew training and exhibition at home and ports of call.
After corresponding with you some time ago I took your advice and epoxy joined only the garboard plank to the bottom.  The rest of the construction has followed traditional methods. The upper edge of the garboard and the remaining planks are dory lapped and copper riveted.  Planks to frames are joined with Si bronze screws.
I think we talked about covering the bottom and up to the upper edge of the garboard with synthetic cloth and epoxy. 
Now areas where I could use advice:
What cloth would be appropriate? I dont think the dory will ever see a beach, but it might. So a light cloth should do.
Is there an advantage to graphite additive to the epoxy?
Any tricks to applying the cloth?
Thanks for your help,
Tony Souza

And part of my reply: -

Dear Tony,

Thanks very much indeed for the up-date, and for the nice photos. The boat looks super to my eyes, and Id love to take her out in the rough stuff - preferrebly with some weight in the bottom to represent the ballasting effect of a load of Cod!

My appologies for the delayed reply - we have been recovering from the devastating flash-flood which wiped us out on January 10, and priorities tend to be re-arranged!

For the cloth, the simplest would be 200gsm (6oz) woven glass. This is light and easy to use, and gives a good level of protection, and more importantly, provides a sort of screed to ensure an even thickness of epoxy. Dynel is also a good option (4oz, I think, but you would need to check with the supplier). Dynel is bulkier than glass for the same weight, and it has superior abrasion resistance - I like it on decks - but it doesnt have the tensile stiffness of glass so it will have less structural effect on the garboard-to-bottom joint. For a hefty boat like yours which may get handled roughly, Id give serious thought to using 400gsm (12oz) double-bias glass cloth. It isnt woven, so it takes bends fairly well, and with the fibres aligned 45 degrees/45 degrees, every fibre crosses the longitudinal joints. It is cheaper than woven glass, but is heavier than the normal 6oz stuff.

I normally use the dry application method (for weights up to 12oz). I lay the cloth over the dry, sanded, and vacuumed surface, and them smooth it into position with a dustpan brush or a wide, dry paintbrush. Tape any troublesome edges down with temporary bits of masking tape. Then start by mixing small quantities of epoxy and pour them onto the glass (or Dynel) and spread them with a squeegee - I use rectangles of 1/16" model aircraft balsa as they can be bent along the grain if required, and the corners dont snag on the glass.  Dont press too hard, as you will end up aerating the epoxy and making it go creamy with minute air bubbles (just like what happens when whipping cream). Just use a gentle figure-eight sweeping motion to get it out onto the surface. Dont fuss about getting it to wet-out - that will happen automatically. Keep on mixing, pouring and spreading until the entire surface is covered. Small batches are good, as they dont heat up so rapidly in the container.

When the surface is covered, use disposable brushes and/or disposable foam rollers with about a 1/8" nap to distribute the resin evenly. I use dry brushes and rollers - they pick-up from the excessivcely wet areas and put down in the dry areas. When all is even, use the squeegees again (held at about 45 degrees to the surface) to scrape off excess resin so you end up with just the wet cloth, but no visible pooling of liquid resin.

After the epoxy has gone off enough to be certain that the cloth wont float up off the surface - this depends on temperature and rate of cure - but when it gets to a "green"state of cure, lay on several more coats of epoxy to fill the weave so that when you finally sand the surface (after removing any amine blush with water and cloths, sponges or Scotchbrite pads) you are only sanding epoxy and not going through to the glass.

Have a look on my website under the button labelled "First Mate Photos 3" for a brief pictorial demonstration - the thumbnails enlarge if you click on them.

Read More..

The End of the First Build Year

The planking was completed in a total of 320 working hours.

December was mostly spent in fairing (smoothing and shaping) the hull, and cleaning the inside of excess epoxy.

Pencil marks were spread across the hull. As the fairing progressed, removing any high spots, the marks disappeared.

The Festool Rotex was the original tool used. It is an aggressive cutter. It has a 6" disc and is a combo rotary and random orbit sander. It worked best for cutting down the high areas of epoxy, and later for aggressively cleaning up the inside.

The Hutchins Eliminator with its 8" disc, is a rotary sander that blends high and low areas the best.

An inline sander was applied to a "fairing board". It will be used in an attempt to create the "ultimate smooth" for the pre-glass finish.

After smoothing the high spots, any low spots were filled with a mixture of phenolic micro spheres, wood flour and epoxy. The wood flour is for non-sag structure, while the micro spheres make the sanding easier once it has dried.

Richard dons his Tyvek (AKA sperm suit) with his 3M Breathe Easy self contained positive pressure hood for the sanding jobs. Cedar and epoxy dust are a bad combo.

The process involved frequent sweat breaks.

A more tedious job than the planking....

After the highs and lows were smoothed, a mixture of epoxy and wood flour was used to fill all screw holes and other voids.

The inside was cleaned up with the aggressive Festool Rotex. I finally climbed inside to view the job. The pressurized hood was an absolute must for this job.

The laminated frames and bulkheads as structural supports are clear.

This is the view looking up toward the engine compartment and lazarettes.

The holes are baffles between the water storage compartments under the sole. All surfaces, hole interiors, etc will be meticulously glassed and epoxied. No water will be allowed to touch any wood. The center board configuration makes drainage of bilges and water compartments slightly more complicated, as there is no right to left connection or central bilge. Since numerous bilge and water pumps will be necessary, we will look at it as bilge and water pump redundancy...


The centerboard box meets up with the bulkhead to form the back of the galley sink cabinet.


The plan for the bulkheads is to cover them with white painted bead board and trim in mahogany, for a very traditional, light look. Most of the "walls" will be covered by cabinetry.

Between these two rounded bulkheads is the Navigation Table. Note the feet working on the outside of the hull...

This is looking forward from the saloon into the storage and head area.

Here is a good view of the laminated frames that create the open area in the main saloon.

The end of the month was when the boat was made mobile for the first time!

The strong back was detached from the floor, and a series of 8 casters were placed under custom boxes. She can be moved by using a little lever action.

Now that she has her own rigidity from the planking she will be able to be pushed from side to side in the small room she inhabits. This will allow her to be positioned better for the diagonal veneer application. Next step...order the veneer.

The grand total of working hours to date is 1150 hours. That is with 13 "no work" weeks.

Lets see what 2010 will bring! Peace and health to all!

Read More..

Folding Mast Hollow Sixteen Sided will end up round

In Woodenboat Magazine #237 of March/April 2014, there is an article written by David McCulloch about building an "In-Mast Hinge" which he has designed and developed. I urge you to purchase a digital issue of this copy if you dont already have it, as Mr. McCulloch has written a good article, and there is an excellent coloured illustration.

 https://www.woodenboatstore.com/product/WoodenBoat-magazine-issue-237-march-april-2014-DIGITAL

David McCollough"s photograph of his "In-Mast Hinge" from the Woodenboat Magazine article. Note the detail in the upper-right corner.

This article inspired a customer of mine to inquire about including such a hinge in a replacement mast for a large, open daysailer he had recently purchased. After some discussion, and an inspection of the boat, I agreed to attempt the project. It was necessary for me to make modified drawings for the plates to fit the mast I was commissioned to build due to its different diameter from that shown in the article.

The location of pivot holes, and the radii of cuts made to all three plates alter depending on the geometry, which is itself dependent on the diameter of the mast. However, this is not at all difficult to work out, and just requires attention to detail.  For those who may be interested, here are some early progress photos: -

One half of the mast being laid up in a female station mould mounted on part of my 12 metre (40 ft)-long bench. The mast is made up of 16 staves, so this half-shell comes from 8 tapered pieces.

All eight staves glued up in the female mould. The first stave was fixed along a marked centreline in the bottom of the female stations, using 18 gauge polymer brads fired from a pneumatic branding gun through the stave and into the plywood edge of the station mould. Subsequent staves were laid up on either side of the "master" and glued using epoxy. The overwhelming reason for using epoxy is that it only requires contact pressure to form a good bond. Careful attention must be paid to priming the gluing surfaces with un-thickened epoxy before applying the thickened mixture. This method allowed me to fire polymer brads into the SIDES of each successive stave to hold it to the one before, because the epoxy did not require clamping pressure. The polymer brads stay inside the shell of the mast, and will of course never corrode. The bradder and polymer nails were purchased from Duckworks. After being glued-up, the inside of the half-shell was given three or four full coats of epoxy to ensure that the inside of the finished mast would always be protected from moisture.

Here is the station mould after the removal of the first mast half-shell. I used adhesive tape applied to the inside  of the cut-out section of each mould to prevent epoxy squeeze-out gluing the mast components into the mould. Alignment of moulds is very important, and you can see the blue chalk-line "snapped" onto the bench surface (now covered with epoxy drips!)

Two half-shells of the mast after being removed from the station mould visible in the top/right of the photo. The outer surfaces are still rough-looking due to epoxy marks. When first removed from the mould, the half-shells had lots of thickened epoxy squeeze out, which I largely removed using a heat-gun and scraper. Any gaps were filled with additional epoxy.

Here you can see the two shells clamped together with cable-ties and hose-clamps. The extra length of the staves has been roughly cut off using a handsaw and you may just be able to see that there is no glue on the opposing faces of the two shells. Note the heavy layer of sealing epoxy on the inside of the hollow mast.

This is a similar photo, but taken from the mast head. The trimming of the extra length  was done quite roughly, and the un-glued faces of the staves still need to be sanded to remove dags of cured epoxy, so the gaps in the un-glued faces are a bit open. This will change prior to final assembly. Note that the taper of the mast resulted in a reduced outside diameter, but the thickness of the staves has reduced as well. The idea is to keep the percentage wall thickness of the mast constant at about 20% of the diameter. This is something which cant normally be done with a "Birds Mouth" mast. (see photo below)  

An off-cut from the tip of  "Birds Mouth" mast I made. a while ago. Note how the wall thickness, which started off at the base being 17% of the diameter, has ended up being so large it almost makes the mast solid.  Compare with the previous photograph.

Three stainless steel plates to make up the hinged section of the mast (refer to the inset in the David McCulloch photo at the beginning of this post to see how this works). These plates are quite heavy, with the outer pair being 6mm thick, and the inner one being 8mm. I had these laser-cut, which saved a lot of time, and was not expensive.

This sketch shows the stainless steel plates extended and folded. The black lines depict the 8mm plate which is buried for half of its length into a solid mast stub which runs from a mast step near the keel to a short distance above the deckline of the boat. The red lines show the two 6mm stainless steel plates, which are fully buried in the base of the mast you can see in this article.

Here is a close-up of the insert from the heading photo in David McCullochs article in Woodenboat Magazine #237.
 https://www.woodenboatstore.com/product/WoodenBoat-magazine-issue-237-march-april-2014-DIGITAL 

There needs to be a solid section at the base to hold the stainless plates. On the free-standing hollow masts which I normally make, I always insert a solid section from the base of the mast, to a reasonable distance above the mast partners. In both my normal free-standing mast inserts, and with this one, I terminate the solid insert with what is often referred to as a "Swallow Tail", the purpose of which is to ease the transition in stiffness from where the mast is solid (i.e. the hollow shell combined with the solid inset) to where it is a hollow shell. Here is a view of the early stages of the solid insert for this mast.

As you can see, there is the "Swallow Tail" section, and at the base, a cut-out slot to accept the stainless steel plates and an 8mm hardwood inset to hold them apart and allow the 8mm tongue of stainless from the mast stub to fit between. At this point I have planed a square blank into an octagonal section - it is on its way to becoming round!

At this point the blank has been planed from octagonal, to 16-sided, and them planed further to 32-sided, and then hand sanded to a round cross-section.. All of this sounds complicated and difficult, but if you start with an accurately cut square blank, and then mark carefully for the 8, to 16, to 32-sided planing work, youll find that the work goes quickly, and is actually a satisfying and relaxing job. As with most boatbuilding work, it just a progression of simple steps. I can tell you Im finding it more difficult to describe than it is to achieve on the bench. Other than the initial sawing of the square blank, I did all of this with a low-angle block-plane you can see in the photo before this one. It did not take long.

The hole you can see drilled through the filler block at the apex of the "Swallow Tail" is just something I do to prevent a crack propagating from the apex. This may be an over-kill, as the block will be contained within the mast shell anyway, but it only took a moment to drill - so better to be safe than sorry... 

Here is where the stainless steel plate assembly will eventually reside. Matching slots will have to be cut in the mast shells.

Checking the fit of the insert. The actual fitting will be done with the two half-shells of the mast opened up, and the plug will be laid into a bed of epoxy in one half, before the pair of shells are finally glued together to form a round, tapered mast. The tip of the mast will receive a similar (but smaller) plug to distribute loads from the shrouds and fore-stay, and to carry the attachments for the halyard blocks

Ill write more about this interesting folding mast experiment as the job progresses.

Read More..