Quick building strategies

Discussion in 'Multihulls' started by simon, Oct 17, 2007.

  1. rob denney
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    rob denney Senior Member


    Cheap and quick compared to any other boat of similar performance and space, yes. If you know of any videos of 30' cruising cats (or 40 or 50 footers for that matter) cruising at wind speed as effortlessly as Rare Bird, please let us know and we can compare prices.

    They are not so cheap if you compare the number of bunks, but if we did the cat trick and filled every available space with bunks (2 more doubles in the lee hull), then they are cheap on this basis as well. Reality is, few people cruise with more than 5 people on board, unless they have boats which require extra crew to handle them. We prefer to build the whole boat round this number rather than try to con owners that 8 people can live and cruise on a 40 footer.

    The only valid part of your comparison with a 30 footer is perhaps the building time, although the Visionarry did include 600 hours building the mast and boom, it was the first example of a totally new type of boat, so the next one will be quicker.

    According to Schionning and Woods, most 30 foot cruisers have about 50% of the payload. None have the performance, sea keeping, safety or internal and external space.

    Not sure where you got the price, but a new 50 footer to cruising stage is about $400,000. Rare Bird is for sale (the owner died after only sailing it twice), ready to cruise for $325,000. http://www.harryproa.com/brokerage.htm

    Please tell us more about the "inconveniences" of a proa.


  2. Trevlyns
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    Trevlyns Senior Citizen/Member

    Everything is relative...

    I think Rob has a some very valid points. I don't think many people have seen the benefits of a larger cruising proa as there simply aren't so many around. I've looked at all manner of sailing craft in depth and am totally convinced that the proa - specifically the modified Pacific proa - is the most efficient and economical.

    My wife and I are in our late 50's and I've just started work on a 12 meter proa of my own very basic, ply over frames design. She will be equipped with two double berths, ample saloon, head, galley and office space and a good safe deck area. I have just acquired all the material to complete the longer leeward hull for a little over £100 and expect to complete the boat for under £1000. Costs are of course relative. Just how much boat do you want? Granted, my hard chine flat bottom design is probably not as efficient or professionally finished as Rob's great designs; but my point is that it is totally adequate for our needs - that is a basic safe quick cruising boat built on a shoestring budget. Over the past two years, I've also gathered 90% of the equipment needed mostly through e-bay. Believe me, there are bargains to be had out there if you only look around!
  3. simon
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    simon Senior Member

    When starting this thread, I did not want to discuss specific design approaches ( proa versus rest ), but wanted to find out more about building strategies.

    I would like to come back to ways to build our toys in a reasonable timeframe.

    As Rob has been convinced by the KSS method, I would be interested in knowing ways to reduce the still huge amount of hours to build his proa design.
    Rob, do you have any proposals or experience?

    Are there any further methods that will simplify the construction?

    Derek Kelsall writes in his website about radius batten to be used for bonding structures together. Any ideas about that?

    What about using prepared standard profiles to bond in Bulkheads and assembling structures? Anyone knows about existing solutions?

  4. rob denney
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    rob denney Senior Member


    The easiest way to lower hours (and cost and weight) is to reduce surface area, concentrate the loads and minimise or eliminate fittings such as the stays on masts, deck gear, daggerboards and their cases. This is why the proa was mentioned. If you want to build a standard bridge deck cat with a good finish and fitout, there are very few cost effective shortcuts.

    The "huge hours" are for a superbly finished strip planked boat and include the rig and a lot of messing about as it was a prototype. In KSS it would be quicker.

    Derek's deck edge radius is a wonderful thing. It is built with the infusion and just needs abrading, some glue and a little bit of bog to complete the join.

    Standard profiles are ok for long straight joins, but are hard to bend. Filletting and tabbing is pretty quick once you get into it. The main tricks are to pre wet the tape and apply it before the fillet starts to cure.

    Computer cutting the foam for bulkheads will save a little time, but it is lost when you have to lay them up. Quicker to infuse big sheets and cut the frames from them, either with paper templates or on a cnc machine. Wastage with modern nesting programs is negligible.

    After surface area and load concentration, the biggest saving is finish quality and interior fitout. My personal best is 450 hours for two strip planked hulls, beams and rudders http://www.harryproa.com/Newsletters/news1_hg1.htm and http://www.harryproa.com/harrigami/hgtimelist.htm for the time sheet. Pretty rough up close, but from 20' away, it looked as good as any other boat. It has since been sold and tarted up to look brand new. http://www.harryproa.com/harry_proa/NZ/2.htm


  5. catsketcher
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    catsketcher Senior Member

    It has happened before


    The idea of reducing building hours has been with us ever since multis have been built. Probably the best boats to build are old tris - the guy who designed the Easys - Peter Snell - built a 38ft Piver tri in about 6 months. The Piver AA38 makes a good boat and really is pretty simple to build.

    There have always been new techniques - quick strip cedar, strip plank itself, vertical strip foam, chined plywood, turbo plank - it has always been thus. KSS is a new technique and like its predecessors will have its advantages and problems. ( No I haven't gone to a workshop but I have friend who did run a KSS workshop at his house. He is not overly enamoured with the technique and we have discussed it a fair bit.)

    Hulls take little time to build compared to the interior and fit out. This is why I do not necessarily agree with techniques that compromise the ability to use computer cut components. You will be able to knock up a couple of 12 metre cat hulls in 3 months roughly faired - no kidding. But these hulls could be used in a 12 metre cat could take 3 years full time to complete.

    Bunks, cupboards, sinks, lights, floors, bulkheads, fridges, seats, benches, basically anything you want inside a boat will take lots of time to fit - because you have to be careful to build a good boat.

    If you want to live in a shell or get rid of the volume and stuff in an interior then you will take less time. Getting a slick boat with a nice interior will take lots of time. There will not be a magic idea to get around the thousands of hours to build a boat.


    Phil Thompson
  6. waikikin
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    waikikin Senior Member

    Simon, maybe you can incorperate some of the facets of melamine molding to the Oram cat? say like instead of premanufactered panels that need joining on site make a nice big laminating table & mold the full length hull & deck panels to shape with gelcoat & also incorperate some tabbing rebates to perimeter so you dont have to fair out the tabbing across a lot of the panel or use the edge radius to hull chine intersections as well. Like Rob has mentioned you can get pretty quick at tabbing especially if theres 2 on the job but there is plenty of it like 30 metres+ per connective bulkhead x 3 or 4 & often bulkhead edges have some uni glass to install too plus all the longtitudinal joins as well as furniture & tankage thats part of the structure. As has been mentioned fitout style & finish has a great influence on build time & is purely your choice, the super "tight" joinery & 16 coats of clear is gunna suck up heaps of hours, the stippled flowcoat & frontrunner or other monkey fur fabric & some satin finished trims & fiddles backscrewed & stopped short of the bench ends for wipeouts are gunna be quicker overall but will still take time but still look nice if neatly executed. Phils no "magic" idea line is correct on the 1000's of hours but there are still margins to be chased but can impact on finish & eventual resale values(they all get sold one day & I'd say Wharrams suffer the most here), the "panel"(duflex?) style boats seem to at least in Oz have acceptance but I dont know elsewhere how they go. Personally I've invested in some pretty sweet production quality tooling for my hull construction but intend to build a few to spread the cost of over but I 'spose thats my own choice. All the best from Jeff
  7. Bruce Woods
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    Bruce Woods Senior Member

    quick build

    I'm not as familiar with the KSS method as with stressed ply, but one would have to assume that bending a flat pannel of foam and glass into compound curves and then cutting bending and glassing gussets is not an exact science.

    Therefore the final hull shape depends on many unknowns relating to pannel stiffness ( state of cure, resin/glass ratio etc etc), and builders eye. There would be little point in computer cutting the interior if it aint going to fit. If this is the case some of the time gained in a quick Build hull skin is lost.

    This system probably still has some advantages if your happy with a hull without topside curvature, flared bows, trying to match gelcoat finish on joins etc etc etc. Being infused ,with its inherent print through problems the finish is never going to be as good as a polyurethane paint finish.

  8. fhrussell
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    fhrussell Boatbuilder

    Catsketcher has hit the nail on the head!

    Maybe the time saving ideas should be concentrated on the interior. Having built many boats, I always find that so much much of the 'sense of accomplishment' comes from turning a completed hull, but that seems to be only one fifth of the way into the whole project. I believe that the cost of the hull construction is also about one fifth the total project. If this is so, then the time saving tactics are likely found on the interior and outfitting the decks.
    Perhaps we should be talking about interior shortcuts instead of hull construction techniques...of course, not discounting the possible time saving ways to build the hull...ie; KSS, tortured-ply, etc.

    My .02
    1 person likes this.
  9. Fanie
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    Fanie Fanie

    I think what may cause the concern is the sheer size of a hull that has to be glass covered.
  10. DGreenwood
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    DGreenwood Senior Member

    Exactly! A 40' boat with a 30' interior is really not very much harder to build than a 30 ' boat...but it sure is a lot nicer at sea. Give me 10 more feet of water line length over a second head any day.
  11. rob denney
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    rob denney Senior Member


    Your first 8 words sum it up pretty well.

    KSS is exact enough for Derek to provide computer generated shapes for the interior, which fit. My windward hull has cantileverd bunks off one side. These, the cabin sides, deck and hull sides were all done from drawings, many with deck radiuses for joining. It all fits together very well.

    The state of cure is near enough complete before bending is done, the table infused resin/fibre ratio is consistent and low, certainly far better than hand layup. There is very little eye balling required, much less than setting up a strongback for strip. There are far fewer variables, and much more complex shapes are possible than with tortured ply. One of our clients built a half hull mould and infused a 20m/66' hull and decks. It was far more complex, stressful and prone to errors than the table infusion Derek uses.

    Topside curvature can be done (with the new foam compounding technique, a lot of mono hull shapes become possible), as can flared bows.

    You are correct about gel coat matching at joins, although as the only one is the hull deck join, it is far easier than fairing and painting the entire hull. A strip can be painted on, non slip can be used, or you can spend a couple of days buffing and polishing gel coat. There won't be any print through if normal vacuuming into mould processes are used (tissue between the laminate and gel, maybe a light layer of csm before the bulk of the laminate goes down). The main problem is getting a perfect table for the gel coat to go on. On my boat, I didn't worry as the finish is immaterial, but if you want a shiny finish, then use sanding gel, and 2 part pu once it is all in one piece.

    KSS and table infusion is not the absolute answer (still needs some hand laminating below the waterline), and paying Derek to alter plans is expensive, but it is faster and less messy than anything else currently in use. You and any other doubters should attend a workshop, or at least have a look at some of the pictures and videos on Derek's web site. There are some of a workshop in Toowoomba, where they made a flawless table. The finish on the (curvy) gel coated hull is as good as any you will see anywhere

    Fanie, Table infusion takes all the concern away. You set everything up dry, taking as long as you like to ensure all is well. Then mix a bucket of resin, open the tap, have a cup of tea, close the tap and come back the next day and 90% (100% on the deck) of the laminating is complete.

    D Greenwood, I could not agree more. And if only one hull needs to be lengthened, it is even cheaper.

    Phil, I would be very interested to hear what you and your friend did not like about KSS.
    It is not the building of the hulls or the interior that is the problem for most builders, it is the fairing and finishing.
    A couple of unfaired strip planked 12m hulls in 3 months (with another 3 months of fairing to go) is pretty good, until you compare it with a couple of 12m hulls and decks, faired and ready for top coat in one month with KSS.


  12. waikikin
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    waikikin Senior Member


    Personally I reckon gelcoat is a fabulous material, matching a hull/deck/transom join with new material probably from the same batch is as good as it gets in that regard- it gets a bit tougher once the boats copped some uv for a few years with different tones apparent on various surfaces but its ussually possible to get close, I've blocked & buffed 20 year old boats that ended up presenting quite nice but of coarse some dont & need a shot of pu. Also I see no reason why there would be too many fit up issues on furniture etc to a kss hull, many years ago I built a Van De Stadt 34 that was computer modeled to give plate developments & all the Knockers & rudder kickers & gunnel leaners said theres no way that'l fold up right but surely enough it did just like stitch & glue style, why not now that the tools of computer modeling & Dereks experience in the technique can work up a nice hull, people have been doing triangulation & working girths to develop hulls for a long time, sounds like he's got a good technique & the talent & experience to back it. The Toowoomba workshop I would liked to have attended, I reckon I could use the table infusion myself for a lot of stuff, I really like the thought of sipping my tea while the job infuses with less stink & slushie action, I think I might order a couple of sheets of infusion foam & resin & have a play around with it. Rob, sounds like the new boats progressing nicely. Regards from Jeff.
  13. doug kay
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    doug kay Junior Member

    I built my Cat in cedar strip and the hulls of a 12 metre would take,including the hardback, about 300 hours, mine is only 9 metre but the two hulls were built but not finished, ie still in their rough stage in 200 hours. Two people working 10 hours a day will have a basic boat in 9 months.
  14. northerncat
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    northerncat Senior Member

    i would agree with spiv stay away from boats with large compound curves if you are after speed of build and dont want to lose things over the side, go for a flat panel design for ease of fairing, as for hull construction my ply easy easy hulls were built over 10 weeks part time and this included glassed and fully faired id have to say this was the quickest aspect of the build

  15. catsketcher
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    catsketcher Senior Member

    Another idea

    I really like the idea of having the curved part of the hull very accurate so that the computer cut interior can be easily installed. I also like having the hulls sit right way up and installing the interior before the skin goes on. This is how my little folding cat is built. It allows you to use the mould frames to give accurate elevations and spacings and makes the interior fit out much faster.

    If I was to build another big cat I may like to consider a similar approach with some premade pieces like the KSS system. Making the rounded hull bottom (up to 50mm above waterline only) in strip foam would take little time - about 2 weeks on your own for a 38 footer (the little 7m folder takes 1 day to strip foam - 2 days to set up mould). It would then be glassed and the interior installed, then the infused flat topsides and decks installed. The hull bottom would need very little fairing as it would be underwater and painted with antifoul. As the rounded bottom (up to waterline) is symmetrical you would not need to reverse the hull mould and be able to make both hulls out of an identical mould.

    This would give you an accurate hull and with glass table infused topsides and decks giving reduced fairing. Strip foam is really fast for curved bits and gives lots of control over the hull shape. It is also nice and sequential with no times when you might stuff everything up - you can also do it all on your own. This approach is similar to the Spirited 380 which I have seen quite a bit of. The ability to remove the topsides to work on the interior saves many tens of hours during fit out.

    I already have three boats so will not be trying this approach on a 38 footer soon. I just put it out there for comment and consideration.


    Phil Thompson
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