THE HAKA BENCH SEAT - AN ALTERNATIVE TO TRAMPS

And then there was 70!


To address the slippery surface on the top of the back-boards, I'm gonna try some of this, and see if it stays on:

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Hobie Island Sailing since 2006

YES! Whew! Thanks Bob.

Is this gorilla type tape?

If you can't get rubber pads to stay glued on the plastic, I might try neoprene sleeves on the Akas. You could use any type (wetsuit material, kayak paddle grips, wine bottle carriers, drink cozies..) Ask Dee to sew some Velcro on them, to wrap around the bars.

In the good old days, (pre Haka) I used to wrap closed cell pipe insulation on the Akas with one wrap Velcro and sat on these.

If she's not in the mood, they make straps like this for marine use:

There's a material called SharkGrip that is mixed into floor coatings to add slip resistance. It's compatible with oil or water base coatings. I'm wondering if there's a coating that could be used to apply it to those slippery spine boards ? It would probably work great in spar varnish for wood Hakas.
http://www.northernsafety.com/Product/3 ... -5-Gallons

3M makes a bunch of Anti slip tapes. I've had good experiences with their adhesive products.

- chris

Ummm....surf wax? easy, cheap, won't chafe your a$$, removeable, smells like coconuts...

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2013 Tandem Island "Victory Lane"
Oahu, Hawaii
www.rotorheadsblog.blogspot.com

surf wax
That's so funny, I had the same thought.
When I was a surfer in High School we used to put some sand in it to add traction.

I was wondering if anyone has experience with marine plywood and whether it would wear well as a Haka in the wet environment after finishing with spar varnish ? I have access to a cnc router that can cut a full sheet of plywood and it got me thinking that I could make something similar to a spine board out of plywood. But I don't have a feel for whether exposing a lot of plywood end grain on marine ply would be a recipe for failure. Is it impervious to water ?
My dad was a cabinet maker for store fixtures and he showed me a technique where they laminated with contact cement a very thin sheet of aluminum to both sides of a piece of 3/8" plywood. It makes a very stiff panel, something like a "stress skin" assembly. I had a piece of it that was a few feet long and I couldn't bend it at all. 1/2" or maybe 3/8" plywood might be thick enough to span aka's with the addition of the aluminum. I suppose you could use stainless steel but I don't know if it can be cut with a router. It's not permitted to cut aluminum on the cnc router I have access to but I was thinking I could just laminate it on later and cut out the features in the ply with a handheld router.
Chris

Marine ply is supposed to be "void-free", meaning no holes inside the plies, and made with waterproof glues. Two things to consider:

-Generally, when using fir faced marine ply for boats, you glass it or risk checking (grainwise cracks on the faces) and potential water damage over time. Okoume and meranti (mahogany) faced marine ply don't check, so they are the better (but more expensive) choice.

-The glue is waterproof, but I would still seal the ends with thickened epoxy or something similar.

But...yeah, it could work. Not sure what the weight savings would be compared to plain old lumber though. Go for it, we need hakas made from every material in the world.

-RH

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2013 Tandem Island "Victory Lane"
Oahu, Hawaii
www.rotorheadsblog.blogspot.com

The laminate sounds like cool stuff. Better for a wing than a Haka maybe. Do they use it for actual countertops or just paneling? That should tell you a lot.

Even 3/8" Marine ply is still kinda heavy. We use 1/2" and 3/8" for the BatWing designs. Both need bracing.

Wrapped in a metal skin, I doubt ply would save you much weight compared to 1X3's. You could perforate it to reduce the weight and allow wind and water to pass through. But that's not ideal.

For any exposed wood, we tried clear water seal at first, but they don't hold up to the sun and salt. A light coat of good UV protected marine (spar) varnish is better. Or a top-quality varathane,

Like Rotor sez, if you don't seal wood edges and screwholes, you'll get swelling and lifting of the laminates. Related to that, I wonder what the different metal and wood expansion rates would do when exposed to the elements?

Take that small board out on a few sails and let's see how it does.

Thanks for the Marine ply info.
I guess I'm going to make one and try it out. I don't get my boat until December but I can probably figure out some reasonable dimensions
for the first one.

chris

Chris, in order to minimise weight, I would suggest going down as low as 1/4 marine ply, and then adding (say) 1/2 by 2 timber on edge on inner and outer edges (making a very wide inverted U shape). This would add heaps of strength for little weight. Solid timber without any skeleton frame is always going to offer an inferior strength to weight ratio.

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Tony Stott
2012 Tandem Island "SIC EM" with Hobie spinnaker

Has any thought about using steel to re-enforce thei HAKA, I think 1/8 x 1" wide steel bar stock weighs about 1/2 lb per ft. If you made the two side rails from 3/4" thick x 2" wide light wood (like spruce), miter in a 1 inch wide slot 1/8" deep into one side, lay the steel in then epoxy a solid piece if Formica counter top material into the exposed face (completely covering and burying the steel in epoxy). Then screw and glue vertical spars about 3/4 thick x 2" wide x about 10-12 inches long (maybe 4 to 6 spars). Then go to walmart and get some of those white PE cutting boards (they cost about $5 bucks ea. then screw them down to the top of the frame with flat head screws. It would take 4 or 5 cutting boards to skin the top, and of course the ends of each cutting board would have to be over a cross spar.
If you vacuum impregnate all of the soft light wood with epoxy you shouldn't need to use any special wood (or pressure treated wood (which is usually heavier)). I think you could build a really lightweight HAKA that can easily support 250 lbs sitting in the center, and with the white 1/4 inch thick PE skin on the top would be very durable. Of course you can easily router in any kind of slots you like into the PE for equipment straps and hand holds.
The 1/8" x 1" wide steel provides all the needed strength as long as it remains sandwiched in the structure. Steel bar stock is very inexpensive ( the Formica countertop material epoxied down over the steel is the key to the design which traps the steel and prevents it from bending and buckling under load). If course none of this has been tested at all, and any of the materials can be substituted for something else (maybe 1/2" marine ply for the side supports and spars). But it's just an idea at this point, I've been trying to think thru how to make cantilever HAKA's for a while now, but they need to carry my girth.
Has anyone tried anything like this, I can work out all the stresses and weights before starting, but that's a lot of work, no point moving forward if some else tried it and it didn't work worth a crap or ended up too heavy. I would like to stay under 12 lbs total, but am starting out with 6 lbs of steel....
Bob

Bob, Bob--you've got to get that "steel" mentality out of your mind. This is saltwater (for most of us), so we need to use aluminum. It is also lighter than steel--big plus. Weight, as we know, is everything on these boats, especially if we want to use them for camping (not everyone does.) In the construction of my "expedition" hakas, I used pine boards, marine varnish, aluminum framing, stainless steel screws. (http://www.hobiecat.com/forums/viewtopic.php?f=70&t=7276&start=240, scroll down to "Construction of Expedition Hakas.")

If people try to use plywood, you get into a catch-22 situation. The plywood is heavy, and marine or not, may not stand up to the toughness that hakas require. If you try to stabilize the plywood with varnish or fiberglass, that is just adding to the weight. If you use thin (1/4 to 1/3" plywood,) you have to reinforce it with metal bracing, driving the weight up--and, how do you attach the metal bracing to the thin plywood.

If you are not worried about weight, fiber-glassed, metal-reinforced plywood might work, but there are many other easy (heavy) options for hakas on this thread.

BTW, Bob, I'm don't know about the white PE (polyethylene) cutting boards at Walmart, but those boards can be heavy. REI sells very light-weight PE cutting boards for camping. Getting truly light-weight, strong hakas (say, 10-11# each) is a tough puzzle.

Keith

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2015 AI 2, 2014 Tandem

"Any intelligent fool can make things bigger and more complex ... It takes a touch of genius and a lot of courage to move in the opposite direction." A. Einstein

"Less is more" Anon

If weight is not an issue, you can build the haka in concrete.

Weight IS an issue, so my question is how many of you, that already made your hakas, have managed to make a (one side) haka under 5kg? Could we get pictures and cons and pros about them?

I understand that some of us have other important criteria and therefore more heavy constructions.
But I am more interested in everything under 5kg per side.
Maybe it is possible to get the best ones even lower in weight by using better materials (carbon fibre) or by crossing ideas from different constructions.

This thread is now very long.
Is it a good idea to start a new thread named "Hakas under 5 kg & light weight quarterdecks"?

br thomas

I think it will be a very short thread. Of course, what we need is Hobie to jump in and develop a light-weight, probably carbon-fiber haka. It seems they are not ready yet to provide serious competition to their tramps, but, I think, Hobie brand hakas are inevitable.

Keith

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2015 AI 2, 2014 Tandem

"Any intelligent fool can make things bigger and more complex ... It takes a touch of genius and a lot of courage to move in the opposite direction." A. Einstein

"Less is more" Anon

Ditto to everything Keith posted.

I don't want to stunt innovation here, but I'm a lazy guy who sails so he won't have to paddle, so if anything, I would try varathaned 1/4" ply on a light aluminum frame and some nice Koa wood laminate flooring on top.



I would not try screwing any rod holders on there though.

I just wish we had access to spineboards down under without horrendous postage costs... They must surely be the lazyman's ultimate haka.

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Tony Stott
2012 Tandem Island "SIC EM" with Hobie spinnaker