Lock Crowther 1962 Kraken 25 trimaran build and rebuild log

Discussion in 'Multihulls' started by Corley, Jun 7, 2011.

  1. Corley
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    Corley epoxy coated

    Just thought I'd share some pictures of my Kraken 25 Trimaran rebuild I've faired off the mould and stem/keelson laminations and am moving on now. The original floats and crossbeams are salvageable and have been stored under cover but the main hull rotted and was broken up when I was a kid I suspect the bronze beaching skids (which were just screwed into the keelson) were the hulls demise as it delaminated from the keelson out.

    I've decided I wont lift the keelson stem and transom which were built to the original specification with the boat and substitute lighter and stronger alternatives in each case. I've just managed to lay up the first layer of veneer in the triple diagonal construction I'm using a paulownia veneer (sometimes called kiri) which has proved very light, stiff and easy to work with. Feels like I'm making some progress now:D

    Background - This boat belonged to my parents prior to me it is the original Crowther Kraken 25 trimaran built by Lock and his family and detailed in AYRS edition #55 some parts of the original boat are still in existence the floats, crossbeams and mast/boom are still in good nick as are the daggerboard and rudder stock and blade. It was built to comply with the C Class rules as they stood in 1962 which means it's dimensions are 25' x 14' with a twin trapeze setup.
     

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    Last edited: Jun 9, 2011
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  2. Doug Lord
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    Doug Lord Flight Ready

    Looks real good! Must be a great feeling getting stuff done-good luck!
     
  3. Corley
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    Corley epoxy coated

    thanks Doug, it's great to be making progress I've found the key to staying motivated is just to do things a little at a time I was actually quite surprised how quickly the first layer of veneer went on about 2 hours work with only a few veneers needing much in the way of spiling.
     
  4. Corley
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    Corley epoxy coated

    more progress I've fitted the first layer of veneers to both sides of the main hull now. I've also restored the rudder and daggerboard from the original boat. I'm going to use twin tiller extensions on the restored boat and shockcord them to the shrouds or a deck fitting (undecided there).
     

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    Last edited: Aug 5, 2011
  5. Corley
    Joined: Oct 2009
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    Corley epoxy coated

    I'm onto the second diagonal lamination and have nearly completed one side of the hull the lamination has a tendency to spring away from the mold at the rear of the boat so I'm holding it on with clamps where necessary.

    When the lamination is completed I'll insert a proper stringer along the gunwhale to hold the shape. I have the other side of the hull to complete then onto the final layer to complete the triple diagonal construction.

    The hull is getting fairer as the laminations go on which stands to reason as each veneer is straight grained and basically a fairing batten in itself.
     

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  6. Corley
    Joined: Oct 2009
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    Corley epoxy coated

    I've completed the second lamination on one hull side now. I'll do the other side then fair it off in preperation for the final diagonal veneer. On the final veneer I'll use packing strap between the staple and the timber to reduce the crushing of the veneer. In this centre layer I've been using up all my short off cut veneers, on the interior and exterior veneers I use full veneers and trim this is in line with the recommendations from the Gougeon brothers on boatbuilding manual.

    I find my block plane set to a shallow setting and a surform perfect for smoothing out the veneer surface and removing any blobs of thickened epoxy left over from the lamination, the surform particularly slides through it like a knife through hot butter and doesnt clog.

    I've found the raised movable strongback a real help, its a huge back saver not having to drop down to floor level when stapling veneers and pulling staples. Its a simple mdf and chipboard box with two bulkheards in its length its filleted with thickened epoxy to help with its dimensional stability I trued it up with a laser when I built it.

    I've trimmed the veneers using a fein multitool with the circular blade (makes it easy) I've also used a small saw for the same job and it works nearly as well just slower thats all.

    When Lock designed this boat he was quite influenced by the Swedish square metre boats with thier long thin hulls and large overlapping genoa. The flat rear section of the hull was designed to promote planing when the float was depressed (I know tri's dont plane, I'm not opening that can of worms).
     

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  7. Corley
    Joined: Oct 2009
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    Corley epoxy coated

    More progress I've now done the second layer of veneer on both sides of the hull. I'm fairing the hull lightly but still leaving plenty of key on the veneer in preperation for the final layer of diagonal veneer. The hull is reasonably fair on boat sides now I've also faired the keelson and placed station marks from the station molds to the hull to help with daggerboard case placement I'll probably use the fein saw to cut the daggerboard slot once the hull is lifted and turned and will use the gougeon brothers method of letting the case into the keelson area. This boat will have a slightly squared off stem like the original.
     

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  8. Corley
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    Corley epoxy coated

    I've managed to retrieve the rest of the boat from its storage location. I'd not been able to look at the floats in their storage racks due to junk being packed around them. I've also had to have a bees nest exterminated from the inside of the main crossbeam. The little critters have done a lot of damage to the structure the weight of the honeycomb has actually cracked the fairing near the centre I'll take some photos soon.

    The float hulls are looking pretty sad the double diagonal construction has suffered considerable glue bonding failures along its length. Maybe this last year being wet after so many dry years has been too much for the old glue because I'm sure they were holding up ok until recently, the good news is it all looks salvageable. At first glance it looks like the wood Lock used is meranti there is some rot evident around the stern on one float where the hull comes to a canoe style transom.

    I'm going to have to decide whether I restore or make new floats I have no worries about the process and the relatively low volume and surface area of the floats makes their construction easy my dilemma is that I'd like to save as much of the fabric of the original boat as possible so I'll have to weigh carefully the pros and cons of repair versus building new.

    The inner layer seems sound so I might remove the deck and stabilise/repair the inside of the boat then remove the outside layer and replace with a full lamination or rebond the existing timber if its in acceptable condition. The main positive I can see is the hulls are dry and dimensionally stable. At worst I may be able to repair the hulls sufficiently that I can use them for show and make a new set for when I'm racing. In my restoration I have attempted to be sensitive to the history of what is quite an interesting and innovative boat but I do want to be able to push the thing with confidence so it has to be light and structurally sound. I'm a huge fan of boats that can be used not just museum pieces.

    The rear crossbeam is in acceptable condition and a good candidate for reuse just needs a clean up. I'll remove the top fairing glue and fillet the internal structure and close up the box again. The main crossbeam has been rebuilt at some stage it looks like non standard timber sizings have been used and its excessively heavy I think I'll build a new one. The worst addition is that they have used about two dozen bolts in the rear of the main ply web. This isnt the original plan spec and is an unnecessary weight penalty.
     
    Last edited: Oct 16, 2011
  9. oldsailor7
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    oldsailor7 Senior Member

    Lookin' good Corley. I appreciate your wish to try and restore the boat as nearly true to the original as possible. :D
     
  10. waikikin
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    waikikin Senior Member

     
  11. Corley
    Joined: Oct 2009
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    Corley epoxy coated

    Restoration is now in full swing. I opened the main crossbeam fairing skin on the underside to get an idea of whether its worth reusing, it might if I remove the very heavy hardwood brace (and bolts) from the rear of the beam and use the correct thickness of ply on the underside it might solve the weight problem. I also removed the honeycomb that the bees had built inside the beam (might make myself some candles they should come in handy when I cant pay the power bill due to buying boat bits :D).

    I've stripped the paint off both of the float hulls now. One is so far gone that its not worth considering the other might be able to be repaired but probably isnt worth it the inner layer on the worst float is riddled with dry rot over 50% of the veneers are gone too far to be worth repairing. What I've settled on doing is to take the worst of the two floats, strip the outside diagonal layer then build two new floats using the inner layer of veneers as the mould. The final floats will be 2.2 mm per hull skin larger than the old but it wont have a negative effect on the boats dynamics and I'll have two lightweight and strong float hulls.

    I'll then use my spare cut off veneers to rebuild the original float hull that I've stripped the exterior veneer from and keep the two original floats as keepsake display hulls.
     

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  12. Corley
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    Corley epoxy coated

    Progress has slowed down a bit lately work gets much more busy this time of year which means less time to dedicate to the boatbuilding. I've managed to get about another quarter of the main hull done with the final layer of veneers. I've also managed to cover one side of one of the original float hulls covered with one layer of veneer.

    I ended up stripping off the outer layer of original veneer on one of the floats and I'll build a double diagonal float hull using the inner layer and float as a mold. The gunnel strip will be a little narrower and the hull will be approximately 4.4mm wider overall at the waterline which should make no difference to performance.

    I'm using packing strap to staple through which makes it easier to remove the staples without dinting or gouging the exterior surface excessively. As I get towards the front of the boat I'm able to wind back the amount of staples required and just staple down the veneer seams.
     

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  13. oldsailor7
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    oldsailor7 Senior Member

    lookin' good Corley. Keep up the good work. :D
    That mould is Yuk!! I've seen mould in my time---but not that bad.
     
  14. Corley
    Joined: Oct 2009
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    Corley epoxy coated

    When I removed the beeswax from the inside of the beam the formaldehyde smell was very strong and concentrated in the honeycomb. I was surprised that outgassing was still present after all that time but I guess it was due to the beam being quite closed with just a small amount of ventilation between the segments.

    The interesting thing is that the beams are really quite sound and the plywood has stood up well. I'd simply paint and reuse them both if the front beam wasn't overbuilt and full of possum nest and beeswax.
     

  15. Corley
    Joined: Oct 2009
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    Corley epoxy coated

    I'm making reasonably rapid progress on the final veneer on the main hull completed slightly over 2/3rds of the hull now. Could not resist sanding back the blobs of epoxy and rough surface for a bit of a beauty shot (well I think she's attractive and curvaceous anyway :D). I've also set the first master veneer on one side of the float mold a momentous moment when your cold molding. The paulownia is so nice to look at it seems a pity to cover it up with paint I'm sure I'll be thanking myself in the future though when maintenance chores come round.
     

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