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 Post subject: Re: Yikes! Rudder out of water another 3 or 4 inches
PostPosted: 21 Dec 2021 17:44 
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Rail Meat

Joined: 17 Oct 2021 23:04
Posts: 16
Lunacy 198 wrote:
The boat is sensitive to weight in ends. When I had the engine out the cockpit water would puddle at the companionway as it was up-hill to the drains.

What caught my eye from your images was the gap between the rudder head the hull. That gap is usually very small, maybe 1/2" or so. Also, it looks like the rudder goes past the end of the hull - it's usually flush.


Hi Dave. Maybe just a matter of angle of vision...I hope. Here's another shot with the helm centered. Thanks a lot for responding.

Rob


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 Post subject: Re: Yikes! Rudder out of water another 3 or 4 inches
PostPosted: 21 Dec 2021 18:27 
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Rail Meat

Joined: 17 Oct 2021 23:04
Posts: 16
Lunacy 198 wrote:
That did it !!! I thought it looked lined up before but obviously not.


Oh, no worries at all...I'm sure my heart rate will get back to normal eventually. Very Happy
Cheers and thanks.


 
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 Post subject: Re: Yikes! Rudder out of water another 3 or 4 inches
PostPosted: 22 Dec 2021 05:26 
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Skipper

Joined: 09 Aug 2017 15:35
Posts: 725
Location: Maine/USVI
There you go. I thought there might be a camera angle issue, but it really looked quite wonky. Mmm Beer


 
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 Post subject: Re: Yikes! Rudder out of water another 3 or 4 inches
PostPosted: 22 Dec 2021 09:29 
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Tactictian

Joined: 06 Aug 2020 09:02
Posts: 142
What nobody is talking about here is overall displacement of the boat. We know anecdotally that everyone who has had a travel lift or crane load cell weight recorded for their boat has come in above 19,000 lbs. That's a full 3,500 lb above the published dry weight! Have you considered that your boat might be one of the rare exceptions and that it is actually on the lighter side? Unless the boat's structure is somehow compromised because of low scantling size or hull thickness I'd be rather happy if my boat were floating high on either end! If you look at a sketch of the design (I'm looking at the inside cover of the Tartan 37 book now) you will clearly see that the LWL is several inches below the top of the rudder.

This is really basic hydrostatics guys. 200 lbs of ground tackle at the bow is not going to cause a trimming moment of several inches on the T37 at any load condition (stand on the bow and see for yourself). So, you may have a light hull and that in combination with light loading (fuel, water, and stuff) all combines to a higher waterline. Maybe you also have a lighter engine? Maybe you have very little associated fixed gear in the transom? Where is the waterline at the bow? Have you put a level on the cockpit floor which, by design, should be slightly angled down by the stern for drainage?

I haven't done the calc but I would guess these hulls come in about 1000 lb per inch immersion. Someone with a known displacement could take vertical waterline measurements from fixed positions on the boat and these could be compared with your boat. Take the mean for each boat and multiply the difference by 1000 and that will give you a ballpark displacement estimate compared to the first boat.

If S&S would allows owners to buy lines drawings then it would be very easy to calculate hydrostatics. For whatever reason they stopped doing this which seems pretty silly to me (Perry will share all of his designs). I suppose some information could be garnered by a good ORC certificate.

I'll stop now. I think I've made my point.


 
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 Post subject: Re: Yikes! Rudder out of water another 3 or 4 inches
PostPosted: 22 Dec 2021 17:42 
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Navigator

Joined: 06 Sep 2020 10:08
Posts: 99
FWIW, here are two pictures of our anchoring platform.

Of course, it's pitching moment might be canceled out by all the crap (davits, solar, bimini) on the stern of the boat...

I think jfalsone is right: overall weight is affecting how the boat floats more than pitch imbalance.

Rado37, your rudder is definitely more out of the water than ours. Our waterline is about where the darker blue paint stops on your rudder.


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File comment: Anchor platform with 2 anchors
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 Post subject: Re: Yikes! Rudder out of water another 3 or 4 inches
PostPosted: 22 Dec 2021 19:03 
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Rail Meat

Joined: 17 Oct 2021 23:04
Posts: 16
jfalsone wrote:
What nobody is talking about here is overall displacement of the boat. We know anecdotally that everyone who has had a travel lift or crane load cell weight recorded for their boat has come in above 19,000 lbs. That's a full 3,500 lb above the published dry weight! Have you considered that your boat might be one of the rare exceptions and that it is actually on the lighter side? Unless the boat's structure is somehow compromised because of low scantling size or hull thickness I'd be rather happy if my boat were floating high on either end! If you look at a sketch of the design (I'm looking at the inside cover of the Tartan 37 book now) you will clearly see that the LWL is several inches below the top of the rudder.

This is really basic hydrostatics guys. 200 lbs of ground tackle at the bow is not going to cause a trimming moment of several inches on the T37 at any load condition (stand on the bow and see for yourself). So, you may have a light hull and that in combination with light loading (fuel, water, and stuff) all combines to a higher waterline. Maybe you also have a lighter engine? Maybe you have very little associated fixed gear in the transom? Where is the waterline at the bow? Have you put a level on the cockpit floor which, by design, should be slightly angled down by the stern for drainage?

I haven't done the calc but I would guess these hulls come in about 1000 lb per inch immersion. Someone with a known displacement could take vertical waterline measurements from fixed positions on the boat and these could be compared with your boat. Take the mean for each boat and multiply the difference by 1000 and that will give you a ballpark displacement estimate compared to the first boat.

If S&S would allows owners to buy lines drawings then it would be very easy to calculate hydrostatics. For whatever reason they stopped doing this which seems pretty silly to me (Perry will share all of his designs). I suppose some information could be garnered by a good ORC certificate.

I'll stop now. I think I've made my point.


Thanks a lot jfalsone. I'm definitely a bit on the dull side when it comes to engineering and design and such (damn momma was right!) but I get your point and it's helped me a lot, so much appreciated. Now I'm musing whether I should go ahead and order the chain and trust that things will balance out when everything said and done or get the other stuff on board and then decide how much chain and additional tackle. Sigh. Rolling Eyes


 
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 Post subject: Re: Yikes! Rudder out of water another 3 or 4 inches
PostPosted: 22 Dec 2021 19:12 
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Rail Meat

Joined: 17 Oct 2021 23:04
Posts: 16
madmike wrote:
FWIW, here are two pictures of our anchoring platform.

Of course, it's pitching moment might be canceled out by all the crap (davits, solar, bimini) on the stern of the boat...

I think jfalsone is right: overall weight is affecting how the boat floats more than pitch imbalance.

Rado37, your rudder is definitely more out of the water than ours. Our waterline is about where the darker blue paint stops on your rudder.


Thanks madmike, much appreciated. If I can add the kind of gear that you have and she ends up pretty much balanced I'll be very happy. Very nice by the way.


 
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 Post subject: Re: Yikes! Rudder out of water another 3 or 4 inches
PostPosted: 23 Dec 2021 00:08 
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Skipper

Joined: 14 Jul 2012 20:36
Posts: 495
Location: Norfolk, Va
Think the rudder gap, looks worst cause the rudder is not centered. T37 are very bow weight sensitive. You're about 1 or 2 up more than ours. How does the bow WL look? We have a smaller roller, a Manson 35#, 80ft 5/16 chain and 200ft 5/8 rode and windlass is a small vertical Maxwell. Bow weight is critical on T37, sailing into a seaway the bow really drops between waves. Going out inlets with opposing current and wind will be a little more fun. I've noticed that the boat slows, when we send someone foward. It would be a concern to me. Boats do sit higher in winter and if the salinity is up.

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Hull #208, Puff Card
Southern Chesapeake Bay


 
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 Post subject: Re: Yikes! Rudder out of water another 3 or 4 inches
PostPosted: 23 Dec 2021 10:41 
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Tactictian

Joined: 06 Aug 2020 09:02
Posts: 142
madmike wrote:
FWIW, here are two pictures of our anchoring platform.

Of course, it's pitching moment might be canceled out by all the crap (davits, solar, bimini) on the stern of the boat...



Cool anchoring platform. All the crap on the back of your boat adds to the pitching moment. FWIW, first order factor in pitching moment for our boats is overall weight and then it comes down to weight distribution. More weight at the ends adds to moment of inertia or "gyradius". Weight at the bow effectively adds more pitching moment than weight at the stern because of the effects of waterplane area - less waterplane, less pitch damping.

I recall once sailing at low speed and being hit by a particularly nasty set of Ches Bay powerboat chop. The boat just sat there at basically zero speed hobby horsing for what seemed like 30 seconds. Our boats are heavy at the ends and the rigging but this is also what makes them a bit more comfortable in a seaway because the pitch motion period is slower. I definitely found this to be the case in the ocean last summer beating 120 miles down the coast in 25-30 knots. It was not bad and the boat was remarkably dry on deck from the mast aft. But, I digress...


 
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 Post subject: Re: Yikes! Rudder out of water another 3 or 4 inches
PostPosted: 23 Dec 2021 17:58 
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Skipper

Joined: 14 Jul 2012 20:36
Posts: 495
Location: Norfolk, Va
T37 are one of the worst sailboats for pitching. The bow with the long over hang (very good looking) but terrible pitching. Two years ago we were racing across the Chesapeake Bay. Going upwing in a nice breeze, we pulled away from our class of 18 boats. The wind then just turned off and there it started. Hobby horsing, it was a helpless feeling seeing boats behind us on the horizon. Come from behind and pass us. We had all the crew sitting against the mast or go below. The boat just stopped. During the summer when we race, we pull the anchor and chain off the bow and use lighter ground tackle stored in the sail locker.

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Hull #208, Puff Card
Southern Chesapeake Bay


 
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