I own a Lincoln 5.3 meter foamcored/vacum bagged glass canoe that I picked up at an auction about 15 years ago that has been heavily used, but not down right abused. It looks, feels and weighs as if it were a frail structure that should be used delicately, but outside of many dings, chips and scratches it has never shown any signs of structual failure. My brother owns a fleet of old Wenonahs built with the same technique and they have even more use and abuse then mine, but are all still serving their master well. My question is this, outside of Lincoln why have all Kayak manufactures avoided building kayaks with this technique. A number of canoe manufactures have and there is plenty of testimony to the strength and durability that they have withstood, never mind the weight reduction. Some of the major kayak manufactures are still useing a lot of resin and mat cloth which might win on an abrasion test,but loose pretty much on all else. Opinions?
I believe that foam cores outgass
and do not last under hard use. That is my belief and I can offer no evidencs for it. Lots of people believe otherwise and that does not bother me. Hope I do not bother them.
When I bought our Bluewater Chippewa,
designed and built by a guy who has made many whitewater slalom boats, I knew that I would not subject the foam core hull to a lot of rapids. The boat is S-glass/nylon/Kevlar, vacuum bagged using heat-cured epoxy, and it is certainly not flimsy, but as eric pointed out, the foam core can’t flex that far, so that internal shearing or outright splitting may occur.
One builder who produces surprisingly stiff and light boats without foam core is Kaz of Millbrook Boats. However, even his AC/DC is not quite the size to make a multi-night tandem tripper.
Nice way to say it Peter…
Some lesser quality and lower density foams will break down under high cyclonic loads… these will also be the ones that might ‘outgas’
It’s always nice to post cure the layup well beyond it’s actual working temp… picture a low density core hand layed up maybe and then painted navy or black… sometimes its not the actual core ‘outgassing’ (as if it is some kind of fault inherent with the foam itself) so much as it is the air contained in the foam simply expanding and pushing a laminate which might be softened beyond it’s HDT from excessive heat outwards and possibly ‘off’ the foam itself… as the day cools so does the laminate and its possible for it to cure as slightly expanded by the swelling core while the core sort of ‘sucks back’.
The guys are right on about the shear too… even it not pushed to breaking… the laminate: core interface can be broken from excessive flex… Some foams are better than others … even for a the same areal weight…
Pound for pound, balsa still rules here.
you are way above y head here pat
as often happens with you, much to my delight.
Foam core & paddles
Interesting dissertation Patrick! I have an older AT paddle that has spent much time in a Yakima SPace Case on top of my car. The outlines of the foam core are now visible, so I am wondering if I am suffering a delamination. Must check when I get home…
What are your upper end canoe builders
doing to prevent some of these possible negative attributes of mixing fabric (glass, kevlar etc.), resin and foamcore into a hull lamination? When you look at some of your open water/tripping hulls like Bell or Wenonah build it seems that the expansion-contraction of the foam, cyclonic flex loads and stress placed on their hulls would equal and duplicate what is placed on a sea kayak's hull. When their hulls are used in a tripping enviroment with heavy loads, hitting submerged objects, encountering different beaching enviroments while loaded and the fact that they aren't a monocoque structure like a kayak is, would really demonstrate whether a vacum bagged foamcore hull can handle this type of use. I believe Ray Jardine (inventer of the climbing protection device "Friends") built a couple of kayaks this way that he paddled extensively throughout the Artic with his wife. Anotherwords if canoe builders and independent builders have had to deal with these same issue and had success is it possible for seakayks to be succesfully built this way providing the right materials are combined properly in the right enviroment?
I assume you prefer the balsa core because the resin can penetrate further into the balsa then it might a foamcore. The Old Town balsa cored canoe that my dad bought over 40 years ago is still going strong even though it has always been stored outside and mostly uncovered.
Link to Ray Jardine’s foam construction