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Thread: A trailerable box keel motorsailer

  1. #1
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    Default A trailerable box keel motorsailer

    For those who are not aware,it all started here:

    http://forum.woodenboat.com/showthre...-Box-Keel-Boat

    Which the developed into here:

    http://forum.woodenboat.com/showthre...-box-keel-boat

    And most recently, here:

    http://forum.woodenboat.com/showthre...ing&highlight=

    So i have been collecting stuff over a period, and feel like at least getting started, if only to clear some of the mess off my desk. I picked up a trailer to shift it, which will need some modifying, but i took a half pattern down to check it would fit between the wheels (it doesnt), and i extended the frame pattern to full size this morning....

    PICT5872.jpg

    Which put the project into perspective, it will have to be assembled outback, as it takes up too much room, and it might take a while to complete.
    I have most of the engine install stuff. The boat is to work around a 330mm/13in Bruntons Autoprop, and i have made an effort to keep the area around the prop clear, and give it good waterflow. I had to double check my drawings to actual sizes, and was a bit miffed to find Vetus had let me down (again) with a keyway on a brand new shaft that was bigger than it should have been, which meant some file work to open up the slot on the prop.

    PICT5875.jpg

    That took all afternoon. My shaft is about 2 1/2in 65mm over length, so i can either cut it, or will look into moving the engine forward.
    Anyhoo, threads have to start somewhere and hopefully it might be helpfull to someone down the road. Apart from the ballast, nothing is cast in stone, so there might be some adjustments and changes as things progress.


  2. #2
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    Default Re: A trailerable box keel motorsailer

    Skara, it would be easier to step the key than the keyway in the prop hub. The birdcage looks good. She is going to be a buxom girlie.

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    Default Re: A trailerable box keel motorsailer

    Quote Originally Posted by rayman View Post
    Skara, it would be easier to step the key than the keyway in the prop hub. The birdcage looks good. She is going to be a buxom girlie.
    I thought about that, but if it needs replacing, i would have to do it again. Also, i have a spare fixed prop with the same keyway, so now i can carry spare keys and props and know they will fit without any file work, but thanks! The birdcage view was not the final deal, and has been tweaked since.

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    Default Re: A trailerable box keel motorsailer

    If you need some foils, I know a guy. Hell need about a three year lead time, but, boy, what a rudder blade!

    She looks great. Are you done, yet?

    Peace,
    Robert

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    Default Re: A trailerable box keel motorsailer

    Ha! Shall i get round to sizing the rudder now and send you the details? No, not really done yet, i will get the keel plank set up with stem and stern knee, and hopefully the frames too, this winter. I will need to clear out back to lay a keel jig.
    My biggest issue at the moment is where to split the 3 layer keel. I could keep the bottom two layers off, with the ballast stub fitted and glass the entire lump, then bolt and bond it to the bottom of the floor, meaning the boat gets built on 1in planks. I think with support that would be fine. It would make it much easier to glass upside down and easier to turn without the ballast. Im not going to attempt sheathing the right way up, but im thinking i would rather have that concrete lump encapsulated in the dead wood, rather than just bolted up on bedding once the hull is turned.
    Im thinking way out in front, space out back is restricted for movement, and although that ballast stub only weighs around 400lbs, that on top of a planked up hull is not something i will be flipping as easily as its little brother. Having said that, the bottom could be planked, sheathed and painted and then turned before the side planking goes on, the sides being almost vertical that sheathing will be messy anyway, and might very well be done on a bench, in 8ft lengths, prior to fitting. Sometimes writing stuff down helps with the thought process......gratefull for the question, makes one think, reason enough for the project to keep ones mind focused on something.

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    Default Re: A trailerable box keel motorsailer

    That description of the keel is about as clear as mud to anyone not reading my mind. I will do a sketch of the intended fabrication.

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    Default Re: A trailerable box keel motorsailer

    Id be tempted to leave the concrete unsheathed. Better to just bolt that big old slab on, especially if you decide you want to change it later...

    I really cant wait to see the full sized version. The mini was cute.

    This is a case where the design constraints co tributes to a certain charming beauty, I think.

    Enjoy!

    Peace,
    Robert

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    Default Re: A trailerable box keel motorsailer

    Not to scale, but should give the idea....

    PICT5877.jpg

    Layer 1 will be held together with floors for the keel bolts and other cleats, temporary if needed. Planking will fasten into this layer, so it will need some bevel work, and so easier done with nothing fixed below it. 2 and 3 will be slightly wider to cover any plank edges, and the two are equal in thickness to the ballast casting.
    Thoughts: Through fastening to the stem and stern knee, most likely to be set in epoxy and bolted, but heads will be forever buried under another 2in of wood, also sheathed. Have to say now, not being built as an heirloom, and the bolts are only backing up an epoxy bond anyway, i think i can sleep ok with that.

    My only concern at present is if 2 and 3 are assembled as one unit and fully sheathed, i really do not want to be lag screwing into it from the bilge side. I could perhaps epoxy some studs into the top of 2, and have more floors inside. Nice as it would be to have the keel face as a clear walking sole, the bolt-on casting and frames need something to fasten to, and if it is all bolted, then perhaps something less than epoxy could be used between 1 and 2, though i cant ever imagine having or wanting to take it off once its all together. The concrete could be taken out with the aid of a grinder from the bottom, i dont ever see me doing it, but i think having that option is worth having.......should i want to replace it with lead.
    Anyhoo, this will be the first timbers cut.

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    Default Re: A trailerable box keel motorsailer

    Quote Originally Posted by amish rob View Post
    I’d be tempted to leave the concrete unsheathed. Better to just bolt that big old slab on, especially if you decide you want to change it later...

    I really can’t wait to see the full sized version. The mini was cute.

    This is a case where the design constraints co tributes to a certain charming beauty, I think.

    Enjoy!

    Peace,
    Robert

    I have thought about it, still thinking about it. Sticking all the timber together as one unit and sheathing it all, in situ, rather than seperately might be better. The skin thickness of the crete over the re-bar is not excessive, and im sure 30oz of glass over it will help bouncing over rocks. I could still sheath the bottom, just need something to seal around the edges and inside face, bitumen compound might be ok for that. Its that gap between the keel and the timber that concerns me, and i did not want to leave any edges that could "peel". Baring in mind it would need to be jacked up to clear the keel bolts should one decide to drop it, that would give enough space for a grinder and a cutting disc to cut the glass between the concrete and wood.
    I dont want to over think it to the point of not moving forward, but at the same point, i really dont want to do it twice! Not that i am in any rush.

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    Default Re: A trailerable box keel motorsailer

    I would plank layer number two crosswise and glue everything with epoxy. Giant 3 layer plywood if you like.
    I would install the garboard on the first layer, fiberglass tape the joint, glue up the second layer and continue building the boat. All bolts end here. Layer 3 after everything is done, covering all bolts. Fiberglass the entire ballast cutout and seal the ballast bolts with butyl tape. No bedding required for the ballast, just paint and you can drop it any time you like.

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    Default Re: A trailerable box keel motorsailer

    Thanks Rumars. My concern with layer 2, if the planking was run in the opposite direction was lots of exposed end grain, but more seriously, a possibly weaker structure down the sides of the ballast casting where its only 4in wide, so i was thing Vendia type plywood might be a better option? Although no reason i could not use long cheek pieces down the side of the casting, and the cross plank fore n aft of that.
    I would glass the entire inside cut out anyway, even if the bottom was glassed over. There still needs to be some kind of soft caulk to seal the edges to stop mud, sand,stones or barnacles getting in between the casting and the glassed timber .
    Regarding bolts. Im sure many would be happy with just epoxy with fixing down floors, but i like the idea they are there, i would sleep better, and if going through 2 layers, it would leave enough to sink the heads and have more material for it to pull through. This is one area where oversize holes filled with epoxy and studs inserted would seem to make sense, if the faith in epoxy is absolute. All floors, aft knee ,engine beds and stern tube to be fitted while flat on trestles.

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    Default Re: A trailerable box keel motorsailer

    Endgrain is not a problem, you can rebate and glue a thin batten all around, or just thickened epoxy and glass over it. You have not said what you are planing to build the bottom (and boat) out of, if solid wood planking what species. If I understand correctly the ballast is 2 inches thick, so we are talking 3 layers of 1 inch thickness? With ply or solid wood sides? Does the keel have any sort of rocker or is it dead flat?
    If you plan to glass over the ballast anyway you can use some XPS foam wedges tapped in place between ballast and keel sides. Just sand them flush and glass over the whole thing. If not then the bedding compound needs to reliably adhere to the gap and that complicates ballast removal. Sikka 11fc is cheaper than the marine variant. Bitumen might crack in the cold.

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    Default Re: A trailerable box keel motorsailer

    The keel plank will be planks of fir. Its dead flat in both directions. Yes 3 layers 1in. Plywood planking on stringers. Foam wedges would work. The issue with leaving any sort of gap is moisture forming in it, especially with the temperture difference we have here. I can build the 3 keel planks up before committing myself. I was intending to have heavy cloth on the bilge to keel panels, inside and out. I do have some of that 6mm blue foam used for underfloor insulation.

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    Default Re: A trailerable box keel motorsailer

    Thanks for the details. Plank the middle layer crosswise, it adds immensly to the strength. Ballast sides can be lenght or crosswise. Blue foam is ok, just wedge it in tightly on the sides. Could be glued to either the ballast or the keel on one side. Even if you glue it to both it is easy to remove with some acetone, paint thinner or gasoline (it eats the foam, just spray it on) or a knife (preferably hot).

    Now I know what I will propose next is subject to local budget constrains, so it's only an idea, and how I would imagine the structure.
    Keel bottom buildt out of 2 layers of 40mm baltic birch glued with thickened epoxy. No screws used during glueup, just some blind dovels for alignment an weighted down with the actual ballast. Planking bevel cut beforehand into the first layer according to lofting. Does not need to be perfect, thickened epoxy to be used, fillet taped over. Ballast covered with 4mm foam to fill the gap, then glass over the whole bottom. Keelbolts installed trough holes lined with fiberglass tubes, sealed with butil tape.
    Stem, sterpost and frame futtocks get fastened to the keel plank as follows: 40mm ply knees (offcuts from the bottom) fitted with stopped sliding dovetails 50mm deep, glued with epoxy, fileted and taped. Frames get one knee only, stem and sternpost two (one either side). Hardwood frame futtocks, stem and sternposts get glued and bolted to them. Floors only where the keelbolts are, screwed and glued to the same knees. Engine bearers also use knees that get mortised into the keelplank, one at each end. The whole bottom then gets glassed on the inside also. Engine bearers and floors come on top of the glass sheating, glued to it with D4 PU. This allows the use of difficult to glue hardwoods like oak and exotics from the exterior decking department.
    This arrangement allows mechanical strength (dovetails) without any fasteners embeded in the keel plank. All bolts are available for inspection and replacement. Hot dipped galvanized machine bolts with big washers would be my choice.

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    Default Re: A trailerable box keel motorsailer

    Thats a detailed thought i have to say. Alas, while down the timber yard for another purpose, i find a new delivery of almost 6m lengths of sawn 8 x 1 . The use of ply would be a really expensive option.I have mentioned it before, but i can buy the same local product in London, cheaper than here where it is produced, sadly.
    The stopped sliding dovetails are a novel idea, i was just going to go for a plain rebate for the centre section of a 3 laminate stems, through bolted. I may not need ply cheeks depending on layup. Heres a picture of a stern post i laid up before, will probably use the same system for the stems, but likely have a laminated plank face for a "soft" bow nose, wider at deck level but narrow at the waterline. At least that has been the current thought.



    With the thought of wrapping the whole keel and ballast in glass, i was considering drilling oversize holes in layer 1 (i note one of my bolts was not 100% vertical, so the holes will have to be bigger), and then fill the holes with epoxy at the time of fitting the keel bolt floors, this is most likely whether its fully sheathed or not.
    Interesting idea of using futtocks, but no floor, i guess it they are made with sufficent siding it might make the floors a moot point, on a bottom this thick. Anyone else want to input on that idea?

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    Default Re: A trailerable box keel motorsailer

    Plywood is unfortunatley expensive, I do know that. Laminating solid planks should also work.
    The way your stem looks in the photo would be almost exactly how I would cut the first frame futtock/cheeks, only with a long dovetail instead of a short tennon. Do you plan on laminating the frames the same way? Meaning glued double sawn? If yes you can still dovetail. What dimensions are you planing for them?

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    Default Re: A trailerable box keel motorsailer

    Im currently thinking the frames will be made from "off the shelf" 2x4. I see no reason to be laminating frames in a single chine chine hull, though the corners could be lapped with a single gusset added, i was thinking of going double gussets with filler blocks, at least on the 4 ,master frames. Most likely "floating frames", notches cut for the first layer of stringer, and subsequent stringer/s laid on top, plywood planking fixed to stringers only, not frames. The forward an aft water tight bulkheads frames will be packed out.
    I am reminded of someones comment on the Wharram cat thread regarding too much wood where much weight could be saved with clever joinery. I am aiming for a self supporting hull that does not require built in furniture to act as part of the hull structure.

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    Default Re: A trailerable box keel motorsailer

    Why notch the frames at all if you want them floating? Just bevel the frame with a rasp where the stringer lands and be done with it. Epoxy and a screw will hold the stringer in place just fine.
    I would always lap, glue and gusset the frames. Solid wood, plywood or metal gussets.

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    Default Re: A trailerable box keel motorsailer

    Quote Originally Posted by Rumars View Post
    Why notch the frames at all if you want them floating? Just bevel the frame with a rasp where the stringer lands and be done with it. Epoxy and a screw will hold the stringer in place just fine.
    Fair comment.I did not notch frames on the half scale "13" , but the forwars frame had quite a bit lopped off for the battens to run fair.My drawings are all to outside of plank, so i have to think about stringer and plank thickness while laying out the full size frame patterns. I neglected this on the 13, which is why the plywood sheet for the decking was just too short. I will bring in the side frames so that the deck can be planked with a full 8ft sheet......having said that, i think i might have a batch of 2.5m sheets that would allow an extra 2 1/2in.

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    Default Re: A trailerable box keel motorsailer

    I've been looking forward to this thread!

    /Fredrik

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    Default Re: A trailerable box keel motorsailer

    Hi Fredrik, been a while coming and unlikely to be at my usual pace. Having said that, i went back to the timber yard this morning and pulled out the longest lengths i could find. The centre plank on the upper layer will have to have a bit added, but otherwise, everything has come out of single planks. Heres the bottom layer..

    PICT5882.jpg

    The slot for the ballast is cut for length, but not width; its likely to be hanging around for a while yet, so i try to keep it as rigid as possible before it gets glued up. I have used one half of the keel plank as a pattern for all four pieces. I will after a bit of thought cross plank the middle layer, i just need to lay out the planks so bolts come up through the middle of a plank .
    Im double -double checking my frame sizes so the top layer can be cut more or or less close to the bevel needed. I could just cut it square and short and back fill with epoxy, but thats going to run up a large amount of epoxy on a project this size , but not as much as yours Fredrik! When you have a 30kg drum of resin lying around, sometimes the thought of spending hours on a joint seems a bit weird, but i prefer making shavings over epoxy dust, there will be a lot of that further down the line, unless i invest in some peel ply. The ball is rolling.......

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    Default Re: A trailerable box keel motorsailer

    Congratulations for the first wood.

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    Default Re: A trailerable box keel motorsailer

    For starters Ian, I cannot see why the bottom of the keel box needs to be more than one plank thick..... bolts run through (the planks that shown already cut and shown above) will do as good a job of supporting the bottom, as the bulky low density timber cross pieces that are also shown in the sketch.
    these bolts or galv threaded bar can be used to fasten the box sides as well.
    By eliminating extra bulky timber from the box, space is allowed for either ballast or foot room.
    Along the same thought line ( to create space in the box), I suggest a rebate in the box side plan, that makes for plywood to continue up to the chine where the garboard meets.
    framing can be reinforced at this junction, by a heavy laminate of double diagonal glass ( on inside/top of chine0, along with bundles of roving laid inside the 'fillet' where the quasi futtocks lap the upright frame member on box inside.These laminated 'knees' in situ with the frame junction, should help the hull become a stand alone structure.
    Plywood gussets at the chine where futtocks meet timbers, should brace the frame well enough.
    So the frame starts off in the side of the box, being a small section timber, then laps a deeper frame member at the garboard keel junction and then remains as you show in the pic, but with a ply gusset at the frame junction/lap, where the chine is.
    Last edited by Lugalong; 11-18-2018 at 02:37 AM.

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    Default Re: A trailerable box keel motorsailer

    Thanks Rumars, i wrote a lengthy response that seemed to have not been posted!

    Lug, no reason it could not be from one plank, if it was 3in thick. I note most of the Atkin boats had keels from solid bits of greenheart,white oak or yellow pine. External ballast was an addition to some of the plans Atkin drew, in addition to internal ballast, so im hoping to have the floor mostly clear of ballast. I need to keep the external bottom flush for ease of sliding on-off a trailer. Having 2in of keel below the garboard planking helps keep the planking off the bottom, should i need to scrub and paint while dried out. I would have settled for 2in had i been able to get the 1in steel plate i was after as ballast originally, but the extra in is external, so i do not lose anything inside.
    That top most layer 1, has sides 16mm less than the 2 keel planks below it, that acts as the rebate for the ply planking, having 2in below this gives a good surface for tape that wont be subject to as much abrasion, as if it was wrapped around the bottom edge of a single plank. Similar to what i did on the 13, though that was only 2 layers.







    I was surprised that Rigadogs seabright 33 was specified with a glassed 12mm ply bottom. It may have a lot of internal floors, but it did not seem too thick given its displacement. Given that the boat will get hauled with all its weight on this backbone keel, im happy with the compromises involved.

    Im happy to talk about different joints, but that will have to wait till later.......i need to make some sawdust. Thanks for the comments.
    Last edited by skaraborgcraft; 11-18-2018 at 03:59 AM.

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    Default Re: A trailerable box keel motorsailer

    Still cutting wood only. Its below freezing out there, so no epoxy. Top layer middle plank was a couple of feet short, so needed an an extension....

    PICT5887.jpg

    And the side planks were taken down in size compared to the next layer down...

    PICT5885.jpg

    to allow for 2 layers of 5-ply 7mm plywood below the chine. I will have to adjust the frame layout when i lay them down on a sheet of ply.

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    Default Re: A trailerable box keel motorsailer

    I bought a roll of 450gr bi-ax cloth especially to deal with the joints at the inside keel-sole, and the top of the box-garboard joint. It could be done stitch and glue style, but i think i need a batten in there to pull the ply home to its correct shape, though it could be glassed external, and then the batten removed, internal edges rounded then glassed.
    My next cutting project will be for the aft end stern posts, shown here the way it was usually done...

    PICT5889.jpg

    And my first thoughts of how i might do it.

    PICT5890.jpg

    I could add large cheeks again over the joints, and pass the bolts through these, or even just stack 2in timbers on top of each other with a ply gusset either side. Shaft runs in a fibreglass tube, i will stick a half height bulkhead at the other end to securely locate the forward end of the tube, which will be fitted with a flexible seal.

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    Default Re: A trailerable box keel motorsailer

    Quote Originally Posted by skaraborgcraft View Post
    Still cutting wood only. Its below freezing out there, so no epoxy. Top layer middle plank was a couple of feet short, so needed an an extension....

    PICT5887.jpg

    And the side planks were taken down in size compared to the next layer down...

    PICT5885.jpg

    to allow for 2 layers of 5-ply 7mm plywood below the chine. I will have to adjust the frame layout when i lay them down on a sheet of ply.
    Disregard what I said in the post above.... it was based on the assumption that sides of the box would be thick planks that needed persuasion in bending onto the base planking.
    Since you are doubling the ply, it changes things.
    All along I was under the impression that a steel plate shoe would be going on the bottom, so that an external epoxy/glass skin would wrap the box.

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    Default Re: A trailerable box keel motorsailer

    No worries lug. The intended steel plate was cast aside over cost issues, but i am still thinking of wrapping the whole thing in glass epoxy. If i need additional ballast, simple enough the nail layers of lead sheet direct to the floor, the difference in headroom would be minimal.

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    Default Re: A trailerable box keel motorsailer

    I got the first scarph joint in the top plank set up under a heat lamp a few days ago. With the daytime temps at zero, and well below freezing at night, and while the lady of the house is absent, i snuck the keel planks into the new conservatory for assembly.

    PICT5895.jpg

    I will have to get some heat out there, and done during the day. I will probably do one half at a time as its a 19ft glue joint either side.

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    Default Re: A trailerable box keel motorsailer

    Haha. Youngest Son was marveling the other day at temps of 20f. How do they live? Hahaha.

    Im sure hell disbelieve it gets below zero where you live.

    Peace,
    Robert

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    Default Re: A trailerable box keel motorsailer

    Ha! might very well be a white out at the end of next week, so hope to get the gluing up done before that happens.

    PICT5897.jpg

    Its been there all day, its only 5pm.......

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    Default Re: A trailerable box keel motorsailer

    Quote Originally Posted by skaraborgcraft View Post
    No worries lug. The intended steel plate was cast aside over cost issues, but i am still thinking of wrapping the whole thing in glass epoxy. If i need additional ballast, simple enough the nail layers of lead sheet direct to the floor, the difference in headroom would be minimal.
    get ya, scar, its just that I am thinking it to be a good idea epoxy/glass skinning the inside of the box as well.... this is were water is going to gather and be the 'bugbear' where a composite outer skin traps moisture.
    Also, can't see why the steel shoe cannot be made from scrap pieces welded together into a plate. This could have a flat bar lip (upturned) on the edge, that can use screw fastenings to hold it on, along with a bolt or two near the ends.
    Shoe surely doesn't have to be more than 10mm thick?, if there is going to be lead internal ballast as well.

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    Default Re: A trailerable box keel motorsailer

    Quote Originally Posted by amish rob View Post
    Haha. Youngest Son was marveling the other day at temps of 20f. “How do they live?” Hahaha.
    Amusing! When I taught in northern Wisconsin, schools would close if it got "too cold"--which meant, colder than -40 F (wind chill).

    Tom
    You don't have to be prepared as long as you're willing to suffer the consequences.

    www.tompamperin.com

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    Default Re: A trailerable box keel motorsailer

    Quote Originally Posted by Lugalong View Post
    get ya, scar, its just that I am thinking it to be a good idea epoxy/glass skinning the inside of the box as well.... this is were water is going to gather and be the 'bugbear' where a composite outer skin traps moisture.
    Also, can't see why the steel shoe cannot be made from scrap pieces welded together into a plate. This could have a flat bar lip (upturned) on the edge, that can use screw fastenings to hold it on, along with a bolt or two near the ends.
    Shoe surely doesn't have to be more than 10mm thick?, if there is going to be lead internal ballast as well.
    I agree with glassing inside the box, that will be my intention up to the chine, obviously the lowest point is right aft, but i will make some kind of dam before the aft stern post, as this is where access might be difficult.
    I could not get the steel, or rather i chose not to pay for it. The local supplier is asking 5 times the going rate, plus a cutting and loading charge. Due to recycling and enviromental stuff, there is no local scrap metal dealers you can just walk in and buy stuff, hence the concrete and re-bar keel, its not ideal, but not everyone might have access to all this stuff anyway or the budget for lead. Im still putting in the same amount of minimal ballast in the keel, its just spread further out, which is no bad thing.
    Edit. A full length steel shoe would be nice, but it carries its weight too close to the ends, so a fully glassed bottom seemed to make more sense, and easier to look after than a steel plate that will always be difficult to access and forever bleeding rust. I have a roll of CSM ,rovings and cloth, better to put it on the bottom of the keel that it sitting around taking up space!
    Last edited by skaraborgcraft; 11-24-2018 at 02:56 AM.

  35. #35
    Join Date
    Jan 2010
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    Northern Europe
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    Default Re: A trailerable box keel motorsailer

    Whilst waiting for the room to warm up for gluing, i decided to weigh the ballast stub.

    PICT5899.jpg

    Using a bathroom scale, a steel tube as an axle and a bit of 4x4

    PICT5900.jpg

    Measure the weight, then shift the load back.

    PICT5901.jpg

    measure the weight again. First reading minus second reading in pounds X the length of pivot arm from roller to scales, divided by the amount moved in inches. Gave me a nominal 423lbs/192kg over several measurements. The left over re-bar i could not pack in would have taken me to the 200kg i was aiming for. Good enough!

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