Reduce plans for a smaller kayak??

I'm a new member, and about to start on a strip and glue build.

The problem I have is that my garage can only easily accommodate about 15 feet, anmd none of the designs I am leaning toward are less than 16 feet.

I am contemplating having the plans reduced in the photocopying process to not more than 15 feet.   Does anybody see any difficulties with this proposiotion?  Everything will be in the same proportions as the original, but smaller.

I've previously done it with a model aircraft, reducing the wingspan to 80%, from 105 inches to 85 inches, and the design is sound.

Any advice or ideas wil be most welcome.


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RE: Reduce plans for a smaller kayak??

The first paragraph should read "start on a strip built project".   I don't see an edit prompt to correct it.

RE: Reduce plans for a smaller kayak??

Immediately after I posted I thought of what would be a major problem with reducing the length.........the beam would also be reduced, and 20" becoming 16" or 18" would probably make it too unstable.

I still welcome others' thoughts.

RE: Reduce plans for a smaller kayak??

hi rossm,

i would begin by saying that 'reducing' a kayak by simply putting it in a photo-copier and setting it to 90% is not the way most naval architects would approach it....it just doesn't work that way.

that said, if you look carefully on the internet you can find treatises on how 'reductions' are approached for kayaks.  i did not bookmark them....but havea pretty good recollection of the ideas.

in most cases, the proper naval architecture approach is more similar to reducing the spacing between forms.   as a quick example of why the photo-copier approach can get you in trouble is the rule of the cube.....so a .9 percent reduction by a photo copier is actuall a .9 X .9 X .9 in volume/displacement  or a ~ 27% reduction in carrying capacity.   just reducing the distance between the forms by 90 % of the original gives a boat that is only 10 % less displacement.   so you will not typically find that well performing shorter boats are simply photo-copier reductions of a longer boat.

anyway, you can see there is a big difference between 27% and 10%.   and if this is for an adult, people are typically no less wide, cockpits typically are not made smaller.   

there are aactually lot of great designs in the shorter boat category if you seek them out....petrel play, for example is one.   if you want to share a bit more about your project - what design you are currently thinking about....what are the parameters of who is going to use it (height, weight, foot size, etc), i bet the folks on this forum can come up with some good ideas.   

fwiw, i do have direct experience on a reduction project.....and i paid some money to the designer to come up with a reduction approach and then CLC cut the custom forms he put on a CAD for me.  i am currently working on a 14 foot boat as a project for people who want something a little smaller and easier to build/move around.  the link to the project is here https://www.clcboats.com/forum/clcforum/thread/50725.html

i hope this helps....i would just say that if you have 15 feet to work with....there are some great options.

h

 

RE: Reduce plans for a smaller kayak??

  Thanks for your comprehensive input.

I had thought of reducing the spacing between forms, but thought that would change the plan dramatically, i.e., no wider,  but it would become wider over a lesser distance longitudinally, but I suppose that's what happens with shorter kayaks anyway??

Happy to give you some details.   I'm currently looking at a Night Heron, and coincidentally, as you suggested, a Petrel Play,  both strip built, the PP already under my 15' requirement, but leaning more toward the Night Heron.

I'm 178 cm/5'10", 76 kg/168 lbs, and shoe size 8, but that's Australian sizing.   It's 25cm/10" toe to heel.

I'll taker a look at the link, and thanks again.

RE: Reduce plans for a smaller kayak??

 "  The problem I have is that my garage can only easily accommodate about 15 feet, anmd none of the designs I am leaning toward are less than 16 feet....."

 

At right angles or diagonally?  You only have one foot difference. What if you build diagonally in the space you have? 

RE: Reduce plans for a smaller kayak??

Hi Ross,

Thanks for telling  us more about the project.. 

Based on the information you shared, you are looking for a standard adult male kayak.  Your weight, height and foot side is a typical adult male and that takes kayaks off the table that are designed for women and small men and teenagers.   So we are looking for a real high performing sea kayak in a package of approximately 15 feet.

In the CLC/Nick Schade Catalog, that leaves you with the Petrel Play, the great auk 14 and, if you want to consider a hybrid, the shearwater sport.

Bjorn Thommasson, a popular designer in Europe has the Jack 14.

Ashes kayaks has the Allwater 15…which looks like a petrel paly with a little less rocker and a less curvy deck.

And Laughing Loon has the  Dark Star…a baidarka……but you would be close to the top of its recommended paddler wight.

So there are plenty of kayaks for adults at  15 feet.  However, you start to see two trends when the length gets shortened.  First, they tend to widen them out to about 23 inches and second, the ends are more vertical (less overhang).  The reason for this adjustment is you have less length to support the same size paddler so you manage the buoyancy by widening out the boat.  And to keep the boat an efficient paddling machine, you try to have the longest waterline length possible so these shorter kayaks can actually keep up with the standard 17-18 foot sea kayak..

The challenge is you are probably not going to be able to get that  night heron looks because the overhangs are dramatic…..and while beautiful, don’t leave you a lot of hull in the water to support an average adult male (170 lbs)…..unless you are prepared to have a boat that is relatively deep in the water….and that creates its own set of issues.. 

For whatever its worth, you see the exact same trends on commercially built, high quality, adult kayaks.  When you want it in a short package, they widen it and the ends are more vertical.

Anyway, I think I can relate to how you feel.  I have two night herons and a petrel.  These boats are really beautiful….but they are long.   As I mentioned,  on my latest project, I want the whole thing under 15 feet….and I am going to play with a petrel play hull and a custom deck…..and see what I can do to make it lovely in its  own right.  Anyway, here are the pictures of  the night herons, petrel, and the 15 footer I have just started:

i hope this was helpful.

h

RE: Reduce plans for a smaller kayak??

just a correction to the last post.   the new project is under 14 feet (not 15 feet).  i am calculating around 13 feet 8 inches becuase  the custom deck i am building will not have as much spring (upward curve in the ends) so this will lower the overall length from the regular petrel play which is 14 feet LOA.

RE: Reduce plans for a smaller kayak??

All good advice above.  I would also suggest reading this from Nick:    Making Little Boats out of Big Boats | Guillemot Kayaks (guillemot-kayaks.com).

You did not say exactly how large your building space is.  One tip for building in a smaller space is to put your strongback on rollers.  This allows you to easily move the boat to give you space where you are working.  I am currently building a 21' kayak in a garage that is nominally only 18.5' deep.  When I am not working, I stick the bow in the space between my air handler and duct work so that the garage door will close.

My suggestion is to look very closely at the Petrel Play.  It is an ABSOLUTELY WONDERFUL kayak!  

First picture is my 20' embryonic Mystery under construction in my small garage.  Note the casters on the work stands.

Second is my Petrel Play.

RE: Reduce plans for a smaller kayak??

   Thanks Grumpr for your suggestion.   I had considered it, but the car then has to be parked outside, something I prefer to not do.

RE: Reduce plans for a smaller kayak??

  Thanks guys, particularly hspira, for your comprehensive input.

I thought I had posted a response last week, but pehaps I didn't hit "Post Message".

I've given the project a lot of thought, and am gravitating toward the Petrel, a foot shorter than the Night Heron, still a little longer than I'd prefer, but if I reduced it by a foot, it would be almost where I want the length, better than reducing the NH by two feet, and as it will carry 250 lbs, it would still be well above my weight and some gear for a day or two with a reduced length.

I'll keep you posted, and thanks again.

 

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