sailboat rehab

Discussion in 'Fiberglass and Composite Boat Building' started by JustinT, Nov 25, 2013.

  1. JustinT
    Joined: Jul 2013
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    Location: Michigan, USA

    JustinT Junior Member

    I have a small, lightly built sailboat from 1968 or 69 with LOA 4.67 m, LWL 4.34 m beam 1.80 m, and sail area 13.66 sq m sail area. The scantling number would be .271. Think Wayfarer with a Mariner cubby cabin. It was originally build with a 34 kg steel plate centerboard at a displacement of 213 kg. It has a solid FRP hull that has seen better days. It has a maximum thickness of about 2.5 mm polyester resin roving and mat. Think more mat then roving. The keel is plywood and has cracked along with the fiberglass. Not sure if that happened before or after the low quality 6 mm plywood bulk head taped in with thin mat rotted away. The centerboard case, small area with plywood core and cubby floor were all tabbed in with thin mat. The cockpit floor is cored with what looks like polyester resin with some sort of filler and with a layer of mat on top. There are numerous voids in the cockpit core under mat that I am working on isolating. The core is very hard but brittle. I am thinking I should remove all of this core and replace with PVC core. My other idea is leave resin core and find, fill all voids and then add PVC core. If I remove it I can reduce some weight.

    I am currently planning on rebuilding almost everything. I was hoping I could lay out my basic plan and get some feed back before I set anything in snot or open my wallet. The boat was lightly built but based on what the designer expected from the boat it was obviously more then sufficient because it lasted over 40 years. My intended use is a camp cruising sailboat for extensive voyaging on the Great Lakes. It will not be a racer it will be a cruiser. Though who wants a slow boat. My basic idea is keep it light, simple and strong. That is easier said then done. Weight adds on quick. I will also be adding cabin doors/hatch on the cubby.

    I have ripped out the saturated foam, centerboard trunk, cubby floor, and rotten bulk head under floor. I am currently ripping out the plywood keel, small plywood core that were all taped in with mat.

    • I will replace the keel with some Douglass fir or larch.
    • Since this boat's FRP is so thin, old ,cracking and I will hit rocks or drag on beach I was thinking core of 6 mm Dvinycell H 80 on the entire interior with a minimum of one layer 12 oz biax inside and out along with a 4 oz finishing cloth. I was thinking I would double that below waterline. This does not include necessary taping on keel, ring frames and bulkheads.
    • Add Ring frame under mast, and ring frame located at cubby opening. (9 mm okoume)
    • Add bulk head in bow with armstrong deck hatch, and bulkhead in front of centerboard closer to shroud chain plates. ( 9 mm okoume)
    • Lower floor in cubby about 7 cm made of 3 mm plywood and 4 oz finishing cloth on both sides. Armstrong hatched in floor for inspection and storage between bulkheads/ring frames. Even though I am using core should I add a couple stringers above floor along cubby sides to break up panel size? Seems overkill for a small boat.
    • I will also be adding storage/ flotation in the stern of cockpit, and in front of installed bridge deck by building waterproof/water resistant hatches.

    This is a simplified basic version of what I am planning. Obviously I need foils, centerboard trunk etc. I am keeping everything I remove to weight it all so I don't add too much weight. I doubt I will add much more if any weight then originally built because everything I am adding is much lighter and the 75 pounds of steel plate will be replaced with lighter foils.

    Well how crazy am I? My feeling don't get hurt easily, and I have invest virtually no money and just my labor so lets hear it. Justin
     
  2. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    Pictures make comments much more sensible and accurate.
     
  3. JustinT
    Joined: Jul 2013
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    Location: Michigan, USA

    JustinT Junior Member

    Here are a few of the pics you all love.
     

    Attached Files:

  4. JustinT
    Joined: Jul 2013
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    Location: Michigan, USA

    JustinT Junior Member

    A few more.
     

    Attached Files:

  5. SukiSolo
    Joined: Dec 2012
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    Location: Hampshire UK

    SukiSolo Senior Member

    Interesting one. Personally I'm not a fan of these older chopped strand built boats as they all seem 'soft'. You have done the right thing in removing all the saturated timber and foam cores. Ensure there is no osmosis, if there is forget the hull.

    When you replace them (the cores) make sure you seal the timber first ie coat it before it is put in. If you wanted to stiffen it, I would lay in an extra layer of medium weight (280 gm) roving or cloth on the back of the CSM layup before adding the foam. This will give you a stiff sandwich with an extra layer inside.

    A few extra stringers or even ribs/half bulkheads would make a massive difference. The Douglas Fir is fine and either a good foam or strip plank cedar will act as a core throughout and marine ply floors would keep things reasonably light. Might as well use epoxy as the resin and you get the option of adding decent fillets too. If that forward floor is going to be stepped on or have an anchor dropped on it I think 3mm core is too thin. More like 6mm.

    It is a doable project, but I would rather build something new if it was my time and money. Either an existing design from lines/offsets or design it yourself. More modern materials and methods will give a stiffer lighter boat which wil give less trouble over the years. You need to know that old boat is a good one before you spend a lot of time on it. Not all old designs (and a few modern ones) are that good. Mostly the newer ones will sail better and still have the sea keeping ability you require. Generally they are much better stressed too giving fewer problems over time.

    Ultimately it is your call.
     
  6. JustinT
    Joined: Jul 2013
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    JustinT Junior Member

    Thanks for your reply. I have planned for one bulkhead in bow and two ring frames, plus one half bulkhead in front of centerboard by chainplates. The boxes in stern and on either side of the centerboard case. Along with the PVC foam core laydown on the interior of the whole boat. I think this should be enough to make a huge difference. The largest area without support is the port and starboard sides inside the cubby. Maybe a m^2 of area unsupported above waterline. Is this too much with 6mm core and biax in and out? I thought about a white cedar stringer from where seat tops meet cubby up to the bow.

    The weight and instillation difference between strip plank cedar and Divinycell seems pretty huge for this project. Marine ply weight even Okoume add up quick. Since the Cubby will barely have sitting head room I won't be walking on the 3mm ply and it will have a lot of support with the half bulkheads, ring frames, centerboard trunk etc. Plus the anchor will go in one of the two boxes next to the centerboard in cockpit or in a bucket under the thwart I haven't mentioned. Given that use do you think the 3mm with light glass on both sides is still too thin?

    Am I where I should be for may laminate schedule?

    Is 6 mm Divinycell with biax inside and outside of hull with light finish cloth sufficient for the floor in cockpit?

    I will build a boat someday. This boat fits well, into what I am looking for. Give me a few years playing with this boat and I feel I will know much better what I want to build.

    Justin
     
  7. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    Does that mean you won't be putting all your weight on it?
     
  8. JustinT
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    JustinT Junior Member

    I hoping that is sarcasm. You don't see a difference in force between walking on something versus sitting/lying down? If 3mm with light glass cloth on both sides is not enough its not enough. I am just trying to pinch weight were I can. Though I suppose I should crunch numbers with three coats epoxy on 6 mm. Justin
     
  9. SamSam
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    SamSam Senior Member

    I have no idea about the construction needed, but because you can't stand up in the space doesn't mean all your weight won't be concentrated like on one knee or something.
     
  10. JustinT
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    JustinT Junior Member

    I get your point Sam. I don't know if 3mm Okoume and light glass on both sides and with a lot of support is enough. I do see a huge difference in force applied to something I may crawl around in then something I walk on. The forces applied by a heel strike seem pretty high. Especially if I wear my high heels when I go out gunkholing.
     
  11. SukiSolo
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    SukiSolo Senior Member

    Well said SamSam. I was envisioning crawling in there with weight on one's elbows, quite a point load. 6mm with rib/stringers will take that. You could even sleep on it, quite happily. 3mm even with glass each side, well I'm dubious. If it were me I'd probably butt WR Cedar and glass both sides at 8-9mm with few battens. Hard to tell, you know the spans, it can't be hard to get a feel for the stiffness with a quick test rig.
     
  12. JustinT
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    JustinT Junior Member

    All of your weight on your elbows. That sounds painful. I do like the WRC for the floor that sounds quite nice. Way more class and style then plywood. Thanks Justin
     
  13. SamSam
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    SamSam Senior Member

    After stripping out the inside, I would pressure wash the interior and wet vac the water and stuff. Put in some fans and dry it out for a few days before laminating.
     
  14. SukiSolo
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    SukiSolo Senior Member

    I'd second that SamSam, but also rub over with degreased wire wool and acetone so you get a bond on the 'depressions'. This technique also works well for repainting non slip deck paint over GRP.

    Might seem like a pain but unless you have a perfectly sanded surface it gives a bit more of a guarantee that the new epoxy will key onto the original fibreglasss. It also removes any residual contaminates.
     

  15. JustinT
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    JustinT Junior Member

    Prep is everything. I planned on a good scrub with TSP, and bleach, rinse repeat. Then either acetone, or MEK wipe down. I have not thought about or ever heard of the wire wool and acetone idea. Sounds like a great idea. I imagine bronze wool is the way to go.

    I probably should not have read any further about foam cores. It can start to make your head spin. Will I have a hard time getting a good bond with hand laying the Divinycell without vacuum bagging? How much of a curve can I bend 6 mm Divinycell H 80 without going to the scored sheets? Thanks for your input you two. I think I was a little long winded in my initial post for most. Thanks for taking the time. Justin
     
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