Boat Building Forum

Find advice on all aspects of building your own kayak, canoe or any lightweight boats

Re: Strip: Shrinking Kevlar?
By:Mike Savage
Date: 5/7/2011, 3:58 pm
In Response To: Strip: Shrinking Kevlar? (Bill Hohensee)

: Slowly but surely I’ve been making lots of progress on my first
: Petrel. What an absolutely awesome design! I even had a chance
: to do some inlay work around the cockpit coaming.

: After glassing the top I separated the deck from the forms some 2+
: months ago. I quickly glassed the inside of the deck as the hull
: sat nicely off to the side with the strongback and forms intact.

: Two weeks ago I removed the strongback and forms and glassed the
: inside of the hull with a nifty orange and black carbon Kevlar
: fiber cloth (ebay id 120708217998). The Kevlar stiffened and
: strengthened that hull like a rock! Though I had to ask myself,
: did it look narrower, or was that a trick of the eye?

: Well, 3-days ago I laid the deck on top of the hull for the first
: time and found … the deck was significantly wider than the
: hull – by as much as 1.3” at the cockpit! Welcome to my
: nightmare!

: My first guess was that the deck slowly splayed while out of the
: forms for those 2-months. So in a panic I quickly cranked clamps
: to the deck looking to correct the difference from the hull. And
: ending up cracking the deck in 3-places!

: Only then did I pull out a tape measure and found what I didn’t
: expect. The deck matched nearly exactly the forms from whence it
: came. It was the recently glassed hull that was way, way out of
: whack.

: So here’s question #1 – has anyone else whose used Kevlar
: experienced this “shrinking” behavior? And question #2, what
: to do next? My guess with some advice from a wise friend is to
: sand off a good portion of the Kevlar particularly around the
: chines, reglass but this time with spacers holding the hull beam
: to spec as the hull cures.

Hi Bill,
As Bill Hamm said, it's the epoxy that tightened up/shrank rather than the carbon/kevlar. And slow cooking and spreader sticks are your friends.
Take your time at it from the widest part to the ends and it should work out fine. Once the hull is spread to the right width and the deck on, it'll hold its shape.

Mike Savage
South West Cork

Messages In This Thread

Strip: Shrinking Kevlar?
Bill Hohensee -- 5/7/2011, 5:31 am
Re: Strip: Shrinking Kevlar?
Bill Hamm -- 5/7/2011, 8:52 am
Re: Strip: Shrinking Kevlar?
ancient kayaker -- 5/7/2011, 11:15 am
Re: Strip: Shrinking Kevlar?
Mike Savage -- 5/7/2011, 3:58 pm