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  1. #31
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    Sep 2012
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    NSW, Australia
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    Dunno. I'm just going by what I found when I went looking. Maybe it was a non-standard mast.
    You know you're making progress when there's sawdust in your coffee.

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  3. #32
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    Aug 2010
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    New Jersey, USA
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    767

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    No, it was an update. His birdsmouth design is a separate supplement though.


    Sent from my iPhone using Tapatalk
    Dave
    StorerBoat Builder, Sailor, Enthusiast
    Dave's GIS Chronicles | Dave's Lugs'l Chronicles | Dave's StorerBoat Forum Thread

  4. #33
    Join Date
    Jul 2005
    Location
    'Delaide, Australia
    Age
    65
    Posts
    8,138

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    Quote Originally Posted by MiddleAgesMan View Post
    The "stock" mast is a box section?

    That's news to me.

    The original masts were all solid rounds, tapered from around the middle to the top, 3 1/2 inch at the bottom and something around 2 inches at the top.

    But I guess MIK could have changed the "stock" mast without my knowledge.
    For

    it was a few years back Archie,

    For a while I had the solid round mast and the box mast as options.

    Then I deleted the round mast and added mention of a separately available (for free) birdsmouth supplement that I email if I receive proof of purchase.

    MIK

  5. #34
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    Jul 2005
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    'Delaide, Australia
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    65
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    Quote Originally Posted by Beaton2 View Post
    I've broken the rules on wood movement on projects and have regretted it. My advice is to not break them. Tests would be sensible. I see a lot of links on a google search for plywood masts being made, from the early 20th century until the present. Maybe it's not suitable for a goat. I don't know, I'm no sailor or boat builder.
    Howdy,

    Plywood has only half the timber going in the correct direction to take the stress. So something that has to be small diameter (mast) would have to be a very large diameter to keep the stresses down to the point where the ply could handle them.

    Terrible for what the air has to do to get around it.

    Look at a ply mast being much heavier than any other option.

    For a boom it can be a good choice, because there is no restriction on the size of the cross section.


    Best wishes
    MIK

  6. #35
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    Jul 2005
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    'Delaide, Australia
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    Quote Originally Posted by Sumbloak View Post
    Ok then, let's do this properly. You know what safety factors you allowed in the original mast design, which I assume was intended to be built in solid oregon or similar, of reasonable but not perfect quality (correct me if I'm wrong). From that it's simple enough to work out the required diameter in any other timber, including just paulownia if anyone wants to try it. Also, from what I recall from Skenes or somewhere similar, a 25% wall thickness is safe for hollow, unstayed spars (assuming overall diameter is suitably chosen).

    So, all anyone needs to know is what you allowed for with the original mast.
    Howdy,


    Mast was originally stressed for three 75kg men hiking out hard from the gunwale. I used the Laser Alloy mast as the starting point for one person, adjusted for three and the difference in beam

    It was overkill looking at the realistic way the boat is sailed. But it has allowed the mast to be hollow later in the design evolution without getting confusing with different mast steps and partners in different boats.

    With a Paulownia mast there is something important to be aware of. Paulownia is prone to denting if it isn't glassed. I would recommend probably three layers of 6oz glass at partner and step. Also might need to consider how to avoid denting from boom and yard pressure or mishandling when rigging.

    Best wishes

    MIK

  7. #36
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    Sep 2012
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    NSW, Australia
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    474

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    Yes that makes sense, and the glass would negate some of the weight savings, especially if it was needed higher up to deal with the yard, etc..
    You know you're making progress when there's sawdust in your coffee.

  8. #37
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    Jul 2005
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    'Delaide, Australia
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    If a square hollow mast was built with Paulownia used for the narrow staves then the wider staves in a recommended timber would protect the paulownia. Plus all the internal blocking in Paulownia except for the block at the top of the mast which takes the halyard fitting screws.

    It would be experimental. And the mast would have to be protected at partner and base by glass taping. But it would strip a few pounds out.

    MIK

  9. #38
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    Sep 2012
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    NSW, Australia
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    Another thought occurred to me. With something like a Laser rig, you want the mast to flex to de-power the sail in strong winds. In fact. Laser rigs flex quite easily even in fairly light winds.

    With a lug rig, you don't want this at all. If the mast flexes with a lug rig it will reduce luff tension and bag the sail up, which is the opposite of what you want when it's blowing hard. A lug mast should ideally be very rigid, with all the automatic de-powering done by the yard. This is analogous to the way skiff* rigs work: rigid lower mast and flexible topmast.

    *Meaning 12's, 18's, etc.

    Anyway, point is that if trying to reduce weight with a lug rig, you would have to think carefully about the resulting stiffness of the mast if you wanted to maintain good sail performance.
    You know you're making progress when there's sawdust in your coffee.

  10. #39
    Join Date
    Aug 2014
    Location
    NJ
    Posts
    57

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    I know a little about building light and stiff. One of my more obsessive hobbies is indoor duration model airplanes. These planes are built right at the edge of structural viability.

    The planes you see in the following video have 65cm wingspans and weight 1.2g sans rubber motor. They fly for over 1/2 an hour on one turn of a rubber band. The motor tubes are rolled from balsa strips that are .011" thick and reinforced with .003" boron fibers.

    Enjoy...



    One more. My friend John Kagan's ship. No, this is not in slow motion.


  11. #40
    Join Date
    Aug 2014
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    NJ
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    And I found another <$100 trailer. This one might be better got the goat:



    It's shorter than the other one. I just need to rework the bunks.

    Update: crap I just realized it's missing a fender. Forget it.

  12. #41
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    Oct 2014
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    United States
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    I'll have to start my own thread soon. So far I have a stem of sorts and two bulkhead frames rough-cut to size. But yesterday I took delivery of 12 sheets of okoume--six for me, and six for Alan, who I'm told picked up his share today.
    Untitled
    As Alan can attest, I still have some cleaning up to do to make room for more than a 2D boat project. But it's too late to back out now I guess...

  13. #42
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    May 2013
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    Rockhampton QLD
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    Welcome to the forum Brian.

  14. #43
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    Oct 2014
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    United States
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    Thanks. I'll just add, before giving Alan his thread back, that that's his boat in front, and mine behind his. Behind them both is a 10' wide projector screen on canvas stretchers. If anyone wants one, he only has to come pick it up from my garage...

  15. #44
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    Aug 2010
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    New Jersey, USA
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    Quote Originally Posted by BrianMCarney View Post
    I'll have to start my own thread soon...

    ...it's too late to back out now I guess...
    Yes, and yes.

    You won't need the 3D clearance for awhile; you'll have plenty of 2D work to take you into the winter months.
    Dave
    StorerBoat Builder, Sailor, Enthusiast
    Dave's GIS Chronicles | Dave's Lugs'l Chronicles | Dave's StorerBoat Forum Thread

  16. #45
    Join Date
    Aug 2014
    Location
    NJ
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    Yep, my ply has arrived. This Bruynzeel stuff is nice. I picked through some other Okoume ply at a local supplier, but passed. I'm glad I did. The Bruynzeel netted out to $15/sheet more, but with all the time that's invested in building something from wood, using anything less than the "good stuff" doesn't make sense to me.

    I also ended up buying that trailer from a few posts above. It was $50 and I can buy or make new fenders. It is very small and light and perfect for a GIS.

    Duckworks has the RSS sails back in stock and I'm placing an order along with the epoxy kit. Q: Anything else I should include in the order?

    Q: I'm starting this build over the winter, but I don't know when I'll finish. Like Brian, I have garage issues to deal with before the hull goes 3D. In the mean time I will get the foils and other 2D pieces done and maybe the spars. Do I want the fast or slow epoxy kit? I'm thinking fast because I'll be working in a semi-heated garage space during the winter.

    The investment so far:
    Ply - $570
    Paulownia - 20 bdft $120
    Doug Fir - 32 bdft - $270
    Epoxy - $360
    Sail - $380
    Trailer $200 (including tires, light kit etc)

    $1900 so far. Not too bad. Still have to buy hardware, lines etc.

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