Replies to This Discussion

Permalink Reply by Joey on January 10, 2013 at 8:57am

 My rocker issue has been solved by adding blocks to front and rear of the boat giving 2 1/2" of rocker which sounds like plenty for my water. I got the whole boated tacked together last night. I may have gone overboard by basically putting in a small fillet in between each "stitch". 

  I am also learning that the Kevlar is probably not the best idea for the boat bottom. Hard to cut and sounds difficult to wet out. I will be ordering more fiberglass for the bottom. 

  Any suggestions on weight of glass needed on bottom for this boat? 

  Also, any ideas on laying glass up the inside the boat on sidewalls? They are pre-finished with epoxy. Maybe I should have glassed the first before stitching together.

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Permalink Reply by Dave Z on January 10, 2013 at 5:58pm

Cypress is an excellent wood.  Rot resistant, dense, but has some squirrely grain, that can be a pain in the but with nails at times.  I use it alot in my boats.  It is pretty heavy though. 

Define "cedar" western red, eastern white, red, etc... all different.  none are real strong.

Look up homestead marine and see how far it is.  They are your side of Sandusky Ohio. 

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Permalink Reply by Lawrence E. Long on January 10, 2013 at 5:33am

Joey:  As to the cyprus/cedar-  The Forestry Handbook rates all cedars andcyprus as very good as per decay.

 The following characteristics  are based on 12% moisture.

Modulus of rupture(psi)    Impact bending with 50# wt(inches)   Hardness (# to imbed a 1/2" ball)

 

Northern W. Cedar        (6800)                 (13)               (350)

 Western R Cedar          (5300)                 (17)               (350)

Baldcyprus                   (7200)                  (24)               (510)

No rocket science here- Cyprus is best

As to the Kevlar- put it on the INSIDE of the bottom.  At the Wooden  Boat School Jason demjonstrated this with a 16 lb sledge hammer.

Good Luck

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Permalink Reply by Rick Newman on January 10, 2013 at 6:31am

Lawrence, tell us more about Jason's demo. Wenonah Canoe used to have a section of canoe that they would provide to stores that sold their canoes. The Wenonah rep asked for a hammer and took a big swing at the canoe section. When the hammer bounced off without any damage we were all greatly surprised. While the section wasn't constructed of Kevlar the S-Glass exhibits some of the same characteristics. when placed in a layup where stress would try to stretch the fibers in the S-Glass they would strongly resist stretching and reduce damage. That section of canoe was around for at least two years and withstood thousands of hammer strikes. I never did see any holes develop.

I do believe that they also used a vinylester resin that allowed the materials to stretch a bit, more than the more common polyester if I remember right. The bottom line is the correct placement of materials can make a big difference in the strength of a composite structure.

Joey, I don't know how rocky your rivers are or how often your boat may have to resist damage from abrasion. There are numerous discussions on what to put on the outside bottom of floors. From just a couple of thin layers of E-Glass, the most common form of fiberglass cloth that is sold, to multiple layers of heavy E-Glass in either biaxial or triaxial format. These materials are constructed of bundles of fibers running at 90 degrees to each other or in the case of triaxail an additional bundle runs at 45 degrees. Check out all the different products and constructions at Fiberglass Supplies on the link that was supplied to you yesterday.

Good luck,

Rick Newman

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Permalink Reply by tungsten on January 10, 2013 at 9:59am

If you plan on back rowing or slowing the boat down in moving water then having the right amount of upstream rocker is important.

i would recommend 12 oz biax 45/45 glass for the bottom,it takes bends easily and will form to the boat without wrinkles.Same goes for taping the inside chine.

I've done this a couple of ways and by far this is what worked for me.Once the glue has cured remove the wires,quick little sand to all shinny surfaces.Mix fillet in a cup or whatever then place in a sandwich bag cut a corner out and use like a pastry bag.Use something say about 2" round to shape the fillet.A billard ball is probably the best.Then i lay out the biax tape on a table with plastic undernieth cut to length lay it out in a zigzag since you probably dont have a 14' table.Mix up some resin, this is where a scale comes in handy or just do the math,if your tape weighs 300 grams you need 300 of epoxy.Wet out the tape be liberal and let it sit so it soaks in.After awhile it will become clear at this point scrape off the extra and roll it with a roller to remove any air.if you don't have a roller just use a piece of pipe or anything round.you can cover it with wax paper so you wont have to clean it.At this point the fillet has had a chance to kick a little.You could wait 2 or so hours before you wet the tape to let the fillet kick a little.(do a test on some scrap to see what kind of kick times your getting with your shop temp)Next is laying the wet tape,you can fold it up a little or roll it onto some 2-3" dia pipe or get some help and pic up the tape all in one shot.Start to lay the glass over the fillet you'll see the fillet through the glass as it touches it so centering it is easy.If you push together the edges it will laydown nice without having to touch the fillet.Having your gloves wet with epoxy also helps, dry gloves will stick.After its all down you can run your wet finger down with light pressure.I would roll it again with strokes towards the fillet and just don't push to hard over the fillet.

At this point you have 2 options,1- clean up any extra goo and let cure.

2-cut strips of peelply say 10-20 " long for the straight areas and 3-5'long for the curved sections.Lay down over the wet glass and roll again till its laying flat and wet out.This has 2 advantages over not using it,1 it holds the glass down so no bubbles will appear as it cures,2 you won't have to sand it as sanding stiched glass is a bear because the stiches are proud of the glass after it cures.

i know long winded responce but i did this on my last build and got profesional results the first time.My first boat i used the common 6 oz woven glass/tape and it looked like crapp when it cured , bubbles and more bubbles ,sanding oh the sanding and filling.

good luck.

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Permalink Reply by tungsten on January 10, 2013 at 10:20am

some pics,

http://imageshack.us/a/img221/8155/boat001h.jpg

wierd way of posting pics,i'll try another way.

 

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Permalink Reply by tungsten on January 10, 2013 at 10:27am

Try this way,The second pic is just fillet no tape yet.

Attachments:

• boat 002.JPG, 627 KB
• boat 010.JPG, 544 KB
• boat 014.JPG, 536 KB

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Permalink Reply by Lawrence E. Long on January 11, 2013 at 5:34am

Joey:   As to the Kevlar installation

Several years ago I took a 2 week course at the Wooden Boat School here in Brooklyn,ME.  It was given by Jason Cajune who owns and operates Montana Boatbuilders in Livingston, MT.  His boats are works of art and are great examples of true craftsmanship.  We built his Freestone boat- around 15 ft long as I recall.

Sunday night(before the actual start of the course)  we scarfed up 2 sections of 1/2 " PW for the bottom.  The next morning we laid on the Kevlar set in epoxy and started on the sides.  The following day we laid out the shape of the bottom using flexible battens and cut it out with a common circular skill saw -blade set to just cut through the PW.  The kevlar did not cover the entire bottom side to side but he said the chine fillets would provide lots of strength.  Cutting Kevlar leaves a "fuzzy" edge but it is later covered with FG.

When putting the sides to the bottom the question as to why put the Kevlar on the inside inspired some discussion.  Jason had us make up 2 samples of 1/2"PW about 12"-18" wide and 4' long coverd with Kevlar on one side.  A day later the sample was set up between 2 concrete blocks.  Using a 16 lb sledge hammerI set the first sample with the Kevlar on the "top" side of the blocks and easily broke the PW.  The second sample set up with the Kevlar on the "bottom" took repeated blows- chewing up the PW but did not break it as the first test.

In other words when installed in a boat the Kevlar on the "inside" - when taking a rock hit - distributes the load over a wide area.  But if it were on the "outside" of the bottom it is a "point load".  Jason's test convinced us to put the Kevlar on the "inside"  He makes his living making breautiful boats and knows what works.

Good Luck

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Permalink Reply by Joey on January 11, 2013 at 5:48am

Makes perfect sense to me. Just going by the material I have on hand, I will lay up 5 oz kevlar on inside of the bottom and 2-3 layers of 6 oz glass on outside of bottom (I don't have any heavier glass than that). Any suggestion on glass tape for the chines? Inside and out. I do not have any bi axial only unidirectional 6 oz. I am not opposed to making another order.

Thanks 

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Permalink Reply by tungsten on January 11, 2013 at 6:11am

Lawrence,would you not get the same result with fiberglass of the same weight at a much lower price?

 

 

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Permalink Reply by Lawrence E. Long on January 11, 2013 at 7:34am

Tungsten:Jason did not make any other comparisons/tests.  I do know that Kevlar is much stronger than FG- has a higher tensile strength than steel.  You can cut FG with a common set of sicssors but will never even cut a fiber of Kevlar Just my opinion.

 

Joey:     Go with 6"wide biaxial tape- will wrap around the chines very smoothly and not have any "puckers"

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Permalink Reply by Rick Newman on January 11, 2013 at 8:07am

Tungsten, do some research and compare Kevlar, E-Glass and S-Glass tensile strengths. I have found that the S-Glass is very close to the Kevlar but not quite the same price. S-Glass is made with different, stronger fibers than E-Glass. If you were to use some of that stretchy resin that Brad Dimock tested you would have a very strong system.

Lawrence, thanks for the information, where you put your materials is much like real estate; location, location, location!

Rick Newman

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