Design of surfski for kids

As there are few skis designed for kids available, and non in my neighbourhood, I am working a a ski design for my daughters. One currently uses MK1, the other a low volume K1. They are aged 10 and 12, the ski is designed for paddles weight 35 to 45 kg.

For building I am going to use a combination of different methods. Strip planking in 5 mm PVC foam with vertical strips on a female partial mould, then resin infusion in the inside, resin infusion on the outside and joining the two hull halves. It is also a kind of limited-budget test case for this method, that I would like to use for a full size carbon ski later.

I am designing in Kayak foundry and will do the details in Rhino. If anybody is interested or willing to give some constructive criticism, I can try to post some details, e.g. the .yak files or hydrodynamic data. I have an example in Rhino (to learn myself using it), but not yet a final design. I am still doubting between two slightly different hull forms. Please let me know what is convenient to post.

Too often, lighter paddlers are omitted from the equation. Perhaps you are totally aware of what to look for in a boat for kids, but I'll share my findings over the years.

To best suit kids, your surfski will have to:
- be light (the weight of a ski will affect them a whole lot more than it affects grown adults).
- from the seat to the bow, the boat must be narrow for a very narrow catch. If you need stability, place larger width behind the seat so as not interfere with their paddling.
- male it fun, because at age 10, they are not necessary looking for an "all white ski". Get couple of fun racing stickers / teach them to rescue one another / do fun things.
- make sure that you are designing a very low volume seating area (just imagine how you'd feel if the walls of your current surfski were 5 inches taller!?!).
- place a lot more get coat on the bow

Regarding the building, I'd personally get 2 pieces of styrofoam together, and hand shape the plug - but there is no one-single-right-way of doing this. The result is what counts.

Would love to see the final product.

I'd be very interested. I have two kid who i'd love to start see paddling, i'm not yet familiar with Kayak Foundry but happy to take a look. Great initiative and good luck

Please keep us updated. I am building a 17' strip kayak in my (very sparse) spare time.

Can you use EPS foam as a solid core for a ski? I mean, I know you could, but I wonder how it would effect the overall weight of the boat. That would seem to be the easiest way to shape it.

Here some new info. I am working on two design ideas. One with the width carried more along the length of the boat, the other with the widest point behind the cockpit. Both are very similar regarding estimated speed (KAPER algorithm) and stability. Both are shown in the attached images.
The bows still will change, as Kayak Foundry has limited accuracy in the generation of steep bows without concavities. Moving the design to Rhino will take care of that. I also attach a preliminary Rhino image of an earlier design, this shows the change in bow form a bit.

Design goals were:

• Sufficient stability (for K1 trained kids)
• low wetted surface area
• Paddler weight 35 to 45 kg
• Limited length (to keep wetted area low)
• High prismatic coefficient (to reduce wave making resistance at higher speeds

The trade off between the designs is having a slightly wider catch (about 1 to 2 cm), versus a relatively wide and flat stern. I am worried about the behaviour of that wide flat stern in quartering waves.

Things I still am doubting about are rocker and width distribution.

Regarding the building method: working in a foam block is relatively easy, but heavy. I want to try my manufacturing ideas, as it should give me a proper way for building light and accurate boats without going for a full female mould. What I want to try is a mix of:
sagakayak.com/ernannaq-raven/building_raven/
and
hawaii-f22-build.blogspot.nl/search?upda...-08:00&max-results=9

Another doubt of mine is if it isn't a better idea to start with a ski for myself. I will spend quite some time on a completed ski (estimated ~ 160 hrs) and I am not sure how much the kids will use it. I really want to own a ski myself, but the EPIC and Thinks are getting priced out of my league, with only the Stellars somewhat affordable. I will be able to build a complete carbon ski for about 1600 euros, that is about half of what a commercial ski costs.