> Airplane fabrics don't usually have to deal with scratches -- whether from
> hitting rocks (not a lot of boulders a 1000 ft above the ground), or
> scraping on sand, while kayaks encounter these at practically every
> launching and landing. As a general rule, thicker fabrics absorb this type
> of abuse better than thinner fabrics. Dacron may be a great material, when
> compared to cotton, but to be a better comparison you would have to
> compare this dacron to a cotton fabric that weighed about the same (say
> somewhere in the 3.5 to 4 ounce range).

> As a reference, denim is in the 10 to 12 ounce range, and a fabric that
> would be a bit less than half that weight would probably be suitable for a
> dress shirt. Fabrics this thin just don't fill me with a lot of confidence
> ! However, when you add a nice thick coating of synthetic rubber or vinyl
> these fabrics may be great reinforcements, and highly durable.

> The rating of 130 pounds per square inch is not one that fills me with
> glee. Some of the more ample (10 to 15 ounce) nylon and cordura fabrics
> have ratings in the thousands of pounds per square inch, and I think the
> 20 ounce nylon I've seen is rated at well over 10 thousand pounds. How
> they measure the tensile strength is unknown to me. They may be using
> totally different methods for these fabrics, which would make comparison
> of these number irrelevant. (Heck, I'm still trying to figure out why it
> is so hard to break 5 pound test fishing line -- and if someone can tell
> me how people manage to catch 20 and 30 pound fish with this stuff I would
> appreciate it!)

> Well, now, here is a design choice. If you are going for extreme light
> weight you not mind compromising on fabric life. If replacing a more
> fragile skin does not impose too much on your time or your wallet, then
> the convenience of an ultralight boat made with these materials may be
> greater than the additional weight of a boat made with heavier materials.

> Once you have the frame, most of the boat building work is done. I'd
> suggest experimenting with the lighter weight materials. If the
> lightweight stuff is not durable you are going to need to replace it. At
> that time you can go to a heavier fabric. As long as the frame is intact,
> it is an afternoon job to strip off the old fabric and put on a new skin.
> Waiting for the coatings to dry takes a bit longer.

> Good luck with your boat. If you haven't cut the frames yet, sometime this
> week I'll send along some newly-calculated graph points that may make
> cutting these simpler, and cheaper. Putz makes his about 30 inches high,
> I'm making mine much shorter to save on plywood.

> Paul G. Jacobson

Hi Paul,

Thanks for the information about the fabrics. They seem light to me as well, but I know nothing about these things. I even gave some thought to using a double layer of the stuff on the hull, and a single layer on the deck. My paddling is at least for now, limited to a nearby reservoir. Launching is easy and there aren't too many places to bang against rocks, etc. (although, I did manage to scrape across some rocks when I launched my Wee Lassie II..... for it's maiden voyage!...oh well, get that first scratch over with and you won't have to worry about it, huh?). I have wondered about the durability of fabrics this light. I don't know where to get heavier synthetics. Do you have an address for Mr. Dyson, and does he still sell dacron? Given my circumstances, I could probably get by with the light stuff, if the coatings were very durable and tough, but my wife and daughters would use the boat too, and I DO NOT want to put them in something unsafe. Which ever I use, I plan to put in some sort of floatation.....float bags probably. I am not a kayaker(yet). The Putz boat seems to present an opportunity to build a nice kayak (or two) fairly inexpensively. If the family enjoys kayaking, then a few strip-builts will be in order. I for one would be interested in the graph point calculations that you have for the Putz. Those big ol' forms seem like a major waste of plywood, especially since I have a strong back sitting in my garage! Thanks again....I enjoy your informative contributions to this board. Garland