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Forum: General Discussion 05-24-2019, 01:30 PM
Replies: 6
Views: 757
Posted By Tad Roberts
First seen 28 years ago on the 75m Martin Francis...

First seen 28 years ago on the 75m Martin Francis design Eco, later called Enigma.



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Forum: General Discussion 01-04-2019, 04:47 PM
Replies: 75
Views: 12,027
Posted By Tad Roberts
Avard Fuller flying a another spinnaker on an...

Avard Fuller flying a another spinnaker on an earlier boat, Pieces of Eight.


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Forum: General Discussion 01-04-2019, 04:39 PM
Replies: 75
Views: 12,027
Posted By Tad Roberts
An offshore motorboat flying a spinnaker. ...

An offshore motorboat flying a spinnaker.



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Forum: General Discussion 07-03-2018, 04:59 PM
Replies: 36
Views: 5,148
Posted By Tad Roberts
The boat is hard-chined with a fairly flat...

The boat is hard-chined with a fairly flat bottom, it really wants to follow the face of the wave (snap-roll) . It sounds like the boat has excellent low angle stability, so it will take...
Forum: General Discussion 05-25-2018, 03:29 PM
Replies: 12,253
Views: 1,667,063
Posted By Tad Roberts
This is not the old low-speed Sabb, it's a four...

This is not the old low-speed Sabb, it's a four cylinder Ford conversion.
Forum: Other Trawler Systems 05-04-2018, 02:24 PM
Replies: 81
Views: 21,189
Posted By Tad Roberts
That "local firm" has installed 270 sets of...

That "local firm" has installed 270 sets of rolling chocks but any data is anecdotal at best. There is a paper out of New England from 20 years ago comparing the performance of rolling chocks with...
Forum: Other Trawler Systems 05-03-2018, 03:41 PM
Replies: 81
Views: 21,189
Posted By Tad Roberts
Hi Murray, Scaling up to real life from...

Hi Murray,

Scaling up to real life from those model tests, for a 45' boat the keels would be 3", 6", and 11" wide, no word on length. Without reading the paper I can tell which was most...
Forum: Other Trawler Systems 11-28-2017, 03:28 PM
Replies: 106
Views: 21,078
Posted By Tad Roberts
Even very experienced people have a hard time...

Even very experienced people have a hard time separating stability and motion. One keeps you safe, the other keeps you comfortable.

Nordhavn is advocating reducing stability by raising the center...
Forum: General Discussion 09-17-2017, 04:51 PM
Replies: 12,253
Views: 1,667,063
Posted By Tad Roberts
Right, not a Feadship. Probably a De Vries...

Right, not a Feadship. Probably a De Vries Lentsch design, built in Holland or Italy. Alternately it might be a Benetti designed and built in Italy, but I lean toward the De Vries.
Forum: Helmsman/Camano 03-19-2017, 04:17 PM
Replies: 152
Views: 24,406
Posted By Tad Roberts
I hope Bob Warman is still collecting his...

I hope Bob Warman is still collecting his royalties on these hulls.
Forum: General Discussion 02-19-2017, 03:24 PM
Replies: 22
Views: 2,518
Posted By Tad Roberts
We pump rainwater through a carbon/ceramic filter...

We pump rainwater through a carbon/ceramic filter and then sterilize with an UV light. It's slow but the water is safe.
Forum: General Discussion 02-13-2017, 03:05 PM
Replies: 19
Views: 3,130
Posted By Tad Roberts
Coastal Cruiser, it will go anywhere a Bayliner...

Coastal Cruiser, it will go anywhere a Bayliner or Mainship will go. I would worry more about construction quality and anti-corrosion efforts than seaworthiness.
Forum: Welcome Mat 01-29-2017, 11:55 AM
Replies: 13
Views: 2,468
Posted By Tad Roberts
Alice Pearl seems to have pretty much the same...

Alice Pearl seems to have pretty much the same hull as the 1968 California built Garden designed Anna D, originally Meridian, now sailing out of Tacoma.

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Forum: General Discussion 01-13-2017, 01:11 PM
Replies: 12,253
Views: 1,667,063
Posted By Tad Roberts
It doesn't need to be a centre mast, the a-frame...

It doesn't need to be a centre mast, the a-frame will work to transfer the loads into the ship but it must be something a lot more substantial than the flimsy square-tube structure on this boat. ...
Forum: General Discussion 01-07-2017, 04:15 PM
Replies: 196
Views: 30,158
Posted By Tad Roberts
I feel that, after length, displacement, beam,...

I feel that, after length, displacement, beam, and draft, the Prismatic Coefficient (PC) is the most important form factor in hull design. For every boat hull there is a correct(lowest resistance)...
Forum: General Discussion 01-07-2017, 01:01 PM
Replies: 196
Views: 30,158
Posted By Tad Roberts
Yes the " ^ " (called a caret) signifies...

Yes the " ^ " (called a caret) signifies exponent.
Forum: General Discussion 01-06-2017, 04:58 PM
Replies: 196
Views: 30,158
Posted By Tad Roberts
Too late to edit the previous post The...

Too late to edit the previous post

The difference between displacement and planning.

it's impossible to define any hull as planing, semi-displacement, or full displacement just by it's...
Forum: General Discussion 01-06-2017, 03:05 PM
Replies: 196
Views: 30,158
Posted By Tad Roberts
As you guys have found, it's impossible to define...

As you guys have found, it's impossible to define any hull as planing, semi-displacement, or full displacement just by it's shape, there are far too many variations possible.

Naval Architects...
Forum: General Discussion 12-26-2016, 04:49 PM
Replies: 61
Views: 5,160
Posted By Tad Roberts
To return to the boat issue. The original...

To return to the boat issue. The original statement is completely misleading. The Damen Shipyard designed and built Stan 5009 is a hard chined semi-planing hull. Designed to run at up to 30 knots,...
Forum: Other Trawler Systems 12-23-2016, 06:59 PM
Replies: 106
Views: 21,078
Posted By Tad Roberts
If you look at the pictures I think you can see...

If you look at the pictures I think you can see that the "wing" is approximately parallel to the keel. If anything this results in them being tipped up at the forward end when the boat is at rest,...
Forum: Other Trawler Systems 12-23-2016, 01:34 PM
Replies: 106
Views: 21,078
Posted By Tad Roberts
Here's a couple of cleaner bat wing...

Here's a couple of cleaner bat wing installations. These are big and heavy, 5/8" or 3/4" steel plate so well over 1000 pounds of additional ballast down low. They are not going to reduce stability....
Forum: General Discussion 12-23-2016, 01:19 PM
Replies: 81
Views: 5,324
Posted By Tad Roberts
Gann's book about voyages and his boats is called...

Gann's book about voyages and his boats is called Song of the Sirens. The best Conrad on boats and sailing is his last book, The Rover. No one mentioned Sterling Hayden's two great books,...
Forum: Boating Safety and Concerns 12-08-2016, 02:15 PM
Replies: 49
Views: 14,081
Posted By Tad Roberts
The Nordic Tug 37 will have positive stability up...

The Nordic Tug 37 will have positive stability up to at least 55-60 degrees heel. That has proven more than adequate for almost all normal pleasure use. Something has to go very wrong (interior...
Forum: Tug Designs 12-03-2016, 06:54 PM
Replies: 39
Views: 5,546
Posted By Tad Roberts
Al, Unless the extension radically changes the...

Al,
Unless the extension radically changes the underwater configuration of your boat, it won't change the handling. What's underwater is far more important to handling than what's above water....
Forum: Tug Designs 12-02-2016, 08:18 PM
Replies: 39
Views: 5,546
Posted By Tad Roberts
Perfect? With that little joke navy anchor...

Perfect? With that little joke navy anchor poking out the bow? Come on.....:D
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