Roofing material for bedding?

Discussion in 'Materials' started by longfellow, May 10, 2009.

  1. longfellow
    Joined: Apr 2009
    Posts: 39
    Likes: 1, Points: 0, Legacy Rep: 17
    Location: upstate NY

    longfellow Junior Member

    I'd like to try traditional reinforced roofing tar to bed keel and stem components. Are there any particular types or brands that are better or worse than others? I have something in my shop from a previous home repair that I believe has some form of reinforcing fibers mixed in which I'd like to use. Mineral spirits clean up is an added benefit.
    Thanks.
     
  2. alan white
    Joined: Mar 2007
    Posts: 3,731
    Likes: 122, Points: 0, Legacy Rep: 1404
    Location: maine

    alan white Senior Member

    I recall using an aluminum-based fiber reinforced mixture to patch a trailer roof, but I wouldn't trust anything with aluminum in it near salt water. Is your mixture silver?
    The fibers--- do they list the ingredients?
     
  3. BLACKIE
    Joined: Apr 2009
    Posts: 8
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: ASHEVILLE NC USA

    BLACKIE Junior Member

    roofing tar is somewhat watersoluble.
    it also shrinks as it dries. fibers or not.
    speaking from experience.
     
  4. alan white
    Joined: Mar 2007
    Posts: 3,731
    Likes: 122, Points: 0, Legacy Rep: 1404
    Location: maine

    alan white Senior Member

    Water soluble? To some degree that is actually noticable or matters? Is this something that's generally known? I know it dries out. But whereas my asphalt roof is close to 25 years old and still okay, I am imagining tar in a crevice not subject to the sun at all. Melting away?
     
  5. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 491, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    There are a few basic types of roofing tar or cement used. You want the petroleum based stuff, not the polymers. Yes, some shrinkage is to be expected, particularly if exposed to UV. The polymer based stuff may very well be slightly water soluble, but I'm fairly sure the petroleum isn't.

    Be warned, this stuff gets all over everything, regardless of how careful your are. You will have a very difficult time painting over it and it will always smell like, well, tar.
     
  6. alan white
    Joined: Mar 2007
    Posts: 3,731
    Likes: 122, Points: 0, Legacy Rep: 1404
    Location: maine

    alan white Senior Member

    Sounds like roofing tar, if petroleum=based, would do best out of sight and under water, say as a bedding compound for deadwood, floors, ballast-to-keel faces, plank lands (below waterline), centerboard trunks (logs and faying against bottom). What do you think, PAR?
     
  7. BLACKIE
    Joined: Apr 2009
    Posts: 8
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: ASHEVILLE NC USA

    BLACKIE Junior Member

    i've used tar in the past on wood boats. i really wanted it to be a good thing. but i won't use it again if i have other choices.
    some reasons--
    it's not springy, so bedding with it just squeezes it out, then when it shrinks it leaves pathways through the bedding. it can't well be painted over. if i were un-experiencd, i'd still be trying it out, because i love the idea of it-- so old school etc., cheap, mineral spirit compatible-- all the reasons that led me to try it out for years.
    now my favorite cheap stuff is Alex Plus 50 yr latex caulk. Even the 35 yr stuff. Home Depot chandleries. It sticks, has body after drying. Elastic as all get out. Cheap. Water clean up. I used it for 6-8 years on an old wood boat. 2 atlantic circles. 5 years in west africa. Another good thing about it is when it's time to repaint, it can be added to, or removed easily-- it's not overkill-tough, like 5200.
    above water only or course.
     
  8. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 491, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Petroleum based tar was and in many parts of the world still is the preferred bedding compound for deadwood assemblies, under strut flanges, between diagonal plank layers, etc. It can be painted, but because it never really gets hard it will crack and split the paint film with any movement or contact. It's more effective then Dolfinite, but used in a similar fashion and has similar qualities.

    I wouldn't call Home Depot or any other home improvement store a chandlery, nor would I use bath room type caulk on any wooden boat. Metal or GRP are better choices for this low grade type of caulk, but not on my boat, it just doesn't hold up to the tropical sun.

    Blackie, there's a fair bit of difference between bedding compounds, sealants and adhesive/sealants. Often one can't be used in place of the other. Given the number of choices and durability of the selection now available, it seems fruitless to be frugal in this regard.
     
  9. BLACKIE
    Joined: Apr 2009
    Posts: 8
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: ASHEVILLE NC USA

    BLACKIE Junior Member

    beg to differ, par. holds up splendidly under the african sun, as i pointed out. these are just chemical compouds, my friend, not gifts from the nautical gods.
    tar has been used traditionally mostly because it was available. meaning home depot hadn't arrived yet.
     
  10. BLACKIE
    Joined: Apr 2009
    Posts: 8
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: ASHEVILLE NC USA

    BLACKIE Junior Member

    and don't get me wrong. tar has a lot of uses on wooden boats. toilet seal wax is also useful. no ****. that's funny. but i mean it.
    bear in mind that "tar" refers to a miriad of substances, with a very broad range of characteristics. fibered black-jack, fer instance is way different than the hot-pitch on your roof, alan.
    and yes, black-jack is fine in any third-world type approach to building, which is necessarily frugal, par. i've used a ton of it. but it's downside (messiness, paint bleed-through, and shrinkage) was, for me, finally not worth it, except for emergency patching and the ilk.
    it's good for sealing the wood after digging out rot prepartory to filling the void with cement when you can get away with it structurally. (drive a forest of little nails half-way home after the tarring, for the concrete plug to anchor by)
     
  11. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 491, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Okay, I guess all us engineers, builders and designers with countless decades of experience must be wrong and lowly old bath room caulk is the answer. Damn how'd I miss that. Frankly, I've tested most of the major brands and formulations and my tests coincide with manufacture and independent studies as well, but hell who are we . . . or possibly more importantly, who are you?
     
  12. longfellow
    Joined: Apr 2009
    Posts: 39
    Likes: 1, Points: 0, Legacy Rep: 17
    Location: upstate NY

    longfellow Junior Member

    Well, I used it and we'll see how it holds up. I am using this first wooden boat as a sort of test bed for materials as well as construction techniques; being careful to only take on acceptable risks so that my boat still gives me a fair number of years of enjoyment.
    So I used a petroleum based asphalt material, but I went with one that has no fiber thickeners - though I did see "clay" in the "contains..." section of the tube. It went on yesterday, between my new cutwater and the stem so it is partially below WL. Since it cleans up with mineral spirits and is a great consistency as far as bedding goes (at least on the cool day that I used it), it made for a very clean looking final assembly with a faint line made by the fillet showing. My hull is Brightside deep blue so it is barely noticable. I am not going to be able to put in the water until after the Mystic show (she is participating in the "I built it myself" display this year.) but I am sure she'll be fine. Thanks all for the useful input.
     
    Last edited: May 11, 2009
  13. peter radclyffe
    Joined: Mar 2009
    Posts: 1,420
    Likes: 66, Points: 58, Legacy Rep: 680
    Location: europe

    peter radclyffe Senior Member

    fwiw, i have to use an approved sealer, sika, or other for any customer for obvious reasons, however if its for your own boat , i think you should look at the expansion jointing compound used between concrete blocks in sea defence walls, it must be tough stuff, & a lot cheaper
     
  14. Boston

    Boston Previous Member

    Ive used my share of Sika and its vastly superior to tar
    I hated using tar and waaaaaaay back in the day pretty much stuck to pine tar ( har har har ) rather than petroleum tar as a bedding for pins and such. It got everywhere and at the end of the day you always ended up smelling like a pine tree.
    Sika also gets everywhere and also cleans up with alcohol has significantly better stick and is highly paintable
    costs a fortune as well
    B
     

  15. TollyWally
    Joined: Mar 2005
    Posts: 774
    Likes: 26, Points: 0, Legacy Rep: 423
    Location: Fox Island

    TollyWally Senior Member

    Well I think weather and style of boat have a lot to do with it. We did some remarkable repair work with roofing tar on old worn fishing boats in Alaska. On the right vessel tar smells kind of good. It didn't get very hot up there and I think that helps a lot.

    Another great product for cooler weather is cosmoline. There were lots of ex military guys around and several people had big buckets of the stuff. Painting hydraulic motors and fitting with this stuff and then wrapping it with this waxy tape product made a messy but bullet proof covering. You would cut it away and find a gleaming motor or fitting underneath. Pretty sweet for gear living on deck and subject to saltwater washdowns every day. With practice we developed a method of wrapping the waxy tape with some sort of cloth tape for several layers and then painting it with porch enamal mixed with a little jap drier. You didn't want to sit on it but it really wasn't too bad and when the underlying parts had to be serviced it made you grin a little bit. Not really yacht grade but effective.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.