At the end of June 2011, I published a post about my idea for moveable side seating in cruising dinghies. The idea is that side seats can be used if prefered (although I like to sit down low in the boat with my weight near the windward turn of bilge) and can also be removed at a moments notice. Most importantly, if they are slid into the centre of the boat they make an excellent sleeping platform, well above the bilge water.
The Phoenix III built by Paul Hernes, showing the side seats in the standard location..............
...........and slid together to form a nice sleeping platform............
.....or removed altogether.
You can find my original post at this address
I am continuing to work intermittently on a First Mate in my workshop - she gets attention when glue is curing on other jobs. Last week I installed the rails to carry the removable side-seats/sleeping platform, and Im delighted to say that in First Mate, the seats are more than 26 inches wide at the upper part of the body when slid together. Here are a few pictures of the rails: -
Here is the seat rail glued and screwed onto the aft face of the midships frame. This frame is made from 12mm (1/2") marine plywood, with 38mm x 12mm (1-1/2" x 1/2") behind where the screws go through. The whole thing is very strong, and the seat rail would be fine with just a glue joint. However, the silicon bronze screws make it simple to position when the epoxy is slippery, so they may as well go in! The rails are positioned to carry a side seat which is 31mm (1-1/4") deep - these will most likely be 25mm (1") framing topped with 6mm (1/4") marine plywood.
A close-up of the aft rail, which attaches to the semi-bulkhead at the forward end of the stern seat (i.e. the "stern sheets"). The centre cut-away is just to allow positioning of the screw-in hatch to that particular buoyancy compartment.
Another shot of the aft seat rail with the rowing foot-braces on the floor below. These foot braces do double-duty as structural stiffening elements as well
This seating arrangement will make First Mate (and Phoenix III) very versatile cruising dinghies - my favourite type of boat bar none!
All of the hull panels in First Mate, including the narrow flat bottom panel,are made from 6mm/1/4" marine plywood. Wayne Jorgensen, who helped build the first boat from the design to hit the water, expressed some concern about the stiffness of such a thin bottom panel. I wasnt particularly concerned, as the panel is only 856mm/34" wide at the widest point, and is very well supported by the centreboard case, 6 bulkheads and frames, and most importantly, by a 66mm x 19mm (2-9/16" x 3/4") external keel batten firmly glued to the bottom of the boat. In addition, I sheathed the boat Im building with 200gsm/6oz glass cloth in epoxy.
In a beach-cruiser, light weight is of critical importance for a solo sailor, and I also wanted to economise on plywood, getting the most possible out of standard sheets - it made sense to use a standard thickness for all panels. Having said that, there is nothing to prevent you from using 9mm/3/8" ply for the bottom panel if you wish.
As part of the design, I drew an adjustable set of foot braces to make rowing more efficient, and also to give something against which to lock your heel to prevent sliding across the boat when heeling under sail. These foot braces gave me yet another opportunity to stiffen the bottom panel. Following are a few images of the set Ive just installed in the First Mate which I am (slowly) building: -
An overview showing how the side rails of the braces are glued to the bottom of the boat, and extend forward and aft to teminate against the bulkheads. This is very important, because terminating a stiffner in the middle of a sheet of plywood risks the formation of a crack in the plywood eventually. Note how the side-deck knees in the background are tapered and lead all the way down to terminate on the chine between the bilge panel and the topside panel.
Blocks to locate the foot brace. In this photo the longitudinal rails had been glued into position, but the blocks were just dry-fitted. They were subsequently glued to both the rails and the bottom panel
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Three photos showing the foot brace dropped into the three different locations. The longitudinal rails are rounded down at the forward and aft ends to allow drainage of water - sort of like an open limber.
With these longitudinal foot-brace rails in place, along with the external keel batten on the other side, the maximum un-supported width of the plywood and external glass sheathing is about 210mm/8-1/4"
There are quite a few examples of First Mate on the water now, but except in photographs, I havent had the opportunity to see the boat sailing.
First Mate with the sprit rig option
I designed this boat for my friend, Ian Hamilton, who wanted a Phoenix III but didnt have the confidence to tackle such a building project. However, having previously built a Bolger Cartopper, he felt that a stitch-and-glue version would be within his capability.
As it turned out, Ian never did build the boat, so I came up with a deal where he would pay for materials, sails, trailer etc., and I would build the boat in my own time. This approach saved him a lot of the money normally required, and it allowed me to test the panel developments I had drawn - the most critical element in a stitch-and-glue boat design. A symbiotic process. The problem from Ians point-of-view was that once I had proved the panel developments, there was no pressure on me to finish the job!
The stage at which Ians boat lingered for a long time
Well, Ive gradually got Ians First Mate finished, and weve had three outings to carry out "Builders Trials" - Im absolutely thrilled with the results so far!
The video link below shows First Mate sailing off Manly, which is a bayside suburb on the south-eastern side of Brisbane, the State Capital of Queensland, Australia. Conditions were good, with about 15 knots of wind from the north-east, kicking up a short, steep chop. The rig on this particular boat is the 76 sq.ft. balance lug, but Ian will probably purchase the 104 sq.ft. sprit rig at a later date. Because both rigs use the same mast, in the same location, it is quite feasible to have interchangeable rigs for different styles of operation.
I was the one with the camera, and Im afraid that there was nothing I could do about the camera shake in the choppy conditions. I was in a 12ft boat which has a quick motion, and was handling the camera with one hand. I have no idea why the final scene is in soft focus....but it is still worth watching. Skipper of the boat was one of my sons, David.
As some of you may know, I have a First Mate under construction in my shed. I started her a number of years ago, with the aim of testing the panel developments for the design prior to releasing the plans for sale.
The significance of the need for testing when dealing with developed panel shapes in a stitch-and-glue design is that it is the size and layout of the hull panels which determines the three-dimensional shape of the finished hull rather than relying on an internal skeleton which has been carefully plumbed and shaped, and around which planking is laid.
One is built from the outside-in and the other is built from the inside-out.
Here is a carefully set-up hull on a strongback showing the stem, internal keel (or maybe keelson) and a large number of transverse molds around which the planking will be laid. In this case the internal structure determines the shape that the planking will adopt.
In this photo you can see the bottom panel of First Mate having the bilge panels attached using cable ties. The boat is already taking up a three-dimensional shape without any internal framework to help. This system relies totally on the accurate design, marking and cutting of the panel shapes.
This is the very same hull in a photo taken about ten minutes later. The topside panels have been attached with a small number of cable ties and the final shape of the hull has already been defined.
The fundamental difference between stitch-and-glue and any other sort of construction (with the possible exception of Birch Bark canoe building and some forms of Scandinavian "built by eye" lapstrake (clinker) building) is that it is the shape of the cut hull panels that determine the shape of the assembled hull, rather than the rigid internal skeleton as with a conventional boat.
Im not saying for one moment that one system is any better than another, but rather I am trying to illustrate why it is so critically important that stitch-and-glue hull panels be absolutely correct in their shape.
Hull panels for a scale model of Three Brothers showing how different the flat panel shapes are......
......compared with when the panels are assembled.
Anyway, to get back to the First Mate that Im building, once the panel shapes were proven? to be correct, there was no urgency in finishing the boat. This may have annoyed my friend Ian Hamilton somewhat since the boat was being sort of financed by him. My boys and I have reluctantly agreed that she may end up being his boat (dont panic, Ian, she is yours...), but there were other things on the books which were more urgent, so First Mate sat in the corner of the shed.
Now the project is up and running again and here are a few photos: -
Foredeck glued into position after having been thoroughly epoxy sealed on the underside. There were three full coats of WEST System Brand epoxy used, with each subsequent coat being applied while the preceding layer was still chemically active, so that a proper bond was obtained. The deck was glued into position while the final coat was still tacky.
Centreboard case treated with epoxy.
Support beams for the stern sheets (aft seat) being treated with epoxy. The inside of the buoyancy compartments have already been treated and thoroughly painted with an epoxy primer/undercoat
Floor of outboard motor splash well glued into position, having been thoroughly sealed underneath
Aft deck being dry-fitted using silicon bronze screws. It was subsequently glued into position using the screws and additional silicon bronze ring nails
Aft seat (stern sheets) glued in after having been epoxy sealed. This view shows how much emergency buoyancy is contained in the sern compartments - this is exactly the same layout as in Phoenix III.
The two 12mm (1/2") plywood centreboard halves being laminated together with WEST System Brand epoxy. In the past I would have vacuum bagged such an assembly, but I lost my compressor in the January floods (the compressor drives the vacuum-generating venturi) so I have had to revert to standard methods. Note the large number of screws which help pull the two laminations together, along with clamps and lead weights. Most importantly, the screw holes allow trapped air to escape so as to give a good, solid bond. The screws are removed just as soon as the epoxy has set, which is the stage you can see in this photograph.
Rudder blade halves being marked out. Note how I have drawn the grid at full-size on the plywood.
Home-cut phosphor bronze plate used to spread the loads from the rudder gudgeon nuts. This is the lower gudgeon mounting viewed from inside the aft buoyancy compartment. It is only dry fitted at this stage, and will be set in bedding compound when fitted permanently.
Marking the top of the rudder blade lamination using a compass
Using a spline to mark out the gentle curves
Using french curves to mark the tight curves
Rudder blade halves spread with WEST System Brand epoxy prior to assembly
Rudder blade halves glued together over a strongback. Note the good squeeze-out, and just after this photo was taken there were bleed holes drilled in the centre portions
I dont know whether these step-by-step photo sequences interest people, so if you feel strongly one way or the other, please let me know. Eventually the website photo pages will get these pictures in thumbnail form, which loads up quickly, and allows you to enlarge only those which are of interest.
Firstly, thanks very much to everybody who wrote in after the previous post. Im very grateful for the responses, and it helps me a lot in deciding if the information on the blog is relevant to the readership, and gives me some indication about whether I should continue writing the blog.
This week, among other jobs, Ive been preparing materials for the hollow "Birds Mouth" mast for First Mate. The timber I selected is Silver Quandong (Elaeocarpus grandis) which is a light hardwood which grows in the coastal areas of northern New South Wales and in Queensland here in Australia. It is an excellent structural timber for small boat construction, taking both fastenings and glue well, and being suitable for steam-bending. It is the same strength (modulus of elasticity) as Sitka Spruce and is very close to the same weight at 500 kg/cu metre (Sitka Spruce is about 440 Kg/cu metre and Douglas Fir is about 540 kg/cu metre).
The particular stock of Silver Quandong Ive got at the moment is unusually dense, and I was concerned that the mast would end up being too heavy. Once the idea got into my head I started having nightmare thoughts, and before long I had convinced myself it was as heavy as Iron Bark and I was ready to throw away two days worth of cutting and machining! In situations like that, the only thing to do is to carry out a test.
All I did was to accurately cut a piece of the material, measure its volume, weigh it, and then calculate the density. The whole thing took me about three minutes using a piece of scrap from the cutting job. The offcut I had on hand was 125.8mm wide, 19.3mm thick, and I cut it to 250mm in length (the sizes are completely abitrary, but must be measured accurately so you can work out the volume). I weighed it on my workshop scales and it came out at 335 grams.
My sample of timber, with the sizes and weight jotted down in red ball-point
0.250m x 0.1258m x 0.0193m = 0.000606985 cu/metre
0.000606985 cu/m = 335gm = 0.335kg
1 cu/metre = 0.335kg/0.000606985cu/m = 552 kg/cu metre
So I discovered that my timber was actually quite light, being about the same as Douglas Fir (Oregon) and lighter than Hoop Pine. Being a very wet 24 hours, the sample was also damp, so its real density is probably a little lower again. The lesson here is not to get fooled by your insecurities - just do a simple test and many problems disappear. Ive applied this principle to many things like testing plywood bonds, paint adhesion, bending strengths of masts etc etc. I always use basic equipment for my testing, but the results are fine for the work I do.
Here are a few pictures showing the method I use for cutting "Birds Mouth" cut-outs: -
Running a mast stave through the table saw for the first cut. Note that I have a homemade finger-board to hold the stave firmly against the wooden saw fence. Accuracy and consistency are important. These staves for First Mate are 16.3mm thick after having been run through a thicknesser.
I finish the cut using a push-stick for safety
This is how the stave looks after the first cut has been completed
Stave has been end-for-ended and the second cut started
The finished cut
Roller-stands are very useful things to have when working alone with long pieces of timber. Ideally, I would like to have a much larger table-saw, or at least a feed-in and feed-out table, but I have neither the money nor the space. However, it is amazing just how much you can do with cheap, second-hand equipment and a buit of determination
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