Thursday, April 21, 2016

Because I Just Can't Help Myself

So I haven't sailed Little Autarkia yet, but if the rain holds off will do so this weekend.  I'm feeling pretty positive about how well it's gong to sail though.  Per a request here are some pics of the sail sheeted out as far as it will go either side for running downwind.  In all cases and from every point of sail the shape is unencumbered by a mast.  I feel very positive about this.




In fact it has inspired me to develop the design further.  In the following case I envision a truss work to support the yard made from 6061-T6 aluminum two inch square tubing.  All of the joints would be gusseted with 1/8 inch 6061-t6 aluminum plate and these gussets would be bonded and riveted to the tubing with aircraft Cherry Max rivets - probably 3/16".  The trusses  would also be X braced with steel cable.  The whole truss structure would weigh just over 100 lbs and would hinge back on the aft joints.  The height of the trusses would be 20 feet, allowing the use of standard length aluminum tubing.

It is beyond my ability to calculate the strength of these trusses, however from my experience with aircraft I know that the two trusses forming a pyramid structure built as I have described would be very, very strong.

The drawing below shows a sail of around 550 sq. ft. and the yard would be 33 ft. long.  I imagine making that from wood, and it would taper from forward aft.



As far as Big Autarkia goes I have a final sanding coat of epoxy to apply to the bottom.  Today, I am running to the metal super market to buy a square foot of copper plate that I will use as a lightning ground.  I'll get a copper stud welded to it so that when I bond it and nail it to the bottom with 5200 there will be no fasteners protruding.

Then per Dave Zeiger's suggestion I will put an epoxy non-ablative antifouling paint on the bottom.  Then right side up and home to Papa.

21 comments:

  1. I have seen a similar setup called "The Flying Lateen". They say that it greatly simplifies getting off the dock and out sailing.

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    1. Yes, it was the Flying Lateen that inspired my design.

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  2. Al,

    I really like this. Stirs my "multi-purpose" imagination!

    Tried to filter all the questions I have. Failed. So, please answer what you want to and have time for. Plus, others can surely jump in and opine.


    General:

    Two-fer: Have you considered / compared this with a two-mast arrangement? This rig on the bow -- and much smaller -- plus a normal mast and junk rig on the stern. Or, on second thought, reverse that. If the lateen/quadrapod is on the back, the sail could stick out way beyond the stern and not get in the way of the other mast or anything else. I haven't given it enough thought to decide if that is workable or cancels all the benefit or not of the lateen/quadrapod. Maybe a future test for this model after this round of experiments for an ambitious nautical scientist such as yourself. :-)

    The rig on the boat in the following photo is not what I'm talking about, but it does give some idea about the rig protruding from the back. Do love that photo! Is it just me or is that boat downright sexy?!?

    http://i50.tinypic.com/ali89k.jpg


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    Mast:

    1) Managing Leverage: It seems that the sail in this type of rig interacts with the mast only at the top of the mast. In other words, the power of the sail is transferred to the mast at its highest vertical position. Skipping lengthy explanations, I'm concerned about moment and torque on the mast and mainly its attachment points to the deck. Secondly, about the potential for the sail/mast combination to act as a really long "handle", rotating the boat in the pitch axis, causing the stern to lift up to some degree.

    Deemphasize the mathematical mumbo-jumbo:
    http://www.learneasy.info/MDME/MEMmods/MEM30005A/moments/Moments_files/moment.PNG

    Forward force on sail substituted for big red box:
    http://askthephysicist.com/images/too_much_moment_tips_truck_forward_640x471_large.jpg


    2) Placement: I noticed the placement of the mast attachment to the deck is significantly different on the model and in the drawing. In the model, it is farther forward. In the drawing, it is farther aft (and seems better to me if a single sail). Oversight or purposeful change?

    3) Similar question for shape and angle of incline of the mast?

    4) Truss work: The "book" is a bit tough to follow, but it sounds beefy. I'll have to wait for the "movie". ;-)


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    Sail:

    1) How would you reef it?

    2) What kind of ... hmm ... ropes would you need?

    (OK, lines, sheets. Said that just to piss off the boat fanatics. You gotta admit that naming a rope a "sheet" on a vehicle with one huge billowing thing that obviously looks like a sheet is a little stupid) (whew! that feels better)


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    Hull Work:

    1. Fiberglass: Did I nod off during the part where you already attached multiple layers of fiberglass to the hull? I'm asking because I didn't read it, but you're talking about painting already.

    2. Copper stud: Trying to imagine this. So, if nothing will protrude (downward), and the bottom of the plate will be flat and smooth, that means the stud is embedded UP into the hull, as an attachment point from inside, for the "Please don't BBQ me" cable?

    OK, I think I'm tired of typing now.

    Yoda

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  3. Alrighty :-)

    General

    I have not abandoned the idea of another sail aft. I think that I might have that flexibility with a truss arrangement forward and a another aft. The aft one could be part of the sheeting arrangement for the forward sail as well as carry a sail of its own. I have not thought it through though.

    Mast

    The truss on the drawing attaches at the fwd cabin bulkhead and then at the bulkhead aft of that where the salon and the stateroom meet. It 'looks' better than the truss on the model in my opinion. It would be functionally quite similar and having all four attachment points on the cabin top keeps all four truss members at the same length.

    The leverage is between the top of the truss, and the mounting point of the fore stay which would be under considerable tension. That is why the yard would be heavier fwd and taper aft. This has come to me only as a result of playing with and manipulating the model by hand.

    Sail

    The shape is not carved in stone. I'll probably play around a lot with this. A possible reefing solution would be to lower the yard and bunch up as much sail against it that you want reefed away, and tie in place. Then raise the yard back to the top.

    Hull

    I'm in belt sanding mode now, leveling the joints in the fiberglass and making things generally smooth. I haven't posted pictures yet because they don't show much. Perhaps after the last seal coat of epoxy and it looks like a piece of fine furniture I'll post some pics.

    The copper stud will be welded to the face of the copper plate that is bonded and nailed to the hull, and protrudes through the hull where it will be bonded to #6AWG stranded copper wire to the rig.

    I've been spread quite thin this last little while. Still I'm hoping to get the hull to turnover withing the next week or so. As far as the project goes in total, that has taken priority over the blog, the model and thinking in general. And life's concerns, obligations and responsibilities so far are in the forefront of it all. Nonetheless, I've been able to keep all the balls in the air. Soon I will be back to Autarkia full time and on all fronts.

    Now MY fingers are tired :-)

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  4. So, all said and done, how many coats of epoxy and how many layers of fiberglass cloth?

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  5. I'm still trying to figure out what this "truss" is. My best guess is that "truss" is synonymous with "quadrapod" -- the four-legged mast. Is that right?

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  6. I first put a seal coat of epoxy on the whole boat. Then a layer of 10 oz cloth on the whole boat with the seams overlapping 2 inches. Then a second layer on the bottom only, again with seams overlapping. Then another coat of epoxy over the works. I'm belt sanding that level now, once done I'll put another seal coat of epoxy and then antifouling paint on the bottom only. I'll do the sides once right side up at home.

    In this case I'm using 'quadrapod' and 'truss' interchangeably.

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  7. A little more on the whole fiberglass epoxy thing: The reference I'm using here is Ken Hankinson's book 'How to Fiberglass Boats'. I have the second edition. Ken Hankinson is well known builder and designer. He maintained that a properly designed plywood boat did not need more than one layer of fiberglass to protect it unless it was subject to heavy use, in which case a second layer could be warranted. Since fiberglass has less strength than plywood for a given weight adding fiberglass to improve strength was a waste. The only advantage of layering on more would be wear resistance. This of course aimed more at pleasure craft than anything.

    The more I thought about the whole thing, the more it occurred to me that since I will have built this boat with my own hands and will have put a lot of blood,sweat,tears,heart and soul into it, I will be very careful with it. I have always been 'bottom conscious' with boats anyway - my Dad drilled that into me since I was young. I don't think that we will be bashing her around. Most of the shallow areas we will frequent are marshes with muddy or sandy bottoms.

    So I stopped so far with two layers on the bottom. It seems quite tough.

    So far I have used three 12 litre kits of epoxy and I'm into another 7.5 gallon kit about half way. That's about $1700 worth of epoxy so far for just the hull. So economy is another factor in my reasoning.

    Having said that though, I've got to finish up the belt sanding and vacuum it off over the next day or two. I'll make a decision then whether I'll add on any more.

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  8. Excellent fiberglass and epoxy info.

    Based only on your description above vs. potential changes to the plan: By my count, on the bottom only, you'll end up with 5 layers of epoxy, and two layers of fiberglass within that. Is that right?

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    1. Thanks Yoda. That's correct but to be more specific the first coat of epoxy seals the plywood. The two layers of glass are saturated with epoxy so I guess we can call them coats too. A fourth coat went on and that is what I'm sanding level. Once that is done a fifth coat will be carefully applied with a foam roller so the finish is very smooth and has no bubbles. Before painting I will scuff this coat with red scotchbrite.

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  9. Al,

    Back to the truss/quadrapod/mast for a minute ...

    Hopefully I can describe this clearly enough to make sense. I'm talking about the yard or top-of-sail boom device. Regardless of actual use while sailing, I'm interested in its range of lateral motion. For example, beginning with the yard in a horizontal position, and then moving it along the yaw axis, its maximum theoretical rotation would be something just short of 90 degrees left and 90 degrees right. It would be prevented from rotating further due to the legs of the truss.

    My question: Using the centerline of the boat as zero degrees, what degree of lateral/yaw rotation is possible with the yard on your model?

    When you have a minute to move it back and forth and estimate the degrees, I'd appreciate knowing the answer. Thanks.

    Yoda

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    1. Well on the model Yoda, I get about 45 degrees. But that limitation arises from the legs of the quadrapod coming to a point very close to where the yard is hoisted up to (if that makes sense with me ending my sentence with a preposition :-)). They could spread further apart with a platform of sorts at the top allowing a lot more freedom for the yard. I intend to play with this with further modelling.

      Also, I found a spreadsheet that calculates the buckling strength of steel and aluminum tubing (I'll detail in an upcoming post) so I found out that I can probably build a quadrapod that tightens the gap between the fore and aft members. This may provide further range of movement for the yard, as well as the sail itself further down. More to come but my head spins as it is :-)

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  10. "This is the sort of bloody nonsense up with which I will not put."
    -- Winston Churchill ... or somebody ... or nobody

    (http://itre.cis.upenn.edu/~myl/languagelog/archives/002670.html)

    I can understand your comment, paraphrased, about the inverted "V" at the top of the truss being the confining factor for lateral rotation of the yard to 45 degrees. Makes sense.

    I'm pondering this set-up for a mainsail mast, but also for double duty as a cargo boom platform, requiring no major added components (extra booms, etc). The yard would also be the cargo boom, and be extra beefy but also light (likely aluminum, likely I-beam shaped). Designed so that lifting could occur at either end, with the truss mounted not in the middle longitudinally, but closer to the middle. Maybe 1/3 back from the bow. This is a revision on my earlier comments about moving the truss to the stern. All still very mentally molten.

    In any case, as a cargo boom, the yard only moving 45 degrees would be very tight, inducing lots of inconvenience. I'd want something more like 60-70 degrees each way.

    So, I'm wondering about a mod to the top of the truss; maybe similar to the "platform" that you mentioned. The inverted "V" would instead become an inverted "U", or a "U" with squared corners. Not sure. Need to balance the greater lateral range of a squared "U" with the greater load-bearing abilities of a regular (arch-like) "U". In either case, it would likely increase the lateral rotation a lot.

    Toyed with the idea of the truss apex being an actual platform (as in square, flat, horizontal piece of aluminum), as a stable base for the yard, but that won't work. It would disallow pitch axis movement, and is unnecessary in any case.

    As for the legs of the truss being closer together, that would seem to allow similar benefits for the sail as you say.

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    1. Spreading the uprights at the top, by whatever means such as a U, or a platform, will weaken the structure a bit and compromise the rigidity. So, even if I were to use aluminum pipe for the uprights I would probably make the platform from welded steel and have the uprights slide on over pins that would fit quite snugly. Still thinking it through...

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    2. I think lateral rotation would be eliminated with x bracing on the sides...

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    3. Uprights/platform: Obsessed minds think alike. Between our last posts, something similar occurred to me re: weakness. I had gotten far enough to think of making the apex/platform separate and detachable. Wrong shape, but a custom piece along these lines:

      http://frameconnector.s3.amazonaws.com/centraltent.net.c1001.260x252.jpg

      Lateral rotation: Either you just had a senior moment or I was heretofore unsuccessful in making the points that all of the lateral rotation I've been talking about so far is 1) of the yard only within a stationary truss/mast, 2) necessary for cargo boom function (and sailing, by the way), and so 3) beneficial and desirable. I wasn't talking about the whole truss rotating/twisting. A truss with Gumby legs would be ... hmm, what's the word ... oh, bad. ;-) Make sense now?

      While we're generally on the topic, have you given much thought to whether the apex/platform itself needs to he hinged, to allow for truss/mast take-down? I don't much like the idea for strength reduction reasons.

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    4. Sorry for the late reply Yoda. I missed your post. In the meantime I've had some serious feedback privately that has caused me once again to go into waffle mode. I'll be posting about it soon. Suffice to say for now that I've reconsidered the truss. Otherwise, I'm ready to flip...getting a crane organized now.

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  11. Hey Al,

    Understand. I assume you're as busy as a one-armed paper hanger. Reminder: Make sure you film the hull turning! Best of luck. :-)

    Yoda

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  12. This is the mast arrangement I was referring to down stream when I mentioned flapping leeboards.

    The more I think about this 'mast' the better I like it.

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  13. have you considered a bi-plane rig

    http://www.pdracer.com/sail/unusual/dave-gray.jpg

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  14. As of now Everitt, I'm still committed to junk sails.

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