BYYB Forums

Hi Tom!  I built your dolly for my Weekender build and I love it.  It moves easily, allows great access to the boat and has room to store stuff.  I do have a question.  I'm getting to the point in the build where much of my work will be inside, standing or lying on the hull bottom.  Do you have any doubt as to the strength od the bottom, supported by the two crossbeams, with the keel hanging freely?  I suspect not, but I don't want to weaken the bottom.  Underway the water supports the bottom.  In my garage...just air!

Dave

Here's a photo of the layout.  As you can see the keel "hangs" from the hull bottom, and the bottom is supported fore and aft but not amidships.

Dave

Dave  If you are worried about it, here is a EZY fix.  Put a 1"X4" board under each side on your dolly. Bud

I am pretty big and weigh 300+ pounds (workin on losing some tho) and I was very concerned about standing, kneeling or laying in my little boat to do the things you need to do in it.  I built 2 bunks/boxes from a sheet of 1/2 ply, some masonite, some 1x1's and a piece of carpet I had lying around the shop.  I cut the plywood into four 12'' wide strips then copied the curve of the hull onto them and cut that curve out.  I then made the 2 bunks/boxes from the ply strips, the 1x1's scrap and tacked the masonite on the cut curve.  I covered the masonite with the scrape carpet.  They are pretty simple.  Eight feet long, about 1 foot tall except for the curves and 1 foot wide.  I would guess about $20 worth of wood and an hours time.   Getting the curve right wasn't hard I just layed a stick on the high spot of the bottom when the boat was upside down then noted the distance to the hull at one foot stations.  Sort of like what you do to get the curve of the bottom and deck.

I use those 2 bunks/boxes as support for my boat when it was right side up.  It is very stable, doesn't rock or move when I climb in or out and the boat floor doesn't sag under my weight.  I think I will build a boat dolly like Tombayus and incorporate the two bunks into it.  When I work on the boat upside down, (hull fairing, sanding and now painting) I use two 2x6's, ripped to a 2x2 and 2x4 then screwed to make them into an "L" layed on the two high points of each curve with a pool noodle flotation thing cut in half for padding to support the boat.  Here's a picture of one of the bunks in case my description is lacking:

Greetings Dave,

I understand your concern.  I have been a little concerned myself.  However, I did cover the top of my uprights with a set of those hard rubber extrusions with a half-moon cross-section used to help keep you from tripping over extension cords and other wiring.  I just happened to have a half dozen of them laying around, so I cut two in half and screwed them to the top of the uprights.  The rubber deflects and spreads the load out over about a one inch wide strip that runs the full width of the boat.

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I have gotten pretty good at sliding the boat forwards and backwards on the cradle by lifting the transom end up on to a pair of saw horses and then jacking the keel upwards an inch with a floor jack.  The cradle then slides quite easily underneath the boat.  I try to keep one of the uprights underneath where I will be standing or sitting, which lately has been in the front third of the cabin as I have been cutting and fitting the shelving to the hull sides.  It turns out that the distance between the bulkheads on the boat is about the same as the distance between the uprights on the cradle, so it is pretty easy to support the floors in both the cockpit and the cabin simultaneously.

I am pretty careful to step into the boat from a step ladder directly above the rear upright and then walk forward along the center of the boat.  I do this in my stocking feet to help keep the dirt down inside the boat and the hull bottom directly above the keel feels rock solid.  I "think" I can feel the hull bottom flex ever so slightly if I step away from the keel, but nothing has cracked.  For the record, dressed in boat work clothes, I weigh about 196 pounds.  The hull bottom is 12 mm Okuome plywood, which is just a tiny bit thinner than 1/2" fir, and a tiny bit more flexible.

So far so good.  Just move around gently.  

I also have the hull sides already attached, so the hull is getting quite stiff in its own right.  The more the hull gets completed, the stronger it will be.

I like Terry's idea of having a "molded" bunk that runs for and aft.  I had thought that a ten foot long 1x4 or 1x6 plank spanning the uprights on each side (just like Bud suggests) laid flat would flex enough to follow the curve of the hull and spread the load out even more than my anti-trip rubber strip, but I never got around to trying it.

I am also counting on the spacing and dimensions of the uprights to be just about right for supporting the boat upside down for glassing.  I will have to tack on a slightly wider board on the cockpit end to span the side decks, but the front upright should fit inside the rails just in front of the cabin right where the front bulkhead is located.  

Cheers,
Tom

Thanks for all the replies.  I weigh about 185 and the bottom seems fairly solid under my weight.  I try to "spread it out" by lying or sitting...standing as little as possible, and over the supports when I do stand.  I'll likely slip a couple of 1X6 's under the bottom for security.

Dave

I was suprised to hear that the okuome was more flexible then fir.  I used hydrotek, a merenti ply.  It is much much stronger with less flex then regular ply or some fir marine ply I have.  Heavier to but when I say less flex it doesn't give even spanning a 42" space.  (The deck area over the nose of the boat)

Greetings Terry,

Well, it kinda sorta depends in the flexibility department.  A given thickness of Okuome by definition will bend more than a given thickness of fir as the modulus of elasticity is about %50 higher in Fir than Okoume.  Meranti splits the difference between the two.

But the Okoume plywood I bought from Plywood Door USA is BS1088 grade manufactured in France and comes with 5 plies for a 6mm thick panel.  The slightly thicker American made 1/4 inch marine Douglass Fir I had access to via Owl Hardwoods only had 3 plies.  The 3-ply Fir plywood was more flexible than the 5-ply Okoume. However, 5-ply Fir should be stiffer than 5-ply Okoume, but I could not find any locally.  

The Okoume plywood is also about 30% lighter (less dense, smaller specific gravity) than the Fir.  I could easily lift the 12mm Okoume panels at arms length.  The equivalent half inch thick Fir panel will give you a hernia if you are not careful.

Cheers,
Tom

12 mm Okoume is just a little less then 37 pounds a metric sheet (which is slightly bigger then our 4x8 sheet).  Meranti will be about 49 pounds for a 6 mm sheet. Fir can be all over the place, with second growth, farm raised, hybrid species inside, etc., but it's generally listed at 50 pounds as a 5 ply.

Greetings all,

Thanks Paul.  Yes, the 50lb 1/2" (12.7mm) Douglas Fir is 5 ply, and the 37lb 12mm (.47") Okoume is 7 ply. 

Random thoughts ...

So, for a given thickness of plywood, a swamped Okoume Weekender will float better than a swamped Douglas Fir Weekender :o

For a given weight, you could use a thicker Okoume panel than a Douglas Fir panel. And if I remember my calculus correctly, bending moments have thickness (height) cubed in the numerator, so the thicker Okoume panel should be about twice as stiff as the thinner fir.  So again, it all depends.

The Okoume is just drop-dead gorgeous. It will be a shame to cover most of it in paint, but I think the finished boat will look better that way.

Cheers,
Tom