2nd catamaran kayak build

[DeaninMilwaukee]

My second attempt at this build turned out much better than the first one. It much lighter at 28 lbs and turns much more easily. It displaces 255 lbs, is 11.5 ft long, has about 2900 in/sq wetted area and a c.p. of 0.53 and a l/b ratio of 13.8 for each hull.

Construction is of hot wire cut pink foam from home depot using titebond 3 glue. More titebond 3 mixed with orange rit dye glued down the fabric covering and gave permanent color with no extra weight.

In the water, it moves at 3mph effortlessly, with good glide between strokes, and I was able to sprint it up to 4.2 mph. Someone more fit than me could probably go faster.

I need to make a backrest for it still, but it's otherwise done and I'm pleased at its performance.

 

[fallguy]

Why are they so close to each other?

 

[rwatson]

Gee- 100 kilos is waaaaay over an ideal weight for 12 ft.

Typically, 2 hulls at 16ft should come in at 60-70 kilos

 

[fallguy]

Gee- 100 kilos is waaaaay over an ideal weight for 12 ft.

Typically, 2 hulls at 16ft should come in at 60-70 kilos

There is no way that thing is 100 kilos.

It does seem like it could be useful if it were wider. You could keep a bit of gear on the platform and fish.

 

[Clarkey]

There is no way that thing is 100 kilos.

The OP said that it weighed 28lb - where did the 100kg come from?

 

[fallguy]

All weight semantics aside. I don't understand the structural integrity.

I built with the same stuff and always glass it to make sure it won't fall apart. Overkill? Not sure.

 

[DeaninMilwaukee]

Why are they so close to each other?

It's ridden sitting on the tunnel with a foot in each hull. The width between hulls is about comfort and winds up with a total width of 32 inches, about the same as most kayaks.

 

[DeaninMilwaukee]

All weight semantics aside. I don't understand the structural integrity.

I built with the same stuff and always glass it to make sure it won't fall apart. Overkill? Not sure.

The construction works just like fiberglassing, and is combined with internal supports to spread the loads over a larger area. The central bridge just bolts on.

 

[fallguy]

It's ridden sitting on the tunnel with a foot in each hull. The width between hulls is about comfort and winds up with a total width of 32 inches, about the same as most kayaks.

Dean - I like it, but I don't think the narrowness is wise. The primary purpose of two hulls is the stability gains. Two 12' hulls seem right at 4' apart. Otherwise you built two hulls wjere a mono would work, right? It is a conversation, not an indictment of your work.

When I look at it I ask why two hulls. I have a Gilpatrick Laker design canoe and the beam is 3'.

Do you think the boat is strong enough?

 

[DeaninMilwaukee]

Gee- 100 kilos is waaaaay over an ideal weight for 12 ft.

Typically, 2 hulls at 16ft should come in at 60-70 kilos

It's 28 lbs, it's design weight with me and all gear in it is 255 lbs at which point it drafts 5 inches.
It would take about 900 lbs to submerge the craft, or 450 to sink one hull. It is capsize proof. I can stand with both feet on one hull and it that hull is only 1/2 sunk.

 

[fallguy]

The other thing to recognize is the stability of a cat is about 110% of beam (per a few well known designers). If you have a 32" beam; the cat is safe in 3' seas against capsize. If you widen it to 4'; you get stability to 4'+ seas.

I think you could close the hulls with watertight hatches and build a wider platform, get the free gains, and extend the platform to make it long enough to stretch the feet forward and improve the overall function.

 

[DeaninMilwaukee]

Dean - I like it, but I don't think the narrowness is wise. The primary purpose of two hulls is the stability gains. Two 12' hulls seem right at 4' apart. Otherwise you built two hulls wjere a mono would work, right? It is a conversation, not an indictment of your work.

When I look at it I ask why two hulls. I have a Gilpatrick Laker design canoe and the beam is 3'.

Do you think the boat is strong enough?

It's two 10 inch hulls 10 inches apart. Stability seems good. I can easily stand in it. If I were a fishermen I could easily stand for casting ect.
As for strength, it was designed for my own use which is river exploring where waves are typically small. I did get some one footers while testing near shore on lake michigan, and all seemed fine. It actually cut through the waves with no apparent speed loss.

 

[DeaninMilwaukee]

The other thing to recognize is the stability of a cat is about 110% of beam (per a few well known designers). If you have a 32" beam; the cat is safe in 3' seas against capsize. If you widen it to 4'; you get stability to 4'+ seas.

I think you could close the hulls with watertight hatches and build a wider platform, get the free gains, and extend the platform to make it long enough to stretch the feet forward and improve the overall function.

I agree with you about widening and stabilty. I am surprised that as is it could handle 3 foot waves. My goal with stabilty was to make it easy to stand and enter/exit the boat dockside which it does, while being reasonably speedy for a non athlete, ie me, to do some decent distance for exploring.

 

[DeaninMilwaukee]

Oh, forgot to mention, if I made it much wider, there could be interference issues with the kayak paddle shaft striking the hull top edge. I have this problem sometimes now with my cheap Walmart 36" wide kayaks.

 

[jorgepease]

28 pounds is lighter than my single hull kayak, fun project. Think I would make it wider and turn it into a standup paddlecat fishing craft ))