Sawn frames.

[dskira]

Originally Posted by Landlubber

...may I respectfully suggest that laminated frames are far superior to any sawn frame, they are very easy to make, have maximum strength for size and cost bugger all.
...sawn frames are the weakest and heaviest frames there are.....

Of course you are right. It was just question of classic way of making frames.
The laminated frames are extremely strong, but not that easy to make.
They need a lot of attention.
I think in boatbuilding we need to be carefull about the word easy, it can be deceptive.
As for sawn frames, no, they are not the weakest. remember that every vessel built with double sawn frames are fully ceiled. The life span is, as we know by seen them sailing today, quite umbelivable. It take a special technic to do sawn frames, mostly for the fastening.
I think we should not dismiss any method who proved good, sawn, steam or laminated, no one bad, all are good. It is often the builder and designer who are more questionable than the method itself.
Daniel

[Landlubber]

It is often the builder and designer who are more questionable than the method itself.

....yep, as in many materials, it is up to the builder to do a proper job, if a jobs is worth doing, it is worth doing properly.....such is life.

[gonzo]

Steam bent frames are the strongest for their size and weight. In boats with mixed (sawn and steam bent) frames, the sawn are usually the ones to fail first. The common failure on steam bent frames is when they are over steamed which makes them brittle.

[dskira]

Originally Posted by gonzo

Steam bent frames are the strongest for their size and weight. In boats with mixed (sawn and steam bent) frames, the sawn are usually the ones to fail first. The common failure on steam bent frames is when they are over steamed which makes them brittle.

Even if you find oportunity to insult me on an other thread, I will respond to you in a courteous manner.
You wrong.
The strongest frame weight for size is the laminated. Every surveyor know that. If you read the post, I know you have to read, we talk about frames and we discuss lamination, sawn and steam.
Sawn frames should have full ceiling, fastened against the whole and on edge.
Like that a life expectancy is 70 years.
Stem bent brake at the turn of the bilge just above or lower to the bilge stringer, due to stress. It is normal and well documented.
Now please be polite in your post to me.
Daniel

[gonzo]

Claiming that every surveyor knows, or anything else categorically does not make it so. I am a surveyor and have a different opinion. Francis Herreshoff agreed with my views. Ceilings are used in heavy construction only. Light displacement hulls with sawn frames don't have ceilings.

[dskira]

Originally Posted by gonzo

Claiming that every surveyor knows, or anything else categorically does not make it so. I am a surveyor and have a different opinion. Francis Herreshoff agreed with my views. Ceilings are used in heavy construction only. Light displacement hulls with sawn frames don't have ceilings.

Francis didn't know and never experimented laminated frames for obvious reason. DuCane experimented before the war with success.
Here you have a good point

Ceilings are used in heavy construction only. Light displacement hulls with sawn frames don't have ceilings

Daniel

[Lurvio]

As I see it, a frame where the wood is closest to its natural shape, is the strongest (if the grain direction is respected). I have not tried steam pending but know the principle from craft school studies. Compared to gluelam it puts a lot more stress on the wood as the outer edge needs to stretch and the inner edge compress, how much is relative to the bend radius and thickness of the piece. In a same size gluelam you have thinner strips, so the stresses to one strip is a lot easier to the wood.

There are wood species that bend well with steam, in gluelam the woods properties don't matter that much. Gluelam has it's down sides, it needs a mold for every shape you want to make (there are many in a boat).You also need a good glue and enough clamping pressure for the glue to work. Steaming needs a mold if the shape of the boat cannot be used.

I have made radiuses as small as 200mm (8'') in oak/birch with gluelam, the piece was 30x60mm and bend the 'easy' way. That piece was made of 2,5mm strips, 12 strips to make the complete laminate. I have serious doubts that could be made with steam pending.

This is the finished chair, the tightest radius is at the seat and backrest transition.


As for sawn frames, I'd say it falls between the above two, if straight pieces can be used and are joined with adequate gussets. Sawn frames is probably the easiest if the techniques.

Hope this helps someone.

Lurvio

There can be no doubt that a laminated frame is the strongest and it can be engineered to some specific properties using different species. No matter if surveyors know, builders know it.

Regards
Richard

[dskira]

Originally Posted by dskira

Francis didn't know and never experimented laminated frames for obvious reason. DuCane experimented before the war with success.
Here you have a good point

Daniel

Daniel you wrong.

Francis experimented the lamination for the fabrication of a anchor davit in wood for the motor vessel Sylva.
They used oak with rivet and glue.
He also used a juxtaposition of steam bent frames for the one at the mast on, if I remeber well, Istalina. No glue "per se" just fastening


Glad I find myself wrong

Daniel

[hoytedow]

A man cannot be comfortable without his own approval.
Mark Twain

[dskira]

Originally Posted by hoytedow

A man cannot be comfortable without his own approval.
Mark Twain

And his disapproval I suppose.
If I start posting to myself its bad.
My wife will blue slip me (I know other will have done that in a heartbeat )
Fortunatly she do not go to the forum, but she help me building the boat.
She is so cute.
Daniel

[hoytedow]

Man does not control his own fate. The women in his life do that for him.
Groucho Marx