Still fairing? Goodness no. I'm such a donkey bottom, I'm on the second set of foils... Ahem.
The first were, um, full sized models.
Great shots of the boat, by the by.
Weighed the "13" on the trailer this evening, came in at 280lbs, my calculations before building came in around 300lbs, so im happy with that. Should allow me to add myself and a wee bit of ballast to bring it down on its 1st waterline. We will then see if i crunched my numbers correctly for the next 4 in, which should bring her transom extension down to the water, and extend the waterline another 12in.
Snow and minus temps again in a few days, but hopefully clear by the end of the week. Need to install some pad eyes for lashing down some concrete flooded batteries before testing righting moments.
As a 26 footer, I think it is looking good for internal ballast, with possibly a steel plate shoe.
But gives me food for thought about usefulness as a design with only al little more in length (say, only as much as 16 ft), and in which case the cost implication of a drop keel with ballast bulb might not be a good idea.
It was only ever intended to be a test bed for for a 26ft design. It was only looking around since i got started that i found similar hull weight and possible loadings with some other small boats, Matt Leydons "swamp Thing" in particular, that has even less beam than the 13.
The box should be efficient at leeway prevention off wind and at low speed, it will be interesting to see the difference , if i can accurately measure it, with a board deployed in both vertical and canted positions, should be a substantial difference between stalling angles.The fact this is intended as a "motorsailer" upwind performance is not an essential part of the design, and depending on the box performance, any additional boards might not be deemed the extra work. External steel plate on the bottom has always been the idea with option of extra internal as batteries, water and maybe even lead bricks; I will also calculate the engine as being part of the ballast as it is low and fixed.
Is the box worth the extra hassle to build over a flat bottom in a boat this size? Maybe, depending on your own needs.
The snow was bang on cue, so time to organise some rigging details. I found if i removed the top rudder pin, my longshaft 4hp is a perfect fit.
In "theory" the 2.5hp should have enough power to allow me a S/L of 1.8, but in the interest of science, i should probably try with the 4hp too, with some extra weight.
As a motorsailer, the box keel seems worth the cost and effort in order to accomodate the motor and shaft where their weight contributes to the stability requirement. Thinking about this a bit more…….maybe a steel fuel tank fitted into the box could have
.Assuming the inside of the box is lined with an epoxy/glass skin, this fuel tank could be bedded into it with enough rubberized compound, in such a way as to lend some structural rigidity to the boat spine.
Any comparison to a Leyden design overlooks the lack of a motor’s mass and bulk, or the lack of it in the case of the sharpie hull with chine runners (like Swamp thing or others), despite the roughly similar beam/length proportions.
Useful space within the box keel has interested me for different reasons to motor placement, and any proportional reduction of beam is therefore counterproductive. Meaning, that A beamier hull with a wide box keel is so vastly different to this design of yours, skaraborg, that I would do best to focus on alternative forms.
In fact, a L:B ratio of roughly 2:1 is more like it for me, and I am talking to John W about using some of his plans.
Lug, the box certainly has advantages. At the current state of drawings, requiring as little overall height as possible and yet retain headroom, we have decided not to use the box as storage in the main accomodation, though that might change. Current thinking is to keep the structure as free of "built in" stuff as much as possible, if stuff is easy to remove it is easily serviced not in the confines of the boat, and makes it easier to keep a clean ship. I think a multi laminate sole of perhaps 5 layers, with a steel bolted steel shoe/ballast plate will be plenty stiff enough, and keep the inside free for maintenance. Built in tanks were considered, and decided against in favour of polyethylene.
The Leydon comparison was one of similar length/beam/displacement. Not everyone wants to use a sweep or oars, and many a Paradox fitted with outboards. The extra weight back aft can be easily compensated by shifting a 15l water container up forward.
I have more focus at present on higher L/B ratios in excess of 3, though in the smaller size size of boat that you are thinking of, that can be a restriction that might not be acceptable. Look forward to seeing what you come up with.
The latter option probably means that I need to spend a lot of my time in a drysuit, so the monohull option has been looking more tempting so far. In fact, I have made contact with John Welsford and am working on a plan to get my specific accommodation layout included in a hull built to one of his designs…..which looks to be feasible so far, but really needs to be mocked up in full scale to accurately assess.
Going with the keelboat option grabbed me when I figured that a small craft(one under 15’), would be manageable (by me alone) even with a ballast bulb on a fin keel. But this idea is not being met with favour. My scheme is to keep the hull as light as possible while in the building stage, as well as when being moved to various yards, and to have the keel detachable until after launching, or possibly when preparing for launching at a boatyard slipway.
A planked keel structure that can be packed with lead ballast is what John is offering and in a way is much the same as your box, in that a steel shoe can bolted under it as well. His design is of rather different volumetric configuration to your box though, so useful space is lacking. Given the overall restrited interior space of a 4m long boat my concern with it has much to do with my building space restriction and the need to manhandle without hoisting gear.
I am confident that I can make a solid fibre reinforced resin fin keel ( GRP, possibly with cf stiffening) that does not hamper any lifting of the hull until after the boat is launched.
When afloat, the diminutive size of the craft is in theory given some help in the stability dept, by the increased length of righting lever, along with reduced ballast weight. Sure, loss of shallow draught is the compromise, with a theoretical gain in lateral grip being the upside.
Given the ability or space to build to a greater length and enough beam for useful interior space, I do like your box.
The keel backbone with ballast i first saw on the Australian dinghy design, i think it has its advantages on being able to spread out the ballast distribution. The only downside/compromise was the low aspect ratio of the keel, something it would appear that many are happy to accept for the no hassle of having to deal with a board and a casing in the cockpit.
Have you seen the keel set up on the Q17 by Dobler? Is the fixed keel combination still too heavy for your transport requirements?
Ships cat keeping a weather eye out, and decided to drop the mainsail....
And took a further precaution of dumping the mizzen and setting the trysail......used as a mizzen staysail too.
Pin strip and ports or naked?
I made a push-pull tiller, as it will not interfere with the mizzen.
I think i can get the Mirror main to work with the mizzen well enough to test the daggerboard set up, now i will not be making a one of sail like the poly main. I expect the poly sail would be ok off wind, but the test of the board is more relevent to upwind work.
With Mirror main.
Im not sure if i will be able to rig it so that its balanced well enough, but i thought i could at least try a reefed sail from my Family Skiff.
At the end of a 13 hour session, i do have some numbers to crunch.
I decided to put the boat in the test pool before filling. I then discovered we had a persistant leak half way through filling, and with a shortage of water, either had to stop and pump all the water back out and repair the damage or something else......like an auto float switch bilge pump stuffed into a crevice between the plastic layers and pumped it back in.....this worked out fine, and soon the "13" was floating....
Recalling that i had made the size of the box somewhat larger after model testing, in order to carry more weight aft, she was floating with 4in below the waterline clear....
Completely unstable in this condition and would flop from one chine to the other.......ballast time!
I was not expecting to add 237kg/ 521lbs to bring her down to the waterline, but that is what it took.
I also realised that despite the deepest part of the ditch being at the other end, i did not allow for the subtle slope in the ground, and found i needed to swop ends to float the weight.
Next job was to sort out moments to heel angle.
I made up a tray to carry weights that had arms run under the hatch coaming. I fixed a vertical marked board to that, with a weighted hacsaw blade as a pendulum.
I was running out of compact heavy weights by this time, and resorted to blocks, not ideal, but good enough.
3 blocks at 45kg / 99lbs, gave me 10 degrees of heel.
4 blocks and a roof tile with a total of 63kg / 138lbs gave me 30 degree heel, and chaos when all the unsecured ballast shifted.
Next was to find out how high it would float on its side, in the picture below there is 22kg /48lb, hovering off the ground, the bend in the mast might not appear to be as big as it was, and i feared it was going to snap with me hanging off it.
I had to sit on the mast, 5ft from the deck, and was just heavy enough to hold her down, i think i weighed in at 70kg with my working gear on.
I was hoping to get a better picture of her on the side, but had nothing heavy enough except myself in a position to keep her down. I was expecting 6in of water over the decks, but got 7in at 45degrees, all deck openings clear of the water, but would not stay in this position as currently ballasted, even with me aboard, will spring upright.
So, I have yet to crunch the righting moment stuff. The boat weighed 260lbs and required 520lbs to bring her down to the waterline. The pool was not deep enough for me to check the next 3 inches of waterlines, i had calculated about 160lbs per inch immersion, and below the chine worked out around 130lbs/in. In 26ft mode, this works out at the waterline for a 6240lb boat, almost 2.8 tons with the transom clear, so the extra box area worked out well for extra capacity.
I need to find some more large batterys as ballast, as water is really quite "high", and she could ,in this size, do with being a bit stiffer. With 100kg of ballast, 221lbs and myself on board, it is not possible to roll her 10 degrees from the sitting position, but if one stands up and leans out she rolls down quite easily. Its a bit more ballast than i was expecting to have to use, and this lowers my pounds per hp ratio where an SL of 1.8 is not going to happen with the 2.5hp. Sitting "on deck" with just 100kg of ballast trying to start an outboard i would class as marginally safe......so i have some things to ponder......
I had thus figured that a proper foil laminated in a wooden female mould, using glass, which possibly includes some cf , would be doable. This foil could have the lead bulb laminated on and would have a slightly tapered box at the top. Inserted into a nearly matching box in the hull, this keel is bedded with epoxy ( ensuring release from it’s in hull tapered box housing, and is subsequently pulled home by bolts and a cap on the box case in the hull. It can be removed for modification or for ease of trailer transport, and in theory will provide performance and stability, whilst having negligible intrusion into my planned cabin space.
Downside is the deep draught, which I have come to regard as inevitable in the case of a very small craft having high stability and good windward ability.
Going with shallow draught in comparison to my above design means either increasing ballast weight and keel drag, or maybe even multihull……..if not settling for the Q17 compromise.
Does she need all that ballast? It being tender when upright a problem if you had to lever the mast down so hard to get her sideways? I'm impressed with your thoroughness!