How to Make a Displacement Hull Plane

The Bartender line of fishing boats has a reputation as a superlative surf boat. The Coast Guard has used them as rescue vessels. As doryman everywhere know, a good surf boat is double-ended and is thus less likely than a square transomed boat to broach on a following wave.

Unfortunately the double-ended hull will not plane under normal, non-surfing conditions, no matter how much power they produce. So, George Calkins designed a spray skirt for his power dories to provide more lift at the stern.

The nineteen foot Bartender in the lean-to out in the boatyard has never been outfitted with a spray skirt, as far as I can tell, but it has one now. Frank, the current owner has been frustrated that this boat tops out at 10 miles-per-hour.

 
Now, that would be just fine with me. Mentioning this to Frank made him laugh.

If this were my boat, Id have no more than a ten horsepower motor on her and be happy just puttering around. The hull drives easily and this could be a very economical package.

The boat has a 40 horsepower motor however, and a rated speed of 25 - 30 mph, which is what we are trying to achieve. The bottom had a keel hog from sitting on a poorly designed, dilapidated trailer which probably contributed to its reduced performance. Ive stressed as much of the hog out as I could, reinforced some old, tired keelson framing and re-welded the offending trailer. All in a days work for a shipwright. The spray skirt was a challenge - the hull shape aft has such a radical camber that the face of the skirt is a helix. I laminated Oregon white oak using polyurethane glue and stainless screws. Didnt have to steam bend anything, but very near.

Frank will be camping aboard this boat at the upcoming Sucia Rendezvous so Ill be able to see first hand how all this works out.

Hope you all had a better solstice than I did. You can see what I was doing on the longest day of the year.

The spray skirt meets the chine at the stern, sweeps up past the waterline about half-way, then on to touch the bow in a fair curve.

Need to clean and polish that bronze half-round for a finishing touch.....








I also prepared some salmon for the Rendezvous. John St Clair is known locally as the Salmonator. He is a prolific fish killer. (many people find it confusing that I spend so much time on the water but dont fish. With friends like the Salmonator, why should I?). Recently he gave me a 20 pound salmon that had been in the freezer for awhile. The best thing to do with a fish thats a bit past its prime is smoke it. I dont have a smoker, so I slow cooked my fish. After marinating it in a brine and sugar mixture for 24 hours, it was spiced with garlic, onion, tariyaki and sesame seeds. It was then cooked at 170 degrees F, for six hours. Dessicated fish is not photogenic, so I will forgo any pictures. Take my word for it. Its delicious!

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Hull UV Protection

Fiberglass over plywood is ridiculously tough.  There are wood and fiberglass boats still around after 50 years.  However, fiberglass has an Achillis Heel -- sunshine.  Fiberglass rapidly degrades with exposure to UV rays.

Thus, it is recommended to paint or varnish fiberglass with something offering UV protection.

We wanted the boat to show off its lovely woodiness, so we chose varnish.  There are fancy marine varnishes that are made for marine applications.  Spar Varnish is one example.  They are relatively expensive (though not compared to epoxy which is ridiculously expensive).  However, there are exterior varnishes that are equally good that you can pick up at the hardware store/lumberyard which are just as good.

  

In a moment of insecurity, I called and checked in with Gayle at Glen-L just to make sure. She gave me a thumbs up on my selection of exterior UV varnish.

After varnishing, it looked pretty much the same as after the last finish coat of epoxy.  But in my mind, I knew Id protected the fiberglass from its Nemesis the big ball of fire in the sky.

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Sheeting the Hull

It looks easy, right?  What could go wrong?  Four rectangular sheets of plywood lined up together on a horizontal surface made to fit them, screwed down on all the edges.

But as soon as we started sheeting the bottom of the boat, we realized this seemingly simple task would be more complicated.  How do we jockey all these sheets of plywood into perfect alignment, secure them together, turn them over to apply epoxy and then put them back into perfect alignment before screwing them down.  And somewhere in there, we had to apply butt blocks to where the sheets came together.

We tried laying out the plywood correct side down and applying one of our patented temporary butt blocks to hold the ends of each sheet to its corresponding partner.   But when we awkwardly tried to turn this paired 16 foot long überblatt over, the warblinesss of it pulled those temporary butt blocks out, causing us later grief.  So we tried another tack.

The plans called for butt blocks at the place where each plywood sheet met another at its short end.  Got that?  Read it a couple more times.  (No butt blocks were needed on the center line because the sheets met in a butt along the keel stringer.)  So we realized we could install the permanent butt blocks and the strength of these would allow us to manipulate each pair of plywood sheets.

These butt blocks were a little trickier than the single butt block on each side stringer because they needed to be installed in the spaces between each of the stringers.  So installing the butt blocks looked like this:

1. Put all four sheets precisely where they needed to go, correct side up.  
2. Crawl underneath the boat and draw lines where the stringers met the sheeting.  
3. Turn all sheets of plywood upside down in place.  
4. Measure (and carefully label) each space where a butt block needed to fit.
5. Cut the butt blocks 6 inches wide.
6. Coat the butt blocks, the spaces where they fit, and the plywood ends with a first coat of thin epoxy.
7. Coat the butt blocks and the ends of the plywood with a second coat of thickened epoxy.
8. Fit the plywood together carefully.
9. Put the butt blocks in place (noting the careful labeling)
10. Screw the shit out of them with screws every two inches

Whew.  And this is only a preliminary step (but really one of the most complicated).

After this cured, we had two pairs of plywood joined end-to-end that were pretty bombproof and could be manipulated awkwardly, but safely.

Somewhere in all this, I found time and space to give all the top surfaces of the boat a first thin coat of epoxy.  Now we gave the hull sheeting a first coat where it would join to the stringers.

We gave that time to become tack-free so manipulating these long joined pieces would be easier.  We took the plywood off the top, and gave the top surface of every stringer a second coat of thickened epoxy.  We also epoxied the edge of the plywood where the two long pieces would meet each other along the keel stringer.  Then we awkwardly person-handled the sheeting into place.

We put in a few screws to hold the sheets in place, and then went around and put screws every three inches.  Kai gave each screw a little tap with the hammer to get them started.  This made my finishing the screw with my power drill that much easier and faster. 

So with screws 3 inches apart on all of edges and 6 inches in the center, it was by far our most screwy day at 448 screws. With all these screws, we got afraid that by the time we got around to the final side the epoxy would have cured, so we put in every third screw on all edges and then went back and filled in.

After this, it was kind of exciting to get up on the boat and be able to stand there.  Of course its upside down, but still.  It felt a lot more boaty than the piles of lumber and sawdust and sticky epoxy goo wed been playing with previously.

After the bottom sheeting cured, I was able to release the come-along which has squared the boat during this procedure.  I was relieved that slowly de-tensioning the come-long was a non-event with no creaky or poppy complaints from the boat.  Sweet.

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Hull Turning Methods

I have shown a few projects in this blog over the past few months with the hulls being turned using different methods. The bigger the boat the more critical this operation is. The risks of damage to property and injury to people increase exponentially as the boat becomes more bulky and increases in weight. Imagine the difference between turning over a plywood hull that is 6.4m (21ft) long, 2.4m (710") wide, 1.2mm (311") deep and weighing 200kg (440lb) or a 50% scaled up version of the same hull. At 9.6m (316") long, 3.6m (1110") beam and 1.8m (511") deep, it will weigh 675kg (1488lb).

It has only increased 50% in all directions but the weight is more than 3x that of the smaller boat. The bulk becomes more difficult to manage and the weight to lift and lower becomes a major factor. If, at the same time as increasing the size, you also change to steel as the construction material, that same size hull could weigh 2500-2750kg (5500-6000lb). Now you are talking about some serious loads that can get out of control, yet the boat is still only 50% bigger in each direction.

Those smaller projects are easily turned over by hand, with friends and neighbours supplying the motive power and the boat having a soft landing on tyres or some other cushioning material. Years ago a client of mine in South Africa turned his 32ft hull by himself. He jacked it up on one side until it reached the balance point, then let gravity take it the rest of the way. It fell against a young tree, then slid down the tree and came to rest flat on the ground. Luckily his hull was relatively undamaged but the tree didnt survive the experience.

There are many ways to turn a hull but that is not one of them. I have a whole chapter on this subject in my book "Shaped by Wind and Wave", to give guidance on how to safely turn your hull. The two Didi 950 hulls that were turned recently in USA and Australia both used the spit-roast method. For each of my own big boats I have used a chain block to do the work, another of the methods explained in the book.

Turning the 38ft "Black Cat" using a chain block on a scaffold tower.

The book can be ordered either as a paperback or as digital for reading on whatever screen device suits you.

To see our range of designs, go to http://dixdesign.com/.

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Hull Turning of Didi 23

Steve Watson is building a Didi 23 in Hood River, Oregon. Last week he and a few friends pulled the hull out of his garage, rolled it over in the driveway then returned it to the garage for work to start on the interior. These photos show the process that they used.

Pulled out of the garage.

Half-way over. A hull is intimidating in this position and must be controlled. Gravity can quickly become the boss.

Safely over and resting on mattresses. Builder Steve Watson at right.

Lifted off the mattresses onto a wheeled cradle to keep her mobile.

Stern view. Steve has added a scoop stern to the transom.

Going back into the garage for work to continue.

A boat-under-construction takes on a whole new character when it is turned right-way up. This is the first time that the builder gets to see it right-way-up and the final shape of his creation.

Hull-turning is a memorable milestone in a big boatbuilding project. This is always a good time to have a party, to take your rewards and gather your thoughts, resources and energy for the next stage of the project.

The way that Steve and friends turned this hull worked for them. The bigger the boat, the more complex the turning process becomes and the more care that must be taken with preparations and equipment to keep this heavy structure under control. Carelessness with this phase of the project can injure or kill people and also damage the carefully-built boat.

To see more of this and our other designs, please go to http://dixdesign.com/.

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Thru Hull Fitting

I decided to make each job I have to do in the engine room its own post vs adding to the "back to work on the boat" post.

Now that Im back working in the engine room I find myself wondering "why in the hell did I do that"? Maybe its an older and wiser thing or maybe I just wasnt thinking right a couple of years ago, but either way I find myself having to do a bit of re-work.

My main engine is keel cooled with dry exhaust. My generator is cooled through a heat exchanger with wet exhaust. I had originally laid out the generator to be installed on the port side, but with all the weight I was putting to port, I thought it better that I move the gen-set over to starboard. Looking at the through hull fitting I had originally installed to service the gen-set ( a 1" pipe welded into the hull and threaded on its end), I began to feel this set up was totally inadequate for my future needs. Having realized just how lame my original thru hull was, the first order of business in the engine room was to remove the that 1" pipe and fabricate a more suitable through hull.

I dont want to punch a bunch of holes in my hull so I decided to fabricate a two inch sea chest that will handle my water intake needs. I want to have a fore and aft wash down set up, I might also want to have the option of raw water flushing the heads if fresh water gets scarce, I also need to think about possibly cooling my hydraulic system, and I need to be able to cool my generator.

I decided to install one 2" water intake using socket weld flanges that will lead to a proper valve, then through a sea strainer to a manifold consisting of four or five 1" valves to direct water as I need.

I bought the socket weld flanges from my local plumbing supply house and used sch. 80 pipe for the thru hull fitting. Because I want to use stainless steel for my valving and manifold, I had to electrically isolate the thru hull from the stainless. I did this with a gasket and isolating bushings for the flange. The flange on the hull side is carbon steel, while the flange on the boat side is stainless steel. In the first picture, you can see the green coating on the carbon steel flange that is welded to the mild steel sch. 80 pipe.

After welding the thru hull pipe to the flange, I gave the piece a quick sand blasting before I welded it in place.

These pictures show the various parts along with the flange welded into the hull. On the last picture you can see the remnants of red dye I used to test the welds. Air testing this piece would have been difficult and while the welds looked good I decided to dye test just in case. Im planning on making a trip to the scrap yard later this week to see if I can find some valves and some piping. In the past Ive been able to buy stainless steel ball valves at the scrap yard for $10.00, and with a little luck Ill also find some couplers and other bits Ill need.

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Didi 950 Hull Skin Completed

Over the last few months we have watched as two builders on opposite sides of the world have worked on their Didi 950 projects. Mike Vermeersch in Ohio, USA, is building his boat from a kit and Fred Grimminck in Queensland, Australia, is building his from scratch.

Fred has taken a break from his boat for a couple of weeks while delivering his recently sold Didi Mini clear across Australia by road, a formidable road trip.

Fred Grimminck delivering his Didi Mini Mk2 across Australia.

Mike has been able to continue and has now completed the fairing and sanding of the radius as well as fitting the bow capping and shaping of the forefoot. His boat is looking very nice, with the final hull shape now clear.

Radius skin completed but still to be faired.

Radius faired and sanded. The jigsaw joints of the side panels are seen below the radiused panel.

Completed stern sections.

Bow capping fitted, ready for shaping.

Bow capping and forefoot shaped and sanded.

Completed bow shape. Clean and shaped from plywood.

Faired and ready for epoxy and the fibreglass reinforced areas to be done.

There are also builds of the Didi 950 progressing in Greece and Latvia.

To browse our full range of designs, please visit http://dixdesign.com/.

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Fairing the hull

The phrase "fairing the hull" took me a while to figure out its origin. My interpretation of what is fair is just that... it feels fair. Running ones hand across the hull sheathing reveals more than what your eyes can see and as you keep running your hand across that hull skin you start to get a feel for whats fair. Fair is not perfect and fair is not feeling bumps and gouges in the metal... fair is fair...it feels pretty fair. Sort of like how Manana does not mean tomorrow, it just means not today.

I bought my steel wheel abraded, primed and plasma cut. The wheel abrading removed the mill scale and left a good profile for the primer to stick to. Im building inside so rust has been a non issue for me and my original primer has remained intact. I started the fairing process ( above the water line only) by grinding all welds smooth. I also hit some of the "weld through" with a grinder if the bumps felt abnormally high. Weld through are areas where the metal pushed out from the welds I created welding the longitudinal stringers to the hull sheathing. After I had all the grinding done I spot sand blasted all the grind marks, rub rails, and any spot that had rust blooming. I then gave the whole hull a light blasting to tooth up the existing primer. I blew off the hull with compressed air and applied three coats of epoxy primer alternating colors between the coats ( white and gray). I then began the process of mixing epoxy ( Gougon Brothers) fairing compound and filled all the areas I had ground such as weld seams and deep weld through marks. After multiple applications and sanding of those areas I sprayed one more coat of epoxy primer then gave the hull two coats of high build primer with the tendency to lay it on thick.

High build primer is like liquid filler putty being extremely easy for one to sand. Using a 30" flexible sanding block and rolls of self adhesive 80 grit 2" wide sand paper I sanded the hull. The high build primer shows every little dip and doodle in the hull. While "long boarding" the hull Id find areas where Id sand back into the metal ( very high spots). If these areas were really high Id hit it with a the grinder, re blast, re prime with epoxy, more filler if needed, more high build, re sand. I really did not use much filler as the hull was very fair when I began. Most of the filler was used up creating a smooth transition from the hull skin to the rub rails, around the port lights, and in the area of the freeing ports and hawse holes. Once I was pleased with the long board sanding I blew off the hull, vacuumed the hull, wiped her down with tack rags and applied two more coats of epoxy primer to seal the high build primer.

I faired the hull one side at a time, working at a pretty steady rate since I was doing this over the winter in the shop. Each side took two months to complete and has landed on the top ten most nasty jobs to date.

Having now looked up at the hull thousands of times in varying light I have found a few areas that will need more a little more fairing before I apply the topcoat. Id guess Ill have two more days in fixing some of these areas so I dont consider them a big deal as most will just involve some sanding and high build primer. My future plan for the top coat is to scuff the few areas that need attention, epoxy prime, high build, sand and repair, more epoxy primer. The whole hull will get a good washing, a scuff with 80 grit, one more coat of epoxy primer, then Ill spray the top coat.

I only have a few pics of the faired hull. For the most part all the body work is finished and shes ready to paint. Ill be able to topcoat a few areas of the hull in the shop prior to attaching the wheel house and salon, but Ill probably save the bulk of the hull topcoat until after the wheel house and salon are attached.

Conall

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Hull Paint

The best way to finish a boat is to apply as many coats of paint as you can afford.  So far I have applied close to a half gallon of paint to the hull (5 coats).  Im going to keep applying paint until I run out. That should be about 12 coats at this rate. That should suffice.

Religion, politics, and boat paint are the top three most controversial subjects in the known universe.  I spent months reading what everyone had to say on the subject. There are a dizzying array of paints available, all with their own sets of pros and cons.  Every type of paint has its proponents and critics. In the end, I decided to go with Porch and Floor enamel. Porch and Floor enamel is the one paint that most people seem to agree, (more or less),  is a perfectly fine paint to use on a boat.

On my last build I used Interlux Brightside.  Brightside is terrific paint.  I was very pleased with the results. It goes on smooth, levels very nicely, covers well, dries hard, but its somewhat expensive.

I read numerous times that Porch and Floor enamel is essentially the same thing as Brightside at a fraction of the cost.  John Welsford also recommends alkyd (oil-based) enamel paints.  So I decided to give it a go. Remember, the best way to finish a boat is to apply as many coats of paint as you can afford.

Interlux Brightside paint is a polyurethane alkyd enamel that costs about $110/gal at the local West Marine.

Ace Porch & Floor paint is a polyurethane alkyd enamel that costs $27/gal at the local Ace Hardware.

After using both, I honestly cant tell the difference.

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Hull finish paint

Of course, in all things boat building, this job took about double the time I figure and posted about in my last blog post. The reason for the underestimated time was worthy of the extra time in my opinion.

When I had completed the body work on the hull, and sprayed the last coat of primer, I had thought I had the sanding to a good enough quality to paint. Thats kind of a loaded  response, as the primer was probably smooth enough to paint, I just wanted it a bit smoother. The problem I was fearing was that not having the primer perfectly flat would cause the top coat to have some blemish. Without more sanding, the top coat would still be shiny and pretty, but the blemish I was worried about would make it a problem to revive the finish years down the road with polishing and wax. The primer needed to be flatter. So given the lessons learned on the transom and wanting a more user friendly finish, I decided to re sand the hull.

Sanding the hull ( Im only talking about the port side today) to 320 grit was not to bad of a job. Its kind of hard to describe what Im talking about, but once you start to sand with 320, minute high spots in the primer start to appear. More sanding flattens the primer, and the high spots disappear. The primer starts to get a shine to it, and it is almost as if it is being burnished by the finer grit sand paper. 320 seems fine enough for a boat paint job, but Im sure body shops working on cars would take primer to at least 400 and more likely 600. There are for sure better ways to spend ones time than sanding primer so I approached in my not getting in a hurry way of doing things. Spending an hour  before leaving for work in the morning and a hour after work in the evening, helped me keep the patience  needed for this type of work.

Wanting to break up visual size of the hull, I decided to paint the rub rails another color. The lower rub rail extends around the back of the boat and becomes the swim platform. I dont know how many of you have painted the color red  in your house, but I can tell you that I now know that red industrial paint has the same problems as red house paint. You have to prime anything you intend to use red paint on. I had already painted the swim platform white, and the swim platform part of the rub rail green. I re sanded the swim platform rub rail, taped it off and began spraying red over the green. The green makes the red a few shades darker than the other ( primed) rub rail. The few spots on the swim platform rub rail  where I sanded through the green in to the white primer, the red does not cover the white. This part of the rub rail is going to  have to be sanded, primed, and re painted. Truthfully, it doesnt look that bad, but it is noticeable enough that I want to re do it.

Taping off the hull took also took quite a bit more time than I had figured. I probably have five or six hours invested in taping. Once I had an area taped, I wiped it down with a tack cloth to remove the dust. I started taping on Thursday night, and finished it Friday after work so I would be ready to spray Saturday morning.

When I blasted and painted the barrier coat on the hull bottom, I brought the barrier coat six inches above the water line. I brought the green two inches down past the barrier coat, so when the boat is in the water, about four inches of the bottom paint will be seen. The white barrier coat will be covered with red anti foul paint. 

The weather here has suddenly turned hot, and Saturdays forecast was for temperatures in the 90s. Figuring it would take four hours to spray the port side, I wanted to be spraying by 7:00 am and finished before the 90s found their way into the barn. As I began spraying, I immediately had an issue with the paint pot which took and hour to resolve. While I finally got the pot working correctly, it caused me to have a less than ideal finish on the area under the lower rub rail, between the water line and the rub rail. Ill have to do some paint repair in this area, but now that I know whats involved in doing that, Im not to worried about it.

Getting three coats of paint on her requires more of the elusive patience, and keeping track of where one is in regard to where one just sprayed. The first coat to hit the metal covers the primer, but not too heavy. The second coat goes on while the paint is starting to get tacky which allows the second coat to cover while not  sag. If the spray gun volume and fan width is tuned in right, the second coat is probably good enough to call the area finished. The third coat gets risky, because you now have some thickness developed and the paint wants to start sagging. The second coat needs to be well on its way to being tacky, or you could develop a sag on the third coat. You have to wait for the paint to tack up to accept more material, but you cant wait too long or it will to dry and you get dry spots where you start and stop the  spray pattern. Im using up to 10% by volume of reducer in the paint, so it tends to dry quicker. I have one spot below the bulwark at the wheel house, where I had a drying issue on the third coat and Ill have to polish it to blend it back together. This is where sanding the primer perfectly flat pays off as it makes polishing much easier.

I still have to finish paint the starboard side, so Im starting prep work on it this week. Given how busy Im getting with work, I doubt Ill have it completed by next weekend, so Im giving myself another week to call the paint work a wrap. Im big time happy to see so much shine when I walk in to the barn but Im more happy to have reached this milestone.

Cheers

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