Replies to This Discussion

Permalink Reply by Kevin C. on January 15, 2011 at 8:57pm

Oh Boy,that sounds like a hum-dinger of a project,Peter.I would suggest taking a heat gun to the glass covering the chine and with a sharp utility knife ,cut that material out and expose the entire chine.Remove the chine cause with the extra ply on the bottom you'll need to move it anyway.Chine caps should be a sacrificial piece,meaning they should be bedded with 101 adhesive and screwed on ,oiled and left exposed to take the abuse from the river bottom,trailer,etc.,not covered in glass.As far as the bottom lumpiness goes (and I'm assuming this is a glassed bottom? )you might try the same heat gun technique,being carefull not to apply too much heat to the surface and srape the high spots down to get a smoother surface.We use a Pro Prep paint scraper with a sharp edge and with just the right amount of heat the epoxy scrapes down nicely.This may seem very daunting at the beggining as you look at the entire surface but it goes fairly quick if you keep at it...and a couple cold ones does'nt hurt.Avoiding sanding epoxy when at all possible is a good idea and attaching a shop vac hose to your belt sander really helps too.Often in restores we find once you start poking around down there you may find some delamination of the glass from the ply floor and it may be easier to just apply that heat generously and remove the entire glass bottom,leaving you with exposed ply and a favorable surface to glue and nail  on your additional ply.If you can just scrape down the existing epoxy and rough sand(36 or 50 grit belt sander), just wet your ply with thin epoxy and apply thickened epoxy to the sanded surface and weight that down evenly with whatever you have ;bricks,sandbags,ancors,etc.and let it set.Using thinner ply (1/4")and doing this twice will allow you to get a better bond because the thinner ply bends easier to the rocker shape although 3/8" would probably work as well.Anything thicker will be a real bear to weight down.As far as ply goes, try to find 1/4' marine grade doug fir with no voids(which is getting hard to do) so that any trauma to the bottom does'nt puncture and collapse the ply and lead to seepage on down the road...hope this helps...

Permalink Reply by Kevin C. on January 15, 2011 at 9:02pm

the general idea.this was the first ply nailed onto the ribs in this restore

Permalink Reply by Peter Foster on January 15, 2011 at 9:02pm

Thanks, Kevin, I now know that to use the chrismas $100 Gift certificate at Home Depot for, heat gun and epoxy by the gallon.The bottom is only fiber glassed to about 6" along the edges , so the whole bottom is not FG.  nails on the bottom VS screws?

what is best material for the chine, I have Port orford cedar  almost has hard as Fir. and no rot.

Permalink Reply by Kevin C. on January 15, 2011 at 9:08pm

We've generally used white oak or mohogany  for chines...as far as epoxy goes check out Raka.com or jamestown distributors.Larry at Raka could help you figure out how much you might need for this project.If you could post some pics of this it would be helpful.

Permalink Reply by Lawrence E. Long on January 16, 2011 at 4:55am

Peter:

Kevin has given you excellent and detailed information on getting the job done.  I  agree-   two  1/4" layers would be easier to lay down.  When I added the 1/4" to my 1/2" bottom   it was suggested by the designer to drill 1/8" or so "weep" holes on around 10" centers all over the 1/4".  Loaded up with cement blocks all over the bottom it was surprising  the amount of epoxy that came up through some of the holes.

Good Luck

Permalink Reply by Kevin C. on January 16, 2011 at 7:49am

good advice lawrence,i'd forgotten about the weep holes,very necessary...

Permalink Reply by Peter Foster on January 16, 2011 at 11:14pm

 I still have some questions guys, if I do one layer of 3/8,  do I nail it, screw it or just glue it.  Depending on the availability of the plywood,  if I get (2) 1/4" do you nail and epoxy the first layer and only epoxy the second layer?

Good Idea about the weeps.  My bottom Hull length is 11'-8"   is plywood available that long? of do you make a seam?

Permalink Reply by Lawrence E. Long on January 17, 2011 at 5:57am

Peter:

My 17'  DB  had the 1/4" just glued to the  1/2".    The bottom was about 54" wide and about 15" long so it required scarfing  the PW.  In your case  you might want to scarf a 4' section of PW to an 8' section such that you end up with a  4' wide piece about  11' 8" long.  If you are not comfortable making  this scarf first time out you might start with adding a 5' piece to the 8'- to give you a shot at making a second(or third) shot at making the scarf.  Depending on the max width of your bottom you would then scarf two sections on either  side of the  12'  long enough to cover the bottom- might be only 5'-8'  long strips 6"-12" wide.  Draw up a sketch to see what you need.  I doubt you can find 12' long  PW.    Get some cheap PW  and practice making scarfs.   Some places will scarf PW for you but some people have found the quality to be bad. 

 

When you get ready to glue on the bottom  I suggest you get a buddie or two over to help out.  Put unthickened epoxy on the "new" bottom and the original bottom.  Let both  "absorb"- you will see some 'dull" spots with end grain sucking up the glue.  Then recoat with unthickend where it has been absorbed.  The final coat with thickened- cabosil/microfibers- about like consistency of runny peanut butter or cold honey.  Lay the sheet on the bottom and put a few finish nails(not all the way) on one side to keep the mess from  sliding around.  Then put the cement blocks to it.  I must have had 10 or so- plus tool boxes etc. 

Good Luck

Permalink Reply by Kevin C. on January 17, 2011 at 8:27am

Good advice from Lawrence,and I'll add a couple things.When attaching a bottom leave all the plywood(width) so you will have more to bend and add weight to.This goes for the end as well.You can start at the bowstem about flush(2") ,screw 2 or 3 screws into the stem and chine log to start it out flush to the bottom(and to keep it from moving during the rest of the process),then use your weights to press it to the bottom as you go .Be sure to lay down visquene in between the weights and the weep holed ply or you'll end up with a big mess.Having plenty of ply hanging over the transom end enables you to get that end to bond flat and flush to the bottom,and here again you can set the end with a couple few screws into the transom and chine logs for a secure connection.As far as the scarfing goes(and if you have never made one),you might try a lap joint scarf for this application.Router  1/2 the plys from the end of one side of the 8' sheet about a foot back and then router 1/2 the plys from the end of one side of the piece your adding and epoxy these together flat with the method Lawrence mentioned above being sure to saturate both surfaces well and adding the thickened to one of them and weighting.Be sure and not put too much weight on any of these joints cause it will end up squeezing alot of the thickened out and starve the joint.I like to make 2 scarfs on each end of the 8' sheet so the joint does not land on the stress area of the rocker bend.A 2' piece up front by the stem and a 3 ' piece on the other end will give you plenty to  work with and ensure your joints to lay in a more favorable spot . Do these scarfs on a flat surface with plastic underneath and let set until the epoxy has fully gone off.Lift the entire sheet onto the bottom and attach,trimming off the excess after cure.The other scarf method ,tapering the ply sheets works well also but may seem a bit intimidating .It's relly not that bad and in this situation I would say try it with a power planer and belt sander  and just read the interior lines of the ply's as you go and you will probably find it's not as difficult as you would evpect.Definately try both these methods out on scrap ply first and you will get a feel for what is more comfortable and practical for you as well as teaching you two different scarf methods... the pic's show a lap scarf we did in place. 

Permalink Reply by Peter Foster on January 17, 2011 at 11:19am

Kevin, How do you keep the proper 1/2 ply depth with a router? I see the first picture showing making a series of groves and that keeps the depth, but how do you remove the rest of the plywood and still keep the depth right?

Permalink Reply by Kevin C. on January 17, 2011 at 12:21pm

a nice sharp chisel will remove all the little squares and a ranom orbital will smooth out any bumps