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Thread: Re-building my Ketch Tonga (1960)

  1. #946
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    Back on the water for a few hours, might be back around 10 am. The wind will pick up but sea is only 2.8 m before it gets bad again. Couldn't resist any more!!!!



    Sent from my SM-G900FD using Tapatalk
    fair winds, Dody
    "They did not know it was impossible so they did it" - Mark Twain
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  2. #947
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    Default Re: Re-building my Ketch Tonga (1960)

    I would like to wish everyone a happy new year!

    Just in case someone was wondering: I didn't get lost at sea :-D! My mates had left 3 sets of nets each (for rays and sole) out, just enough to get them in between 2 weather-systems and be back in port before it gets rough again. I slept on board and got up the moment Ze started the engine, something around a quarter to 4 in the morning. There was nothing nice in the weather but it was just awesome to feel the movement of the ship in the waves again and the wind in my hair. I've missed that terribly!!! Funny enough Avo Ricardo's movement through the water was exactly as smooth and nice as Tonga's, even against the waves when we were heading out, which was a very special extra-treat for me. The trip wasn't a huge success for my mates, but not too bad either and around 10:30 we were back in port. I didn't get my camera out, the water was coming from everywhere. Back home the skin of my face felt like sandblasted, I was tired and exhausted, but warm and happy as hell!

    Now, back to boatwork. I've got nothing to show yet.

    One of the stronger winds had ripped the plastic protecting the hull aft on the portside to pieces and also some of my cover from the top aft. It was a bit weird as it looked like something went in from the top and exited on the portside. When replacing the cover on the side I used my scaffolding of course and found out that the top-plank was completely rotten (of the scaffold!). Got rid of it and bought 3 new ones - unfortunately I could only find the 30 cm wide ones, nobody had the 40 cm wide ones in stock, never mind. And I got myself another crosspiece and 2 new bars - I had rescued the uprights of an old scaffolding a while ago. It's rusty but still in usable condition. Which means I've got 3 complete ones now and I even could interconnect them having a "walkway" - well, when I finally get there one day.
    Repairing the top-cover ... still not sure if it's worth the effort as hopefully I won't need it for long and in theory the really strong rainfalls should be over by now. Still, it reminded me that I've got no workspace in my workshop since Alec was so nice to move some of his junk out and I never got around to tidy it up. And the bad light-situation in my workshop. So, when buying the planks etc. I also got me some fluorescents, cable etc. I started sorting the workspace today, got quite far actually, when I remembered the lovely sunshine outside and the fact that it's actually Saturday today, I still had to get the washing on the line and and and.

    Then, also today, I started re-reading all your input about the knee aft. Yes, the knee! Because, I still haven't installed it yet and I'm super-happy that I can read it all again and again as it's on the Wooden Boat Forum, ready for me to read at any time, awesome!!! But, I also found out that I've got to work out some more - it only just came to me that the top of the boltheads of course need to be flush with the backbone. No idea what I was thinking there! But, this also means I'll go for a small diameter bolt, like 6 mm or so. Hope that will be strong enough still. And then of course, I am wondering if I can use threaded bar, or if it has to be proper bolts with a thread only at the top? And the bolthead with hemp wrapped around? - Yes, it's gonna be planked and and and fibreglassed, there should be no ingress of water, but ...?

    Photos, struggling. Again. Somehow posting photos with Tapatalk doesn't want to work at the moment. Copying my photos from the phone to the computer doesn't want to work - even with a micro-USB-stick and a special App. Guess I better stop using the camera on my phone altogether and go back to my good old camera.

    However, that was just to let you know I'm still there and haven't given up, to the contrary :-D!
    Last edited by Dody; 01-04-2020 at 09:09 PM.
    fair winds, Dody
    "They did not know it was impossible so they did it" - Mark Twain
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  3. #948
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    6 mm bolts doesn't sound like much.

    Sent from my CPH1851 using Tapatalk

  4. #949
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    Default Re: Re-building my Ketch Tonga (1960)

    If you ever use threaded rod, make sure it is high tensile. The commonly available stuff is made of cheese.

  5. #950
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    Default Re: Re-building my Ketch Tonga (1960)

    How wide and deep is the backbone timber, and width of the knee? I can look up the suggested bolt size, 6mm threaded rod would be way too small. There might be those who will say an epoxy glue joint is enough.......

  6. #951
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    Default Re: Re-building my Ketch Tonga (1960)

    Quote Originally Posted by lexi View Post
    If you ever use threaded rod, make sure it is high tensile. The commonly available stuff is made of cheese.
    The cheese, and it is cheese, has a tensile strength around 55000 psi*. I can give some numbers for material strength, but perhaps Nick, Ian or Phil can use them to give a better recommendation for size and number.

    The shear strength of the low strength threaded rod (also called all thread) is 1000 lb for 6mm, 2000 for 8mm, 3000 for 10mm, and 4400 for 12mm. The high strength will be proportionally higher. Once you sort out which grade, you can refine the numbers. These shear strengths are based on SAE Grade 2 and stress areas calculated according to ASME B 1.13M, which is very similar to ISO or DIN sizes.

    https://www.allthreadrod.com/grades/ It sounds like ASTM A193 Grade B7 may be the usual high strength rod, which has a tensile strength of 125 ksi.

    The threaded rod available in Portugal should be similar in strength. This has some detail on the comparison, but I can't sort it out from here: https://www.hunker.com/12485643/thre...specifications

    This says that their high strength threaded rod is grade 10.9 https://www.strathcon.com/fasteners/...duct-list.aspx

    The thing I like about the EU grades is that the numbers mean something. 10.9 means that the tensile strength (10) is 1000 MPa and the yield strength is 90% (.9) of the tensile strength. SAE grades 1-8 increase arbitrarily with the numbers.

    If you are using stainless steel. It comes in grades with A followed by a single digit, 1-5, sometimes that is followed by a dash and two more digits which indicate the strength. If there is no dash number, assume 50, which translates to cheese, but very tough cheese. Avoid A1, which is free machining sstainless, or 303 in the US. It has added sulfur which is good for cutting and really bad for pitting. OK, I found a link; https://www.westfieldfasteners.co.uk...ngth_Spec.html

    *I am an old school American who thinks in psi and can't easily work with MPa without a calculator. 1 MPa is 145037.7 psi. 100000 psi is 6.894757 MPa.
    Last edited by MN Dave; 01-05-2020 at 08:53 PM.

  7. #952
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    Default Re: Re-building my Ketch Tonga (1960)

    Dody, unless you are paying for "pro" tapatalk, it only lets you post one medium size photo at a time.
    I stopped using it needless to say.
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

  8. #953
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    Default Re: Re-building my Ketch Tonga (1960)

    Whow, I just came home and found all your very useful input! It's midnight here, I won't start digging into it tonight but got to wait for tomorrow. My first reaction is: maybe threaded rod isn't a good idea after all. Rod with a thread at the top and the bottom? Can't be galvi as it would have to be galvanized after cutting the thread on a rod cut to measure and I haven't got an idea where this could be done right now, so it's probably got to be steel or stainless. Being above the waterline possibly stainless. Hm. Wonder if that's gonna let me get some peaceful sleep tonight :-D

    And thanks Denise!!! I knew nothing of this, the app just told me each time that "Tapatalk has stopped working" or so, and if I would like to report the error? No point in doing this then or hoping it will solve itself.
    Last edited by Dody; 01-05-2020 at 07:31 PM.
    fair winds, Dody
    "They did not know it was impossible so they did it" - Mark Twain
    www.tongabonds.com

  9. #954
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    Default Re: Re-building my Ketch Tonga (1960)

    Quote Originally Posted by Dody View Post
    I would like to wish everyone a happy new year!

    ...But, I also found out that I've got to work out some more - it only just came to me that the top of the boltheads of course need to be flush with the backbone. No idea what I was thinking there! But, this also means I'll go for a small diameter bolt, like 6 mm or so. Hope that will be strong enough still.
    Yes, Happy New Year!

    I have no idea what you are up against, perhaps because I have been too lazy to re read a lot of posts. You are attaching the large wooden sculpture to some timbers. Can you have an exposed nut on one end? Is it important to be able to remove the bolt someday? I am just throwing out some ideas for you to throw out when you think of a better one. Sometimes you find a good solution by criticizing a bad one.

    West systems ran some tests around 40 years ago and found that if you set a bolt in an oversized hole with epoxy, the bolt will break before it pulls out. They didn't say how deeply the bolt had to be potted in, or perhaps after 45 years, my memory is a little hazy. Having said that, they were talking about wind turbine blades, not boat parts that can get soaked for long periods. I use epoxy, but don't completely trust it. You can set a bolt this way, but it is not going to come out.

    If, as with most boat parts, the tensile strength of the fastener is not important because the load is almost all shear, there are always trunnels.

    There are weld nuts that are not easily torqued up unless you glue them in, but they can be flush.

    Flanged nuts could be driven upside down into a wooden beam by drilling a shallow hole with a diameter roughly the wrench size. For an M10 start with a 22mm hole ~4mm deep, then 15mm to 10mm, then a 10+mm through hole. Torqueing the other end should draw the nut into the wood and resist turning.

    Then there are E-Z Lok threaded inserts. Simple to use, maybe not simple to find in larger sizes.

  10. #955
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    Default Re: Re-building my Ketch Tonga (1960)

    Quote Originally Posted by MN Dave View Post
    The cheese, and it is cheese, has a tensile strength around 55000 psi*. I can give some numbers for material strength, but perhaps Nick, Ian or Phil can use them to give a better recommendation for size and number.

    The shear strength of the low strength threaded rod (also called all thread) is 1000 lb for 6mm, 2000 for 8mm, 3000 for 10mm, and 4400 for 12mm. The high strength will be proportionally higher. Once you sort out which grade, you can refine the numbers. These shear strengths are based on SAE Grade 2 and stress areas calculated according to ASME B 1.13M, which is very similar to ISO or DIN sizes.

    https://www.allthreadrod.com/grades/ It sounds like ASTM A193 Grade B7 may be the usual high strength rod, which has a tensile strength of 125 ksi.

    The threaded rod available in Portugal should be similar in strength. This has some detail on the comparison, but I can't sort it out from here: https://www.hunker.com/12485643/thre...specifications

    This says that their high strength threaded rod is grade 10.9 https://www.strathcon.com/fasteners/...duct-list.aspx

    The thing I like about the EU grades is that the numbers mean something. 10.9 means that the tensile strength (10) is 1000 MPa and the yield strength is 90% (.9) of the tensile strength. SAE grades 1-8 increase arbitrarily with the numbers.

    If you are using stainless steel. It comes in grades with A followed by a single digit, 1-5, sometimes that is followed by a dash and two more digits which indicate the strength. If there is no dash number, assume 50, which translates to cheese, but very tough cheese. Avoid A1, which is free machining sstainless, or 303 in the US. It has added sulfur which is good for cutting and really bad for pitting. OK, I found a link; https://www.westfieldfasteners.co.uk...ngth_Spec.html

    *I am an old school American who thinks in psi and can't easily work with MPa without a calculator. 1 MPa is 145037.7 psi. 100000 psi is 6.894757 MPa.
    Cheers Dave. 10.9 in mild steel threaded rod and A2 stainless (above) and A4 (below) water (fresh) is what I normally use. I go by that in messing with houses and the like too. Cheeses come in different tensile of course. If you get slapped with some Brie and then got hit over the head with a lump of old Parmesan, you can feel it without actually measuring.

  11. #956
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    Default Re: Re-building my Ketch Tonga (1960)

    OK, just a rough idea about the dimensions for the moment, will try to make a drawing because I don't seem to be capable to explain it (and don't know if I manage a proper drawing either):

    Backbone: 80 mm wide, 285 mm long. Tapered which means the afternmost part is 55 mm high, further forward 70 mm.

    Assembled, as a rough guess, I think I might need bolts in the sizes of - this is provided I did understand correctly how this is meant to be, corrections and ideas more than welcome!!!:
    160 mm plus thread
    210 mm plus thread
    240 mm plus thread
    250 mm plus thread
    170 mm plus thread
    120 mm plus thread
    fair winds, Dody
    "They did not know it was impossible so they did it" - Mark Twain
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  12. #957
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    Default Re: Re-building my Ketch Tonga (1960)

    Photos to make it less confusing.
    Backbone from below (notched into stern-assembly):

    1-IMG_0391.jpg

    and the knee etc. how I understood this was meant to be (what is sticking out at the top will be cut flush once everything is properly bedded and installed):

    1-IMG_0394.jpg
    fair winds, Dody
    "They did not know it was impossible so they did it" - Mark Twain
    www.tongabonds.com

  13. #958
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    Default Re: Re-building my Ketch Tonga (1960)

    Please note that both of those drawings are NOT to scale!!!

    1-IMG_0396.jpg

    and this is more or less where I would like to use the bolts:

    2-IMG_0397.jpg

    As the backbone is only 55 mm thick at the far end I haven't got a lot of "meat" to "waste" with nuts, washers etc. if you know what I mean. For this reason I certainly wouldn't like to use 2 nuts chinched together. As I - hopefully - will never ever get there again, I don't want to use anything that can come undone and I don't trust locknuts in a buried place forever. A nut with a springwasher and a washer is taking quite some space too. So I'm thinking of either getting me bolts with a head in the proper length made, or tackweld the nut onto the bolt.
    I'm not concerned about what's sticking out inside, once it's all done up properly I would be happy to just cut off what's not needed and be done.
    fair winds, Dody
    "They did not know it was impossible so they did it" - Mark Twain
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  14. #959
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    Default Re: Re-building my Ketch Tonga (1960)

    Is there any reason not to just drill a large enough shallow hole to bury the heads of some hot dipped lag screws? This question is for anyone here, preferably those who know more than I do.

    This place has a variety of materials. Other than that, I don't know if the prices or vendor are good, but their web site was convenient.
    3/8-7 x 8" Hex Lag Screw LOW CARBON HDG
    https://www.mutualscrew.com/product/...hdg-109120.cfm
    $11.97 pack of 10.

    3/8 X 7-1/2 Lag Screws (Bolts) 18/8 Stainless Steel
    https://www.mutualscrew.com/product/...teel-40902.cfm
    $13.16 for 1 piece

    3/8 X 6 Hex Lag Screw Silicon Bronze
    https://www.mutualscrew.com/departme...rews-12422.cfm
    Price: $25.62 for 1 piece

    3/8 X 7 Hex Lag Screws 316 Stainless Steel
    https://www.mutualscrew.com/product/...teel-39516.cfm
    $113.67 for Pack of 2 pieces
    That's only $56.8353 per piece (Their words, not mine)

  15. #960
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    Default Re: Re-building my Ketch Tonga (1960)

    If there is somebody around who can cut threads on a piece of rod that might be a better way to go.You can add a bead of weld to the nut at the "head" and treat it as a bolt and not having a helical leak path the entire length of the fastener is no bad thing.It also gives more bearing surface in contact with the wood when loads are applied.Once done your transom should be pretty solid with that rugged laminated knee in place.
    Last edited by John Meachen; 01-08-2020 at 03:41 PM.

  16. #961
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    Default Re: Re-building my Ketch Tonga (1960)

    I don't see any problems at all. The outside heads will be housed in a hole in the planking leaving the backbone thickness alone. Remember there is the laminated plywood skin to come covering it all. I suppose the transom will be the same, but even if not you have enough meat there to countersink the heads.
    As to what to use for the heads simplest is a wide washer followed by a nut. You either weld the nut on beforehand or peen the rod over the nut after torquing down. Measure the needed lenghts and have the threads cut, any mechanic will have the needed die.

  17. #962
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    Default Re: Re-building my Ketch Tonga (1960)

    The pieces of wood you are going through will limit your maximum size of fastening. If we take your 80mm width as the minimum, according to Gerrs, a bolt diameter should not exceed 25% of the woods dimension at right angles to the fastening, so we get a size of 20mm maximum.
    Your bolt pattern looks fine, I have used threaded rod with bitumen/pine tar coating with the threads "haired", in the past, but make sure if you use it, that only pukka hot-dipped galv, and not zinc plated. Threaded rod is a bit better as its better driven in to the wood tight, but i wouldnt lose any sleep with 20mm threaded rod, and it might be a little cheaper than getting rods cut,threaded and hot dipped.....its your budget. You could of course fit slightly smaller 18mm rod in the same hole, with epoxy, i have no doubt the system works, but in a long hole, making sure everything is wetted out and the mix is everywhere it needs to be in anything but a vertical hole, seems tricky.....you might have more patience.

  18. #963
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    Default Re: Re-building my Ketch Tonga (1960)

    Thank you all heaps for your input! It's awesome and gives me different options to think about and finding a better solution for the problem.

    Working my way through possibilities and haven't decided yet.

    Dave's idea would be the most simple and straightforward one, but even though it probably can't come apart caused by the different angles something inside me is shouting out loud that the pieces need to be entirely under compression. Meaning something sticking out on both ends that fixes/tightens it all together. A lag screw would do that only partly. Maybe I'm wrong here.

    Rumar's idea of not boring the head and the washer into the backbone but leaving it proud and buried in the plank instead to not compromise on the thickness of the backbone certainly is a possibility I will keep in mind. It does feel a bit bodged up by an amateur who doesn't know any better - which certainly I am, no doubt about it.

    This is pretty interesting Ian! If I get that right, you are talking of the maximum diameter of the fastenings. I agree everybody is right that 6 mm was a bit on the extremely thin side. But 20 mm? Only the nut would have a thickness of 16 mm and then I need to add a washer. Alright, it's entering the backbone in an angle so the way inside is a bit longer but still. Boring for the M20 nut and the washer would leave me with around 40 mm of wood on the backbone to pull against the knee. It does feel a bit like overkill. So far we (together with the shipwright) have only used M12. And let's say I would take 20% of 62.5 mm thickness (the intermediate between 55 mm and 70 mm of the backbone) I would come out with 12.5 mm. Using M12 the nut would be 10 mm and the washer about 1 mm which is quite a bit less than M20. I start to like the idea of using M12 - please shout out loud those who don't think it's enough!!!

    Hm, if Phil is reading here, next time you are on your boat, would you mind measuring the thickness of your bolts and let me know please?

    Epoxy and bolts at this place is not for me I think. And I will definitely go for rod instead of threaded bar because it makes sense.
    fair winds, Dody
    "They did not know it was impossible so they did it" - Mark Twain
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  19. #964
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    Default Re: Re-building my Ketch Tonga (1960)

    Dody, I can't comment on the tensile strength questions but looking at your diagram I wonder if you will have room for three bolts into the horn timber/backbone as you have indicated? They look very close together where they exit the knee. The bolts in the upright/filler piece seem to be similarly close as well. I'd be thinking two bolts into the backbone, one into the filler piece and one into the transom frame crossmember. Once your transom is covered, and presumably the upright and the crossmember are tied to the transom cheeks by the planking/plywood, I would think that the entire assembly would be sufficiently braced/fastened. You would then have two bolts locating the knee in each plane.

    Hopefully someone with actual engineering experience will come along and comment here...
    - Chris

    Life is short. Go boating now!

  20. #965
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    Default Re: Re-building my Ketch Tonga (1960)

    Pardon the long winded approach, I am thinking as I type, trying to anyway. I feel guilty clicking the "Post Quick Reply" button.

    I started out thinking that threaded rod was a good choice, even if through bolting might not be. As far as I know (and that might not be far enough) through bolting is used to tie built up frames, knees and deadwood together. This is a laminated member, so is through bolting still needed? The trouble with all thread is that it is better to have a smooth surface with an interference fit where two members come together.

    If after someone with actual large boat experience agrees, I would recommend lag bolts or trunnles, perhaps in combination with a smaller number of through fasteners. You could tighten up the joint with lags, then wind a threaded rod into a tight hole, but short of greasing it and using a massive amount of torque, you might just twist it off halfway through. Maybe just drill undersize for a few inches on both sides of the faying surface.

    This is where I talked (typed anyway) myself out of threaded rod. Bolted joints in metals should not move. When bolting metals (thick, not sheet), friction between the parts due to the high clamp load generated by the fasteners, not the shear strength of the fasteners, resists shear loads. In a lightly clamped joint there can be some movement so the shear loads are taken by the fasteners. That is why you drive keel bolts into tight holes. Movement causes problems, and tight holes prevent movement. That is where threaded rod is problematic. Threading the ends of a smooth bar is one way around the problem. Threading a galvanized bar removes the corrosion protection in the most exposed areas. Then you bury them with glop in a countersunk hole and cover it with a plank, so... (help me out here). So how do you smooth up a threaded rod without spending enough time and money to buy a new boat? You might tape off the ends and smear the rest with thickened epoxy, while keeping it impossibly smooth...?

    Fastener size and strength: Even the low strength 4.6 (SAE grade 2) 20 mm threaded rod has a yield strength of 20,000 psi (94,000 N). We never utilize the full strength of metal fasteners in tension because they are generally strong enough to crush the wood surface too much. Except for bolts holding keels, stanchions, and other things that do load the bolt in tension, mostly we use bolts to resist shear. There are any number of pictures of badly corroded keel bolts that didn't break after wasting to less than half of their original diameter.

    Iroko
    has a Janka hardness of 1,260 lbf (5,610 N). "The actual number listed in the wood profile is the amount of pounds-force (lbf) or newtons (N) required to imbed a .444″ (11.28 mm) diameter steel ball into the wood to half the ball’s diameter. This number is given for wood that has been dried to a 12% moisture content, unless otherwise noted." We use large keel bolts to fit the large washers needed to spread the load without crushing the wood. The surface area of the ball that you can bury half way with a 20mm cheese stick is 20,000/1260 = ~16 times that of a .44" ball, so the diameter of that ball is 4 x .44" = 1.76" (~45mm). Obviously, without a coil nut, ogee or bridge washer, you wouldn't torque a 20mm bolt anywhere near as much on wood as you would on metal. For metal you tend to torque to somewhere between 75 and 90% of yield, because that reduces fatigue cycling. With wood, you are limited by the softness of the material, so the bolts are lightly loaded to the point where fatigue isn't an issue.

  21. #966
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    Default Re: Re-building my Ketch Tonga (1960)

    Dody, the 20mm size was a maximum given the size of the timber. I dont have the data here to tell me at what pressure your laminated knee would fail in sheer, and you only need bolts big enough, plus a saftey factor, to match the wood. Are you going for a bonded or bedded joint?





    Everything Dave said about threaded rod is correct. I use under size holes and the rod is wound in like a big screw, its as effective as the depth of the threads and the type of wood its going into, i had a hard wood sample with no nuts on either end, and the wood split before the grip on the threads gave way. Im happy using it on an all epoxy joints, and some might say the bolts are uneccessary given a good glue surface area. The top of any vertical holes could have a short counter bore to act as an epoxy resevoir to act like a water stop and a nut. If you trust the gougen method, you would not need the nut on one end that is making you concerned, you could just bond it, as an option, and they suggest threaded rod for this purpose. I heard it said that 3 bolts is way more resilient than 2 in regards to movement, and i would rather place three smaller diameter bolts each side of a joint, than 2 larger. I have been using a mix of 12-16mm threaded rod, oversize for my needs but the loss of diameter due to thread does need to be taken into account.

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    Default Re: Re-building my Ketch Tonga (1960)

    To add: I dont want to reproduce one of Mr Gerrs charts here, but if you can measure the cross section of the jointing faces, i can check what his chart reccomends for fastening diameter, which might put you in a better ball-park.

  23. #968
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    Default Re: Re-building my Ketch Tonga (1960)

    Will come to your input in a bit, only for info: I was planning on bedding it as I did everything else till now, the plan was not to epoxy-glue it.

    I went to have a closer look at things today which was a bit frustrating. It starts already with me not having a long 12 mm drillbit - easy to buy one of course. Then I tried to figure out a way to drill a long hole from the inside to the outside. I need to cut off the knee on top to have more space of course, but there is still only 2 positions where I might be able to drill 2 of the holes I need as there is no access. The rest I'll have to drill from below or I don't know what.
    But then Mr. Gerr ... the name was ringing a bell. I had a look at my books and - tata tataaaaa!!! - Dave Gerr, The Elements of Boat Strength. Chapter Ten "Fasteners, Straps, Knees and Details" let's see what we can get from there to add to the discussion
    fair winds, Dody
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    Default Re: Re-building my Ketch Tonga (1960)

    Will come to your input in a bit, only for info: I was planning on bedding it as I did everything else till now, the plan was not to epoxy-glue it.

    I went to have a closer look at things today which was a bit frustrating. It starts already with me not having a long 12 mm drillbit - easy to buy one of course. Then I tried to figure out a way to drill a long hole from the inside to the outside. I need to cut off the knee on top to have more space of course, but there is still only 2 positions where I might be able to drill 2 of the holes I need as there is no access. The rest I'll have to drill from below or I don't know what.
    But then Mr. Gerr ... the name was ringing a bell. I had a look at my books and - tata tataaaaa!!! - Dave Gerr, The Elements of Boat Strength. Chapter Ten "Fasteners, Straps, Knees and Details" let's see what we can get from there to add to the discussion
    fair winds, Dody
    "They did not know it was impossible so they did it" - Mark Twain
    www.tongabonds.com

  25. #970
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    Default Re: Re-building my Ketch Tonga (1960)

    Result! than you are as well informed as i am. I have had luck with finding long spade bits at very reasonable prices, though if you need to push hard, ones with a long shank can often bend a bit, meaning one end of your hole might not come out where you wanted. You could set up a batten as a drill guide and use a shorter drill bit from each ends if needs be, if the space allows.

  26. #971
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    Default Re: Re-building my Ketch Tonga (1960)

    Originally Posted by Dody

    Then I tried to figure out a way to drill a long hole from the inside to the outside. I need to cut off the knee on top to have more space of course, but there is still only 2 positions where I might be able to drill 2 of the holes I need as there is no access.


    Warning, armchair boat builder advice: Every time I think of an approach, by the time I write it down, it seems flawed and then the next idea falls apart. Maybe one of them will help find a good one.

    One of many problems that I see is that it is very hard to know where to start drilling from the outside and at what angle until the knee is in place where you don't have any room for the drill. Starting from outside, you are drilling blind. So you need a guide on the inside to drill through the backbone, then install the knee and drill the hole through the knee from outside.

    You could drill the holes in the shop, then drill through the framework after you secure it in place. By putting the drill bit in place before sliding the knee in place, maybe you can gain enough room for the drill, or a right angle drive can buy you better access. Once the drill comes through, you can loosen the chuck and pull it through.

    For planning purposes you could mock up a Styrofoam model that fits the back and bottom surfaces. Then you can see the drill hole path and mark the hole paths with a Sharpie. The thickness is not important. It only needs to be used as a guide for the location and angles.

    I drew a sketch on your sketch to look at the access -- ouch. Another hare brained idea was to make some drill guides, which are the red things, they are on the sketch and I'm not redoing it. The curve on the inside only has to be drawn, not cut... OK, you have a problem. Some bits are better than others for straight holes, and spade bits aren't on the list. I think something like an auger bit? Shell auger bit? The black circles are a clamping idea. Pipes drilled for two threaded rods on either side of the knee with a bracket cut from a 2x6 that hooks on the keel.
    dodys stern.jpg

  27. #972
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    Default Re: Re-building my Ketch Tonga (1960)

    Drilling a long hole from the outside is a lot easier if you can attach a straight edge along the line of the hole and get a helper to sight the line of the drilling operation from the side.Staying parallel to the straight edge keeps you centred too.

  28. #973
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    Default Re: Re-building my Ketch Tonga (1960)

    Thank you all heaps for your very helpful tips on drilling, and Dave I absolutely love your idea of how to clamp the knee in place for drilling, it's awesome and very inspiring!!!

    As I first need to work out the diameter of the bolts, I've done some reading in "The Elements of Boat Strength" by Dave Gerr which I find quite helpful. As you all know, unlike many builders, I haven't got any plans for Tonga telling me about materials, thicknesses, diameters etc. and I'm not an experienced boatbuilder. All the boatbuilding-books I've been reading so far always told me to consult the designer the moment it got interesting for me instead of helping me to find an answer, but not this one :-D! For the moment I went straight to chapter 10 "Fasteners, Straps, Knees and Details". He is using formulas to calculate the needed diameters of bolts etc., and they base on his Scantling Rules and Scantling Numbers which are explained at the beginning of the book and can be easily calculated as long as one knows the LOA, Beam and Depth of Hull (midships from the sheer down to the top of the keel inside the boat).

    According to his Scantling Rules, Tonga has a Scantling Number of 4.9453 or 4.95

    Following his Formula 10-6 and advice, I should use a diameter of 10.85 mm for Floor-to-Frame fasteners etc.. Here the Fastener Diameter must not exceed 30 percent of frame molding and heavy washers must be used under the heads and nuts of all bolts.
    Following his Formula 10-7 and advice, I should use a diameter of 15.83 mm for Floor-to-Keel fasteners and general tie-rods. Here the Bolt Diameter may not be larger than 33 percent of the floor siding, 2 bolts in each floor (1 x pt, 1 x stbd). At the bar near the stem and the narrow deadwood aft, a single bolt on the centerline where unavoidable. For general tie-rods the bolt diameter may not be larger than 33 percent of the thickness of the thinnest member it penetrates. Where the diameter exceeds 33 percent, reduce diameter until a 33 percent ratio is achieved. Heavy washers must be used under the heads and nuts of all bolts. Most of the other structural tie rods at the mast, engine beds, cabins and sides should be of this diameter.

    Now, the smallest member the bolts penetrate with the installation of the knee is the backbone. At the far end, when I reduce the thickness for the nut and washer (and don't take the angle into account, which makes the hole itself longer of course), the maximum I'm supposed to use is a 12.54 mm bolt which means I would have to use M12. For most of the rest I could use M16.

    There is lots more reading to be done for me in this book, and so far I hope I didn't miss out on something really important. For now I've got the address of a company in Leiria (about 45 K from here) who is meant to have 316L rod in 6 m lengths. I haven't been to this shop before, so I don't know if they also sell washers and nuts. And I don't know what kind of diameters they might have. Just in case I might be successful I've already got the angle grinder and extension-lead in the car to cut it down to 3 m. Fingers crossed!!
    Last edited by Dody; 01-10-2020 at 08:48 AM.
    fair winds, Dody
    "They did not know it was impossible so they did it" - Mark Twain
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  29. #974
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    Default

    12 and 16 sounds much better. Of course stainless has its issues. I think backbone fasteners an my boat might be Monel, but that's pricey and unobtainable these days.

    Sent from my CPH1851 using Tapatalk

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    Default Re: Re-building my Ketch Tonga (1960)

    Dody, that filler piece looks like an excellent candidate to epoxy onto the rear face of the knee, which it is really just an extension of. The gluing surface is huge, but if you really wanted to go belt and braces you could add two or three lag screws.
    I don't think bolts 2 and 3 in your diagram add anything (other than a lot of work and $) by going all the way through the filler and the knee - they don't tie anything into the existing structure of the boat, the way the other throughbolts do.

    Pete
    I have seven trolls on ignore

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    Default Re: Re-building my Ketch Tonga (1960)

    Quote Originally Posted by Phil Y View Post
    12 and 16 sounds much better. Of course stainless has its issues. I think backbone fasteners an my boat might be Monel, but that's pricey and unobtainable these days.

    Sent from my CPH1851 using Tapatalk
    Yes Phil, I think so too! Monel ... hm ... to be honest I used Monel-rivets on my masts but it never occurred to me that one could have bolts and nuts in Monel as well. Dave Gerr mentions Monel in his book as first choice and now you mention it too. Hm, guess I've got to do some more research for a few bits I haven't got a solution yet. For the moment I'll stick with stainless. I agree concerning the issues, but at least the 316L is the lesser of the evils and it's above the waterline.

    By the way, me not having television I only just learned about the terrible fires you had in OZ. Are you and your people, friends and 4-legged ones okay?
    Last edited by Dody; 01-18-2020 at 03:56 PM.
    fair winds, Dody
    "They did not know it was impossible so they did it" - Mark Twain
    www.tongabonds.com

  32. #977
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    Default Re: Re-building my Ketch Tonga (1960)

    Quote Originally Posted by epoxyboy View Post
    Dody, that filler piece looks like an excellent candidate to epoxy onto the rear face of the knee, which it is really just an extension of. The gluing surface is huge, but if you really wanted to go belt and braces you could add two or three lag screws.
    I don't think bolts 2 and 3 in your diagram add anything (other than a lot of work and $) by going all the way through the filler and the knee - they don't tie anything into the existing structure of the boat, the way the other throughbolts do.

    Pete
    Ayyyyy, Pete, back to Epoxy ... but I must admit you really have a point there, a good one! And also with both of these bolts. Especially as I was planning to bolt the planks to the frame and wanted to have one of these bolts going through to the knee, something I still haven't worked out properly yet. Thank you, good thinking!!!
    fair winds, Dody
    "They did not know it was impossible so they did it" - Mark Twain
    www.tongabonds.com

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    Default Re: Re-building my Ketch Tonga (1960)

    The easy bit was: I managed to get 4 m of 316L in 12 mm and 6 m of 316L in 16 mm and was positively surprised that this was far from emptying my purse :-D (I'll need the 316L elsewhere as well)! It was just walk in, get it, cut it, load it into the car and pay, simple as that!

    From then on things became more complicated.

    A friend told me about a place some 25 K to the North where I might get the nuts and washers. Got into the shop and yes, nuts A4 in M12 and M16 in stock, awesome! Washers and splitrings? No problem, we'll order them for you, they will be here tomorrow! They didn't arrive the next day. The guy called to make sure they're under way, I left my phone-number and got a call the day after "they arrived". When I got there some of it had arrived but the washers in M16 were still missing. They should have arrived Friday but he didn't give me a call, I'll check again on Monday. Then it's only measuring and have the threads made - either in the shop in the next village or the guy next to the Monastery in Alcobaça (17 K), who ever has the few minutes to do it straight away.

    The day I found the 316L bars in 12 and 16 mm I managed to get hold of some longer and shorter Auger bits in 12 and 16 mm, got myself some cheap galvi threaded bar and nuts to secure stuff temporarily, a new electric drill and, maybe one or the other remembers my shower-problem? I gave in and bought one of these electric instant water-heaters. I had talked with the main distributor for Portugal a while ago and, with the details of the electrics in my workshop (that is according to my bill), we found the one that would work with mono-phase and the amperage I've got available.

    So far so good. Now just get the cable, plugs, water-connectors, throw it all together and done. Done? No, still not done.

    1-IMG_0398.jpg

    5-IMG_0402.jpg

    7-IMG_0404.jpg

    9-IMG_0406.jpg

    I managed to get it working without leaks. For a few seconds at least, and then the circuit-breaker went off. Got myself a 32 Amp circuit-breaker and also the intermediate between the mains and this one (40 Amps in case it turns out I should need to use it with the more powerful setting, that one was only 25 Amps before). As I haven't really got a clue about 240 V in houses I didn't want to mess around with the circuit-breakers and asked a mate who's electrician to replace them for me. During this operation he found out that the cable running from the circuit-breaker to the socket where the heater is plugged in is only 2.5 mm square - not the 4 mm square I was told. Well, I had my doubts about the cables the moment I installed the 32 amp socket but ... Even so it's running now, but the temperature of the water coming out at the heater is only 27º C with the heater set to 55º C.

    Back to the Electro-shop again (3rd time), got myself 6 mm square cable to replace the 2.5 mm square and also got me some insulation-material for the warm water tubing (Friday evening). If that doesn't solve the problem I will have to read the instruction manual again, but more probably, get the guys from Docapesca to give me 40 Amps instead of the 30 I have at the moment and re-program the heater for the higher amperage.

    And then of course find space elsewhere for the stuff I was keeping in the shower, which I've nearly sorted today.

    3-IMG_0400.jpg

    Needless to say: all this took too long and I slowly started to get desperate for a shower, so gave in and spent another 1.50 Euro at the Clube Naval to take a shower.
    Last edited by Dody; 01-18-2020 at 04:14 PM.
    fair winds, Dody
    "They did not know it was impossible so they did it" - Mark Twain
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  34. #979
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    Default Re: Re-building my Ketch Tonga (1960)

    Ahh, the joys of single phase water heaters. When I was in our Air force, we sometimes drew overnight recruit babysitting duty. The duty office had an attached en suite bathroom with one of those - the options seemed to be a miserable dribble of hot water, or a pathetic flow of body temperature water. Neither very appealing when it was -5C outside first thing in the morning, and not much warmer in the bathroom!
    Funny story, I got a phone call one evening I was on babysitting, from a distraught mum who hadn't heard from her little darling since joining up. This kids name wasn't on the list, five minutes later, I'd established that none of my batch of recruits recognized the name, and a call to the MP's revealed this individual wasn't even on this airbase. "Mum, how long ago did precious join up"? "Oh, just over a year ago" she says. It was nearly a coffee out the nose moment, as recruit training was only around three months long. I diplomatically informed her of all this, and suggested that she contact the base admin section the next day, as they should have better information.
    Anyway, good luck with the plumbing project. Correctly sized cables should help some as they'll have a lower voltage drop, and you need a super economy showerhead to minimise flow and maximize heating time.

    Pete
    I have seven trolls on ignore

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    We've been fine with the fires thanks Dody. One was a few KM away and made us nervous but no problem for us.

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