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Thread: Any tips on using magnets in boat carpentry?

  1. #1
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    Default Any tips on using magnets in boat carpentry?

    I bought a new fishfinder/chartplotter for my small open skiff (a Cackler) and I'm making a little three sided box for mounting and to protect it from water. The roof and three sides will be removable so you can adjust and remove the display unit. So I was thinking of installing small magnets on the cypress cleats I put on the plywood base and the corresponding cleats or trim on the inside base of the sides and back panels. I ordered some small magnets from McMaster Carr but I have not used them before so I don't know if they should be epoxied into a hole and be exposed or covered with epoxy and/or paint. Thanks

  2. #2
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    Default Re: Any tips on using magnets in boat carpentry?

    I've been doing that with these things since not too long after they became widely available. Use 'em for 'hidden' closures in all kinds of things, they're small enough to go mostly unnoticed whether left 'bright' or painted over. Even hidden under thin veneer they'd be useful, as I've seen on various kinds of packaging this last year.

    My practice is to use a Forstner bit to drill a shallow hole just a tad larger than the magnet, then bed each one in epoxy. A small bit of smooth wood covered in clear packing tape can then be clamped over everything, leaves you with a flat surface once the wood spline gets removed though you may have to do a bit of scraping to take the squeeze-out off surrounding wood if desired. They don't need to be in intimate contact when poles are opposed to work well.
    "The energy sources we use to make electricity can be renewable (such as wind or solar) or nonrenewable, but electricity itself is neither renewable nor nonrenewable."

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    Default Re: Any tips on using magnets in boat carpentry?

    How to avoid deranging the compass?

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    Default Re: Any tips on using magnets in boat carpentry?

    I have not used magnets. I would be concerned about, as Jim stated above, the effect of magnets on my compass and on electronic screens.

    I have used suction ( vacuum cups) cups. The Sea Sucker brand works great for holding things down in rough seas yet remaining removable. There's all types. The basic one allows you to bolt your device or thing to the housing.

    Screen Shot 2022-08-17 at 9.30.01 AM.jpg



    As an aside: You don't need to protect your chartplotter from water, though I understand there may be other reasons for building a box to house it.

    Let us know what you do and how it works out!

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

  5. #5
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    Default Re: Any tips on using magnets in boat carpentry?

    Keep magnets away from your compass and electronic equipment.

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    Default Re: Any tips on using magnets in boat carpentry?

    Recovering dropped steel/iron tools amongst the shavings.

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    Default Re: Any tips on using magnets in boat carpentry?

    Thanks, Clark. That is kind of my plan with Forstner bit etc

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    Default Re: Any tips on using magnets in boat carpentry?

    Just a thought: I would consider using the magnets on the cover itself, and then steel where they will connect (perhaps potted in epoxy to prevent rust). That way, you can keep the cover and the magnets FAR from the compass and electronics when using, but still available when you need.

    I say this as a way to make the magnets work. Personally, it would not be as visually pleasing but I would use a heavy duty velcro type product like 3M Dual Lock: https://www.3m.com/3M/en_US/dual-loc...-fasteners-us/

    Don't get me wrong: I love rare earth magnets, and they will work as you propose. There just may be some unintended consequences.
    Heute ist so ein schöne Tag...

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    Default Re: Any tips on using magnets in boat carpentry?

    Interesting that you raise this as I’ve been considering something similar myself for my GPS/chart plotter box.

    The magnets do need to be sealed in and protected from spray to stop them from rusting - unless they say that they have already been protective coated...???

    As far as positioning them with equipment goes, I hear what the guys are saying but (in my case anyway) the single magnet “catch” would be about five to six inches away from the GPS so I’d have thought that shouldn’t be an issue....???

    But Don Z’s suggestion of mounting the magnet in the lid to get it further away when the GPS is operating would work just as well.

    I intend to seal and protect the magnet in place with epoxy and varnish and for the steel striker/catch plate (probably 304 SS) to be treated and also sealed with varnish to protect it from rust.

    [IMG]IMG_3902 by Greg Larkin, on Flickr[/IMG]


    [IMG]IMG_3901 by Greg Larkin, on Flickr[/IMG]
    Larks

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  10. #10
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    Default Re: Any tips on using magnets in boat carpentry?

    I'm not a metal guy but magnets don't hold on my stainless steel fridge.


    • "304 stainless steel is non-magnetic and exhibits high resistance to corrosion and oxidation against atmospheric, chemical, petroleum, textile, and food industry sources."

    They sell magnets that are covered for corrosion protection. I don't think these small magnets are going to affect the unit but if so I'll do something else. After all the Bond films tell us that GPS trackers are fine when attached to the underside of a vehicle with a magnet. In real life too I guess

    magnets | McMaster-Carr

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    Default Re: Any tips on using magnets in boat carpentry?

    Quote Originally Posted by gray duck View Post
    I'm not a metal guy but magnets don't hold on my stainless steel fridge.


    • "304 stainless steel is non-magnetic and exhibits high resistance to corrosion and oxidation against atmospheric, chemical, petroleum, textile, and food industry sources."

    They sell magnets that are covered for corrosion protection. I don't think these small magnets are going to affect the unit but if so I'll do something else. After all the Bond films tell us that GPS trackers are fine when attached to the underside of a vehicle with a magnet. In real life too I guess

    magnets | McMaster-Carr
    Where on earth did you find that claim? It’s completely wrong.

    The easiest way to tell the difference between 316 SS and 304 SS (if it is not labeled) is that 304 is magnetic, while 316 is not magnetic. Furthermore 304 shows only moderate resistance to corrosion and should not be used in a marine environment as it does rust.

    "The two most common stainless steel grades are 304 and 316. The key difference is the addition of molybdenum, an alloy which drastically enhances corrosion resistance, especially for more saline or chloride-exposed environments. 316 stainless steel contains molybdenum. 304 stainless steel does not."
    Larks

    “It’s impossible”, said pride.
    “It’s risky”, said experience.
    “It’s pointless”, said reason.
    “Give it a try”, whispered the heart.

    LPBC Beneficiary

    "Keep away from people who try to belittle your ambitions. Small people always do that, but the really great make you feel that you, too, can become great!"

  12. #12
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    Default Re: Any tips on using magnets in boat carpentry?

    Quote Originally Posted by Larks View Post
    Where on earth did you find that claim? It’s completely wrong.
    Yep, s'trudat:

    https://www.kloecknermetals.com/blog...-steel-vs-316/

    https://www.gibsonstainless.com/304-...ess-steel.html

    https://www.microgroup.com/understan...ainless-steel/
    "The energy sources we use to make electricity can be renewable (such as wind or solar) or nonrenewable, but electricity itself is neither renewable nor nonrenewable."

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  13. #13
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    Default Re: Any tips on using magnets in boat carpentry?

    internet. I know you guys know what you're talking about and you have to be careful reading things but this looked pretty legit...
    304 Stainless Steel Properties - EngineeringClicks

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    Default Re: Any tips on using magnets in boat carpentry?

    Quote Originally Posted by Larks View Post
    Where on earth did you find that claim? It’s completely wrong.

    The easiest way to tell the difference between 316 SS and 304 SS (if it is not labeled) is that 304 is magnetic, while 316 is not magnetic. Furthermore 304 shows only moderate resistance to corrosion and should not be used in a marine environment as it does rust.

    "The two most common stainless steel grades are 304 and 316. The key difference is the addition of molybdenum, an alloy which drastically enhances corrosion resistance, especially for more saline or chloride-exposed environments. 316 stainless steel contains molybdenum. 304 stainless steel does not."
    Indeed! The best practice is to bring a magnet with you when you go to the store to buy stainless fasteners. (I learned this after installing a track on a 40' mast using what the chandlery clerk swore were 316 "marine" stainless.)

  15. #15
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    Default Re: Any tips on using magnets in boat carpentry?

    I don’t think I’ve heard that magnets affect a GPS receiver.
    Has anyone got a reputable source on this?

  16. #16
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    Default Re: Any tips on using magnets in boat carpentry?

    Fixed magnets should have no effect whatsoever on GPS reception.

    Unless you use a mountain of them to make a Faraday cage around your antenna, then maybe.
    Dreaming of sailing in Iowa, building a Carnell Nutmeg.

  17. #17
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    Default Any tips on using magnets in boat carpentry?

    Magnets wont affect GPS reception. Magnets will not affect an LCD screen like they will a CRT display.

    A magnet can wipe the memory card on which the charts for the GPS are stored.


    Sent from my iPhone using Tapatalk Pro
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    Default Re: Any tips on using magnets in boat carpentry?

    Quote Originally Posted by Breakaway View Post
    Magnets wont affect GPS reception. Magnets will not affect an LCD screen like they will a CRT display.

    A magnet can wipe the memory card on which the charts for the GPS are stored.


    Sent from my iPhone using Tapatalk Pro
    that's a new claim to me, there's nothing in a compact flash card or sd card which uses magnetic fields
    I'd much rather lay in my bunk all freakin day lookin at Youtube videos .

  19. #19
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    Default

    Quote Originally Posted by P.I. Stazzer-Newt View Post
    that's a new claim to me, there's nothing in a compact flash card or sd card which uses magnetic fields


    Thank you, PISN. That Is a myth I have been laboring under for some time.

    I stand corrected.

    Kevin




    Sent from my iPhone using Tapatalk Pro
    There are two kinds of boaters: those who have run aground, and those who lie about it.

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    Default Re: Any tips on using magnets in boat carpentry?

    Quote Originally Posted by Larks View Post
    Where on earth did you find that claim? It’s completely wrong.

    The easiest way to tell the difference between 316 SS and 304 SS (if it is not labeled) is that 304 is magnetic, while 316 is not magnetic.
    About as true as the other claim. Both grades are austentitic and become magnetic by working. How strongly magnetic depends on the amount of work done, it locally changes the austentitic into a ferritic phase. If you deep draw a sink or pot from 316, it will be magnetic afterwards.
    Magnetism also doesn't have anything to do with corrosion resistance, Duplex 2205 is strongly manetic all the time, and has better corrosion resistance then 316.

  21. #21
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    Default Re: Any tips on using magnets in boat carpentry?

    My boat points about twenty degrees higher , with careful placement of the portable speaker.
    If I wanna go faster, I knock a few barnykills off the sumlog blades...no need to scrape the whole damn boat.

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    Default Re: Any tips on using magnets in boat carpentry?

    Quote Originally Posted by wizbang 13 View Post
    My boat points about twenty degrees higher , with careful placement of the portable speaker.
    If I wanna go faster, I knock a few barnykills off the sumlog blades...no need to scrape the whole damn boat.

    Jeff

  23. #23
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    Default Re: Any tips on using magnets in boat carpentry?

    Quote Originally Posted by Rumars View Post
    About as true as the other claim. Both grades are austentitic and become magnetic by working. How strongly magnetic depends on the amount of work done, it locally changes the austentitic into a ferritic phase. If you deep draw a sink or pot from 316, it will be magnetic afterwards.
    Magnetism also doesn't have anything to do with corrosion resistance, Duplex 2205 is strongly manetic all the time, and has better corrosion resistance then 316.
    Huh????? 'not sure how this helps anyone here Rumars - 'fact is if you pick up a piece of 316SS and put a magnet on it it won’t hold, pick up a piece of 314 and it will hold. It’s an accepted way of quickly telling the difference between 316 and 304 SS nuts bolts screws, rods, plate etc, given that these are the most common types of SS that you bare likely to find laying about.

    Steel will austentize and become non magnetic when heated above critical temp’, but does that really make any difference to anyone here in this context??
    Larks

    “It’s impossible”, said pride.
    “It’s risky”, said experience.
    “It’s pointless”, said reason.
    “Give it a try”, whispered the heart.

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  24. #24
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    Default Re: Any tips on using magnets in boat carpentry?

    The simple fact is that in unworked state both 304 and 316 are not mangnetic, and if you detect magnetism an a piece of stainless laying around you can't say anything about its grade.
    You don't have to believe me, there is enough scientific literature on the subject.

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