Results 1 to 10 of 10

Thread: mast wedges from plastic?

  1. #1
    Join Date
    Jul 2018
    Location
    San Francisco, CA USA
    Posts
    9

    Default mast wedges from plastic?

    Getting ready to step the masts in my Atkin Erin (36' schooner. main mast is 10"dia doug fir, Awlgripped), and making new wedges. Yard recommends using Starboard instead of wood. I said "I was planning to use Alaska Yellow Cedar", he says "water will get in there, and when the wood swells it will crush your mast."

    Is there any sense to using hard plastic?

  2. #2
    Join Date
    Mar 2011
    Location
    Mukilteo, WA
    Posts
    1,865

    Default Re: mast wedges from plastic?

    Many plastics swell more than wood when wet. Starboard is probably pretty good in that regard, but I'd be worried about it slipping out under load. Wood is well proven. The load from swelling is small compared to the load under heavy press of sail when you dump the runners. AYC is softer than the fir mast.

    Starboard would be fine too I think, if you like paying quadruple and filling your sawdust collector with plastic.


    Also, a 10" mast on a 36 ft schooner? Wow.

  3. #3
    Join Date
    Oct 2009
    Location
    South Puget Sound/summer Eastern carib./winter
    Posts
    15,294

    Default Re: mast wedges from plastic?

    Yard guy ever set foot on a wood boat?
    Chances are the spars are solid at the partners.
    AYC is an excellent choice.
    I'd prefer it not get wet,but if it does, ...meh.
    I sailed from Antigua to Lunenburg a few years ago on a 65'gaff schooner. Owner had had the spars out and upon re launching he could not remember where he stashed the wedges. Well, He grabbed a few plastic ones, taped up the boot and we were off!
    For the next 15 days EVERY wave, puff of wind,movement of the boat sent SHRIEKS of SQUEEKS through the vessel.
    .....those plastic things.

  4. #4
    Join Date
    Feb 2000
    Location
    San Francisco Bay
    Posts
    11,654

    Default Re: mast wedges from plastic?

    What Madison said. I've been around a long time now and I've never seen a mast "crushed" by a properly fitted wedge swelling. Properly shaped wedges should bear equally across their surface and should be shaped to the circumference of the mast for this reason. The picture below shows proper wedges which will have to be further fitted (the wedges on the other side of the mast are lower than the ones pictured) because the rake of the mast was not taken into account when initially laying out the wedges. In this case, the difference is a bit extreme. Usually, it is less of a problem with less rake to the mast. Note these are numbered so that, once fitted, they can be removed and then replaced as finally fitted.


  5. #5
    Join Date
    Nov 2004
    Location
    Port Townsend WA
    Posts
    11,819

    Default Re: mast wedges from plastic?

    Normally mast wedges are made of wood that is softer than that of the mast. When I worked for Carl Chapman Boat Works a dummy mast was made up for fitting the wedges to the collar casting so that the collar and dummy could be used for fitting the mast coat by the canvas shop. If the mast was round, we would spin the wedges from a cedar block on the wood lathe. This saved a lot of fussing later when stepping the mast for real. They would be wide enough to give cradling support to the mast with a well fit inner curve. The gapping is made so that the inner portion of the wedges has the veed gaps at the mast but touching each other at the outer portion of the circle. This insures air flow while affording support that will not chew the mast at the collar and partners. The fact that they touch at the outer portion of the circle keeps them from walking, squeaking and mooving when the mast is loaded in a seaway. Once fitted, the wedges are numbered, as Bob as done, so as to allow them to always be fitted back correctly if the mast must be pulled for maintenance and then re-stepped. The outer ring portion of the wedges is usually slightly rounded off so as to not abrade the canvas mast coat and cause leakage.
    The mast coat is best padded with fluffed out oakum. The canvas coat is shrunk in place with boiling water and painted with oil based enamel that has had a bit of melted paraffin mixed into the paint. This causes it to remain flexible and not crack.
    Jay
    Last edited by Jay Greer; 09-19-2018 at 10:07 PM.

  6. #6
    Join Date
    Mar 2001
    Location
    Grosse Pointe, Michigan, USA
    Posts
    13,933

    Default Re: mast wedges from plastic?

    Crushing the mast isn't the issue. Wood distributes the "crushing" load at the mast collar much better than a soft plastic.

  7. #7
    Join Date
    Aug 2016
    Location
    Queens, NY
    Posts
    158

    Default Re: mast wedges from plastic?

    my boat has an octagonal mast with eight painted wedges and no mast boot.
    the original wedges were a hardwood (mahogany?) but four needed replacing.

    i elected for w red cedar because it was available, easy to work, and offers some rot resistance.
    i was worried they might not stand up to the hammering in, but that was not an issue..
    i've have not done much sailing yet, but they seem to be holding up fine and are not letting water through.


  8. #8
    Join Date
    Nov 2004
    Location
    Port Townsend WA
    Posts
    11,819

    Default Re: mast wedges from plastic?

    We usually used Port Orford or Eastern White Cedar as it is not as soft and brittle as is Western Red. Alaskan Yellow works very well for this too.
    I should qualify the reference to "Crushing" the mast. "Scaring" is a better description. A hard wedge can both scar and dent a spruce mast. It is a matter of personal choice. Those octagonal wedges are very nice!
    Jay

  9. #9
    Join Date
    Oct 2009
    Location
    South Puget Sound/summer Eastern carib./winter
    Posts
    15,294

    Default Re: mast wedges from plastic?

    Something else to maybe consider , related.
    In san francisco, are the spars coming out annually , like in New England?
    Mine , fer instance, has not had her spars out since they were put in , the day after launch, in 1984.
    Thus, I put epoxy filets on the top of the wedges at the mast and another filat at where the wedges meet the deck, then I dyneled thewhole lot with several overlapping pieces.
    How many rotten , termite eaten,mildewey partners and mast steps have we seen due to canvas boots being left in place too long?

    This is a buddies mizzen I did up , after his step went ka poot from sweetwater intrusion.

  10. #10
    Join Date
    Jul 2011
    Location
    Lindstrom, MN
    Posts
    2,237

    Default Re: mast wedges from plastic?

    Quote Originally Posted by J.Madison View Post
    Many plastics swell more than wood when wet. Starboard is probably pretty good in that regard, but I'd be worried about it slipping out under load. Wood is well proven. The load from swelling is small compared to the load under heavy press of sail when you dump the runners. AYC is softer than the fir mast.

    Starboard would be fine too I think, if you like paying quadruple and filling your sawdust collector with plastic.


    Also, a 10" mast on a 36 ft schooner? Wow.
    No argument with anything but the highlighted text.

    The plastics that swell the most are the poly amides, imides, amide/imides and imidazoles. Maybe PVA too, but I'd have to look it up. Nylon 66 is one of the worst common plastics for swelling and it will only swell 2-3%. Starboard is a polyolefin. Polyolefins (PE, PP, TPX) have very low moisture absorption and swelling,

    Plastics do not swell as much as wood due to moisture, but the thermal expansion is much higher than wood. Thermal expansion data on wood is useless because the moisture expansion swamps the thermal expansion and will change when trying to test thermal expansion. Wood Handbook, Chapter 04: Moisture Relations and Physical Properties of Wood https://www.fpl.fs.fed.us/products/p...rouping_id=100

    This has swelling figures for a number of nylons, but the graphs are oddly set up. This is not the place for a detailed discussion of the oddities of the data presentation. PM if you must. https://knowledge.ulprospector.com/1...re-absorption/
    More nerd food: https://www.domochemicals.com/files/...2017-final.pdf
    Management is the art of counting beans. Leadership is the art of making every being count. --Joe Finch

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •