Continuing of my dumb questions; Where are the bulkheads?

[pointbob]

So, continuing my theme of dumb kayak questions; Where are the bulkheads on the tandem kayak below? Supposed to be 4 of them.

I put numbers 1 2 3 by the hatches.

I also placed the letters ("a" thru "r") below to hopefully correspond/guide me on where the bulk heads should be? (I want to store the kayak and the bulkheads are the recommended spots for sawhorses).

Any "schooling" appreciated....I googled "bulk heads" and "hatches" and found that hunks of foam were considered "bulkheads" but I couldn't see any foam in the actual kayak. Is this always the case? So the genius I am figure they must be hidden lol? OR would the bulkheads in the case of this tandem simply be the sealed hollow area of the hatches?

 

[Astoriadave]

Re: Continuing of my dumb questions; Where are the bulkheads

Bulkheads at D I K O more or less. To form a watertight space in the bow, in the stern, and between the paddlers. D I amd O should be simple cross panels, perhaps made of closed cell foam, perhaps another material. K may be a cross panel, but more likely curved with the convex surface facing aft, to accomodate the rear paddlers feet at the sides of the boat while maximizing the storage in the center compartment.

Don a headlamp and look inside. If the bulkheads are not obvious, you do not have them. Take the boat back.

 

[DALAJS]

Re: Continuing of my dumb questions; Where are the bulkheads

Where are the bulkheads on the tandem kayak below?

In the case of this particular boat, the bulkheads are not closed cell foam. The Delta 20T has plastic bulkheads.

The bulkhead is simply the wall of plastic that separates one compartment from the other. If you look behind each seat, you will see a vertical wall of plastic that completely separates the cockpits from the hatches.

The reason that you want the sawhorses under the bulkheads, is that the bulkheads provide more structural support. If you placed the sawhorses elsewhere, you would likely deform the plastic over time.

 

[pointbob]

Re: Continuing of my dumb questions; Where are the bulkheads

You guys are great - thanks again. It makes sense about the plastic bulkheads now that I re-examine it.

 

[pointbob]

Re: Continuing of my dumb questions; Where are the bulkheads

Do I require to place saw horses under each of 4 bulkheads?

It's a weird space patio I'm in and I can place really only 2 sawhorses under the kayak - would it be ok to place them under as seen in the pic below? One under 2nd bulkhead and one sawhorse under 4th bulk head?

 

[Dan_Millsip]

Re: Continuing of my dumb questions; Where are the bulkheads

Do I require to place saw horses under each of 4 bulkheads?

No. I own a Delta 18 and I never worry about placing my cradles or supports directly under bulkheads. Never had any issues in the past 6 years.

I think it's important with rotomolded boats to store them with support under bulkheads -- thermoformed and composite, not so much.

 

[Astoriadave]

Re: Continuing of my dumb questions; Where are the bulkheads

Like Dan says, probably not an issue with a thermoformed boat. 2 and 4 would leave the boat perhaps tippy, anyhow. 1 and 4 or similar better. Best to fashion a cradle to the cross section of the hull if you can. Or, use thick padding, like several layers of toweling, or closed cell foam like pipe insulation.

 

[mick_allen]

Re: Continuing of my dumb questions; Where are the bulkheads

hmm, I would have thought that it was an (minor) issue with a thermoform as my assumption would be that in hot temps (exposed sun - which is unlikely, but for the sake of considering) it could creep and re-thermoform somewhat.

 

[Astoriadave]

Re: Continuing of my dumb questions; Where are the bulkheads

hmm, I would have thought that it was an (minor) issue with a thermoform as my assumption would be that in hot temps (exposed sun - which is unlikely, but for the sake of considering) it could creep and re-thermoform somewhat.

Mick, IIRC, the materials used in thermoformed boats demand substantially higher temps to deform than the materials used in rotomolded boats. I think most of the former are made of polycarbonate, while the bulk of fhe latter are made of polyethylene, mostly LDPE, sometimes HDPE, and idiosyncratic variants. HDPE and its near cousins are the highest melting of the polyethylenes. I believe Starboard is HDPE, and many plastic cutting boards are likewise, in case you have some devilish experiments in mind. There may be some thermoformed boats made of acrylics, but these would be much less impact resistant and much more susceptible to UV damage. Polycarbonates are extremely tough, with high impact resistance, and are virtually impervious to UV damage, even the clear, unpigmented products.

Eddyline made thermoformed boats from PC, early on, and a few cracked along the keel line where the PC had been stretched too much when formed over the plug. Later, they figured out they had to use sheets with a nonuniform thickness, having greater thickness where stretching occured during forming. No more keel cracks. PC does "work harden," for lack of a better term, when formed, losing some of its innate toughness, which no doubt contributed to the incidence of keel cracks.

 

[mick_allen]

Re: Continuing of my dumb questions; Where are the bulkheads

they figured out they had to use sheets with a nonuniform thickness

Now that is interesting (as well as the rest of your post: the higher temps and the high UV resistance of polycarbonates). So sheets with specified local thickness is available in some manner. . . . I wonder if that was a possible solution to some of the fits of despair some kayak thermoformers had at forming the sharp ends of some kayaks.

 

[Astoriadave]

Re: Continuing of my dumb questions; Where are the bulkheads

Yes, the scuttlebutt at the time included fine ends as well as sharp bends at keels. I don't know how they make the custom sheets with varying thicknesses. This all happened in the mid to late 1990s when Eddyline first released thermoformed boats. Probably all old technology today.

The real knock on thermoforms is there is no practical way to deal with abrasion, over the long haul, aside from add on patches of polycarbonate. Kind of unsightly. Fiberglass boats are much simpler when it comes to making an attractive restoration.

 

[Roy222]

Re: Continuing of my dumb questions; Where are the bulkheads

Back in the day (1970's) I had a freind that attempted to build themo formed Car chassis. He was able to vairy the material thickness by blocking heat from selected arears.
When the material was stretched into the mold the colder spots just stretched less and remained thicker. He almost sold American Motors on the idea. If he had , the Javlin would of been all plastic construction.

Crud technology, but it worked. Could be used to build thermo formed Kayaks.


Roy

 

[Astoriadave]

Re: Continuing of my dumb questions; Where are the bulkheads

Back in the day (1970's) I had a freind that attempted to build themo formed Car chassis. He was able to vairy the material thickness by blocking heat from selected arears.
When the material was stretched into the mold the colder spots just stretched less and remained thicker. [snip]
Roy

That works, except the areas deformed under greater stress remain stressed and are more likely to fracture if the kayak hull hits something. After forming that way, an annealing cycle on the form can remove those stresses, pretty much.

Too bad the buddy did not reach market with his idea. Would have made him a very wealthy guy. I think cars nowadays use thermoformed technology for quite a few exterior parts, don't they? Not to mention interior panels.

 

[Roy222]

Re: Continuing of my dumb questions; Where are the bulkheads

Dave,
Thermo forming is way to slow for most car parts. The exception might be blow molding. Load floors, seat backs, and package trays are sometimes blow molded.
Some inner fender liners are glass filled thermo plastic that is heated and hot stamped. The cost save is not all that great because the parts must also be die cut.
Plastic exterior car parts are usually injection molded or press molded from fiberglass/resin. The bigg attraction of palstic car parts is it's light weight and low tooling cost. Front fenders make great injection molded parts.
But for high volume it hard to beat steal. A stamped part will cycle thru the tools in seconds while a fiberglass will cycle in minutes. Seconds really mean a lot when production volumes exceed 100,000 a year. (pick up trucks)



Roy