Re: hatch hole reinforcem

Posted by LeeG on Jul 18, 2004

The original hatch design for the Chesapeake was a hole in the deck with only two strips of 4mm ply at the fore/aft edges of the hatch hole.

That left the sides of the hatch hole consisting only of unglassed 4mm deck ply cantilevered out from the sheer and suspended between the two extra under deck strips. The directions/plans weren't specific to hatch placement or tended to place the hatch close to the coaming which placed further stress on the one 4mm ply strip. The hatch construction also relied a LOT on the hatch ribs not delaminating. In rescue practice with the original Chesapeakes,,the very first ones built and used in demos,,I experienced two aft deck/hatch failures during a paddle float rescue and cowbow rescue on flat water. Failures as in the deck/hatches could flex up/down 2" allowing water to pump into the aft compartment because the foreward strip was broken and the hatch ribs delaminated. With the above aft deck construction (only two strips of ply at hole, no deck glass) you're pretty much guranteed to have deck cracking or deck failure at the aft hatch with a heavy paddler during rescues or deck cracking at the hatch hole simply by pulling/pushing large dry bags into the hatch. I'm not sure if The New Kayak Shop Book shows hatch reinforcements but the plans CLC sells do.

The extra reinforcements are wide pieces of 4mm ply under the deck connecting the original sheer to sheer strips PLUS narrow strips framing the hole on deck. Thereafter 3" glass tape under the hatch ribs stopped the tendency of the hatches to delaminate from the ends of the ribs. I'm guessing that some of the reason the hatches are getting mounted too close to the cockpit was because the under deck side hatch hole reinforcements prevented placing the hole far aft without cutting the strips narrower. So on some narrower hulls (WR18?) a person not knowing where a hatch should go would look at the allowable positions for the hole as determined by the relatively wide underdeck strips and cut the hole accordingly. So now the hatches/holes are pretty much overbuilt with three layers of 4mm(1/2") at the opening, which is good for maintaining flotation integrity of the compartment,except the reason for the reinforcements was also general deck strength between the coaming and hatch to prevent cracking sounds or to withstand a big butt from sitting on the aft deck at the beach or during rescues. Sure some glass kayaks can barely handle that,,and skin boats are different things altogether, but the glass/ply construction is rigid stuff with the consequences of okoume flexing a lot being little cracks allowing waterstaining. That's why the Chesapeakes have cockpit glass and the earlier Cape Charles didn't,,it was evident after a couple years that the cockpits of the unglassed boats were developing a LOT of waterstaining cracks. People ignore it in the cockpit but it's hard to ignore under 5coats of varnish on the deck. So if a big person (225lbs+) is using one of these kayaks built as designed where rescues or sitting on the aft deck behind the coaming is a possibility then 4oz deck glass over 4mm deck ply between the coaming and the aft hatch with nothing underneath really doesn't cut it to prevent the cracking sounds from showing up. With the reinforced hatches and hatch holes it's pretty much bombproof.

But between the hatch and coaming is 4mm ply with 4oz on top and nothing underneath.

Think of it this way,,the cockpit has 6oz on the outside of the hull, 4mm Okoume bottom panel and 6oz cloth on the inside. That is generally recognized as the "do-all" composite for impacts and stress. It holds up just fine for nearly every use and is strong as anything. A 225lb person concentrating their weight on a 4mm deck with 4oz glass is the same kind of loading the bottom panels get when a kayak lands at shore where the kayak rests on uneven surfaces. During a rescue a paddlers weight could be in one hand or forarm resting on that 4mmply with 4oz glass or while sitting at shore it's not uncommon to want to sit on the aft deck to adjust a backband. So 4oz deck glass with nothing underneath in the area between the coaming and aft hatch will be like having a Chesapeake 17 with 4oz hull glass and no cockpit glass. Hmmm. If you don't do rescues, don't sit there, or weigh less than around 175lbs it's not an issue. If you do then putting glass under the aft deck between the hatch and coaming makes as much sense as cockpit glass or 6oz hull glass.

In Response to: hatch hole reinforcements by Mischa on Jul 18, 2004