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question about sunfast3300 dehler OD and others


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why are these semi-sport boats have rudders integrated in the hull?

wouldn't it be better to have 2 lifting rudders so owner will be able to lift one while on the heel and go a little bit faster? also a tad bit of internal space

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Lifting rudders would be sweet, but are very complicated and expensive systems, especially with proper below deck quadrants for autopilot integration. I don't think we've yet seen a production offshore boat with lifting rudders.

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11 hours ago, Alberta said:

Lifting rudders would be sweet, but are very complicated and expensive systems, especially with proper below deck quadrants for autopilot integration. I don't think we've yet seen a production offshore boat with lifting rudders.

what's so difficult about it in building with lifting rudders, as i see it-its easier to install lifting rudders and if needed-adjust them than make mould modifications 

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13 hours ago, pironiero said:

why are these semi-sport boats have rudders integrated in the hull?

wouldn't it be better to have 2 lifting rudders so owner will be able to lift one while on the heel and go a little bit faster? also a tad bit of internal space

Both mention double handed, Sun Fast even single handed, in their sales jargon. That saved internal space would be hard to use when you would have steering stuff, including auto pilot, over it. And then the autopilot would be in the weather.

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1 hour ago, Snowden said:

and twin wheels... yuck

That was my first impression, too, it somehow doesn't seem to fit the concept.

I think it makes sense if you want to 'force' weight aft for downwind runs, the standting position also seems to provide a good overview.

Also, mind you, the boat is a bit overengineered. It has two showerheads, one outside, one inside.

Caution: volume.

 

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3 minutes ago, Snowden said:

it's just compromised by having to be so narrow for EU towing regs

Yes.

I think the next generation of these boats will be much narrower but sport foils to compensate for a lack of beam. If you can make that compliant with offshore regs, that will be an interesting proposition, more so than the Dehler 30 that needs much sail area to get going in light winds.

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2 minutes ago, Matagi said:

I think the next generation of these boats will be much narrower but sport foils to compensate for a lack of beam. If you can make that compliant with offshore regs, that will be an interesting proposition, more so than the Dehler 30 that needs much sail area to get going in light winds.

I think the problem you have going down that route is lack of static righting moment, which for foils is effectively zero so they don't help the gz curve?

The problem with offshore boats in this size range is you need >3 ton MMOC as well as STIX of 32+ to get Cat A, so any sort of sport boat design won't cut it unless the rules change.

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That is the outdated way of looking at it, I think, and it is the main design flaw with the Dehler 30OD and the likes.

Teams - ONYX compasscup 2021

Onyx 850 as one example: Cat 0 per ORC, and an LPS of ca. 132 degrees.

8.50 m long, 2,20 m wide. It weighs 900 kg, 500 of which are 180 cm down the keel. No GZ curve problem. 

Add a plumber bow and foils to that and you will compensate for the water ballast in the fat bottomed boats. You will fly by them every time, better upwind, better in light air.

Is it 'Fastnet' offshore? No. Is it Silverrudder or even Channel Race offshore capable? Yes, esp. if you set it up only for two, don drysuits and just endure it for two days.

 

I confess, that was a short way from the original topic to what is essentially a Swiss Lake sportboat.

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If you want to do Cat B offshores you've been able to do that in a J/80 since the early 90s.

I think the foil will be quite painful in light air given the lift/drag equation and I'm not sure it would solve the pain of reaching in a narrow design like that?

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From a production point of view it is complexity, potential warranty issues and cost to make a system that they’re happy to put on the market. Rudders hung on the transom can also create structural problems, a J88 I race (and a few others in our local fleet) had the transom fall apart which needed a rebuild. Also it sounds strange but some customers see more perceived value if their boat has rudders integral to the hull and not “stuck on the back”. Some of the UK SF3300s have a toe adjustment system and I know that JPK offer it fitted from the factory, it can be a good compromise between reducing drag whilst having the rudders under the boat. 

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True, the J/80 is a fantastic boat, would actually be my weapon of choice in terms of bang / buck. And it's a fair comparison, the 30 OD is not for Cat 0 either.

The foils wouldn't need to stay below, this is a very good example of how this could work:

boat-lago26-foil.jpg

Mind you, I mean the arrangement only, the Lago 26 is fully flying with a trapeze, much closer to an 18 footer than a 30OD or the likes.

Or you give it the Figaro 3 arrangement, where the foils are not necesserily in the water unless the boat heels, that would work in light air.

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  • 1 month later...
On 1/22/2021 at 7:22 AM, pironiero said:

why are these semi-sport boats have rudders integrated in the hull?

wouldn't it be better to have 2 lifting rudders so owner will be able to lift one while on the heel and go a little bit faster? also a tad bit of internal space

they are also marketed as racer cruisers and 2 rudders sticking out the back would be a shit for docking.  I would not want my SF3200 to have 2 rudders out the back.

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It may sound trivial, but unless solved by engineering then just keeping your boat somewhere is going to be a challenge.

The dock master may look kindly on the Vendée competitor, but he's going to make you pay for it. That's assuming you can avoid knocking the fucking things off coming into your birth.

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22 minutes ago, European Bloke said:

It may sound trivial, but unless solved by engineering then just keeping your boat somewhere is going to be a challenge.

The dock master may look kindly on the Vendée competitor, but he's going to make you pay for it. That's assuming you can avoid knocking the fucking things off coming into your birth.

You would definitely want the full 180 degree kick up rudders for this

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