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Thread: Lofting the Brewer catboat

  1. #5216
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    Default Re: Lofting the Brewer catboat

    Quote Originally Posted by RFNK View Post
    Thanks! Never heard them called that.

    Rick
    Rick, if I recall, they were used to attach fenders ( over the tires ) to automobiles, and were made large to allow some adjustment for gaps between fenders and doors and hood / trunk (bonnet ? )

  2. #5217
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    Default Re: Lofting the Brewer catboat

    Makes sense. I looked it up and they're also called mudguard washers. I use them quite a lot but I call them 'those big washers with a little hole'. Not anymore though!

    Rick

  3. #5218
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    Default Re: Lofting the Brewer catboat

    I thought they might have been different again from a Les Paul washer, and a Gibson washer, and an entirely different animal than a Stradivarius washer. Dirty instruments need cleaning y'know...
    Jarndyce and Jarndyce

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  4. #5219
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    Default Re: Lofting the Brewer catboat

    Let us consider for a moment the rub rail, or guard, or what have you. We all know what's meant so there's no point quibbling.

    Simple stuff, a half round or trapezoidal sectioned length of material, sometimes capped with metal and fastened to the top of the sheer plank, something to come between a barnacle encrusted piling and your fresh painted topsides.

    If you're building a barge you can just run them through the table saw and fasten them on. Same goes for a boat with the same flare fore and aft, like a dory, the same cross section works anywhere on the hull.

    When the hull shape gets more complex, where the topside flare changes, then things get interesting. Add in some tumblehome and the single-sectioned rub rail might become unworkable.

    A trapeziodal section rail consists of four elements, a wide back that fits up against the sheer plank, a sloped top face that sheds water outboard, a narrow outer face where the metal band is fastened, and a heavily sloped lower face, heavily sloped to reduce the chance of hanging up on an obstruction.


    Consider the sloped top face. There's a narrow window of ideal angles, too shallow and the water doesn't drain, too much and the available material needed to make the bottom face angle upward is reduced. I'm going to go out on a limb here and say that ten degrees is the ideal slope for the top face.


    Skipping ahead, lets divide up our catboat sheer into six equal bits and draw what the rub rail should be at each section. From the photo it should be readily apparent that one cross section can't work, from the tumblehome bow on the left, through the flared mid-section, and into the heavily tumble homed aft section.

    This is enough to get going on. You can see the changes in the angle of the sheer plank. The top angle is a consistent ten degrees. The outer face is plums and wide enough for the metal band. The bottom angle changes to make up the difference.

    There is also the matter of taper, both in height and thickness, but a lot of that gets planed in later.

    Jim


  5. #5220
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    Default Re: Lofting the Brewer catboat

    So why not just go with a half-round and be done with it?


    That's a mighty fine coffee cup. Nice wide base to resist spillage.
    There's the plan, then there's what actually happens.

    Ben Sebens, RN

    15' Welsford Navigator Inconceivable
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  6. #5221
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    Default Re: Lofting the Brewer catboat

    Quote Originally Posted by BBSebens View Post
    So why not just go with a half-round and be done with it?

    Hiya, Ben. There's no actual difference between the behavior of a half-round or a trapezoidal cross section in these circumstances. I believe that half rounds should be relegated to craft under sixteen feet, and even then some tweaking of the cross section would be beneficial in a lot of cases.

    Look at the far right section in the above photo, the one labeled "A". That represents the maximum tumblehome by the transom. Imagine a half round applied to the hull side here. It would be pointing distinctly upwards while creating a gutter for water against the hull side.


    Anyhoo...diagram in hand it was the work of mere minutes to rip out a corresponding set of sample sections and tack them up to see how they looked.


  7. #5222
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    Default Re: Lofting the Brewer catboat

    Remarkable progress, thanks for the update and the tutorial behind the rubrail profiles

  8. #5223
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    Default Re: Lofting the Brewer catboat

    "There is also the matter of taper, both in height and thickness, but a lot of that gets planed in later."

    What would it look like if the bottom edge of the guard narrowed out at the ends of the boat? I'm thinking more in profile, but I expect you might taper in plan view also for balance. I think this might another place where the art aspect comes into play. Looking forward to your process regarding this task at hand. / Jim

  9. #5224
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    Default Re: Lofting the Brewer catboat

    A few years back I ripped four strips off an Angelique flitch. The strips finished up at an inch and a half thickness and were over three inches wide. They've been underfoot ever since, so it will be good to get them fashioned and fastened on. Two of the strips became the toerails, as we have seen.

    We're going to start by working one edge, the top edge. The back of the rubrail will be one of the wide faces of the strip, a little flattening with the plane and we're good. The top edge of the rail will be cut on one of the edges of the strip.

    Excuse me for posting the same picture twice but it might be instructive in following the process. As can be seen, the top edge is holding the same declivity on all the stations, while the topside of the hull is winding from tumblehome to flare and back to a more pronounced tumblehome at the stern.







    The top edge, in relation to the back needs to be planed in in much the same way as you would a beveled plank edge. You pick up the bevels, cut corresponding flats on the edge of the stock, connect the series of flats with a long batten, remove the waste and plane smooth.

    Which is what is going on in this photo. You can see the flats chiseled into the edge, the flat in the foreground being the heaviest cut where the aft tumblehome occurs. The batten has been clamped in place and a line about to be marked.

    The second rail can be seen patiently waiting behind.



  10. #5225
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    Default Re: Lofting the Brewer catboat

    I love how you have pieces of wood squirreled away for years, just waiting for the moment to reemerge into the light.
    I was born on a wooden boat that I built myself.

  11. #5226
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    Default Re: Lofting the Brewer catboat

    Quote Originally Posted by Jim Ledger View Post
    A few years back I ripped four strips off an Angelique flitch. The strips finished up at an inch and a half thickness and were over three inches wide. They've been underfoot ever since, so it will be good to get them fashioned and fastened on. Two of the strips became the toerails, as we have seen.

    We're going to start by working one edge, the top edge. The back of the rubrail will be one of the wide faces of the strip, a little flattening with the plane and we're good. The top edge of the rail will be cut on one of the edges of the strip.

    Excuse me for posting the same picture twice but it might be instructive in following the process. As can be seen, the top edge is holding the same declivity on all the stations, while the topside of the hull is winding from tumblehome to flare and back to a more pronounced tumblehome at the stern.







    The top edge, in relation to the back needs to be planed in in much the same way as you would a beveled plank edge. You pick up the bevels, cut corresponding flats on the edge of the stock, connect the series of flats with a long batten, remove the waste and plane smooth.

    Which is what is going on in this photo. You can see the flats chiseled into the edge, the flat in the foreground being the heaviest cut where the aft tumblehome occurs. The batten has been clamped in place and a line about to be marked.

    The second rail can be seen patiently waiting behind.


    Bearing in mind the tumble home in the stern, and if the shear strake is shaped to create that curve, will backing out the faying surface be of benefit?
    If the guard is only screwed on, backing out will facilitate using mastic between guard and plank as well.
    It really is quite difficult to build an ugly wooden boat.

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  12. #5227
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    Default Re: Lofting the Brewer catboat

    Perhaps it's an optical illusion, but to my eye it appears that the slope of the top surface increases at the bow?

    Maybe because it's already sloping downward (aft) the additional 10-degree slope is magnified?

    I love a good mockup!
    No adversary is worse than bad advice.

  13. #5228
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    Default Re: Lofting the Brewer catboat

    I wanna know whats in all those drawers??

  14. #5229
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    Default Re: Lofting the Brewer catboat

    Good thing, that patient timber!

  15. #5230
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    Default Re: Lofting the Brewer catboat

    Quote Originally Posted by Figment View Post
    Perhaps it's an optical illusion, but to my eye it appears that the slope of the top surface increases at the bow?

    Maybe because it's already sloping downward (aft) the additional 10-degree slope is magnified?

    I love a good mockup!


    You can't beat a mockup for this kind of detailing, Mike, anything to get off the paper and into the realm of what you can see and manipulate.

    As far as the illusion goes you might be right, things might not seem as they are, but you have to trust the bevel gauge and level to establish a baseline. I worried about the same thing, that the angle of the top surface was somehow off. To test this I made a small wedge of wood at a ten degree angle, placed it atop the samples and put a level on it to see if the angle was correct. Even allowing for the rough nature of the test the results were close to what was wanted.

    Keep in mind that the sections drawn out represent a slice of the rail taken normal to the curve of the sheer plank, which translates directly to the piece being cut. This is the real working angle in this case, but might not be what the eye sees from all angles.

    Jim

  16. #5231
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    Default Re: Lofting the Brewer catboat

    Quote Originally Posted by Rich Jones View Post
    I love how you have pieces of wood squirreled away for years, just waiting for the moment to reemerge into the light.
    I had to cut a hole in the end of the boathouse to withdraw the pieces, with so much stuff built and piled on in the intervening years it was the easiest thing.

  17. #5232
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    Default Re: Lofting the Brewer catboat

    Quote Originally Posted by willin woodworks View Post
    I wanna know whats in all those drawers??
    Gotyer paint roller drawer there, the caulking drawer, several filled with electrical and plumbing bits, bronze casting drawers, cabinet parts drawers. Half of them's empty still, like an unfinished portrait, whodathunk?

    Jim

  18. #5233
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    Default Re: Lofting the Brewer catboat

    Quote Originally Posted by Peerie Maa View Post
    Bearing in mind the tumble home in the stern, and if the shear strake is shaped to create that curve, will backing out the faying surface be of benefit?
    If the guard is only screwed on, backing out will facilitate using mastic between guard and plank as well.

    Yup, Nick, you're right on that one! The aft section of the rail will definitely have to be hollowed on the back to fit against the sheer plank.

    Jim

  19. #5234
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    Default Re: Lofting the Brewer catboat

    Quote Originally Posted by Aquinian View Post
    Good thing, that patient timber!

    Aye.

  20. #5235
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    Default Re: Lofting the Brewer catboat

    Iím gone ten minutes and I come back to find weíre talking about Jimís drawers?

    Peace,
    Rub Railington, Esq.

    Nice to see you back at it.

  21. #5236
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    Default Re: Lofting the Brewer catboat

    Quote Originally Posted by amish rob View Post
    Iím gone ten minutes and I come back to find weíre talking about Jimís drawers?

    Peace,
    Rub Railington, Esq.

    Nice to see you back at it.
    Nice to be back, Rob, a few well-earned days in the cold wading through chips. Life is good.

    Speaking of drawers, here's a peek into the roller tray drawer. You have to open a drawer to clamp anything down on this bench. A minor annoyance.

    This is the bottom face getting roughly beveled off. The outer face, facing the camera, has been marked to width using a piece of the brass half round. Everything between the line and the far top corner is being removed, first with a slick followed by a plane.

  22. #5237
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    Default Re: Lofting the Brewer catboat

    Here we are...just shy of a finish planing and ready to fasten onto the boat. The fastening-on will be a two-step project, an initial fastening where all the holes get bored, and then removal of the piece for final planing and sealing. The sheer plank needs to be faired and sealed prior to the final installation of the rails and then there's some sealing of screw holes needs doing as well.

    The twist worked into the rails to compensate for the aft tumblehome can be seen clearly here. The twist is continuous all along the length, although to a lesser degree.



  23. #5238
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    Default Re: Lofting the Brewer catboat

    Would a reasonably bendy wood like white oak fit the hull without having to do the rolling angle changes?

    Well, after looking at it more you are right of course. Even if the base would bend to fit the hull, the same shape fore to aft wouldn't work. Nice work as always!
    Chuck Thompson

  24. #5239
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    Default Re: Lofting the Brewer catboat

    Hi Jim hope you are feeling well.

    First of all I apologize to the Posters who were rightly outraged by my trying to provoke Jim to put more effort into his build. I would not have been so insensitive if I had known of his ongoing health problems until I was informed by PM.

    Thanks for that Steven.





    [QUOTE=Jim Ledger;5747730]Let us consider for a moment the rub rail, or guard, or what have you. We all know what's meant so there's no point quibbling.

    Simple stuff, a half round or trapezoidal sectioned length of material, sometimes capped with metal and fastened to the top of the sheer plank, something to come between a barnacle encrusted piling and your fresh painted topsides.

    If you're building a barge you can just run them through the table saw and fasten them on. Same goes for a boat with the same flare fore and aft, like a dory, the same cross section works anywhere on the hull.

    When the hull shape gets more complex, where the topside flare changes, then things get interesting. Add in some tumblehome and the single-sectioned rub rail might become unworkable.

    A trapeziodal section rail consists of four elements, a wide back that fits up against the sheer plank, a sloped top face that sheds water outboard, a narrow outer face where the metal band is fastened, and a heavily sloped lower face, heavily sloped to reduce the chance of hanging up on an obstruction.


    Consider the sloped top face. There's a narrow window of ideal angles, too shallow and the water doesn't drain, too much and the available material needed to make the bottom face angle upward is reduced. I'm going to go out on a limb here and say that ten degrees is the ideal slope for the top face.


    Skipping ahead, lets divide up our catboat sheer into six equal bits and draw what the rub rail should be at each section. From the photo it should be readily apparent that one cross section can't work, from the tumblehome bow on the left, through the flared mid-section, and into the heavily tumble homed aft section.

    This is enough to get going on. You can see the changes in the angle of the sheer plank. The top angle is a consistent ten degrees. The outer face is plums and wide enough for the metal band. The bottom angle changes to make up the difference.

    There is also the matter of taper, both in height and thickness, but a lot of that gets planed in later.




    Jim it looks to me that the bevels you have arrived at are taken on a horizontal plane which leads to inaccuracy as the path taken by the timber has to follow the Sheer line in an upward direction taking it away from the horizontal plane too.

    It may be that that particular build has very little Sheer but even then it alters things in my experience.??
    Last edited by Chippie; 12-09-2018 at 08:15 AM.

  25. #5240
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    Default Re: Lofting the Brewer catboat

    Quote Originally Posted by chuckt View Post
    Would a reasonably bendy wood like white oak fit the hull without having to do the rolling angle changes?

    Well, after looking at it more you are right of course. Even if the base would bend to fit the hull, the same shape fore to aft wouldn't work. Nice work as always!

    The Angelique bends quite easily once it's reduced to it's final dimension, Chuck. There will be some clamping problems near the bow, but I suspect they will be solved without too much trouble. Alongside the cabin and cockpit opening the rail can be clamped up with bar clamps going to the inside of the deck.


    Quote Originally Posted by Chippie View Post
    Hi Jim hope you are feeling well.

    First of all I apologize to the Posters who were rightly outraged by my trying to provoke Jim to put more effort into his build. I would not have been so insensitive if I had known of his ongoing health problems until I was informed by PM.

    Thanks for that Steven.

    Jim it looks to me that the bevels you have arrived at are taken on a horizontal plane which leads to inaccuracy as the path taken by the timber has to follow the Sheer line in an upward direction taking it away from the horizontal plane too.

    It may be that that particular build has very little Sheer but even then it alters things in my experience.??


    Chippie, let's try not to exaggerate the extent of my decrepitude based on some Bilge rumor. If things are moving too slowly it's because I'm working on other projects, not because of any infirmity. But, apology accepted, nonetheless.


    Now, about those little cross section diagrams. They were never intended to offer definitive geometric proof such as an engineer might imagine. They are more in the line of a jumping-off point, fifteen minutes of scribble, a way to wrap ones head around what's required.

    You know the situation, the topsides of the hull on the one hand, two twenty-eight foot two-by-fours on the other, hands all a-tremble. You need something to bridge the gap, something on which to pin a faint hope of success, something to embolden to the poor weak heart before cutting into those prime bits of wood.

    The little diagrams are soon tossed aside in favor of the planes, chalk, the long batten and the mighty squinty eye of truth.



    Jim

  26. #5241
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    Default Re: Lofting the Brewer catboat

    The little diagrams are soon tossed aside in favor of the planes, chalk, the long batten and the mighty squinty eye of truth.
    What? No lipstick!?

    Thanks, as always, for sharing, Jim.

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  27. #5242
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    Default Re: Lofting the Brewer catboat

    The Mighty Squinty Eye of Truth. Wow, what an apt description of the boatbuilder's art. The moment when everything looks right. My squinty eyes have spent countless hours trying to determine if battens are lined off "just so" or if the thwarts I designed are "just right". Etc., etc.,etc.
    Jim, you've got to copyright that phrase!!
    Last edited by Rich Jones; 12-10-2018 at 07:17 PM. Reason: Mistake
    I was born on a wooden boat that I built myself.

  28. #5243
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    Default Re: Lofting the Brewer catboat

    Quote Originally Posted by Jim Ledger View Post
    Yup, Nick, you're right on that one! The aft section of the rail will definitely have to be hollowed on the back to fit against the sheer plank.

    Jim
    Jim,
    By your comment I'm surprised you won't be backing out the rail in it's entirety. Any little piece of debris or curvature will make it stand off otherwise.

  29. #5244
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    Default Re: Lofting the Brewer catboat

    Quote Originally Posted by Rich Jones View Post
    The Mighty Squinty Eye of Proof. Wow, what an apt description of the boatbuilder's art. The moment when everything looks right. My squinty eyes have spent countless hours trying to determine if battens are lined off "just so" or if the thwarts I designed are "just right". Etc., etc.,etc.
    Jim, you've got to copyright that phrase!!
    In honor of the holiday season, I raise my (imaginary ) glass to Jim's Mighty Squint Eye of Truth --- Well spoken, Sirs !!!

  30. #5245
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    Default Re: Lofting the Brewer catboat

    [QUOTE=Chippie;5750683]
    Hi Jim hope you are feeling well.

    First of all I apologize to the Posters who were rightly outraged by my trying to provoke Jim to put more effort into his build. I would not have been so insensitive if I had known of his ongoing health problems until I was informed by PM.

    Thanks for that Steven.QUOTE.


    QUOTE. Chippie, let's try not to exaggerate the extent of my decrepitude based on some Bilge rumor.
    If things are moving too slowly it's because I'm working on other projects, not because of any infirmity. But, apology accepted, nonetheless.QUOTE


    Although I am concerned about your wellbeing, as I indicated in my PM to you, I was merely saying Hi!

    My apology was directed toward the Posters who were upset at my post.




    QUOTE Now, about those little cross section diagrams. They were never intended to offer definitive geometric proof such as an engineer might imagine. They are more in the line of a jumping-off point, fifteen minutes of scribble, a way to wrap ones head around what's required.

    You know the situation, the topsides of the hull on the one hand, two twenty-eight foot two-by-fours on the other, hands all a-tremble. You need something to bridge the gap, something on which to pin a faint hope of success, something to embolden to the poor weak heart before cutting into those prime bits of wood.

    The little diagrams are soon tossed aside in favor of the planes, chalk, the long batten and the mighty squinty eye of truth.
    Jim QUOTE

    Don't I just, toss in the sleepless nights, and the anguish when you realise that all that worry wasn't in vain and the Bustard isn't going to fit.

    I admire your confidence observing that you have been brave enough to cut BOTH sides (I was awake all last night you swine )

    Perhaps Nick being a Draughtsman could point out an easier way of picking up the bevels or a developed "gunnel" sheer shape to be more amenable to bending around?

    I think chuct #5238 is describing the problem admirably.

    QUOTE [Would a reasonably bendy wood like white oak fit the hull without having to do the rolling angle changes?


    Well, after looking at it more you are right of course. Even if the base would bend to fit the hull, the same shape fore to aft wouldn't work. Nice work as always!


    Chuck Thompson] QUOTE
    Last edited by Chippie; 12-11-2018 at 07:41 AM.

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    Default Re: Lofting the Brewer catboat

    PS.
    Jim do they fit?

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