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Thread: Mast foot size

  1. #1
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    Default Mast foot size

    i will soon be fitting a couple of mast feet to a fibreglass canoe for a ketch rig and was thinking of glassing some oak blocks in for this and wondered on what depth the mast needed to be in for support, masts are 1.5" and 1.25" diameter and whether any other material would be more suitable ? ,any suggestions appreciated

  2. #2
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    Why oak? Just because you have some? It goes a bit black after lots of water soaking, which it will get! I've used ash because I had some handy and it matched other woodwork on the boat, but that suffers similarly and is almost as heavy. Marine ply (possibly in a few glued layers might be better and not so prone to swelling in the damp that could cause it to come unstuck. Using some urethane sealant/adhesive that stays slightly flexible after curing reduces the risk of it coming unstuck in this way (Sikaflex, Tigerseal etc).

    Depthwise I would say 3/4 inch or so - depends if the boat will flex and possibly cause the heel of the mast to jump out - can be catastrophic to the mast thwart (or "partner" for the Americans watching!)

  3. #3
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    hi keith
    YES ,basically i have a selection of decent seasoned oak in the garage ,im not to fussed if it goes black ,though this is usually with the presence of iron and i dont think ally will have the same effect .The inside of the boat is black anyway and i was intending to glass right over with black so it would not be noticeable .The boat should not flex to badly as i've already glassed in a rib along the length of the bottom and the because its a ketch rig the mast feet will be towards the ends where the boat has a bit more stiffness anyway

  4. #4
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    Ok, that all makes sense. A depth of couple of cms should be fine then. Unless others have different experiences?

  5. #5

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    Actually, I think mast thwart is much more intuitive. Mast partner seems like some politically correct terminology.

    Not sure of your use of the word "glass". I would think that using an epoxy resin to set the feet would be better than using a polyester resin, but I don't know how the UK side uses the word "glass" in this instance. I like the gap filling capabilities of epoxy, probably because of my careless workmanship. I've used the previously mentioned marine plywood and have had no problems.

    wd0d
    USA
    Last edited by wd0d; 13th-January-2013 at 01:07 AM.

  6. #6
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    I don't know the type of sailing intended relative to this post, but I build tricanoes with very large sail areas. Trimarans require alot of strength at the mast step and at the partner (there's that word again). I feel that stronger is always the way to go, so here's a couple of pics of the latest job. This is in a Royalex canoe, so there is a prep required but you don't have to flame it. The same prep applies to fiberglass. Just rough it up good by hand - not by a power sander. Use 60 or 80 grit paper. The area in the pics is about 2.5ft square, going well up the bilges of the inner hull. Roll on a generous gooping of epoxy then lay down a covering of glass. Repeat with another layer.

    Cut your blocks from whatever wood you have. It doesn't matter because you will thoroughly coat the blocking with epoxy, rendering it waterproof as it will ever need to be. I used two blocks of 1/2in plywood, ordinary quality. Mark and cut your hole thru.

    Locate the block centraly in the pre-laid mat and maybe shape it so it "saddles" into the bottom a bit. No need to fit it like a piano. Make sure you have it will coated with epoxy and glue it down with thickened epoxy. Very thickened epoxy. While wet, begin wetting the whole area and laying glass over the block and the whole area you previously laid. Use strips about 8inches wide and 2ft long. Lay it down in multiple directions for maximum strength. Make your layers at least 4 thick and overlap all edges by about 30%.

    It will NEVER fail, especially if you have a canoe with no outriggers because the heel will help relieve pressure on the step and...partner. The glassed area will be very stiff and strong.

    Disregard the little aluminum square - it is for a Grumman mast foot. More pics and descriptions upon request.



    Last edited by OutnBacker; 13th-January-2013 at 02:42 AM.

  7. #7
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    OutnBacker's method is really strong but rather "belt and braces" - good, nay essential, for the larger sail areas carried. Some great advice about how to use epoxy and glass, too. Comments about whether to use polyester or epoxy resin are relevant. Fully cured polyester from the which the OP's canoe is presumably made will only provide a mechanical bond - for which epoxy is so much better and stronger than more polyester - especially important for a high demand fitting like a mast foot.
    Glyn - have you seen Solway Dory's web-page on fitting a mastfoot? I know it's for a plastic canoe but there are some good generic tips there, too.

  8. #8
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    Here's a few photos of my mastfoot, made up of three blocks of plywood epoxied together, the mast only sits in the first two blocks, the third one is solid to distribute the load onto the hull. It is bolted through the hull with two countersunk stainless bolts. The other bolts shown with the wing nuts were countersunk within the block before bolting to the hull to provide fixing points for mast thwart braces.

  9. #9
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    OutnBacker

    I don't know the type of sailing intended relative to this post
    gentle bumbling is more my style ketch rigged lugg at 11' mizzen and 30' main

    windorpaddle


    fully cured polyester from the which the OP's canoe is presumably made will only provide a mechanical bond - for which epoxy is so much better and stronger than more polyester - especially important for a high demand fitting like a mast foot.
    yes keith its polyester (snake river) are you saying it would be wise to use epoxy as opposed to polyester or could i get away with polyester

    Glyn - have you seen Solway Dory's web-page on fitting a mastfoot? I know it's for a plastic canoe but there are some good generic tips there

    yes certainly have !just ordered an exped lee board&thwart and some other smalll bits and bobs from dave

    unk tantor
    Here's a few photos of my mastfoot, made up of three blocks of plywood epoxied together, the mast only sits in the first two blocks, the third one is solid to distribute the load onto the hull.

    i was going to make it out of 1 piece but maybe 2 would be much easier as i dont have a forstnet bit that size !

    thanks to all for your help

    can someone please link me to how to reply to "part of a post without linking to all of it ?"




    Last edited by glyn.c; 13th-January-2013 at 12:42 PM. Reason: computer illiterate

  10. #10
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    Quote Originally Posted by glyn.c View Post
    fully cured polyester from the which the OP's canoe is presumably made will only provide a mechanical bond - for which epoxy is so much better and stronger than more polyester - especially important for a high demand fitting like a mast foot.
    yes keith its polyester (snake river) are you saying it would be wise to use epoxy as opposed to polyester or could i get away with polyester

    Epoxy makes a much stronger mechanical bond than polyester - there is a risk that polyester might fail and wreck the thwart

    can someone please link me to how to reply to "part of a post without linking to all of it ?"

    use "Reply With Quote" but then edit out/delete any stuff you don't want included, so as to concentrate on the key point(s) you want to ask/make


    Keith

  11. #11
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    Gly.c,
    In the case of your low aspect rig, you wouldn't need to use so many layers of glass. Maybe one for the base layer and another two or three over your block. However, I advise you not to scrimp on the adhesive. Use epoxy. If you can get it in the UK, I highly recommend MAS brand. It is very forgiving of slight mis-match and is very high quality while being targeted for DIY'ers. I have found some frustration in using West System, but I've heard that they have been listening and have developed a more user friendly product. Use colloidal silica as a thickener. Round off any sharp edges on your block. Again, it's not a piano but anything worth doing is worth doing well. Thickened epoxy not only works to fill gaps left by slightly poor fit, but it also adds structural strength, as in the case of stitch-n-glue construction. In the case of a mast foot, a precice block-to-hull fit with a thin film of epoxy will be less strong than a less precise fit with a thick bonding sandwich of epoxy.

    unk tantor,
    Good and practical work on that Grumman ( I presume it is a Grumman by the many closely spaced rivets). I very much like them for the ease with which they can be modified. Very little fuss.

    EDIT NOTE: After checking in at SD per Keith's advice, you should do just fine there. G-Flex is very good stuff.
    Last edited by OutnBacker; 13th-January-2013 at 02:36 PM.

  12. #12
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    Quote Originally Posted by windorpaddle View Post
    Keith
    [/INDENT][/INDENT]
    thanks keith

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