plywood

Just wanted to get an opinion on using 7/16 plywood for the bottom?  I found a local mill that has some 7/16 ab marine fir that they will sell me direct.  They don't do much 1/2 in so I was wondering if the 7/16 will work.  I plan on glassing both sides as well.  Thanks for any input.  Thomas

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Permalink Reply by Rick Newman on March 19, 2012 at 9:24am

Thomas, will you be building a McKenzie or Rogue River style boat? How are your boating skills?

Thickness reinforced with appropriately placed fiberglass will lead to a stronger bottom. What kind of fiberglass and what weights do you plan on using?

Since it appears that the majority of plywood boat bottom injuries come from a puncture type wound it is my opinion that the reinforcement on the inside will reduce the potential damage. I chose S-glass because the strength is greater than E-glass, I quote from the web ""E" glass has a tensile strength of 500,000psi and "S" glass has a tensile strength of 625,00psi" and a cost that today was about 2.5 times that of E-glass. When I purchased S-glass the price disparity was not so great. However Kevlar was about 6 times the cost of E-glass, but the strength quoted on the web was 550,000 psi. While my sources may not be absolutely correct I have to assume the strengths are close.

So my point is, for not much more money than the traditional cost, but for much less than an exotic fabric I can gain strength on the inside floor and the inside of the boats sides.

I haven't yet tried a puncture test because I haven't done a test piece. However experiences with Wenonah canoes constructed of S-glass contribute to my belief in the fabric. While my layup of S-glass 3.7  and 12 ounce biaxial s-glass on the inside and 18 ounce Bi-axial E-glass on the outside, which will be covered with epoxy and graphite may not be unbreakable I am hoping that it will shatter or star but not blow out allowing me to finish a float without a major repair.

So my point to you is you may be able to use a thinner floor section but you will probably make up the cost in epoxy and fiberglass. However I would still incur similar reinforcement materials costs even if I used 7/16" marine plywood.

What kind of durability do you want your boat to have and how much time, money and effort are you willing to expend to achieve your goals. Greg Hatten, one of the more frequent posters here on the site has tested unreinforced plywood against the rocks of the Rogue River. He has had to spend considerable time and some money to repair his boat. I do not remember any fiberglass fabric on the sides of his boat repair pictures so I have to presume he didn't use any.

The sides, especially at the chines and the front third of the bottoms of drift boats seem to take the most damage that is where the reinforcement should be placed. For example Ray Heater and Cyrus Happy install a stainless steel reinforcement on the outer chine rail to reduce damage and I suspect to spread out the shock load to a greater area.

I hope that my opinion helps, I am sure that there will be others and that you can sort through them to determine what you need for your boat.

Rick Newman

Permalink Reply by Thomas Hood on March 19, 2012 at 9:50am

Sorry, I should have clarified that I plan on glassing the bottom inside and out.  I haven't really thought about the type that I was going to use yet.  Probably what the folks on this forum recommend.  I am also going to go with a light glass on the hull to keep the fir plywood from checking.  I am planning on building the Pritchett boat out of Fletchers book.  The mill I was going to buy this stuff from has ab marine in 48x134 or close to that on the length.  On the Rogue Dory that would save me a scarf on the 1/4 in plywood for the hull.  They have 7/16 in the same dimensions but no 1/2 in.  So that is why I am trying to see if that is a bad idea or will it work if I reinforce with glass?  

Permalink Reply by Lawrence E. Long on March 19, 2012 at 12:54pm

Thomas:  check the PW before hand- must have 5 plys and no voids.  I have seen "marine PW"  that had 4 plies.  The supplier in Maine has given up on DF PW as the quality is terrible.  You are lucky if you can get to the mill  and see the stuff "in the flesh"

Good luck 

Permalink Reply by Thomas Hood on March 19, 2012 at 12:59pm

Yeah, its five ply.  They say its still good quality, but I wouldn't expect them to tell me its junk either.   

Permalink Reply by Lawrence E. Long on March 19, 2012 at 2:19pm

Thomas:  One thing you could do is overlay the 7/16"  with a layer of !/14"  I did that thing with a 1/2" and 1/4".  If there any any voids the odds of them being in the same spot are as likely as getting hit by lightening while an alligator is chewing on your leg.

Good luck

Permalink Reply by Rick Newman on March 19, 2012 at 3:37pm

Lawrence, not to long ago on the TV show "Swamp People" one of the Alligator hunters had that happen to him! The funny thing was it was a clear day and no clouds in sight.

Well, not really, but it was fun to write it. I was looking up the Lloyd's Register Standard BS 1088 just to see what it entailed and found a good sight that compare boat building materials and discusses the British BS 1088 Standard and the American PS 1-95 plywood standards. Here is the link: http://www.worldpanel.com/FAQ.htm not only does it discuss these two standards but it also documents the other common materials for boat panels. Not only drift boats, but big sea going vessels and such. I found it quite informative, hopefully it will help Thomas and others to understand what is for sale.

PS Some time I would like to see pictures of your Peapod. I spend a lot of time looking at  Wooden Boat Forum and have seen some nice Peapods on there.

Rick Newman

Careful about spending time in a swamp during a lightning storm!

Permalink Reply by Lawrence E. Long on March 20, 2012 at 4:56am

Rick:  The Peapod needs 2 more coats of varnish on breasthooks,gunwales fore and aft sternsheets(10 total) varnish, leathers and turksheads on the oars.  Then if I can figure out how to post pictures I will try.  Probably 2 weeks or so

Good info on building  panels- will look it up for the next build.( the wife dosen't know about this yet)

Permalink Reply by Rick Newman on March 20, 2012 at 6:48am

Lawrence, I'm sure that I am not the only one that would enjoy seeing your Peapod, but also some of your other boats you have built. I just posted easy to follow picture posting directions on Phillip Westendorf's recent posting. I would be more than happy to help you through it. Email me if you need help.

Speaking of varnish, what are you using on your Peapod? Also who was the designer?

Respectfully,

Rick Newman

Permalink Reply by Lawrence E. Long on March 20, 2012 at 10:37am

Rick:

Finished  #9 varnish coat.  One more to go.    I have been using Pettit Captains #1015 for many years. Alittle less costly than Flagship,gets good finish.  There is one varnish- very pricy from europe  that claims you can "hot coat it"- meaning as soon as it is dry to the touch you can lay on the subsequent coats- with out sanding between.  One oldtimer boat builder told me this is BS.  I sand with 325 between coats.

Getting pictures of my boats(except the current job in the basement) will be difficult.  A 17' DB is out in Lyle,WA.  One canoe is in Kalispell,MT another in Salmon,ID,others in MA.

The Peapod is a D. Hylan design and the sail will be made by Dabbler Sails in VA.  Oars are my design- with a lot of R.D. Culler influence.  Shafts are DF- 20+ growth rings to the inch and straight as a string- no grain runout in 8 ft.

Regards,  

Permalink Reply by Rick Newman on March 20, 2012 at 11:08am

Thanks for the informative response. The American Rope and Tar site does suggest that LeTonk is the cat's meow. I think that good brightwork on boats can look very nice. I look forward to seeing the results of your craftsmanship on your Peapod. Which of the Hylan Peapods did you build, 13' or 15'? They both look like wonderful vessels. So either you travel a great deal or your canoes have migrated to family members. I am not too far from Lyle, WA about four or five hours. Do you get out there often to fish? If so do you fish the Klickitat? I think that Mr. Culler had some good ideas for oar design. Thanks again.

Respectfully,

Rick Newman

Permalink Reply by Eric Loudenslager on March 19, 2012 at 8:02pm

I built S&G with 3/8 in hydrotech, kevlar and glass on both sides and it has held up well.  So, the 7/16th should work with adequate reinforcement.

If you can, confirm the quality of the plywood.  I would ask them to guarantee return if you cut the ply and it contains substantial voids.  Voids will make construction more difficult - fasteners will crush the ply, cut edges will have collapsed edge material if it includes a void.  Just as important, water vapor will condense in the voids eventually leading to rotting from the inside.  Not good.

The hydrotech has very thin veneers, so any voids are have a small "depth" and they are not more than a millimeter or so square. 

Good luck

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