We had better pay closer attention to our builds..

[jlapratt]

In this months Professional BoatBuilder, pg. 168/169, Dave Martin talks about how a 3/32" modification in the bottom of his 40' Ocean hull resulted in several knots increase in speed over an otherwise identical hull.

That's almost unimaginable; that little of a change in that large of a hull making that big of a difference.

Makes me wonder if the converse isn't true; a minor mistake in squaring up a S&G hull resulting in a large loss of performance. Or are we talking apples and oranges here? The average home-built hull not being high-tech enough to make a big difference in performance with a building error?

Still amazing how such a small change makes such a difference.

Jeff

[RonW]

I will be the first to say it, a 3/32 or less then a 1/4 difference in a 40 ft. hull resulting in a gain of several knots, Sorry but I don't buy it for one minute.

A true, fair and balanced hull over a sloppily built unfair and balanced hull, I do buy..but there has to be more to the story then this mynute change.......

[erster]

I will be the first to say it, a 3/32 or less then a 1/4 difference in a 40 ft. hull resulting in a gain of several knots, Sorry but I don't buy it for one minute.

A true, fair and balanced hull over a sloppily built unfair and balanced hull, I do buy..but there has to be more to the story then this mynute change.......

I will go out on a limb and without actually knowing the context of the article and address the older 40 ft. Ocean, which I take it to be the sportfisherman that were built in New Jersey? If so, its also possible that with the quality control that was some issue and liteweight construction, coupled with just maybe the boat listed in the article had been sitting around somewhere on the hard for quite some time, maybe waiting to be sold, the boat could have hogged, too from inproper blocking, if you have any past experience with them.

Its quite possible that the bottom was also blistered, and full of moisture, and there was a botom job of stripping the gelcoat blisters off, drying the hull over a period of time, and then sealing it up, fairing and recoating the bottom, making the boat lighter, and truer, increasing the speed, too. Along those lines, I bet the running gear was also gone over, if this was the case, and this also contributed to the increase of speed? Just a wild guess,,,,

[George Roberts]

I expect a boat would have to be in a lot of trouble for 1/4" to make any difference.

Perhaps he changed the length of 1/4" on his scale so a 1/4" became almost 1/2" and now the hull speed has increased ...

[erster]

I expect a boat would have to be in a lot of trouble for 1/4" to make any difference.

Perhaps he changed the length of 1/4" on his scale so a 1/4" became almost 1/2" and now the hull speed has increased ...

Those boats can vary three to four mph. with trim tabs up or down
and trim angle off from level. I wish I had the article in front of me.

[Mike Vogdes]

The 40' Ocean is better known as a flexable flyer due to the poorly designed stringers.

Oyster Mike, perhaps you recall the pix I sent you last spring of the 40' Ocean I had surveyed, then backed away from, due to the delaminated fore deck caused by inproper placement of the straps from the travelift. The boat also had some delamination on her bottom around an engine intake. Be carefull if your contiplating an older Ocean...

[jlapratt]

He was tank testing two hull models (actually towing behind a boat on the river) one of which had "deformed" while the 'glass was curing nad performed better. He included the "deformation" to the full-size hull. Says it was 3/32 on the full-sizer.

Seems like too small a deformation to have such a large affect. He did say it was deformed "in the right place."

I think this is a stepped hull, if so, could the 3/32 make a difference if associated with the step?

Jeff

[merlinron]

iam certainly no expert, but when i read this i had to say something....

i can imagine 3/32 making a difference on a scale model tested in perfect conditions and that depending on the scale used, it might show when scaled up to full size. and i can imagine 3/32 on a full size boat mathematicly showing an advantage in the case of a onedesign because math is perfect ( i believe the star class is restricted to no deviation greater than 1/8 inch anywhere) , but realisticly, given the conditions of real-life performance, i can't imaging 3/32 or 1/8 showing an actual measerable difference in performance, even in a one design. i think even in star boats( just as in most any arena of competative activity where comparative size needs to be kept as similar as possible), the 1/8 inch ruling is made so that no-one can make a big bees nest of litgation when a boat that is known to be outside the rules does well and someone comes up with a bunch of mathamatial mish-mash that says that 1/8 inch deviation actually helped performance. realisticly, the line in this case has to be drawn somewhere, and 1/8 inch of uniformity is relisticly achievable, so that's where the control is set.
i know this thread has nothing to do with the rules about the star class or any other one design matter, but i thought using the star boat rule would illustrate my point.