What is our book really about

"Fundamentals.." is an intriguing romance between plank and frame, the steamy cherry bending to her masters wishes. Meet the curvaceous "Annie Buck" and learn the story of how she got to be the way she is. Watch out for the "slicers" and the "whittler", see what the protaganist learns in the bedroom, We cant tell you the finish, but sometimes it involves a good shellacking...

See what the critics are saying:
Fine Woodworking calls it: "intense". Good Old Boat says:"My learning curve would have been much less steep if Fundamentals of Model Boat Building had been available." James J. B. says: "provides great insight". Chris P. says: "A great resource for anyone". Lisa F. says: "Remarkable detail." Gail G. H. says: "I highly recommend this book."

Come meet us at The Calvert Marine Museum in Solomons, Maryland on October 8th and 9th, 2011 and get your own personally autographed copy.

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Plumbing Has Come To Life

This morning I fitted the taps and made the final plumbing connections.

Kitchen

Bathroom

Shower

Once the cold side was checked and the calorifier filled I fired up the diesel heater and in half an hour I had seriously hot water.

I am not very happy with the water pump.  Its very noisy so I am going to mount it on some soft substrate.  If that dont work then I will be looking for another one.  The one in my motorhome is the same capacity but is "for motorhomes" as opposed to "for boats".

With all the water working I was able to fill and test the macerator toilet.  When I say test I do mean a  clean test.  Ill have to trust that it will deal with matters once afloat.

And finally as the water tank filled the water tank gauge came to life with some readings.  Once the tank is full I can calibrate it.  That is if I can find the instructions!

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Head Scratched Protection Added

After some discussions with my fellow boat builder Ted, it would appear that the side wood strips at the rear of several boats like ours have been added not necessarily as splash rails but as protection against bumps. The shape of the side of our boats at the rear makes bottom edge of the boat prominent and susceptible to getting bumped and marred. A rubstrip along the shearline would be ineffective at the rear. However, since the boat side twists, getting something to fit takes a bit of head scratching.

I decided to build some stationary assists for fitting these bumper strips. I used the 2x6s from the forms and cut vertical pieces at the planned front and rear height and connected with a stringer at floor level. I then split them in half on the table saw so I could make one for each side of the boat. They were attached to the ping-pong table and then belt clamped underneath the boat to bring the verticals tight to the boat.

A 2" wide board was cut to rough length and placed up to the side of the boat. It was placed so it gapped about 3/8" at the front and a like amount at the rear. Then using a scrap piece of wood about 1/4" thick and 1 1/2" square, I sanded a chisel edge so it would ride up against the boat along the board. I drilled a small hole 3/8" in from the edge to allow a pencil point to project through. I laid this piece flat on the board and pushed it up against the boat side and traced a line on top of the board, and then repeated this on the underneath side.

I then took the board to the band saw and cut a line in from the edge every four inches and rotate it as needed to cut to the marked lines top and bottom. Then I set the band saw table to the initial angle needed and cut off four inches at a time and readjusted the table angle as I went along. This cut a spiral shaped surface along a curved line of sorts. Then a trial fit and some filing - some more filing - sanding - filing - and it got close to fitting - sort of.

Then duct tape was put on the side of the boat so epoxy would not adhere. Some scraps were put underneath with more duct tape to catch any epoxy drips. A batch of well thickened epoxy using the brown fairing filler was put on the board and clamped to the boat and allowed to cure. It took some mallet hits to get the board lose after cure but it appears to now have a surface that matches the boat. Filing of top and bottom sides of the board should clean up the excess epoxy.

This last picture shows the epoxied surface, which is now a curved line with a spiral twist - you can kind of see that in the photo.

Ill do the other side and then determine the final shape or line to cut the outside of the board. It will probably end up being a straight taper - narrow at the front and gradually getting wider toward the rear of the boat. I decided to reinforce the sides at each screw attachment point with another piece of 1/4" plywood. To keep it simple and light, a flycutter was used to cut some 1.5" diameter "washers" from 1/4" plywood. These were epoxied in place on the inside of the boat and held in place with a screw and a temporary duct taped block on the outside of the boat. I am not going to permanently attach these rails until the boat is out of the basement. Hate to add any unaccounted for width.

After a bit a trying different lines, a straight line did not work as it made the forward foot or so look like it bulged out due to the shape of the boat side. So I used a strip of plywood to create a curved line and cut it on the band saw and sanded out the bumps and saw lines it until I had a smooth surface.

I plan on putting a 1/2" or 2/4" wide stainless steel rubstrip along the outer edge.

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Outboard Lake Testing

Yesterday was a beautiful day and time to give the outboard some time on the water. My son Bill and daughter Katy joined me for some time on the lake. We loaded up the motor and went over to my friend Teds house and after a bit of switch-er-roo, put my motor on his aluminum fishing boat. Unfortunately, the transom center motorboards were about 1/8" too thick to mount my outboard. So we put it to the side of center where there was a trolling motor mount.

The one issue with the motor is the recoil starter pawls arent flipping out and engaging the flywheel reliably. This often results is half the rope pulling out before anything happens. So the first start was a bit difficult. Hopefully removal of the recoil unit and a bit of lubrication will fix it. Luckily, Bill is young and strong so he kept pulling and I tweaked the choke until it fired up and ran.

We had a nice couple of hours on the lake. Bills GPS said our max speed was 21.7 mph! Im sure with the motor in the center of the transom, some tilt adjustments, height adjustments, and tossing a child overboard, we could have gone faster!

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Joining Plywood Stepped Scarph Joints

A stepped scarph joint is the mechanically produced equivalent to a hand-planed sloping scarph joint. It is normally cut on a CNC router that has only three axes of movement, namely forward/backward, side-to-side and up-and-down. The sloping face of the hand-planed scarph is replaced by a series of small steps, each comprising a small vertical face and a broad horizontal face that coincide with mating faces on the other piece to which it will be bonded.

The main problem with stepped scarphs is similar to that with sloping scarphs. That is attaining proper alignment when gluing the joint and keeping it aligned until the glue has set. A sloping scarph can and will slide in almost any direction as soon as the slippery glued surfaces are brought together, so it has to be very carefully clamped. A stepped scarph cannot slide forward because the steps prevent it but it can slide back or sideways. Again, it needs careful alignment and clamping.

Various methods have been developed by different companies to overcome this problem. These methods are not patented, so can be used by others.

Mechtronics in Cape Town, South Africa, use a dowel peg system to lock the joints. The holes for the pegs are drilled by the CNC machine and hold the joint so securely that the panel can be moved right after the joint is made, without having to wait for the glue to set. After the glue has set the joint is sanded smooth with a belt sander, which also trims the dowels flush.

Mechtronics panel as it comes off the CNC machine

Mechtronics stepped scarph joint completed.

Ertug in Istanbul, Turkey, achieve a similar locking effect by programming the CNC machine to form islands in the one half of the stepped scarph that lock into holes that are cut into the other half. This is also a very neat solution.

Ertug stepped joint details.

Stepped scarph joints are good for any size of boat but care needs to be taken in high load situations or where there may be flexing of the panel. The weakness of this joint is in potential cracking along the surface joint lines, either from stress in the panel or from bending. Joints should, where possible, be kept away from edges of openings that might align loads along the joint to promote cracking. Edges of openings must be reinforced with wood perimeter frames or with glass or carbon tapes to spread the loads away from the corners and into the panel surfaces. The weak areas of the joint can also be reinforced with glass tape laid across the surface joints. Joinery shelves or locker tops that span across the joint also help by stiffening the panel, preventing flexing that might initiate surface cracking.

The CNC operator must take extreme care when cutting scarph joints to ensure that the plywood is hard against the sacrificial backing board during cutting, or the accuracy of the stepped surfaces deteriorates. There must be a vacuum on the table to suck the sheet against the table, as a basic requirement. If this is insufficient then plastic nails should be used to mechanically fasten the sheet to the table. All waste material must be efficiently removed as it comes off the router bit so that there is no chance of it getting between the sheet and table. This is best done with vacuum right at the cutting tool. Finally, the cutting paths need to be programmed so that any puncturing of the full depth of the sheet happens as the last stage of the cutting process. If it happens earlier it will increase the chances of waste material getting under the sheet and it will weaken the vacuum that is sucking the sheet against the table.

See our range of designs at http://dixdesign.com/ .

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Making Keel Cooling For A Friend

A very good friend of mine had a new engine fitted recently.  The boat was an ex hire boat and only had a 35hp engine which is fairly normal for a hire fleet boat. The hire companies do this deliberately as they want to control the speed the boat can achieve and they probably govern the engine as well.

The beauty of these boats is they can be bought for very reasonable price, they come well equipped with quality fittings to stand the riggers of hire and the hulls are well built.

So the internal skin tank was set up for a 35hp engine, a fact the professional boat company installing the new 52hp engine somehow overlooked?  Hmm?! IMO the first thing to work out when fitting an engine is how to cool it.  If you cant cool it you cant run it.  Well you can but so long as you dont call up all the horses or want to destroy it. 

The problem only manifested itself when Sue needed to punch against the flow on the Thames, which of course needed more horses than poodling on a canal which she had been doing since the new install.

There were 2 options to solve this, another internal skin tank linked to the original which would require the engine bay to be cleared of things like the errr! engine!  The other option an external skin tank, or keel cooling which is really what a skin tank is requiring just 2 holes made and welded in the hull.  No engine removal and just a few hours work in a dry dock.

Theres a well regarded formula for working out the cooling area / engine hp.  Its HP divided by 4, so a 52hp engine needs 13sq/ft of surface area.  The most compact way of doing this is with tube, in this case 80 x 40 box section which gives 1sq/ft of surface area every 16" of length.  To further compact this a serpentine patten is the norm.

This is it.

So this is what I came up with and made for Sue & Vic.  See the links below as she takes up the story on her blog.  Read backwards from here:-  Sadly I wasnt able to fit it for her, but the local floating dry dock did a great job.

If you like boating blogs, you will love Sues.  Hers is constantly ranked in the top 10 UK boating blogs, its has a great balance of travelogue, opinion, and lifestyle showing the good and not shy of speaking about the not so good. Always punctuated with great photos and on the sidebars masses of excellent links, tutorials and resources as well as a massive list of fellow boater blogs.

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Decking Structure

After flipping the boat, it was time to figure out what to do next. The carlings had to go in as they provide the structure for between the main deck beam and the transom. After planing some honduras mohogany down to 5/8" thick, it did not want to bend into position so I got out the soaking pipe and rigged it into the stairwell again and soaked the wood for a day. I rigged up some extensions so the carlings could be pulled into the proper curve above the boat, let dry, and then marked and trimmed to fit. It required some creeping up on compound angle cuts until the angles and length were slowly tuned in.

A mid-front deck beam was added per the plans and then I decided to create an auxiliary dash beam to support the deck strongback (longitudinal middle support) and deck battens so the dash could be made removable while designing and fitting in place. The dash is at a 20 degree angle and Im using Teleflex steering "The Rack" mounted upside down so the cable routes inward and loops under the deck following Squirt builders Bill & Linda Whitney in Glen-Ls WebLetter 65.

I did a lot of playing around with mocked up seat boards after getting the steering wheel in place to determine seat fore-aft location. Then after a lot of circular thinking and planning, eventually built the seat bottom and put in a couple of holes for holding drinks or whatever. With the seat bottom in place I can finalize the seat back angle and mid deck beam.

In order to use a scrap piece of 1/4" plywood for the seat, I rabbeted the seat bottom frames and deck beam to utilize an 8 long strip of plywood only 12 1/2" wide. I used a forstner bit to bore some half round drain holes at the junction of the seat bottom and seat back to allow any water that gets on the seat to drain through. I plan on having upholstered seat cushions at some point, but wanted a functional and structural seat in place without the cushions.

With the motor mounted I figured out where to place the rear most beam while allowing a 6 gallon gas tank to be loaded in between the beam and transom and slid into the corner. Its a bit tricky due to the transom knee, but can be done. Im planning to build a two door hatch in the deck that opens from the center and hinges to each side. The thought is to allow the center of the boat to open up without the hatch lids being in the way and permit easier access to the outboard since it is a manual start. I also am planning the hatch to allow loading a 6 gallon tank as once all the remote connections to the outboard are mounted, Im not sure if the back will still be easily accessed. I added the corner radius reinforcements to the opening and added short beam extensions to tie the rear beam and carling to the shear. With these bits in place, the improvement in rigidity of the structure is amazing. Im working on the corner radius pieces at the dash and then it will be time to tackle the hatches.

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