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Search: Posts Made By: MikeJohns
Forum: Sailboat Design and Construction   15 Hours Ago
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

All the research test tanks use a carriage that the models affixed to, not a towline.
There's several ways of restraining a model for testing with a complex linkage it's possible to fully fix or...
Forum: Sailboat Design and Construction   3 Days Ago
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

Come on Brent, you don't understand your own structures, and now you want to pass expert judgement on Finot's !

Because you didn't understand what the framing was there for doesn't mean it was...
Forum: Sailboat Design and Construction   4 Days Ago
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

Bob, yes it's a great book. I have the two second editions, there was a second, "second edition" with around 70 pages added on IOR measurement. Otherwise they are the same.



Yes the 100% is a...
Forum: Sailboat Design and Construction   4 Days Ago
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

A decade or two ago I looked in some detail at twin keels.

I have a lot of data somewhere involving the development of "Bluebird of Thorne". The design of a twin keel boat has many more variables...
Forum: Sailboat Design and Construction   5 Days Ago
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

Still having a bit of trouble with this Brent?

A body lines plan with scale would illustrate the curvature correctly. Then you could post some facts by putting numbers to it, that's all that...
Forum: Sailboat Design and Construction   1 Week Ago
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

Actually an inverted pressure vessel end is parabolic not spherical, the material takes the load in compression. It's quite a different structure and not applicable to an argument for the omission...
Forum: Sailboat Design and Construction   1 Week Ago
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

And what is thickness to radius ratio for that bottle v's the boat hull ? The only place this is applicable in your hullform is in the continuation of the chine aft where it becomes a curve, the...
Forum: Sailboat Design and Construction   2 Weeks Ago
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

Brent likes to say 200 boats have been built but that's hulls only. The reality, as others have pointed out before, is that only a part of the BS origami hulls pulled together are actually completed....
Forum: Sailboat Design and Construction   2 Weeks Ago
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

Yes but not when you started espousing 60 footers. I'm sure you can dish it up now. Your knowledge has been slowly improved and your tales slowly whittled down to size. You have made it abundantly...
Forum: Sailboat Design and Construction   2 Weeks Ago
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

I'd predict what is called snap-through buckling. It would have resulted in something looking a bit like hollow half hull with the stronger parts of the interior "embossed" on the pushed in shell.
...
Forum: Sailboat Design and Construction   2 Weeks Ago
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

Brent's boats are certainly short enough at 36' but he had been saying the same design paradigm goes for boats up to 60 feet which is plain wrong. Brent has shown he has no idea how loads scale with...
Forum: Seamanship & Navigation   3 Weeks Ago
Replies: 20
Views: 1,018
Posted By MikeJohns
Re: Silly : Exercises balls as insubmersible sailboat device ?

It's a standard procedure for salvage to insert float packs and inflate them to bring the boat to the surface. Inflating a life raft in the main cabin can be enough for a smaller boat but it's still...
Forum: Sailboat Design and Construction   3 Weeks Ago
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

Conic sections are not cones and the radius is very shallow compared with the hull plate thickness. When considering the ratio of thickness to radius of a boat hull the theory of support from conic...
Forum: Sailboat Design and Construction   07-22-2015
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

This is a good example.
It's precisely what happened in the BS marketing hype about one of his designs T boning a barge (at hull speed no less).

Witnesses to the event said the boat was...
Forum: Sailboat Design and Construction   07-16-2015
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

Jeff
I had a client 4 years ago who wanted his steel Wittholz altered below the waterline, I designed a fin keel and balanced double hung rudder to replace the shoal draft full keel and transom hung...
Forum: Sailboat Design and Construction   07-08-2015
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

He doesn't like any quality strength or construction standards because he disregards them all. But he's referring to ABS OSRY and Lloyds being the pertinent standards of his day. Now replaced with...
Forum: Sailboat Design and Construction   07-08-2015
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

Attached are some of the more extreme events where steel boats remained intact and afloat. The 1st two yachts were hit by ships. A terrifying aerial assault by a whale off Cape Town. And a dent from...
Forum: Sailboat Design and Construction   07-08-2015
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

You cannot see it but all materials have an elastic response to a load. The hull plate does flex, the shrouds do stretch, the hull wracks, twists hogs and sags and the stresses should all flow nicely...
Forum: Sailboat Design and Construction   07-06-2015
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

That's getting better but you are still using Ultimate tensile strength rather than yield :-)

But you are making too many assumptions without being able to show that they are valid. The load is...
Forum: Sailboat Design and Construction   07-05-2015
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

Brent
That's another straw man that you have invented. Again you are avoiding the real issue; the compression post landing directly on the hull plate.
That is not a tensile strength calculation,...
Forum: Sailboat Design and Construction   07-03-2015
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

The mylar ruler was for you to try to teach you about contraflexure and stress transfer. Its actually interesting and pertinent to your design.

As you know, I went to some effort modelling one of...
Forum: Sailboat Design and Construction   07-03-2015
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

That's invalid. Again.....

The pertinent fact is that the compression post in your design lands on the hull plate, next to a chine which is immaterial. It still lands on the hull plate with no...
Forum: Sailboat Design and Construction   07-03-2015
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

Tom ( a metalworker/welder by trade) had already added significant framing to the hull that wasn't specified by Brent. Tom thought it was required, and added it.
Then Tom had questioned Brent over...
Forum: Sailboat Design and Construction   07-02-2015
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

Brent gets a wee bit confused with engineering numbers and Naval Architecture concepts both. He'll post the same argument every time no matter how gently people tell him he's off base by a country...
Forum: Sailboat Design and Construction   07-02-2015
Replies: 1,142
Views: 52,354
Posted By MikeJohns
Re: Steel vs Fiberglass

Bob
I don't know Jim Betts, is he a composites tech guru?

I said I saw it specified recently, I thought I'd made it clear I wasn't enamored by it. I think the idea of the Kevlar is to add...
Showing results 1 to 25 of 119

 
 
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