Jump to content

Sign in to follow this  
JohnStan

Probably another silly newbe question...

Recommended Posts

I'm a 60 something 5'11", 235lb man living on the west Florida panhandle coast.  I have lots of bayous, creeks and bays to explore, but am tired of the plastic boat scene. I've been looking at the Curlew and am wondering if any of you experienced salts might impart some wisdom.  I do not have a shop to work in and have access to only dimensional lumber.  I can special order marine grade plywood (how silly is it that living on the coast, I have to "special order" marine grade plywood?), but have no way to thickness plane or rip stringers and gunwales; scarfing for length is no problem.  Being a bit thick (out of shape,) I am considering using 1"x2"s (3/4"x1-1/2") cedar for the stringers and gunwales and raising the height of the foredeck about an inch along with adding a small peak to the after deck.  I've built S&G boats in the past, so am not entirely new to boatbuilding, just new to fuselage type SOF.  Any insights or recommendations?

Share this post


Link to post
Share on other sites

Hi John,

There are several small boat designs called the Curlew.  Which one is of interest to you?  The one by Devlin Boats?  So I can't comment on your choice for stringers and gunwales.

 

Generally dimensional wood and plywood is OK if you are selective.  Start visiting your Home Depot and Lowes and look for clear lumber with tight (closely spaced) growth rings of the sizes you want.  There may be one or two pieces in each batch that are great.  Pick through them and purchase just the good ones, and start stockpiling them.  

 

With plywood I would avoid the standard A/C in the thinner sizes.  I have found that 5mm underlayment plywood really works well for the thinner sheets.  In Florida you might be able to find A/B pine plywood which I think works better.  Home Depot does carry plywood from Ecuador that has almost no voids in it and more plies than the usual (1/2" has 7 plies instead of 5).  I have build two boats with it with great success.  

 

In any case, I have always covered regular plywood that is not marine grade with glass (4 or 6 oz) and epoxy (just in case there is a void somewhere that might cause problems).  I add pigment to the epoxy so I don't have to worry about painting (ever!).  To avoid possible degradation of the epoxy from UV sunlight I spray several coats of satin marine spar varnish on (Minwax Helmsman Urethane spar varnish is the brand I use since it is the only brand I have found that also comes in a spray can).  Three cans were enough to cover the 21 ft Sharpie I just finished. 

 

Tom 

Share this post


Link to post
Share on other sites

Thank you for the reply, Soundboats.  The Curlew I'm interested in at the moment is the 15' Kudzucraft kayak.  I've thought about substituting 1/2" A/C plywood for the frames.  Would you glass each individual frame? 

Share this post


Link to post
Share on other sites

John,

I would not use plywood for the frames.  if you cut a strip of plywood you will note that half of the layers will have the grain perpendicular to the long side.  This grain has very little strength when compared to grain that runs parallel to the strip.  So as a rough estimate, a frame of 1/2 inch ply will have only 1/2 the strength of a similar sized piece of wood.  The value of plywood in boat building is its ability to span large surfaces without the need for joints and its resistance to punctures.  However, it does not compare well with regular wood in terms of bending strength.  Furthermore, plywood has very little resilience (bounce back) compared to regular wood.  This ability to absorb shock and bounce back is critical in frames. 

 

You can convince yourself of this by doing a simple experiment.  Cut a 1" strip of 1/2" (or 3/4")  plywood that is 18" long and a strip of wood of similar size.  Put each piece between two blocks and add weights to the middle until the strip breaks.  Instead of weights I like to use a 50 lb hand held scale and hook it to the middle - pulling either up or down.That will be give you an idea of how the different materials compare.  You can use this technique as well to test the breaking strength of different woods you might be able to purchase at the lumber yard. 

 

Tom 

Share this post


Link to post
Share on other sites

Perhaps 'Soundboats' meant to say "don't use plywood for the stringers". Plywood is commonly used for the frames of fuselage frame boats. Just get a good quality from your local supplier. We have Menards here and they have started carrying marine plywood.

For your stringers and gunwales, dimensional lumber is fine. No need to thickness plane. The cedar I can get here is 7/8" thick. I rip it to the desired width, then round over all the corners with a 1/4" or 3/8" roundover bit. It reduces weight some without giving up much strength. 

Share this post


Link to post
Share on other sites

OK I stand corrected.  I agree that plywood will work for frames if they are circular and the stresses can be transmitted around the entire piece.  The same can be said of a solid frame that spans the entire cross section of the hull (e.g. a transom).

 

I am not familiar with the design of the kayak being discussed, and did not realize it has "circular" frames.  My reference to not using plywood for frames regards frames that are U or V shaped where the frame has to bear the pressures only along one side.  I have used plywood with a hole cut out in the middle for the first and last set of frames (bow and stern) in the Rob Roy canoes I have built.  I have never had problems with plywood in these situations in the 9 canoes I have built. 

 

Tom 

Share this post


Link to post
Share on other sites

Hi John,

 

Epoxy coating might be a good idea but I'd avoid using glass on the ply frames. I've always just used 'tung oil finish' from HomeDepot and not had any problems (so just about anything else would be a step up) :)  Some people paint the entire frame too, but the best way to protect a kayak is to make sure it's drained and dry before putting it away.

 

If you go with 1x2s for the stringers you're going to have a much heavier boat than intended. It probably won't be a problem, but if you could split those lengthwise they'd most likely work better. Make sure to change the dimentions of the stringer notches on the frames if you do change the size of the stringers.

 

Here in San Diego we've got a couple of lumberyards that will rip lumber for you, it's expensive but not too outrageous ($3 - $5 a cut). You also might have better luck looking at lumberyards that focus on decking supplies. They're competitively priced and usually have better quality than box stores.

 

-Scott

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  



×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.