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Thread: Screws or bolts?

  1. #1
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    Default Screws or bolts?

    When attaching a pintle to the rudder should wood screws or through bolts/nuts be used? The rudder is laminated 3 layers of 1/2" Meranti plywood- (1 1/2" total thickness).

  2. #2
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    Default Re: Screws or bolts?

    I would use copper rod and peen it over on both ends. The benefit of a bolt, but lower profile.

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    Default Re: Screws or bolts?

    What boat?

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    Default Re: Screws or bolts?

    It does kinda beg the question of what boat? A traditional design would look good with bronze pintles and peined rod fasteners (which have the advantage of being tightenable); a newer design would look fine with SST through bolts (also tightenable, but bulkier looking). So where are the pictures? There are supposed to be pictures!?!

  5. #5
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    Default Re: Screws or bolts?

    I've used both, but bolts are probably easier...and if SS, also stronger than copper.
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

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    Default Re: Screws or bolts?

    Stainless dinghy fittings or cast bronze? If cast I would definitely use copper, but bronze screws will work. The holes in Peerie Maa's gudgeons and pintles do not line up, so she has had screws for over 50 years.
    It really is quite difficult to build an ugly wooden boat.

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  7. #7
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    Default Re: Screws or bolts?

    Bolts.

    Screws work their way out after time on rudders.

  8. #8
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    Default Re: Screws or bolts?

    Quote Originally Posted by Peerie Maa View Post
    The holes in Peerie Maa's gudgeons and pintles do not line up, so she has had screws for over 50 years.
    Quote Originally Posted by lupussonic View Post
    Screws work their way out after time on rudders.
    You must have used the wrong screws or crappy wood.
    It really is quite difficult to build an ugly wooden boat.

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  9. #9
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    Default Re: Screws or bolts?

    I'd say it depends, if the pintle is so small so you only have say two holes in it a bolt or similar would be my choice. If it's large enough for 10 holes I see no problem with screws.

    /Mats
    Yes the avatar depicts me; yes I drew the comic boat pic, it's a joke on the pop song I'm not a robot by Marina and the diamonds

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    Default Re: Screws or bolts?

    Quote Originally Posted by lupussonic View Post
    Bolts.

    Screws work their way out after time on rudders.
    That's what happens if you have too few fastening points in anything, rudders are not different from doors in that respect.

    /Mats
    Yes the avatar depicts me; yes I drew the comic boat pic, it's a joke on the pop song I'm not a robot by Marina and the diamonds

  11. #11
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    Default Re: Screws or bolts?

    Quote Originally Posted by lupussonic View Post
    Bolts.

    Screws work their way out after time on rudders.
    Ask my Twin David Graybeal about that problem. The screws holding the rudder cassette on his GIS came out...while being sailed by the visiting designer Mic Storer! Ooopsie...
    "The enemies of reason have a certain blind look."
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  12. #12
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    Default Re: Screws or bolts?

    I would not trust screws into plywood.

    If the boat is large and not dry-sailed, I'd consider bolts into epoxy plugs.
    Countersunk flat-heads would look clean.

  13. #13
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    Default Re: Screws or bolts?

    Thanks for the input guys. Actually, I was leaning towards the bolts. so I'll go with them- brass, to match the fittings I'm making. Yeah, yeah, I know everyone says bronze, but it's too expensive, and not that readily available. I will turn down the bolt heads and nuts a bit to make them look less "clunky" and then peen over the ends to fair into the nuts. BTW, it's an 18' version of Wm Garden's TomCat.

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    Default Re: Screws or bolts?

    Quote Originally Posted by GregH View Post
    Thanks for the input guys. Actually, I was leaning towards the bolts. so I'll go with them- brass, to match the fittings I'm making. Yeah, yeah, I know everyone says bronze, but it's too expensive, and not that readily available. I will turn down the bolt heads and nuts a bit to make them look less "clunky" and then peen over the ends to fair into the nuts. BTW, it's an 18' version of Wm Garden's TomCat.
    If you are peening the threads anyway you might as well just countersink the holes and use copper rod rivets.
    It really is quite difficult to build an ugly wooden boat.

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  15. #15
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    Default Re: Screws or bolts?

    It depends on a number of things. If the fastenings are in shear as with Peerie Maa, then screws are, in most cases, acceptable, but if, as with a transom boat, they're in tension then it may be that an impact with the bottom can pull screws out. The holding power of screws can be considerably improved by boring a pilot hole full depth for the screw, then counterboring about 3 x the diameter of the screw a little more than half depth, filling the lot with thickened epoxy, coating the screw very lightly with silicone car polish as a release agent then driving the screw through the epoxy and into the pilot hole while the epoxy is still wet.
    Other thoughts, if using bolts, use big washers or backing plates. I go to the trouble of boring rudder pintle holes at about 20mm diameter and filling them with high density epoxy filling then boring the "real" hole through that. The process not only considerably increases the strength of the fastening, it prevents water ingress into the end grain through the hole.
    If watertightness is a serious issue I countersink the hole and put a thick neoprene o ring around the bolt, coated with anhydrous lanolin.

    Rudder fittings get a hard time if you're in shallow water a lot as I am, and plywood is vulnerable to water in the end grain so I take the trouble to really seal it off.

    John Welsford
    Last edited by john welsford; 01-11-2019 at 09:42 PM.
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    Default Re: Screws or bolts?

    My rule of thumb is this: If in doubt, the answer is a bolt. Sort of like it's time to reef as soon as you ask yourself, "Is it time to reef?"
    -Dave

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    Default Re: Screws or bolts?

    Quote Originally Posted by GregH View Post
    Thanks for the input guys. Actually, I was leaning towards the bolts. so I'll go with them- brass, to match the fittings I'm making. Yeah, yeah, I know everyone says bronze, but it's too expensive, and not that readily available. I will turn down the bolt heads and nuts a bit to make them look less "clunky" and then peen over the ends to fair into the nuts. BTW, it's an 18' version of Wm Garden's TomCat.

    Please don't use brass. It has no place in any load-bearing situation. boat jewelry, sure. But not something important like rudder hardware.
    There's the plan, then there's what actually happens.

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  18. #18
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    Default Re: Screws or bolts?

    Brass is expensive junk, so use marine grade stainless if you don’t want to buy silicon bronze.
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  19. #19
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    Default Re: Screws or bolts?

    For things that can be easably inspected I see no problems with brass, just replace when wore down.
    In my waters brass is said to last about 50 years, in more salty situatuons it may be only 20. I don't know.

    /Mats
    Yes the avatar depicts me; yes I drew the comic boat pic, it's a joke on the pop song I'm not a robot by Marina and the diamonds

  20. #20
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    Default Re: Screws or bolts?

    The big problem with brass is not that it wears quickly, but that its zinc is consumed by electrolysis, leaving a weak copper sponge. It's an alloy of copper and zinc.

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    Default Re: Screws or bolts?

    As I said, brass is junk -- particularly for fasteners. Might be OK for cleats or some other thick hardware above the waterline, but NOT recommended for fasteners. You won't find any professional shops using brass fasteners on wood boats of any kind, with the possible exception of restoring older freshwater canoes and small boats that were originally fastened with brass 80+ years ago.
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

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    Default Re: Screws or bolts?

    Quote Originally Posted by JimConlin View Post
    The big problem with brass is not that it wears quickly, but that its zinc is consumed by electrolysis, leaving a weak copper sponge. It's an alloy of copper and zinc.
    By wear I mean exactly that.
    It is a known problem with (some) old Folkboats, where the garboards were fastened to the keel with brass screws.
    I don't think I'd recomend anyone using brass, but if used for rudder fastenings or as said cleats and such it's not a big deal if regularly inspected and replaced.
    The problem is of course that you cannot see the wear, or decay if you will, so back one screw out a bit and hit it with the screw driver to test it.

    /Mats
    Yes the avatar depicts me; yes I drew the comic boat pic, it's a joke on the pop song I'm not a robot by Marina and the diamonds

  23. #23
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    Default Re: Screws or bolts?

    If the boat is to be used in salt water brass fastenings will disintegrate very fast, possibly leaving you rudderless! This usually happens at the worst possible time like clawing off of a lee shore in a blow. Copper rod is your friend. Brass fastenings are your enemy!
    Jay

  24. #24
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    Default Re: Screws or bolts?

    On a small boat one rarely gets to fit more than 2 fastenings.. one per side of a gudgeon or pintle. I have had screws pull out several times, on my early boats, and sailing other peoples boats. It's really a no brainer where a rudder wangs sideways thousands of times on a screw...fit something better, bolts or peened copper rod. Neglecting to do this is like fitting rubber hoses on your cars brake lines. Just don't.

  25. #25
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    Default Re: Screws or bolts?

    Another thing to consider doing is getting the fittings a bit tight and carve out slots for them, then they won't wiggle and the screws will most likely not come loose.
    This is not the prettiest of examples of that, it's my boat, my work, I'm not extremely proud but whatever.
    BTW It's SS, not brass


    /Mats
    Yes the avatar depicts me; yes I drew the comic boat pic, it's a joke on the pop song I'm not a robot by Marina and the diamonds

  26. #26
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    Default Re: Screws or bolts?

    Quote Originally Posted by Canoeyawl View Post
    Bolts are only as strong as the minor diameter.
    A 1/4" bolt has the shear strength of a 3/16" rivet, and even less rigidity because the threads are bearing instead of a smooth shank and likely to soon work loose.
    Depending on how the attachments are actually laid out screws may be far stronger than bolts.
    This isn't how it is supposed to work. Bolts are supposed to be torqued to the point that they exert enough compressive stress on the fastened pieces that there is no lateral movement. What holds the parts stationary is the compression load between the fastened pieces, not the sheer strength of the bolt. The bolt should only see tension.

  27. #27
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    Default Re: Screws or bolts?

    Quote Originally Posted by Favorite View Post
    This isn't how it is supposed to work. Bolts are supposed to be torqued to the point that they exert enough compressive stress on the fastened pieces that there is no lateral movement. What holds the parts stationary is the compression load between the fastened pieces, not the sheer strength of the bolt. The bolt should only see tension.
    Which means that you should never use bolts in a boats construction, as the wood compresses, works, frets and the friction is lost. However if you drive the bolt through a tight hole it will also resist shear loads.

    However, in this case as the nuts will be peened any way to lock the treads, bolts are an ugly solution with as much work expended as copper rivets headed up in countersunk holes.
    It really is quite difficult to build an ugly wooden boat.

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  28. #28
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    Default Re: Screws or bolts?

    On one little boat I used bolts with a bit of modification. Round head SS bolts. Very tight tolerance holes in wood and steel. The pintles were on the rudder. I threaded the holes on far side of the tangs and screwed the bolts in bringing all snug. Then I put a nut on and brought it down snug. Then out with the trusty grinder. I took the bolt head down till the slot just disappeared. On the other side, I cut the protruding bolt flush with the nut and then ground the nut down to about half thick. With a small metal grinding blade on the end of my little Fein I shaped all protrusions into sort of flattened domes.

    And a prayer of pity if anyone ever has to take it apart.

    All things considered bronze rod and bronze washers for the roves are best for attaching tangs to the rudder. Copper rivets are fine for light planking as many fastenings spread the load, but this is a higher stress application calling for bronze. No heat in the peaning. Just lots of light tapping. I cheat a little with a couple of light taps to the end of the rod with a succession of three fine to blunt punches to get the mushroom starting.

    For the bits going through the transom, bolts with washers are fine. Put the nuts on the inside.

  29. #29
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    Default Re: Screws or bolts?

    I used copper nails peened over SB washers for the rudder mounts on my Chamberlain Dory Skiff and they've held up well for over a decade. But the rudder is kickup and has never hit anything really hard. I always worried a bit about the sheer strength of the copper fasteners...

    "The enemies of reason have a certain blind look."
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  30. #30
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    Default Re: Screws or bolts?

    Quote Originally Posted by Peerie Maa View Post
    Stainless dinghy fittings or cast bronze? If cast I would definitely use copper, but bronze screws will work. The holes in Peerie Maa's gudgeons and pintles do not line up, so she has had screws for over 50 years.
    Hey, Nick --

    two questions for you:
    The wife wants to know what kind of boat this is.

    I'd like to know how long you had to wait for a bright sunny day to come along?
    Peace,
    Bill
    "The future is already here it's just not very evenly distributed." William Gibson

  31. #31
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    Default Re: Screws or bolts?

    Quote Originally Posted by Peerie Maa View Post
    Which means that you should never use bolts in a boats construction
    Bull****.
    as the wood compresses, works, frets and the friction is lost.
    So does everything else. You just have to design the joint to account for the material being used.

  32. #32
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    Default Re: Screws or bolts?

    Quote Originally Posted by webishop14 View Post
    Hey, Nick --

    two questions for you:
    The wife wants to know what kind of boat this is.

    I'd like to know how long you had to wait for a bright sunny day to come along?
    Peace,
    Bill
    She is a Shetland model. The owner/builder would call her a 12 foot of keel whilly boat. She is the smallest of the family that included fourerns and sixareens.

    We live in England, bright sunny days come along quite often. You were maybe thinking of Scotland, where bright sunny spells also occur daily, interspersed with fog, rain, sleet, and snow.
    It really is quite difficult to build an ugly wooden boat.

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  33. #33
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    Default Re: Screws or bolts?

    Quote Originally Posted by Favorite View Post
    This isn't how it is supposed to work. Bolts are supposed to be torqued to the point that they exert enough compressive stress on the fastened pieces that there is no lateral movement. What holds the parts stationary is the compression load between the fastened pieces, not the sheer strength of the bolt. The bolt should only see tension.
    Quote Originally Posted by Peerie Maa View Post
    Which means that you should never use bolts in a boats construction, as the wood compresses, works, frets and the friction is lost. However if you drive the bolt through a tight hole it will also resist shear loads.
    Quote Originally Posted by Favorite View Post
    Bull****.

    So does everything else. You just have to design the joint to account for the material being used.
    I was being ironical.
    Bolts are OK when driven into tight holes so that the wood is able to transfer shear loads through the bolt, just as dumps and nails do. It is the transfer of shear loads not the friction due to compressing the faying surfaces that makes for a lasting joint. If the holes become enlarged over time as the boat works so that shear loads are not effectively resisted she becomes loose and leaky.

    Why do you think that Lloyds Rules, Herreshoff''s and Nevin's Rules always size bolts by diameter, which calls for a bolt way over the strength needed to crush the wood if the bolt was torqued up to its tensile strength? It is because they are considering the compressive strength of the wood along the grain and the shear loads being transferred across the joint.
    It really is quite difficult to build an ugly wooden boat.

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  34. #34
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    Default Re: Screws or bolts?

    Quote Originally Posted by Peerie Maa View Post
    I was being ironical.
    Ah. Then you should have used the (galvanized) ironical emoticon

    Cuz there's a hunnerd bolts within eyesight right now in an 80 year old boat that's been used hard and put away wet, and she's as tough as the day she was first dropped in the water. So it can be done .... they aren't being used as threaded nails, either. They really are clamping the 6x8's together.

  35. #35
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    Default Re: Screws or bolts?

    Quote Originally Posted by Favorite View Post
    Ah. Then you should have used the (galvanized) ironical emoticon

    Cuz there's a hunnerd bolts within eyesight right now in an 80 year old boat that's been used hard and put away wet, and she's as tough as the day she was first dropped in the water. So it can be done .... they aren't being used as threaded nails, either. They really are clamping the 6x8's together.
    Ever tried getting one of them out? What weight of hammer did you have to use to drive it back out?
    It really is quite difficult to build an ugly wooden boat.

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