Mike`s Framed Drift Boat Build

Hi, started a build with no solid plans. Built my strongback, laying out the ribs, got the spacing but hoping someone could give me a idea what to go with for the height for the side ribs. I`m thinking 2 ft (or less) in the frt and tapering smaller to the transom? (but how much). Does that make sense to get 2 sides out of the 4` ply?

Also someone suggested I dado the ribs so I started doing that. I got 2 done and decided it was a bad idea when it comes time to attach the chine with no meat to screw too. Any thoughts?

Can anyone suggest how high to set the ribs for the rocker, I`m guessing starting in the center? Thanks much, Mike

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Permalink Reply by Phillip Westendorf on June 22, 2015 at 6:48pm

Mike,

Our rivers here in Michigan aren't all that fast flowing even in spring and you won't be bouncing around on the rocks like you might out West in their rivers.  That being said, you can get away with 3/8 ply but I'd add a couple of 10 oz. layers of cloth on the outside and a single layer of 6 oz (min) on the inside surface.  That'll give you enough strength to handle anything we have here and most other places.

Dorf

Permalink Reply by Eric Loudenslager on June 22, 2015 at 5:04pm

I presume the mahogany is Hydrotec, also called meranti. If they have that in 3/8 it could be used for the bottom. Many prefer fir for the bottom because the fibers are stronger.

Okume is lighter, but not as strong, as the meranti. Jason Cajune at Montana Boat Builders uses Okume for side panels.

I have no opinion about okume for the bottom. My meranti bottom is 3/8, with the layup: 6 oz glass, 5 oz kevlar, 3/8 meranti, 5 oz kevlar, 6 oz glass. My dory is stitch-and-glue, not frame. I have run lots of class III and a couple class IV, and hit a few rocks. Things have held together OK.

If this is primarily going to be used on moving water without significant rapids, I would have no hesitation in using a 3/8 bottom with a layer of glass on each side of the ply. Many on this forum use fairly heavy biaxial glass on the exterior bottom. I have no opinion on that level of abrasion protection. A layer of 6 oz on the inside is important - it keeps the ply from fracturing when hit from the outside. Dynel is another option for the exterior - 6 oz glass, 6 oz dynel. The dynel is way more abrasion protection than glass, but not as strong in compression and tension.

Lots of options. Most should provide a reasonable outcome. You do not need to laminate 1/4 okume to produce a 1/2 bottom panel for your little dory.

Permalink Reply by Mike Thomas on June 23, 2015 at 5:59pm

Thanks Eric and Dorf. Theres no mahagony at all so it looks like I have no other choice than to get the 1/4" and 3/8" Okume. I kinda figured I would just have to use that, and I`ll glass it.  Not sure what color that wood will be when its cleared, but I guess it really doesnt matter too much. I was hoping to stay with all light shades of wood on the inside. I`m getting a order ready for Jamestown bolts, nuts and screws so I`ll order some glass to get started on all the inside panels, and try to figure out how I can get to the lumber place to pick up the plywood during work hours. I`m off July 6-10 so I might have to wait till then to get it.

Thanks Dorf, I read through Guy`s complete thread a couple times, then went back through a few pages a couple more times.   His frames and build is similar to mine, though what he did with computer programs and all the engineering work, I was limited to, and had to do with just a couple batten strips, a bevel and a tape measure. I like his open floor plan, but I`ll go with the conventional benches with low back boat seats. His boat like yours is a very awesome boat.

As always thanks for all the help from you guys

Permalink Reply by tungsten on June 23, 2015 at 7:34pm

Well theres probably a few on here that will say no to okume for the bottom but the good thing is an okume 3/8 sheet is 10 lbs lighter then meranti.So you can go to town with glass and goo.

Plywood alone will absorb about 40 grams sq/ft so about 3 lbs per sheet per side.12 oz  biax glass wetted is about 6 lbs per sheet per side. 

Permalink Reply by Gregg Maddock on June 23, 2015 at 8:08pm
Mike, You'll be fine with 3/8 on the bottom. Just get some heavy 'glsss and layer up the epoxy/graphite mix. This is my 14' that I just completed on it's maden voyage on the Clark Fork River in northwest Montana! These 14' handle like a sports car on water. Keep going. It has been fun following this thread.
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Permalink Reply by Mike Thomas on June 24, 2015 at 3:54pm

Thanks Tungsten, good info. Thanks Gregg, your boat looks nice, I think Ive been through your build on here too. Mine has now turned into about a 15` boat, as the stem angle got a little longer....not sure what happened (scratching head...)It wont have the rocker yours has but here in Michigan its nothing like out west.

I`m gonna go for it. I know more weight on the bottom would be more stable but I dont have much choice. That glass weights Tungsten posted up will make it up some.

For a first build its all good. I should have named my thread something else, as at first I thought any framed boat would be a Mckenzie style, of course now I know better and like everyone Ive learned alot from this site. As far as longevity, I`m almost 60 yrs old so I`m not looking to get 30 yrs from the boat, and I`m sure it will take me fishing for a while. Who knows I might build another yet some day too.

So for now I`m held up a little, but I can still start sanding everything I have done to prepare for the plywood and varnish on the inside. I bought one of these little triangle sanders cause even with the barrage of sanders I have, can never have too many right? lol, actually Ive wanted one of these but never really had a reason. It will make sanding and getting into the tight corners nice around the frames and chines

I tried making a paper pattern of the side to use for the plywood, that didnt work out too great. Pretty hard to lay it over the frames, but if I cut a little oversize the wood can be trimmed on the boat. Not sure if I`m gonna get 2 sides out of the 4`x16` sheet. Worst case, I`ll just have to get 2 more sheet of 1/4"

One thing I dont have is a straight plywood edge like most plans show, but I guess its from the angles of my frames which are more like a pram than a Mckenzie. Thats ok I guess

Permalink Reply by Mike Thomas on July 29, 2015 at 8:02pm

OK, figured out my side pattern is not right because the lengths of my frames are not right. Not a problem as the frames can get cut to size. Got my 1/4" scarfed. Made and tried using guys scarfing jig, jig came out nice but the attempt

to use it was a major fail. Didnt have a good enough table to do it on.

Ended up just using the belt sander and it came out pretty decent for a first try.

That dry fir looked pretty good, but the epoxied joint didnt come out as nice, but still will be usable. I also went with deviding the 4`x16` sheet in half to get 2 sides. I made a paper pattern of half first to see how it worked out. I`ll be cutting the frames down some which will be better making for lower sides.

Realized I put the pattern on the frames upside down, when I turned it over it fit better but I didnt get a pic of it. I cut the plywood in half and got a couple coats of epoxy on the inward sides. Trying to cut some cost and time I`m not going to glass the insides. I`ll just sand it all good and varnish it.

I`ll get these sides on and scarf my bottom and get it on. I am planning on glassing the outside, still not sure, I`m leaning towards painting it, but if it looks pretty enough I might just leave it natural.

Heres a question, I`m still a ways away but when I get ready to glass the outside, should I epoxy the glass onto bare wood, or should I get some epoxy on it and sand first before the glass??

Permalink Reply by Eric Loudenslager on July 30, 2015 at 6:47am

I`m still a ways away but when I get ready to glass the outside, should I epoxy the glass onto bare wood, or should I get some epoxy on it and sand first before the glass??

Both approaches are used. I've epoxyed the panel, let it cure, and sanded lightly before putting on the glass. The rationale is that you will use the same amount of epoxy in either layup. If you put glass on the panel and then wet it out there is a chance that the bond between the glass and panel may be starved of epoxy. Also, the wood will outgas and put bubbles in the epoxy. If done as a single task bubbles can get trapped under the glass. If done in two stages any bubbles that don't pop can be sanded smooth.

In warm weather let the sun heat up the wood panel and apply the epoxy late in the day as the panel is cooling down. This will suck the epoxy into the wood panel as it cools. Also, the panel will not be outgassing.

Another approach is to wet out the glass and then put it on the panel. I've never tried that.

6 oz glass is standard for this type of boat. If you leave it clear it will need to be varnished annually to protect the epoxy from UV.

Permalink Reply by tungsten on July 30, 2015 at 8:10am

Well if you believe the epoxy venders they say two coats of epoxy then glass.First coat to seal second to build film thickness.

Permalink Reply by Mike Thomas on August 1, 2015 at 2:53pm

Thanks guys for all the help with my learning curve project, I kinda like the idea of a couple of epoxy coats before the glass, cause the first coat of epoxy over the plywood leaves it really rough. Sanding and then the 2nd coat of epoxy came out pretty nice and then sanding again came out really smooth.

OK here I go, sanded the frames on one side of the boat, sanded the 2 coats of epoxy on the plywood (nice and smooth now) and Ive got the side plywood clamped to the frames. I`ll have to do a bunch of trimming, along the chine rails, the stem and the transom. Gonna try out that new dremel with a cutting blade and see how it does.

Heres the questions for the experts;

This plywood looks really nice with the epoxy on it and will blend with the transom nice, so assuming I wanted to epoxy and then glass the outsides leaving it natural,(instead of painting)

1) do I want to just sink the screws in the side plywood flush with the plywood, or countersink them just a little and fill over the screws? and if so what would I fill them with so they dont stick out like a sore thumb?

2) If I start my screw pattern 2 1/4" from the top of the plywood (gunnel top) what kind of spacing should I use. Tatman said something like one at the top, one at the bottom, one in the middle, then one between the middle and top, and leave the middle to bottom of boat empty of screws for the rub rail to screw on. Does that sound good?

3) Should I put some screws into the chine rails through the 1/4" ply, how far apart if so?

4)The stem and transom will get double rows of screws 3" on center alternating between rows, does that sound right?

Permalink Reply by Mike Thomas on August 2, 2015 at 7:11pm

Tried many searches, didnt find answers to these questions.

Permalink Reply by Rick Newman on August 3, 2015 at 6:30am

1. There isn't enough plywood thickness to countersink screws. You can mount them flush with the surface. (Some of us use silicon bronze ring shank nails, however they present their own issues.)

2. I would agree with Greg. The frame lengths probably vary in length so you will need to mark each individually.

3. I didn't go out and measure my chine cap so I don't remember the measurement I used. Since you will also be installing screws into the chine rail from the bottom it can become problematic when you also add the screws to the chine cap. So you need to figure out where you will be installing those screws too so you don't try to place two screws in one place. If you also add screws under the chine cap through the plywood into the chine rail you need to coordinate those locations with the other screws.

4. If my memory serves me right three inches sounds correct.

Others may have different opinions and I respect whatever they may add. As long as the load is spread out or shared evenly then the physics of the situation should be fine. The esthetics are going to be most important to you. Avoiding putting two screws into the same space also makes good sense, don't ask me how I know about that situation!

Rick N

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