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Forum: General Discussion 01-24-2024, 01:11 PM
Replies: 14
Views: 5,607
Posted By Tad Roberts
The 20' appears to be an attempt at a higher...

The 20' appears to be an attempt at a higher speed hull, it has a hard chine aft just below waterline while the 15' is round-bottomed right to the transom.....
Forum: General Discussion 01-24-2024, 11:43 AM
Replies: 14
Views: 5,607
Posted By Tad Roberts
That's a scan of a design review from Yachting...

That's a scan of a design review from Yachting Magazine of the day. I've not seen anything on the 20', I believe there were very few built.
Forum: General Discussion 01-15-2024, 01:16 PM
Replies: 37
Views: 3,289
Posted By Tad Roberts
In retrospect this was insane.....luckily the...

In retrospect this was insane.....luckily the boat was very lightly loaded. Ferries have been lost (Estonia ('94) and Herald Of Free Enterprise ('87)) with 100's of folks drowned due to water on...
Forum: Boating Safety and Concerns 12-16-2023, 10:52 AM
Replies: 150
Views: 10,002
Posted By Tad Roberts
I guess everyone has a different idea of what...

I guess everyone has a different idea of what "expensive" might be, I don't think of it as cheap, but also it's not wildly expensive. If the owner provides an accurate hull lines drawing, inclining...
Forum: Boating Safety and Concerns 12-15-2023, 03:26 PM
Replies: 150
Views: 10,002
Posted By Tad Roberts
This is a question of degree. If you are adding...

This is a question of degree. If you are adding 1000 lbs up high on a 15,000 lb boat, that's a big deal.....On the other hand if you're adding 1000 lbs up high on a 65,000 lb boat, it will raise the...
Forum: Boating Safety and Concerns 12-15-2023, 03:16 PM
Replies: 150
Views: 10,002
Posted By Tad Roberts
Obviously it will make a big difference if...

Obviously it will make a big difference if there's significant flair, with most boats it's not really a huge factor so max beam can be used. Again, the roll-timing is a crude approximation, but will...
Forum: Boating Safety and Concerns 12-15-2023, 02:19 PM
Replies: 150
Views: 10,002
Posted By Tad Roberts
Roll timing was really useful in the days before...

Roll timing was really useful in the days before the PC and easily available hydrostatic software. It gives only a vague indication of stability characteristics, and is too crude to give a exact...
Forum: General Discussion 05-01-2023, 01:00 PM
Replies: 12
Views: 1,668
Posted By Tad Roberts
The photos are just another clue showing the...

The photos are just another clue showing the folly of trying to say anything definitive about stability from a visual assessment.....it doesn't work. You must go through the calculations and you...
Forum: Other Trawler Systems 01-22-2023, 11:52 AM
Replies: 105
Views: 7,868
Posted By Tad Roberts
Probably about midships, almost all west coast of...

Probably about midships, almost all west coast of North America fishing boats have the stabilizer poles set well forward. Which reminds me about another load on the system; with poles forward the...
Forum: Other Trawler Systems 01-21-2023, 02:12 PM
Replies: 105
Views: 7,868
Posted By Tad Roberts
Compressive strength perpendicular to grain for...

Compressive strength perpendicular to grain for Douglas Fir is 870 psi, strength in tension is about half this and strength in sheer and bending is quite a bit higher than this.....so the 10 psi load...
Forum: Other Trawler Systems 01-20-2023, 06:06 PM
Replies: 105
Views: 7,868
Posted By Tad Roberts
The force on the fish or on it's towing line is...

The force on the fish or on it's towing line is dependent on more than it's size and speed. The work it's doing (stabilizing the boat) is an additional load. That load is dependent on the boat's...
Forum: Other Trawler Systems 01-20-2023, 03:44 PM
Replies: 8
Views: 734
Posted By Tad Roberts
As David states above, the force on the fish or...

As David states above, the force on the fish or on it's towing line is dependent on more than it's size and speed. The work it's doing (stabilizing the boat) is an additional load. That load is...
Forum: General Discussion 05-24-2019, 01:30 PM
Replies: 6
Views: 910
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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89115
Forum: General Discussion 01-04-2019, 03:47 PM
Replies: 75
Views: 18,289
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, 03:39 PM
Replies: 75
Views: 18,289
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: 7,371
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: 13,835
Views: 2,154,164
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: 82
Views: 26,164
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: 82
Views: 26,164
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, 02:28 PM
Replies: 106
Views: 29,330
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: 13,835
Views: 2,154,164
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: 29,577
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, 02:24 PM
Replies: 22
Views: 2,907
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, 02:05 PM
Replies: 19
Views: 3,976
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, 10:55 AM
Replies: 13
Views: 3,053
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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