Kurt Hughes Daycharter 36

Discussion in 'Boatbuilding' started by Charly, Mar 10, 2010.

  1. Corley
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    Corley epoxy coated

    Charly, the lines that go through the net operate the jib furler drum. The instruments are great and the boat is raced frequently you find the extra information helpful. I'd never sailed a boat with that much instrumentation before either but you find when sailing to get the best out of the boat you often refer to it as there is less sensation of breeze over the deck and the apparent wind makes it hard to judge what the true wind is doing.
     
  2. ThomD
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    ThomD Senior Member

    I own a variety of vac systems, and they all have their downsides. I made my Hughes, which is a lot smaller than yours, but still had a lot of vac bagging cycles. we did weird things like join scarphs with it, so it ran a lot more than 12 cycles. It was fine all along. Ours was a pre QSP 30 dollar model, the absolute cheapest there is. I don't think big models have any advantage. The top end pressure is the same, one is just moving a lot of air, that in the end isn't doing anything but cooling the oversized motor. My tiny one was great, and eventually died when I used it on drywall without full understanding of what that entailed. Ours was so noisy we always set up the vacs overnight, and ran to the car wearing out ear muffs. We were building in a shop, so we could leave it running at night without disturbing the neighbors. It probably does pay to buy a small one and remove all filters and use it only for the bagging. Who wants to fill the air with contaminants, or make the motor run harder, because the vac is full of toxic waste. My waste vac is a QSP with a goretex filter. And I have learned over the years how to build without sanding...
     
  3. ThomD
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    ThomD Senior Member

    What I did when my cockpit delaminated was i just removed all the inner layers of failed ply. They were rotten and the glue line delamed. But the last layer of ply and the glass were well bonded for obvious reasons. that was enough to start the rebuilding. I used a proprietary method, but one could laminate, or use foam or whatever. Essentially you have a female mold. I couldn't get under the stringers, but there was only one of those so I just bogged it in. Great thing is the exterior paint and base fairness remained un affected.
     
  4. Charly
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    Charly Senior Member

    Hey ThomD, good to know you are still around!

    <<And I have learned over the years to build without sanding...>>

    :D I am not there yet. The last few weeks I have been sanding my A** off. I understand one of the central ideas to Cylinder Moulding is to produce a fair hull, and now more than ever I realize how important it is to get things right from the beginning! ie, perfect scarph lines, plumb and fair stems, even sheer radius, no lumps or bumps etc etc. I hope to actually start priming soon. The sun is brutal here and working outside takes a lot of effort to keep things covered up.

    Re the shop vac, since that exchange, I have bought two new small cheepies, and yes, they work fine. Better even than the big one did. They are much easier to handle below decks as well. I am still bagging up a lot of parts, etc.
     
  5. ThomD
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    ThomD Senior Member

    "<<And I have learned over the years to build without sanding...>>"

    There could be some exageration there. I really try to never sand glass. That is my main toxic concern. I don't worry much about sanding wood, other than on efficiency grounds. I try to cut as much stuff off, rather than sand it down. I try to do wet finishes as much as I can. I don't use peel ply, because I am too cheap, but that works for many. Lots of little tricks. I see Russ Brown has a new book out, and it may have some tips in it. I don't try to get my boat looking too good. It is a waste of time to try to make the boat look like it popped out of a mold, there isn't a good pay back. But since the biggest I have built is 24 feet, I don't have much at stake. If the boat is big it needs to sell, or too much money may be lost, but I don't think people will pay one to do the level of finish one might like to have.
     
  6. ThomD
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    ThomD Senior Member

    "Thanks Charly: that doesn't sound as difficult as I was beginning to think. From what you have written the scarfing and vacuum bagging are the crucial steps."

    I was really dying to do some vac bagging, and wanted to build a CC hull, but I got sucked into the CM world, and it has been good. I was all worried about the whole VB thing. It was a piece of cake I just didn't find it all that critical. One of the easiest parts of the project. Folding up was easy also, but I did get some problems just behind the stem, but you wouldn't know it in the finished boat, which is decades old now. I had bought a lot of 1" nylon webbing, and some metal cam buckle, to take the load, but the thing mostly flopped into place.

    You should scarph the CM hull panels, and while there are issues, it is not that critical because you can add a little bog, and it will deal with any minimal gaps. The ooze wants to go into any voids in the scarps that result from cuts, or minor wobbles. What you do need, are tapers in the edges, that when bedded in the glue are scraphs not butts, but they don't necessarily need to be scarphed to the adjacent wood.

    " One builder tells me a single layer of ply is OK, cheaper but that puts a premium on the strength of the scarf joints - he's a professional - and the description of the process on Kurt Hughes' site clearly calls for vacuum bagging. Another one writes of butt joints - I'd want at least 3 layers with that!"

    That would be tortured ply, or Stressform (to use the Gougeon term). yeah, in theory you need good scarphs, though that shouldn't really be a problem, you can do them by hand to perfect accuracy, and there are power methods that are a lot faster, but maybe not always as accurate. However, I once built an ama where both sides had wonky scarphs. The outer skins were only less than a mm thick so that meant that the overlaps were say 6 mm, and while that sounds like a lot, you don't have to have a lot of skid before things get seriously out of line. I was moving the panel out of doors and the scarph snapped and barn doored 90 degrees. Once the shears are on, the panels will stay put, and then you fold it up, and the keel is also solid. You loose fiber continuity, but all you do is take a little bog, and use a squeegee, and go up the inside making a butt typ lump of bog over the seam, then bias that with some 4 oz. When you finish up, you do the sheathing. All in all it is hugely strong. SO yeah, perfect work should happen, but if you know how to build, it will all turn out OK, anyway. John Marples has reputedly said that you could make the skin out of toilet paper and it would probably be strong enough. Kurt takes the longi fiber global loads approach, however the flip to that is the shears and keel with fiber over the short span approach. It probably helps to have an idea, and be sure you get there in some coherent way.

    On my tri, the amas were stressform and the main hull was CM. This was provided for in the plans. Kurt's boats often use stressform with core inside. He ought to know.

    "The hulls are very narrow and, I suspect, somewhat cylindrical for much of their length which would simplify the wiring of a pair of hull halves along the keel,"

    That is true, Kurt ama hulls often have a lot of rocker in them, at least my generation. Gougeons often were straighter and rounder. The gougeons were surprised at how low the spread angles were, however, once the keel was faired the shape was excellent, very rounded. The new hulls I have seen plans for are very rounded.

    With stressform, you can tape the keels together, then they just open like a book. The end result is a great shape, and an easy build, but I haven't seen an option for that with CM hulls. Zip ties are very popular, but where not common when I did my build, and for the stiffest parts of a CM panel are probably not strong enough, unless you have handcuff grade.


    "with the stems more readily accessible. There is evidently less stress built into the hulls than I thought, which is a comfort! The deck flange is obviously important and I have only recently fully understood its role. More reading for me . . ."

    Mostly non issues. One just has to start building. However, all my hulls were one width of ply. I think on a really large scale you need more skill, as in this build. The deck jig is like a full length work bench. It is super convenient. Way better money burn than a building jig.

    The final ama I made for my tri took 15-20 hours to get to the point where the deck goes on. Most of the boat I did with the help of my wife, but that ama was single handed. The first one took a lot longer, like evening work over 1.5 months. I built the main hull in between.
     
  7. Charly
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    Charly Senior Member

    First coat of primer

    I was up with the chickens this morning. The first coat of the system three primer went on. The directions recommend humid conditions... Georgia coast, in JUly? :rolleyes: No problem there.

    I think the stuff is wonderful! Very little smell. I didn't even need to tip it. This is Primer, though, mind you. Everyone says that, if you are a novice, when you paint the first coat, you will be amazed at all the imperfections you missed. They aren't kidding. Though I am going to take Thomd's approach and not stress about it.
     

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  8. ThomD
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    ThomD Senior Member

    Sometimes I have been known to fill a few pin holes with 5 minute! Looks really great!
     
  9. groper
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    groper Senior Member

    Yep looks the business now mate, how are you applying the primer?
     
  10. Charly
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    Charly Senior Member

    In this case, I just rolled it on with a 1/4 inch nap roller. I was prepared to tip it with a dry brush but there was no need. It was about 74degrees F, and the humidity was very high. The hull had been prepped the night before and covered.

    I hope my luck holds out...I still have a lot of paint to put on.
     
  11. Charly
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    Charly Senior Member

    Kick up Rudders

    Well, the build is advancing along, on several fronts at once.

    A few older photos here of the rudder trunks, then a fast fwd to the building and rough in of the cassettes. They pivot up and down on an aluminum crosstube (black wrap is a graphite/epoxy bushing layup). Then the rudder itself (not yet built) is mounted through bushings that are glassed to the cassette so that it pivots side to side.

    A few problems have come up, For one, the cassette pivot hole is too far fwd. When kicked up the quadrant piece (atop the rudder post) bumps into the bulkhead, so I will have to move the pivot farther aft. I would have been smarter to have waited and checked its operation before drilling the hole, but it was much easier access with the drill before the deck was glassed on around the trunk.

    Also, I am thinking that, if grounded when the rudder is hard over, it will bind on the trunk. So I am thinking I need to cut more of a "wedge" in the back side of the trunk to allow it to rise up. Maybe a more sloped cut on top of the rudder itself will make it easier to kick up when turning and grounding at the same time? The plans stress that it is important to keep the gap between hull bottom and rudder top as tight as possible though.

    Any comments appreciated
     

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  12. Charly
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    Charly Senior Member

    It looks like to make it work out I need to move the pivot point to the new spot shown- about eight inches aft of the first try. The picture here shows the new position and the approx. position of the connector tube.

    The designer says its OK to move it aft a bit. What I don't understand very well is the consequences of doing so. Moving aft, the keel slopes upward, so moving it aft changes the amount of blade in the water. If I do move it aft, then the blade must be either lengthened overall, to fill the gap created, or shortened up (if the designed blade length is to stay the same). One or the other has to be done in order to keep a close clearance between the top of the blade and the bottom of the hull. Maybe I am making too much of this, but I am leery of making such changes when I don't have a clear understanding of the principles.

    Other Questions:
    Why is minimum clearance between top of rudder blade and bottom of the hull so important?
    What happens with kickup rudders that have rectangular cutouts in the keel, when rudder is hard over and the boat runs aground?
    Kurt mentions that Farrier type kickups have a wedge-shaped hole to allow the rudder to kick up when boat is turning, but the plans don't show this option. There must be a reason.

    I really appreciate all input
     

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  13. groper
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    groper Senior Member

    I dont see how moving aft changes the amount of blade in the water charly, only the depth of the blade changes unless the stern lifts clear of the water when your pushing her hard and heeled. Most cats that are designed to be sailed that hard, would have enough rudder with only the lee rudder in the water anyway.

    The clearance at the top of the rudder is very important because the hull acts as an end plate for the rudder foil. There is significant turbulence generated at the ends of any immersed foil where cross span flow can occur, the end plate eliminates the span direction flow and essentially forces the flow only across the chord of the foil - the direction its supposed to go.

    The implications of having excessive gap at the top of the rudder, or no end plate on a foil, means the following;

    1. reduced lift - less effective rudder force.
    2. Increased drag - will reduce your sailing performance and speed.
    3. You may even experience vibration in the steering or through the entire boat from the turbulence generated, usually at high speeds.

    I dont see a problem with moving the rudders to the new location, however I would reshape the tops of your rudders to fit the hull neatly. Wouldnt take much work to do it.
     
  14. Charly
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    Charly Senior Member

    Thanks Groper. That all makes good sense.

    I went ahead and moved it to the new aft position. it still is going to be a challenge to get it all hooked up- when kicked up the rudder quadrant still is a little too far fwd. I will either have to make some bends in the connector somewhere, or fur out the traveler on the back of the beam or both.

    I could cut an angled hole into the back of the bulkhead, and run the connector arm through there, if I wanted to run it straight, but that would open up some new structural issues. Kurt advises against that option. (has anyone seen it done that way in real life?)

    Another way to go would be to reverse the rudder quadrant 180, which would mean adding an extra set of blocks at the tiller/quadrant/traveler to reverse the motion.

    I've been pulling a string and trying to sight down it, to see which option works best. At this point at least I know it can be made to work one way or the other.

    With the farrier type rudder (see photo)with the wedge shaped hole, it looks like that the end plate effect of the rudder clearance under the hull would be a non issue. Kurt's concern with my doing it that way was more of a structural thing, because of the side loads involved. But the way he sees it, when sailing at speed, the rudder would not be at so much of an angle that it would bind up under the slot if the boat was grounded, and that if the rudder was over at such a hard angle, it would only occur at a slow enough speed that there would be no damage to the gear.

    All opinions welcome. Thanks
     

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  15. SamSam
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    SamSam Senior Member

    Will you use the rudders to steer when using your engine? Would that be enough speed to damage things?

    If you reversed the 'quadrant', would there be any chance of it flipping up when under load or a hard angle (instead of 'pulling' on it you would kind of be 'pushing' on it), or would you make it so it attaches solidly?

    Has anyone ever cut the top of the rudder off level and attached an end plate to it instead of using the hull as the end plate? Looking at it from the front or back it would resemble a T. If that worked, I would think an I shape would be even better.
     
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