Hello folks,

I promised in an earlier post to update you on my re-bottoming project.

I purchased this 17' Tatman and it's in excellent shape, except it was 18 years old and the UHMW plastic on bottom was getting very brittle.  The screws were working loose and the plastic had to go.  There was even a slow leak along one row of the screw holes where they missed the framing member.

I decided that instead of replacing the UHMW sheeting on bottom, I would instead try a slick bottom treatment called Wetlander.

To make up for some of the protection and strength I was giving up, I decided to try a single layer of Kevlar fabric (11oz) and multiple coats of WEST system epoxy.

I removed the plastic and this is what I found:

Bottom in good shape, except lots of screw holes to fill.

So I filled each hole with WEST system epoxy and a dowel or matchstick or toothpick, depending on what would fit.

When all that was set up, I sanded and then cut a single piece of 11 oz Kevlar fabric to fit the bottom.  In retrospect, I would have been better off to put the Kevlar on untrimmed and then grind off the edges.  But it didn't go too badly.The photo above shows the Kevlar after it has first been laid.  WEST system, then this piece of Kevlar, then a good soaking / rolling of WEST system.

 

Below is a closeup of the edge, which I grinded off and sanded to taper down a bit.

And below is the bottom with Kevlar finished, ready for some edge patching and multiple coats of WEST.

Below, the edges have been patched and more WEST system added.

And below is after I have coated with the Wetlander primer and top coats.  As you can see I also used the Wetlander on the little side panels just for a design accent.  The plastic piece leaning against the stem is a UMHW polyethylene product called Tivar 88.

In addition to the stem piece, above, I had two 10-foot strips cut of 1/2" Tivar 88, with angles for securing to the chine battens along the middle of the boat on each side.  One of these pieces is shown below:I'll bevel each end down before mounting these to the chine battens.  

These go on with the large flat side (bottom as shown) up against the chine battens, with the sharper angle (45) down when mounting — up when the boat is turned up right.  The 30 degree angle works nicely coming off the bottom.

I'm planning to use 1" stainless steel wood screws, counter-sunk just below flush.  The screws I have are threaded all the way up.  I'm not sure that's best, because I'd like to leave a little wiggle room around the screws where they pass through the plastic.  This is because of the expansion and shrinkage of the plastic that occurs with temperature shifts.  My thinking is I need a slightly oversized hole through the plastic, then a taper into the wood of the right size for the screw, with a small counter-sink up top.

What do you fellows (& ladies?) think?

Also, I'm thinking of using gaffers tape or gorilla tape to just tape these plastic strips up and drill the whole hole, as it were, with one bit at one time.  Anyone have advice on this?  If that works, it looks to me like I could tape it up, drill and screw, one at a time, starting at center and working out both directions.  I have to map my holes ahead of time to look out for existing screws plus the plugged holes from the screws previously holding plastic in place.

Also, another cry for help:

I'm thnking of, just prior to putting each screw in, squirting a little bit of 3M 5200 marine sealant in the hole...to put a little flex-quasi-seal around those screws through the plastic... what do you think folks?

Thanks in advance for any suggestions...

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Comment by Tom Thompson on February 5, 2014 at 10:20am

Mike,

I've had the boat in the water only a few times but the wetlander seems to be holding up well. It sure is slick, I'll give it that. So far only a few scuffy looking places on it, no scratches through. I would use it again.

Comment by Mike Baker on February 5, 2014 at 9:02am

Hey Tom,

I was playing on the interweb and found this post. I am wondering how the wetlander product has held up. It sounds like the perfect bottom coating. is it or is it too good to be true?

Thanx

Mike

Comment by Tom Thompson on January 9, 2013 at 12:39pm

Thanks, Guys, each of you, for your input.  Lots of sound advice.

Chris, I did take your advice and ran that plastic proud to the bottom, and I feel good about that.

Phillip, I did go to Harbour Freight and get that same set of tapered drills.  Exactly what I needed!

Lawrence, thanks for your input and confirmation that an oversized hole was in order.  I did end up using 5200, because I believe that is what was originally used as a bedding compound for the screws trough the original plastic, and I was able to get them out.  Nothing really sticks to that UHMW plastic, I think that's the key.

Anyway,this whole deal is an experiment, so we'll see how she goes.  After the boat has sat unattended for a while (I finished her up in late Sept. or early Oct.), an examination makes me optimistic as to how she'll wear.  Anyone in Salt Lake or near the Green River want to go?  I need a partner....that is, if there is enough water in that river to drift.  I believe I saw 830 cfs.  Seems awful little.  Am i wrong?

Thanks everyone else who has commented at one time or another as well.

Comment by chris towles on September 18, 2012 at 8:46pm
Make sure to run those strips proud of the bottom edge. This will cover the joint of where the Kevlar meets the edge of the chine. Most times when you glass this way running the fabric to the edge it will quickly start to delaminate the layer of fabric. Happened on my buddies old tatman. The chine batten usually covers this joint. With your 10 foot strips you should get most of the way on the chine so if you run it proud and protect a that joint from impact you'll probably be less likely to hit that spot and start to tear the layer off. I wonder how that kevlar will work in that capacity. While Kevlar is really tenacious stuff, it does have its own set of drawbacks...first, it doesn't wear very well...tends to fuzz and make a mess. While the fabric almost always stays together in an impact, the weave can get soft and mess up the bias of theweave of the fabric. Usually kevlar is used as the inside layer of a layup...ie I would have covered it with a layer of glass on top which wears better and would add stiffness in compression to the laminate, an area where Kevlar is lacking....it fairs significantly better in tension...it's strong point. Last point about kevlar, in regards to delam issues is that it tends to float in a layup, ie not soaking up much resin, where the fabric is more encapsulated on either side by resin.nthis can lead to bonding issues. It really is miracle fabric in some capacities, but it needs to be used correctly. You did a nice job though, and I think if you protect the joint you can probably keep the layer from peeling. Let us know how it wears.

As for the expansion on the strips, what about neoprene washers as spacers under the head of the screw. This would allow a certain amount of squish in the system. Counter sink well, and bed the screws with marine caulk, I like sikaflex 291, but there are plenty of non permenant bedding compounds. 5200 is pretty permanent. That should work good. When I did my strips aj recommended not going into the side panel, just into the chine batten, I used 3/4" screws
Comment by Phillip Westendorf on September 17, 2012 at 8:50pm

Tom,

Recently I picked up a set of tapered drills (7 sizes ; No. 5-12) with adjustable position countersink and adjustable set collar to set the depth of the countersink.  I think they'd work just as you described.  They were purchased from Harbour Freight, Item No. 07608.  I don't remember the cost but it wasn't a lot.

For the sealer as you put the screws in I'd recommend West System G-Flex Epoxy.  It will allow an amount of movement and can be removed later as needed.  I used a phillips screwdriver engaged  in the screw and heated the screw driver shank with a propane torch.  The heat will allow the screw to be removed with the screw driver with little effort.

Hope this helps,

Dorf

Comment by Lawrence E. Long on September 17, 2012 at 7:41am

Tom:  Have not used any "plastic" but when I attach a gunwale,rub rail etc I  drill an oversized clearance hole in the piece  as you suggest.  As to the 5200-  you will never get the screws out this stuff is "permanent"  Suggest you use a "sealing type" of compound rather than an adheasive.

Good Luck 

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