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Old 20-03-2022, 11:27   #1
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Polar diagram for Wharram 35-42 anyone?

Hi,

while we do not have either of the boats mentioned above, we have a very similar hullshape and suspect a polar from either one to be a reasonable close as start to create one for our boat.
Easier than starting from scratch.

So does anyone happen to have Polar diagram for one of the Wharram cats between 35ft and 42ft?

Thanks for sharing if you have one.

Franziska
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Old 20-03-2022, 14:51   #2
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Re: Polar diagram for Wharram 35-42 anyone?

Hi Franziska, sorry I don't have the polar, but I am also looking for a polar for my boat (Allied Luders 33) which I can't find, but I am unclear as how to look for one of a similar boat. What are the characteristics that you used to look for a similar boat polar?
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Old 20-03-2022, 15:26   #3
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Re: Polar diagram for Wharram 35-42 anyone?

Franziska the only polar diagram I know for Wharrams is warm breeze-clothes off, stronger breeze-pants on, strong cold breeze-tops on nips out!
Cheers
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Old 20-03-2022, 17:47   #4
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Re: Polar diagram for Wharram 35-42 anyone?

Wharrams are tropical, leave the polars to the mono masochists.
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Old 21-03-2022, 02:15   #5
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Re: Polar diagram for Wharram 35-42 anyone?

I'm well aware that the Wharram sailors are a special crowd, but in this day & age even some of them are using computer based weather routing and navigation.

While I can reasonably well guesstimate how we progress, it is helpful to have a polar diagram & it's data to run routing in OpenCPN or similar.

I also know that there are tools to start from scratch, but existing data of boats similar in hullshape, displacement and sailarea is an easier start. Especially as you can adjust that data over time.

Obviously this is not about racing as our boat is a pure cruising boat as well, but it's a helpful tool when looking at weather scenarios. Of course you do not decide your route solely based on gribs.
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Old 21-03-2022, 03:20   #6
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pirate Re: Polar diagram for Wharram 35-42 anyone?

Never used one, don't see the need as conditions can vary so much over a distance.. maybe you can find something useful here...
https://www.seapilot.com/features/download-polar-files/
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Old 21-03-2022, 11:24   #7
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Re: Polar diagram for Wharram 35-42 anyone?

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Originally Posted by boatman61 View Post
Never used one, don't see the need as conditions can vary so much over a distance.. maybe you can find something useful here...

https://www.seapilot.com/features/download-polar-files/
Boaty, thanks, but all links on the list lead to nowhere..

I need to correct, while the links per boat lead to nothing, the link providing all files works.
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Old 21-03-2022, 12:17   #8
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pirate Re: Polar diagram for Wharram 35-42 anyone?

Quote:
Originally Posted by Franziska View Post
Boaty, thanks, but all links on the list lead to nowhere..

I need to correct, while the links per boat lead to nothing, the link providing all files works.
Sorry Fran.. did not check just took their word that they had poplars for the boats listed..
My bad..
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Old 21-03-2022, 17:58   #9
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Re: Polar diagram for Wharram 35-42 anyone?

You can Google VPP polars


and also try these people https://www.avalon-routing.com/en/polars/
I have not tried anything yet...
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Old 22-03-2022, 02:15   #10
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Re: Polar diagram for Wharram 35-42 anyone?

Hi Franziska... I have the polar files that were distributed with Maxsea. Simple text format that contains true wind angle and true wind speed as input and outputs expected speed. Very simple to modify for your own boat. Send me a PM with your email address and I'll zip up the files and send them to you.
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Old 22-03-2022, 02:51   #11
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Re: Polar diagram for Wharram 35-42 anyone?

Quote:
Originally Posted by Jeannius View Post
Hi Franziska... I have the polar files that were distributed with Maxsea. Simple text format that contains true wind angle and true wind speed as input and outputs expected speed. Very simple to modify for your own boat. Send me a PM with your email address and I'll zip up the files and send them to you.
Sure I'll do. Thank you.
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Old 22-03-2022, 03:04   #12
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Re: Polar diagram for Wharram 35-42 anyone?

I also have a boat with no documented polars and needed some to be able to play around a little with weather routing. I considered creating my own, but as I don't have any good data for it, that's a project for later.

In the end I took the polars of a random ship that seemed to be roughly similar (in my largish heavy monohulll with cutter rigg) and adjusted the efficiency to my estimates of speed on key courses. So while the theoretical value for the original boat should have been 12 knots on a broad reach, knowing that I do comfy 7.5 knots on a similar course with my tired sails, I estimated the efficiency to 65%. I then used spot checks whether this gave me reasonable results to what I experience close-hauled or on a beam reach.

Not perfect, but good enough to for rough planning. This assumes you have actual experience with the boat. If it's just for meditation-purposes over pointless numbers, that won't help you.
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Old 27-03-2022, 10:47   #13
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Re: Polar diagram for Wharram 35-42 anyone?

Not exactly polars by any means but along the same train of thought as the other posts, you might find some of what you're looking for (or other somewhat comparable cats that more info is available on including -perhaps- polars) using the multihull comparison tool atMultihull Dynamics, Inc. - Home requires email sign up. I know they have a few wharrams around that size listed.
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