Installing UHMW bottom

I am about to re-install the UHMW bottom that came with the tatman used boat I just picked up.    What size stainless steel screws should I run down to Home Depot and buy to get this job done?  Should I screw them in along with any sealant?

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Permalink Reply by Randy Dersham on January 22, 2011 at 1:18pm

Use a 1" screw and make sure to screw only along the chine or into a bottom frame.  Counter sink the screw so it is 1/8 of an inch below the surface of the UHMW.

 

Using more screws will only introduce more places for rot, so don't get too agressive with the number of screws you use.  Screw down about five inches apart around the edges of the UHMW.   Then put one line of screws down the middles of the boat at each frame, then one line of screws midway between that center line and the outside edge. That will be about 12 inches on each side of the center line.

 

Bed each screw with 3M 5200.  That will stall the UHMW from backing out the screws but it wont prevent it. 5200 is not all that great at holding sharp screw edges from rotating.  

 

Check your boat bottom before you launch each year, once mid season, and before you put it away for the winter. (if you do)  Any screw that has been worked out to level with the UHMW surface should be removed and re-bedded with 5200.  If the screw won't bite and acts like it is stripped out it means the area around the screw has gone soft.  It might not have started to rot yet but it will no longer hold the fastener. Do not be tempted to simply put in a longer screw.  To properly maintain your bottom you remove the shoe, drill out the soft area, plug it with a wood plug, epoxy it, then re-install the UHMW with the screw in the same location going into the new repair.

 

If you maintain your boat bottom this way your UHMW shoe will last about ten to 15 years and you will prevent any rot in your bottom.  If you don't take care of the screw areas the UHMW will work them lose and you will need to replace the bottom of the boat in about ten years.  This is the most common repair request at our shop.  The UHMW shoe became very popular about 20 years ago.  The people that have not maintained the bottoms of their boat are now seeing some larger rot problems.

 

UHMW is still the most slick shoe you can put on the bottom of the boat and it continues to be very popular. 

Permalink Reply by Greg Hatten on January 22, 2011 at 6:57pm

I am in the process of doing the maintenance Randy describes above... UHMW shoe is "off", checked my bottom for the previous "patches" to see how they are holding up, and have three or four screws holes that I just filled with epoxy because they weren't holding the screws.  When the epoxy dries tomorrow, I'll bed the screws with 5200 and reattach the plastic shoe.  This will be my 6th season on the water and the plastic is holding up very well.  When I originally attached the shoe, I used Bee's wax - I switched to 5200 after removing the bottom a couple of times.

I'm a big fan of UHMW - it's slick and sturdy.

GH

Permalink Reply by lhedrick on January 23, 2011 at 2:34pm

This is just for discussion.

 

A while back I am sure I came across someone who said they bonded UHMW to epoxy/fiberglass with Gflex epoxy using a vacuum process.  I have looked around and I can't find the place/forum where I read it.  

 

I have yet to work with Gflex epoxy.  Has anyone here used it yet?  I am currently trying bond some closed cell polyethyele foam to glassed plywood.  Raka epoxy has nt stick at all.  As usual 5200 holds well enough.  

 

If anyone has any of the West Gflex it might be worth a test to see how it sticks to UHMW.  Not sure it would replace screws or if that is advisable since it might make removal a problem if it really did bond.

 

 

 

 

Permalink Reply by Randy Dersham on January 23, 2011 at 4:19pm

http://linktech-inc.com/  is the website of the UHMW that you can bond.  It is a patented product that includes cloth in the making of the plastic. 

 

Our member Kurt Sallaz works for that company.  I have used it and love it but the cost is very high.  A bottom after instillation is $1000.00 or up depending on the size of the bottom. A customer can screw down UHMW plastic for about $300.00.

 

It is the cloth backing in the manufacturing process that is the magic ( hence the patent).  Noting, I mean nothing, will stick to UHMW plastic. At the shop we use it on clamps for epoxy joints so it will easily lift off, including G-Flex.

 

FYI G-Flex is a fairly thin epoxy so it doesn't fill gaps all that well.  It's magic is that it is more flexible than other epoxy joints but less flexible than 5200 or similar flex bedding adhesives. It is made to bond dissimilar materials that will expand and contract at different rates.  Unfortunately still won't bond to UHMW.


Permalink Reply by lhedrick on January 24, 2011 at 7:49am

1000 for a bottom cover, that is pricy.

 

Thanks for the information on the subject.

 

L

Permalink Reply by Jason Knight on January 23, 2011 at 3:32pm
The only thing I have to add to this discussion is to skip Home Depot for your stainless hardware. Find a good local hardware store and you can by good stainless by the box for a fraction of the cost of the prepackaged stainless they offer at big box places...
Permalink Reply by Rick Newman on January 23, 2011 at 5:39pm

Jason is accurate in his recommendation.  Various members have had great luck sourcing screws and hardware via the Internet.  Perhaps a search on the site will help.

 

Rick Newman

Permalink Reply by Jason Knight on January 24, 2011 at 5:03am
Also check with site sponsors for boat hardware products ;)
Permalink Reply by Robb Grubb on February 10, 2011 at 3:54pm
Eugene Fastener in Oregon has a pretty good selection of SS, flat head screws on the shelf as well as being able to order... just be sure to confirm flat head versus round head with the human head behind the counter...
Permalink Reply by Michael stark on February 10, 2011 at 3:42pm
Thanks for all the replies gang.  I sourced some great hardware from a sponsor and the 3m sealant.  After doing it I flipped the boat and found two screws that missed the spar and came up through the bottom about a 1/4 inch where the water drain cut out is.  What should I do?  Seal over the protrudding screw?  Back it out and seal up?
Permalink Reply by Greg Hatten on February 10, 2011 at 5:34pm

I'd back it out and seal it up.

GH

Permalink Reply by Terry E Walsh on February 10, 2011 at 8:55pm
 Hey can I get away with putting UHMW on,... in the Colo-Wyoming climate? I am wondering if it moves to much with the shifting temps.

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