Shot Across The Bow

[Dockhead]

Originally Posted by wgerstmyer

Everett Pearson formed Tillotson Pearson in ‘66. Their Freedom sailboats made Mate Ferrenc’s Worlds Best Sailboats list. In that book you can read how his fiberglass research and building practices are second to none. For instance, his glass hulls are designed to withstand flexing on their own, before adding in the additional structure of the bulkheads. We have an ‘88 F36 and it practically looks brand new. So I would feel secure in a Pearson boat.

That book was written almost 30 years ago!


We owned a Pearson, and it's true they were very solidly built. But they were solidly built on account of massively heavy layup, not good engineering. That was a common approach with first generation glass boats. Yes, it's safe, but does not make for good sailing qualities.

[s/v Jedi]

Originally Posted by Dockhead

That book was written almost 30 years ago!


We owned a Pearson, and it's true they were very solidly built. But they were solidly built on account of massively heavy layup, not good engineering. That was a common approach with first generation glass boats. Yes, it's safe, but does not make for good sailing qualities.

The big change @ TPI happened in 1990 when they filed patents for the SCRIMP process. Jedi was laid up in 1993 using SCRIMP and is very light displacement. I know the J boats and cats they built used SCRIMP as well.

https://ocw.mit.edu/courses/mechanic...p_overview.pdf

[Dockhead]

Originally Posted by s/v Jedi

The big change @ TPI happened in 1990 when they filed patents for the SCRIMP process. Jedi was laid up in 1993 using SCRIMP and is very light displacement. I know the J boats and cats they built used SCRIMP as well.



https://ocw.mit.edu/courses/mechanic...p_overview.pdf

Yes, and to this day, vacuum bag resin infusion, with balsa or foam core, is state of the art. Far greater strength and rigidity for far less weight. Only drawback is cost, which is why mass produced boats are not built this way.

[wgerstmyer]

Yes, 30 years ago. Actually Read the Freedom chapter and tell me there’s no engineering.

[Dockhead]

Originally Posted by wgerstmyer

Yes, 30 years ago. Actually Read the Freedom chapter and tell me there’s no engineering.

I didn't say there was NO engineering. I said that massive layup was used in lieu of GOOD engineering. It's not an accident that no one builds boats like that anymore. There has been a lot of technological progress since then.

[s/v Jedi]

Originally Posted by Dockhead

I didn't say there was NO engineering. I said that massive layup was used in lieu of GOOD engineering. It's not an accident that no one builds boats like that anymore. There has been a lot of technological progress since then.

I think the massive overbuilding they did was the result of unfamiliarity with fiberglass construction, the temptation of just shooting more to be sure with the convenience of the chopper gun and the prevalence of random fiber instead of directional and woven fabrics at the time.

With a random distribution of fibers, you get random strength and it only averages out when a minimum thickness has been achieved. Even when they would have accurately aimed for minimum required strength for every part, that would still mean massive overbuilding for 99% of the parts.

[Dockhead]

Originally Posted by s/v Jedi

I think the massive overbuilding they did was the result of unfamiliarity with fiberglass construction, the temptation of just shooting more to be sure with the convenience of the chopper gun and the prevalence of random fiber instead of directional and woven fabrics at the time.

With a random distribution of fibers, you get random strength and it only averages out when a minimum thickness has been achieved. Even when they would have accurately aimed for minimum required strength for every part, that would still mean massive overbuilding for 99% of the parts.

Well, exactly. We can certainly understand how that happened. But that doesn't mean that we would ever build that way today. The art has advanced considerably since then.

[wgerstmyer]

Oh how I wish people would read before they spout. If you did you would read that thanks to needing to do industrial fiberglass, like 100’ windmill blades, Everett had to be very conscious of weight to strength when compared to other boat builders. Way before anyone he used computers and sensors all over his hulls and decks and researched the best techniques for how to lay up perfect glass. All prototypes were then tested and tweaked and re-thought and honed. They had t be perfect because his company couldn’t afford replacements due to warranties.
He also saw that deformations in a glass hull hurt joins and boat speed and decided that, before bulkheads were installed, his hulls would take ALL the loads so they wouldn’t deform. The Freedoms were meticulously built and had some of the lightest weights for boats of their volume—not due to random thinness but engineered thinness. The tall no-stays carbon fiber masts are cantilevers with huge mainsails and exert enormous pressure on the bridging at deck level which had to be engineered without any precedents.
Perhaps that is why my ‘88 has zero crazing.

[Dockhead]

Originally Posted by wgerstmyer

Oh how I wish people would read before they spout. If you did you would read that thanks to needing to do industrial fiberglass, like 100’ windmill blades, Everett had to be very conscious of weight to strength when compared to other boat builders. Way before anyone he used computers and sensors all over his hulls and decks and researched the best techniques for how to lay up perfect glass. All prototypes were then tested and tweaked and re-thought and honed. They had t be perfect because his company couldn’t afford replacements due to warranties.
He also saw that deformations in a glass hull hurt joins and boat speed and decided that, before bulkheads were installed, his hulls would take ALL the loads so they wouldn’t deform. The Freedoms were meticulously built and had some of the lightest weights for boats of their volume—not due to random thinness but engineered thinness. The tall no-stays carbon fiber masts are cantilevers with huge mainsails and exert enormous pressure on the bridging at deck level which had to be engineered without any precedents.
Perhaps that is why my ‘88 has zero crazing.

So what others have posted in this thread is "spouting"? That's kind of rude, isn't it?


Building a 21' daysailer is an entirely different engineering job compared to a 30-odd foot cruiser. Nothing comparable at all.



I owned a Pearson 365 for almost two decades. I stand by what I wrote. Beautifully made, beautiful to look at, and certainly hella strong, but a very poor sailing boat, due to being overweight and with poor hydrodynamics of the keel and rudder. Typical of boats of this era, and this is a result of the engineering approach Jim accurately described.


Engineering to be rigid without the bulkheads? Why? Bulkheads are a key part of the structure of the boat. Like engineering a roof to stand up without rafters. Sure, it can be done, but why? This kind of approach leads to the kind of overbuilding which results in poor sailing qualities.