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Thread: How to repair damaged dynel sheating on stem?

  1. #1
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    Default How to repair damaged dynel sheating on stem?

    Ahoi!


    We've just started the new life adventure on 'yeswhen' and one of the first repairs to do before we can go anywhere is to fix two damaged points on the stem that somehow have been subject to some sort of impact. We don't believe the past owner (deceased) did the damage, as he was very cautious and careful of his vessel, but nevertheless the damage still needs to be repaired.


    The hull is diagonal double planked oregon and as far as we know is all sheated with dynel. I have been reading extensively about this material and as far as my understanding has gone it's not a strenght-supportive material rather a waterproof-base for a good paint but as well able to resist abrasion and hold together in tough impacts.


    As you can see in the pictures (quality is just OK, they're taken from the camera screen) the impact has gone trough whatever the layer and has left the timber to be seen from outside.


    I have little experience with most of repair materials but I learn quick and I follow instructions easily allowing some leeway to make mistakes that will get better with time, therefore I humbly ask for help and advice in order to keep the knowledge growing!


    Very happy to own a wooden boat and be able to share the story in this magnificent forum.


    Thanks in advance,


    Jorge

    IMG_0863.jpgIMG_0862.jpg

  2. #2
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    Default Re: How to repair damaged dynel sheating on stem?

    You not only need to identify the type of fiberglass cloth used, like Dynel, but the type of epoxy. Most modern boats are built with epoxy resin over various types of cloth, but in the past there was a lot of polyester resin used -- the stuff that makes gelcoat -- because it is cheaper than epoxy resin. Many downsides to polyester resin (try a forum search) but the big one is that it doesn't adhere well to wood and nothing adheres well to it. One way to identify it is to sand it -- if it stinks badly it is probably poly resin. Others here will know a lot more about this issue!

    From the photos it looks like rust, so I'm assuming there is some sort of ferrous material under the front of the stem -- possibly a steel bar or half-round to give impact protection? I think you'll want to pull as much of the fiberglass off the stem area as possible to determine what is there, then we can see about how to fix it.
    "The enemies of reason have a certain blind look."
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  3. #3
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    Default Re: How to repair damaged dynel sheating on stem?

    Looks like there is paint under the outer layer of materials. Epoxy or any other resin will not permanently adhere to painted surfaces.

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    Default Re: How to repair damaged dynel sheating on stem?

    Get out the grinder, remove all of the loose material and see what you have under those bumps and tears. Be ruthless, get to the bottom of it. But be careful. Sounds contradictory? Not really. Just do it and then post more pics so we can help. Right now it is a mystery until you expose it.

  5. #5
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    Default Re: How to repair damaged dynel sheating on stem?

    That doesn't look like any kind of cloth at all to me. It looks like Bondo, a polyester based filler used on auto bodies.

    It cracked, as Bondo over wood so often does, and water got in a nd rusted something ferrous based.

    You can probably remove it much more easily and safely with a screwdriver or other prying device. If you bang it with a hammer it will most likely break and be easier to remove.

    Sorry. I hope I'm mistaken.
    Last edited by Gib Etheridge; 04-30-2019 at 10:34 AM.

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    Default Re: How to repair damaged dynel sheating on stem?

    Agreed. Cloth sheathing - fiberglass, nylon, Dynel, etc. does not break cleanly. It would have some ragged broken fibers hanging out. That looks more like some sort of flaking filler, which could be polyester based, or it could be epoxy based. Once you start stuffing either type of resin with a lot of minerals to make a thick, non-sagging filler material, it will lose a certain amount of its ability to stick to other surfaces and is more prone to flaking off or delaminating on impact. The epoxy versions are generally going to stick better than polyester versions, but they are still by no means immune to such damage. You can also get areas of fill which aren't stuck very well to the layer beneath it by not prepping that layer properly before adding the fill.

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    Default Re: How to repair damaged dynel sheating on stem?

    Quote Originally Posted by Oldad View Post
    Get out the grinder, remove all of the loose material and see what you have under those bumps and tears. Be ruthless, get to the bottom of it. But be careful. Sounds contradictory? Not really. Just do it and then post more pics so we can help. Right now it is a mystery until you expose it.
    +1 You can't solve a problem until you know what it is.

    It does not look like there is any fiber in the cracked coating. The presence of cloth would make a difference, but the type of cloth, if any, is not important at this point. The resin is important to some extent. Polyester isn't good, but if it is intact, I would leave it alone where it isn't damaged. Unless it is Bondo anyway. I doubt anyone would cover a whole boat in that stuff, but they might use it to fair a small area. As far as the repair is concerned, you would use epoxy regardless of the original resin.

    There are several threads with a lot of detail on abrasion and fabric coatings. The type of cloth makes some difference, but the overall thickness makes more. Background information if you are interested, but not directly relevant for this repair.
    http://forum.woodenboat.com/showthre...ion-Resistance
    http://forum.woodenboat.com/showthre...olyester-cloth
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    Default Re: How to repair damaged dynel sheating on stem?

    All of that^.
    You got a rust problem goin on too that needs checking out.

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    Default Re: How to repair damaged dynel sheating on stem?

    Hi Jorge, welcome to the forum. There certainly is a wealth of knowledge here and I'm sure you will be guided well.
    Just like to add, does she need anti foul? Looks to me like a job for in the hard.
    Last edited by Geftb; 04-30-2019 at 03:30 PM.

  10. #10
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    Default Re: How to repair damaged dynel sheating on stem?

    Have to agree, that does not look like cracked dynel or glass. OTOH, and it might be the pixilation of the photo, but there does appear to be some type of print through weave of the undamaged portion, which does tend to make one think dynel. I would be concerned with the possibility of a polyester resin as opposed to epoxy also. If it is epoxy, I doubt if you need to know the type that was used (as Thorne said, but I think he just meant to know if it was polyester resin or not). Definiely get the grinder or disk sander out and start clearing away all the bad stuff to see exactly what is under it all. I am not for sure it is rust, it could be thickened epoxy with 407. That's not good either, as it should not have been sheathed on top of fairing compound.

  11. #11
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    Default Re: How to repair damaged dynel sheating on stem?

    The print thru shows on the sand or water or whatever that is, so it's probably not cloth.

    It looks to me like the ferrous stem band was too wide for the wooden stem and got faired in with Bondo. If that's the case it all needs to be removed because the bond is failing and water is being held underneath. You can see blisters to the left and below in the first pic. The whole stem and maybe the plank ends will rot out next. There may be more of it elsewhere too. Like I said, a hammer and screwdriver will be the right tools.

    I hope I'm mistaken.

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    Default Re: How to repair damaged dynel sheating on stem?

    Quote Originally Posted by Gib Etheridge View Post
    The print thru shows on the sand or water or whatever that is, so it's probably not cloth.

    It looks to me like the ferrous stem band was too wide for the wooden stem and got faired in with Bondo. If that's the case it all needs to be removed because the bond is failing and water is being held underneath. You can see blisters to the left and below in the first pic. The whole stem and maybe the plank ends will rot out next. There may be more of it elsewhere too. Like I said, a hammer and screwdriver will be the right tools.

    I hope I'm mistaken.
    Ya, you are right, I did not look close enough.

  13. #13
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    Default

    What they said. When they say grinder, what you want is a small angle grinder with 16 grit paper, with a rubber sanding backer behind it. The rubber bit can be hard to find, but it's usually somewhere down the back left corner in Bunnings tool section. Just grind everything back to clean. Work out where the rust is coming from and how to deal with that. It might just be a stainless fitting. Then fair and glass and fair and paint. I think Ted Hoppe did a similar repair on his stem a while back after a right of way incident.

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    Default

    Looks a bit like the rust stain might just be running down the stem from the anchor? These guys can give you nightmares sometimes with their speculation!

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    Default Re: How to repair damaged dynel sheating on stem?

    If it is then water is running down with it. Not good.

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    Default Re: How to repair damaged dynel sheating on stem?

    More I think about it, it looks like a really bad repair that has failed. I am eager to see pics after you do a bit of exploring weather it be by grinder,hammer, screwdriver, or whatever. As soon as you see sound material, dont dig any further, but do try to clear away all of that grungle.

  17. #17
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    Default Re: How to repair damaged dynel sheating on stem?

    Wow!! Thanks everybody, I do feel a little overwhelmed by all your good advice and different theories of what might or might not be!

    The rust issue I'm pretty sure it's not related to the damage (although who knows untill it's all open) since the rust stripes are coming from an unnateded steel plate at the bow that sadly needs attention too:

    IMG_0864.jpg

    There's three points like this one that will be adressed as soon as we've ticked other jobs upper on the job list. As soon as we've started looking deeper into things I've found out major things broken or heave˝y loose (both water/fuel separators, hanging on one ver loose bolt and a dropping nut) or pipes from the cooling sydtem that ste hanging on for dear life on a mm away from making a huge mess in the bilge.

    We'll tackle the rust chipping as deep as it goes, and getting it to shine before primer and paint, hopefully not having affected the core of the plate.

    As soon as I start getting into the job I'll post some more pictures. Thanks a lot for the hige help already and we'll see what this interesting project keeps bringing. I'll aim to tale a couple of better pictures tomorrow of the stem and other bits of the hull that I'd like to put attention on to keep the post going.

    fair winds!

  18. #18
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    Default Re: How to repair damaged dynel sheating on stem?

    Jorge, what kind of boat is this, sail or power?

  19. #19
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    Default Re: How to repair damaged dynel sheating on stem?

    The danger of rust on a wood boat is not the damage to the fitting itself , but the damage done to the WOOD around the fitting and especially rusty fastenings.
    Sounds like your boat has suffered from a lack of knowledgeable maintainance.
    Google up “ospho “, a brand of phosphoric acid. I promise it will become a favorite item aboard .

  20. #20
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    Default Re: How to repair damaged dynel sheating on stem?

    IMG_0846.jpg

    Oldad, this is the beauty itself.

    I did not get around taking detailed pics today, got the engine running and there was no water coming out! Solved it. Tomorrow maybe!

    Thanks wizbang, i'll have a look for ospho around. The last owner seemed to use "Coldgal", you know about this product?

    cheers and thabks again!

  21. #21
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    Default Re: How to repair damaged dynel sheating on stem?

    Another opinion - probably worth every cent you've paid for it...

    My boat was originally iron fastened & had iron tie rods & the like in a number of places. I have, over the years, replaced every bit I could, as the iron was damaging the wood around it - badly. In some places I had to replace major pieces of wood the regain structural integrity.

    Looking at the pic in post #17 gives me the willies. That rusted piece is doing damage to everything around it! IMO, it's way too far gone to coat with anything (whether ospho or cold galvanizing). It needs to go away & be replaced with a non-ferrous piece.

    This iron keelbolt completely destroyed the floor timber it went though - I literally pulled the "timber" out with my hands. That's not even talking about how it no longer held the keel onto the boat!

    OldKeelbolt.jpg
    "If it ain't broke, you're not trying." - Red Green

  22. #22
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    Default Re: How to repair damaged dynel sheating on stem?

    Probably not a good idea to try to make those repairs on the water. Time for a haulout.
    And Garret is right.

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    Default Re: How to repair damaged dynel sheating on stem?

    I have never been able to find Ospho in Aus. Cold gal I have always found to be pretty useless. You need proper hot dip.
    And yep, time for a haul out.

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    You do need to chip away all that paint and whatever up at the bow. Might not be as bad as it looks. Or might be worse. Lots going on up there with cleats and fairleads and stem fittings. It's quite an important part of the boat so have a good look inside and outside. I'm not sure why there would be a mild steel plate up there. But that being where the rust stains are coming from, your stem repair is likely just cosmetic. Grind it out, epoxy, glass and filler. There's no indication that your keel is about to fall off!

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    Default Re: How to repair damaged dynel sheating on stem?

    I know some don't mind grinding it all back in the water. But really, the ocean doesn't need more dust size fillers freely dispersed. Have a chip at it for sure. You can park the dingy under it and catch most of it. But save the grinding for the boat yard. My 2c

  26. #26
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    Default Re: How to repair damaged dynel sheating on stem?

    You could try this:
    Partsbrella.jpg

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    Default Re: How to repair damaged dynel sheating on stem?

    Quote Originally Posted by Geftb View Post
    I have never been able to find Ospho in Aus. Cold gal I have always found to be pretty useless. You need proper hot dip.
    And yep, time for a haul out.
    Pretty much the same as Ospho https://www.bunnings.com.au/chemtech...mover_p1107356
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

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    Default Re: How to repair damaged dynel sheating on stem?

    Thanks for all your great feedback and knowledgeable advice. At this stage and with your suggestions this repair will come first thing of attention as soon as we've got the cleaning up and inventory of the more than plentiful stuff done. Bureaucrazy is also time consuming as well as just life on board. We're moving aboard (we're houseless) so that takes a bit of time too.

    After yesterday's rain we also know where are some noticeable leaks in different spots. The bow definitely takes in water, but it seems to be more from the pulpit connections to the deck (sure there's a better word for it) that are to be adressed in another thread.

    I've just gone to bail out the rainwater from the dhingy and took some boat porn repair pictures for your eyes. Lets
    's go from 'easier' to 'major' repairs in my humble little knowledge of this materials:

    #1: Seem to be from the diagonal planking, mildly superficial. There's like 7 of this ones in different sizes:

    IMG_0898.jpg

    IMG_0891.jpg

    IMG_0892.jpg

    #2 Stern / Transom. Also superficial with sheating exposed

    IMG_0890.jpg

    (Continues in next thread, just discovered max of 5 pics to upload!)
    Attached Images Attached Images

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    Default Re: How to repair damaged dynel sheating on stem?

    #3: On stb side, random sort of bubble but sheating underneath looks ok. First picture is as found, second one after peeling a bit to expose sheating:

    IMG_0896.jpg

    IMG_0897.jpg

    #4: The stem damage from the thread topic, with more detail. I could peel off a bit of the sheating in order to show it here but definitely wood inside is exposed.

    IMG_0893.jpg

    IMG_0894.jpg
    Attached Images Attached Images

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    Default Re: How to repair damaged dynel sheating on stem?

    Sorry about last post with extra pix, still getting head around posting.

    #5: This, as most of you say, looks quite major. I overexposed the picture to be able to show the level of rust but yeah, quite serious stuff goong on in there. From the inside the stem looks OK with no major rust but i guess you never knoe untill you pop it out and look. Looks like the last owner layered ColdGal on it and not much further for time. Strange, since he took a lot of care of the majoroty of the vessel, but truth is that age and sickness was coming hard on him on his last years of life, and the bow its definitely hard to access.

    IMG_0895.jpg

    image.jpg

    image.jpg

    image.jpg

    I dislike a lot the look of the forestay sitting on the rusted plate, surely we won't go anywhere before is all fixed.

    Is there anything we can do, now, today, temporarily, to stop it from getting potentially worst? We wont be hauling out just yet, but will consider t as soon as we've tackled first things.

    Thanks again for your kind help and please remember that I'm learning by doing and I don't know some of the terms or materials yet. Ex: someone said, "replace with non-ferrous material" - Not putting a plate fastened to the stem? A lot of the structure is reinforced with galvanised steel and is in good condition. And what's Hot dip against Cold Gal?

    cheers!

  31. #31
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    Default Re: How to repair damaged dynel sheating on stem?

    The difference is cold gal is painted on from a can. Basically a zinc rich paint.
    Hot dip can be read about here. https://en.m.wikipedia.org/wiki/Hot-dip_galvanization
    there will be plenty of places in Sydney that do it. It may require some pieces being remade others may sandblast up ok before hand. I don't think you can hot dip something that's already been hot dipped previously. I have been told two different stories on that so your local service will clarify.

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    And non ferrous metal is stainless or bronze.

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    Default Re: How to repair damaged dynel sheating on stem?

    This is going to be a great thread. Please keep the pictures coming!

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    Default Re: How to repair damaged dynel sheating on stem?



    This is an intriguing picture. There are what, 5+? layers of quite thick paint (or something) and the very first one doesn't appear to have a very good grip on the sheathing. I think you have a lot of deferred maintenance to catch up on. Beautiful boat, looking forward to seeing the interior.
    Steve

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  35. #35
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    Default Re: How to repair damaged dynel sheating on stem?

    Seems to me the sooner you can get the boat on the hard, the sooner you can begin to attack the problems in a serious way.
    Would your yard allow you to live and work on the boat while it is hauled?
    I would not wait any longer.

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