Seeking feedback on ski design

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13 years 5 months ago #3184 by Boof Head
Does anybody have any drag data for a current model ski. Would be intersetd to know what the drag figures are at around 6 knots so that I can teweak my design to match.
Cheers, Boof

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  • StuartXpat
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13 years 5 months ago #3185 by StuartXpat
Replied by StuartXpat on topic Re:Seeking feedback on ski design
coming in the next month or so. Just waiting for our weather to calm down enough for some measured runs.

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13 years 5 months ago #3186 by Hiro
The closest I could find is data for the Epic 18X kayak... didn't find anything about surfskis. Chack on the Sea Kayaker Mag website.

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13 years 5 months ago #3187 by onnopaddle
Coming a little late but just wanted to say the shaped foam prototype / plug glassed light will yield a real world weight boat but the weight might be a little off ( heavy ) @ the ends .. Still works great.

Gotta second Brads weight balance method. Next best thing is to have a the exact seat you will use for location in the boat ... don't forget to find the CB of the board itself before you sit on it too.

Aloha,
pog

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13 years 5 months ago #3188 by Boof Head
Hiro, downloaded info and will have a better look when i get back from my Sunday paddle. Had a quick look and doesn't seem to have drag data.

Onno, I came to surf skis from a sea kayak building/paddling background and I know very little about the fibreglass building techniques, so wood it is.

I hope I don't offend anybody with this statement, but I find surf skis very flimsy and fragile and although I won't be able to achieve a boat under 17kgs, I will end up with a very durable craft that should be able to handle some punishment. Unlike my favourite boat (RIP) which weighed 20kgs and made me shudder every time i went over the top of a wave and came down a bit heavy.


:blush:

Once bitten, twice shy.
Cheers, All.

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13 years 5 months ago #3189 by Hiro
You're right... No drag data :blush:

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13 years 3 months ago - 13 years 3 months ago #3353 by Boof Head

My ski design has been evolving a bit since last post. I've taken on board, advice from here and kayak building forums.
The boats dimensions are an amalgam of internet info and some measurements taken from my deceased Red7. What I don't have is info on how much rocker to incorporate. Can anybody shed some light, please? I appreciate that minmal rocker equates to straight tracking, lots of rocker for turning ability, so I am after something in between. I could take some measurements for my Red7 but it is a terrible turner.

Current rocker is 102mm at rear waterline & 109mm at front waterline.

If anybody is wondering why the design looks like a kayak, its because I am using a kayak specific software. The length of the cockpit in image is aproximately the same as my Red7. a bulkhead will be fitted at the front end of cockpit with the stern profile carrying through to the bulkhead.
Cheers
Last edit: 13 years 3 months ago by Boof Head. Reason: adding more info

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13 years 3 months ago - 13 years 3 months ago #3357 by latman
Having a pronounced V in the rear third of the boat (where the section is shown) will also slow the turning ,I would look at completely circular X sections below the waterline (edited to say rear 1/3 to 1/4 only), unless you want to use it without a rudder ? Lats
Last edit: 13 years 3 months ago by latman. Reason: more detail

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13 years 3 months ago - 13 years 3 months ago #3358 by Boof Head
Done. Thanks Lats, i hadn't considered that aspect.

what about the amount of rocker though? there is a fair bit there; advantages /disadvantages

What brand/ model skis have lots of rocker? what sort of conditions do these boats excel in?

The hydrostatics of the design lie somewhere between a Mako6 and EpicV10 (or so the internet tells me). How much rocker do these boats have?

p.s. I'm not designing this for any commercial purposes. its a personal project that i'm working on for fun + i can't afford another ski. the design files are readily available at the KayakFoundary website.

Cheers
Last edit: 13 years 3 months ago by Boof Head.

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13 years 3 months ago #3359 by latman
More Rocker will make it "loose" and more responsive to the rudder, The Van Dusen kayak designs proved highly rockered craft can be ultra fast,They have less deadwood and they also have lower wetted surfaces.As long as you can keep the waterline length with the appropriate paddler/ski weight(displacement) .But then you also need to decide what to do the above waterline for heavier seas.
I have just made a plug/mould for an ocean ski and also tried to split the difference between EpicV10/V10L and Fenn elite . One big difference will be the 3cm drop i have from seat to footwell, It may make it too tippy for the novice but the ergonomics are important for experienced paddlers and make more difference than people realize.
I have drawn a few hull shapes in KF also (K1s, K2, Single spec, Double spec and Ocean ski ) but not taken any designs out of the Computer. I would love to have the time/money to do some as it took me till Mk4 spec ski to have a well selling ski.

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13 years 3 months ago #3360 by Boof Head
Good info, lats. I'll have a squiz at the van dusen boats. What spec ski ddo you make/sell?

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13 years 3 months ago #3361 by westo

www.propertyscience.com.au
This email address is being protected from spambots. You need JavaScript enabled to view it.

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13 years 3 months ago #3374 by Boof Head
Well there ya go. I've got a stealth paddle.
Have looked at this website before and added it to my favourites as i think the CF decks look awsome. Cheers.

Regarding the rocker, I have reduced it. after a bit of poking around on the web, i discovered that the Fenns have a lot of rocker compared to others and my design had heaps more than a Fenn. I'm not trying to be innovational, i just want to build a good solid alround ski.

i have also raised the sheer line atad to around the same as my Red7

Cheers

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