Lofting the Brewer catboat

[TerryLL]

...the subtle, understated sheer of a Cape Cod catboat...

I don't believe I've ever seen that combination of words before.

[Figment]

FWIW, the Crosbys used to lay the boats on their side to plank the bottoms. I might do the same.

Of course, then you'll need stilts because the keel will be ten feet in the air.....

[P.L.Lenihan]

....but imagine what a fine pair of stilts they'll be, with blind joints and fancy dovetails and God knows what other exotic wonders of joinery and all done with an equally exotic hard wood!

Just dropping in to say hello Mr.Ledger and to wish you well with your building progress. She is begining to look awefully handsome and so soon, with but a few frames and molds set up.She'll be most fetching once you get to the planking stage, I'm sure!


Keep a good thought!



Cheers!


Peter

[Mrleft8]

The Ledgend stopped by on Thursday morning, on his way to Boston for his daughter's graduation... He mentioned off hand that he was ready to launch this coming (next) weekend! I assume that this launching will be of the existing cat....... Not this museum piece.

[donald branscom]

How goes the build Jim? Have you sliced all that locust up yet into frame material? I'll be interested to see your setup for laminating frames. . .

'I would buy a nice creeper with balloon tires, drink holder, and two adjustable lights on board .

No...no..I take that back, to heck with tradition. I would tilt the hull over and stand up like a man, and have that bottom plank at working height almost level... with a table for drinks,radio, and snacks. Why suffer.

Be able to put the screws in downwards just leaning on the drill. LOL...lol

[Mrleft8]

.... Well.... Indeed, mere seconds after I posted here this morning, Mr. Ledger stopped by on his way back from Boston. He was scoping out my collection of miniature porcelain unicorns when he thought I wan't looking.....
But it seems that Sea Rover needs a lil paint before she gets wet.... But the clam tongs are freshly sharpened, and polished, so it can't be long before we start hearing tales of salty adventure!

[P.L.Lenihan]

So......which is it, waiting for the paint to dry on Sea Rover, waiting for enough clams to fill the buckets or has he found another daughter to marry? There has got to be a reasonable reason for no pictures of artful and careful cat building.


Cheers!


Peter Patient

[Mrleft8]

I think he's been playing with a piece of bronze prop shaft from my grandfather's old boat "Bonnie Belle", that I gave him when he stopped by last month......

[Breakaway]

Oh..so you gave Ledger the shaft?

Kevin

[Duncan Gibbs]

Nice bump Mr Lemmonyfresh!

'Sup Jim? Howzitgoin'?

[donald branscom]

Paul, that Locust I bought home last summer is dry enough to rip into laminations, but we're not there yet. Much needs to be done before the ribbands get screwed onto the molds. Only the bottom four are on, which allows for the fitting of the floor timbers and somewhat limited access to the keel. Once that chore is done, and it's a lengthy task, the rest of the ribbands can be applied and work on the frames begin.






Richard, should anybody stop by and see me laying on anything other than a piece of squashed cardboard they'd be looking around to see what they could steal once the infirmity really took hold. With any kind of luck I'll be doing the work in the dead of winter, padded with multiple layers of fabric.

FWIW, the Crosbys used to lay the boats on their side to plank the bottoms. I might do the same.

"FWIW, the Crosbys used to lay the boats on their side to plank the bottoms. I might do the same."

That sounds very smart. Why lay on the ground. @!#!!$ that!

[P.L.Lenihan]

I think he's been playing with a piece of bronze prop shaft ......

Playing? Did you say playing, Doug? I didn't know Mr.Ledger played! I always thought he just worked,worked and worked some more.Well, if he is playing, I for one hope he is having a ripe old time of it and look forward to when he returns to working on his catboat in waiting.

Thanks for the good news!


Cheers!


Peter

[Mrleft8]

I've been dragging that piece of prop shaft around for 26 years.... My Grandfather dragged it around for probably another 45 years before that..... I think the Bonny Belle was decommissioned in the early '40s.... And this was a piece of shaft that was left over from a refit sometime before that..... So I guess it's time for someone to play with it..... And I figured Jim could use a diversion.....

[Jim Ledger]

The pencils have once again been sharpened en masse. File cards cut up into little labels and put into the slots on the steel drawers so it's now possible be sure which drawer actually contains the straight screwdrivers and which the Phillips without opening both drawers and doing a quick estimate of the majority of the contents. The glue bottle nozzles have been cleaned. A shelf put up. The old clock which spent the better part of a year on my bench is now hanging in the dining room. Sweeping and vacuuming...

The long-established protocols have been observed, and now a tiny chink in the mountain of things-to-yet-be-done has been found. A floor timber set on end on the bench (clean) with two bronze angles snuggling close. It's just captivating.

The floor timbers in the way of the centerboard trunk are held to the keel with bronze angles. The plans were never clear if one angle or two were to be used. I cast enough angles for two, so that's what we'll use. These get fastened to the floor in some yet-to-be-determined through-fasteny manner, and screwed to the keel with round head screws (straight slots).

One consideration best undertaken at this point is the fastener pattern. I know, I know, just drill some holes and be done with it. It's better though if the bolts and screws fall into a logical pattern as far as spacing, number, stagger pattern and placement goes. It just looks better. Because the floors vary in height the bronze angles are different lengths so the fasteners have to follow some simple formula to achieve a consistent look.

[Jim Ledger]

A careful search through the drawers labeled "SBMB >3"" and "SBRHWS 1-2"" turned up these two contenders. One, a #14 round head wood screw, 1 1/2" long, to screw the flanges to the keel. The other is a 1/4-20 machine screw, 2 1/2" long, which would be fine to through bolt the whole sandwich together.

I'm thinking countersink the bolt head and tap the opposite angle for the bolt threads...no nut needed. A quick hit with the angle grinder will sand the heads and anything poking out he other end, flush. Clocking is not out of the question, if for no other reason than to annoy McMullen.

[TerryLL]

Sweeping and vacuuming...

Hey Jim,
I'm glad to see you're back at it, and have your priorities in order. Nothing like a spanky clean floor to get the creative juices flowing.

I don't approve of clocking those screws, except for the reason stated.

[Peerie Maa]

The pencils have once again been sharpened en masse. File cards cut up into little labels and put into the slots on the steel drawers so it's now possible be sure which drawer actually contains the straight screwdrivers and which the Phillips without opening both drawers and doing a quick estimate of the majority of the contents. The glue bottle nozzles have been cleaned. A shelf put up. The old clock which spent the better part of a year on my bench is now hanging in the dining room. Sweeping and vacuuming...

The long-established protocols have been observed, and now a tiny chink in the mountain of things-to-yet-be-done has been found. A floor timber set on end on the bench (clean) with two bronze angles snuggling close. It's just captivating.

The floor timbers in the way of the centerboard trunk are held to the keel with bronze angles. The plans were never clear if one angle or two were to be used. I cast enough angles for two, so that's what we'll use. These get fastened to the floor in some yet-to-be-determined through-fasteny manner, and screwed to the keel with round head screws (straight slots).

One consideration best undertaken at this point is the fastener pattern. I know, I know, just drill some holes and be done with it. It's better though if the bolts and screws fall into a logical pattern as far as spacing, number, stagger pattern and placement goes. It just looks better. Because the floors vary in height the bronze angles are different lengths so the fasteners have to follow some simple formula to achieve a consistent look.

Are you going to spot face those tapered flanges for the round head screws, or drill skewed holes?

[StevenBauer]

It looks like your visit on Marmalade has sparked your creative spirit. Nice. But I thought you guys were sailing this afternoon. Did Paul and Kat miss their ferry?



Steven

[Mrleft8]

My shop floor wouldn't have any splatters of paint-like substance on them....
My shop floor is blemish free, and pristine!.....

[ChrisBen]

My shop floor wouldn't have any splatters of paint-like substance on them....
My shop floor is blemish free, and pristine!.....

And certainly wouldn't have a stray pencil cluttering up the floor.

[Breakaway]

Hey Jim

I know you build things for a living, and I dont, so far be it from me.....

But, I was always told that, for the very best holding power, a fastener should protrude from a nut by a distance of at least one diameter. If that's true--and I am ready to be corrected if its not-- but if its true, then is tapping the plate for an important structural member the best course of action?

Kevin

[TerryLL]

My shop floor wouldn't have any splatters of paint-like substance on them....
My shop floor is blemish free, and pristine!.....

Probably due to the 4 inches of sawdust covering it.

[SMARTINSEN]

Rivet?

[Captain Intrepid]

Hey Jim

I know you build things for a living, and I dont, so far be it from me.....

But, I was always told that, for the very best holding power, a fastener should protrude from a nut by a distance of at least one diameter. If that's true--and I am ready to be corrected if its not-- but if its true, then is tapping the plate for an important structural member the best course of action?

Kevin

The only reason I could think of for that be true is in case the fastener backs off at all.

[Candyfloss]

Hey Jim

I know you build things for a living, and I dont, so far be it from me.....

But, I was always told that, for the very best holding power, a fastener should protrude from a nut by a distance of at least one diameter. If that's true--and I am ready to be corrected if its not-- but if its true, then is tapping the plate for an important structural member the best course of action?

Kevin

No.

I'm no engineer either, but my dad, who was, told me that a bolt is only as strong as the nut, anything after that is superfluous.

[Mrleft8]

Depends on the load. If the load is directed longitudinally (IE: along the length of the bolt) the strength is dependent on the nut/head. But in this case, the load is more likely to be sheer, (IE: across the bolt) and the nut/head are pretty much there to hold the bolt in place.

[Jim Ledger]

Depends on the load. If the load is directed longitudinally (IE: along the length of the bolt) the strength is dependent on the nut/head. But in this case, the load is more likely to be sheer, (IE: across the bolt) and the nut/head are pretty much there to hold the bolt in place.

Depends on the load, indeed...how deeply piled and thickly spread in laymans terms.

No, Kevin, my apologies to your mentor, but I'm going to tap through a quarter inch of bronze, which will provide more thread than any nut. I can see leaving a little tail if you're tying a knot in monofilament fishing line, but a bolt is another matter.

The ingredients...

[Jim Ledger]

I think he's been playing with a piece of bronze prop shaft from my grandfather's old boat "Bonnie Belle", that I gave him when he stopped by last month......

That was a dirty trick you pulled on me, Doug, asking me to just "bore a little hole in the end".

Derailed me for a month.

[Jim Ledger]

My shop floor wouldn't have any splatters of paint-like substance on them....
My shop floor is blemish free, and pristine!.....

Actually, it's the bench top, not the floor.

This days boaty accomplishments consisted of fitting a pair of midship floors. A little flurry of activity towards the end of the day saw the angles cut and bolted in place, although only temporarily. It only took about a half-dozen different size drill bits, countersinks and taps. I expect the method and sequence of the drilling will be further refined over the next six pairs. As it was, the second went much better than the first.



While on the subject of things that need further refinement, here is a pile of angles much as they were when pulled out of the molding sand a year ago, just a bit cooler now.

[TerryLL]

Clocked to the max. I gotta wonder about you guys who think perfectly aligned screw slots is more important than properly torqued fasteners. Seems like affectation to me, appearance taking precedence over function. But then, building an art piece ain't the same as building a workmanlike boat.

[Jim Ledger]

Now, Terry, I'd just like to point out the alignment marks that insure an nice, accurate clocking.

You don't want to do this freehand.

[A.Greever]

I can't wait to see those installed!

[St.J]

Depends on the load. If the load is directed longitudinally (IE: along the length of the bolt) the strength is dependent on the nut/head. But in this case, the load is more likely to be sheer, (IE: across the bolt) and the nut/head are pretty much there to hold the bolt in place.

It's a bit blurry but I recall my metal work teacher telling me that the load on a bolt holding two pieces together should, mostly, be longitudinal. The bolt draws the two pieces tightly together so that the friction between the two pieces resists the sheer force. If the bolt is loose and there is little contact between the pieces then the sheer force falls on the bolt which is then much more prone to failure.
Unless of course the bolt is working as an axle...
I'll ask a mechanical engineer...
St.John

[Peerie Maa]

It's a bit blurry but I recall my metal work teacher telling me that the load on a bolt holding two pieces together should, mostly, be longitudinal. The bolt draws the two pieces tightly together so that the friction between the two pieces resists the sheer force. If the bolt is loose and there is little contact between the pieces then the sheer force falls on the bolt which is then much more prone to failure.
Unless of course the bolt is working as an axle...
I'll ask a mechanical engineer...
St.John

Your bro' is a bit busy at present, but,

You're right, StJohn.
All the strain on a bolt should be in tension, not shear (sp).
That tension is taken on the threads in the nut: excess thread does nothing.
The tension through the nut and bolt creates friction between the two parts (3 in this case) being held:
that's what holds them.

Drilling and tapping the second flange is an elegant solution.

Yous guys got to remember that this is boat building in wood. Fastenings in boat work in shear, with the load transmitted to the timber through the reaction pressure of the area (length x diameter) of the fastening in the wood. That is why there are construction rules setting out the number and gauge of things like plank fastenings. The surface of the wood components are not hard or stable enough to transmit shear loads through friction, the faying surfaces simply wear away, loosening the joint.

[St.J]

The surface of the wood components are not hard or stable enough to transmit shear loads through friction, the faying surfaces simply wear away, loosening the joint.

I don't think there's going to be much movement between these bronze angles and the timbers. The clamping force of the bolts and the friction generated stops them moving.
If they moved against each other - yes, they'd wear away.
However the bolts will be tight enough so that the faying surfaces have so much friction that they don't move against each other.
Clamp two pieces of wood together and hang the uppermost one in any way you see fit and hang a big weight from the bottom one.
The clamp exerts pressure to create friction which stops the two pulling apart.
Much harder with a substance with less friction - e.g. PTFE where the pressure would have to be higher to create the friction needed to keep the two surfaces from moving.


Jim,
Sorry to distract from the beautiful work you're doing.

[Mrleft8]

That's what I was saying... I think....
And yes, Jim.... I was often chided by my elementary school teachers for distracting the class by asking a seemingly simple question, which would invariably send the teacher on a long, circuitous explanation of something completely unrelated to the topic at hand.... But not until she realized that the bell was about to ring, and she'd just wasted 45 minutes not teaching us something important....

[donald branscom]

And certainly wouldn't have a stray pencil cluttering up the floor.

A pencil on the floor is dangerous. If you step on it it rolls. Needs to get picked up right away.
Not kidding.
Anything round laying on the floor should get picked up if it could be stepped on.

[Peerie Maa]

I don't think there's going to be much movement between these bronze angles and the timbers. The clamping force of the bolts and the friction generated stops them moving.
If they moved against each other - yes, they'd wear away.
However the bolts will be tight enough so that the faying surfaces have so much friction that they don't move against each other.
Clamp two pieces of wood together and hang the uppermost one in any way you see fit and hang a big weight from the bottom one.
The clamp exerts pressure to create friction which stops the two pulling apart.
Much harder with a substance with less friction - e.g. PTFE where the pressure would have to be higher to create the friction needed to keep the two surfaces from moving.


Jim,
Sorry to distract from the beautiful work you're doing.

You have obviously not spent enough time around old wooden boats, or thought about why the construction rules specify the diameter of the fastenings to be used. The post that you challenge is based on an understanding of how wood behaves when joined into a structure that spends all of its life in an environment of cyclical forces. Living in a sea way cases hulls to hog and sag, wrack and twist. Varying heat and humidity causes the topsides and internal structure to shrink and swell across their sideing and moulding. All of these stresses cause the faying surfaces to fret, crush and wear away loosening the joint and leaving an imprint of each component in the timber that it fays.

[hokiefan]

Hey Jim

I know you build things for a living, and I dont, so far be it from me.....

But, I was always told that, for the very best holding power, a fastener should protrude from a nut by a distance of at least one diameter. If that's true--and I am ready to be corrected if its not-- but if its true, then is tapping the plate for an important structural member the best course of action?

Kevin

In the industrial world a bolt should protrude through the nut by one full thread. Any less and you risk less than full threads in the nut weakening the joint. Any more and you have an exposed length of bolt that will get gummed up and/or corrode, making disassembly more difficult when required. And most bolts should be lubricated when installed so the torque goes to creating bolt tension, not overcoming thread friction.

If you want to infuriate a maintenance guy, let a contractor use too long studs with nuts on each end instead of the correct length bolt. A true PITA to take apart 5 years later.

Cheers,

Bobby

[donald branscom]

In the industrial world a bolt should protrude through the nut by one full thread. Any less and you risk less than full threads in the nut weakening the joint. Any more and you have an exposed length of bolt that will get gummed up and/or corrode, making disassembly more difficult when required. And most bolts should be lubricated when installed so the torque goes to creating bolt tension, not overcoming thread friction.

If you want to infuriate a maintenance guy, let a contractor use too long studs with nuts on each end instead of the correct length bolt. A true PITA to take apart 5 years later.

Cheers,

Bobby

In the aircraft world when a mylar locknut is used 5-6 threads must protrude. It does get checked! And signed for.
It the engine world a nut that is tightened would be 10% tighter when torqued, with oil on the threads.
A washer has 4 purposes. Act as a bearing surface,acts as a spacer,can be a locking device,can provide corrosion protection.

[hokiefan]

In the aircraft world when a mylar locknut is used 5-6 threads must protrude. It does get checked! And signed for.
It the engine world a nut that is tightened would be 10% tighter when torqued, with oil on the threads.
A washer has 4 purposes. Act as a bearing surface,acts as a spacer,can be a locking device,can provide corrosion protection.

Then there's bellville washers which act as springs.

You are right about different rules for different worlds. It is quite interesting. In a pipe flange application a lubricated bolt doesn't require as much torque as the unlubricated bolt. That is because more of the torque turns into bolt tension, ie gasket compression. Sometimes the devil truly is in the details. We fought flange leaks for 3 weeks while trying to startup a new hot oil system. Heat transfer oils will find leaks that aren't there!!! Started reading and digging, and determined most of the flanges weren't torqued anywhere close to right. Took 5-6 mechanics working around the clock 5 days to retorque the 700 flanges in the system. Didn't have another flange leak.

Cheers,

Bobby

[donald branscom]

Then there's bellville washers which act as springs.

You are right about different rules for different worlds. It is quite interesting. In a pipe flange application a lubricated bolt doesn't require as much torque as the unlubricated bolt. That is because more of the torque turns into bolt tension, ie gasket compression. Sometimes the devil truly is in the details. We fought flange leaks for 3 weeks while trying to startup a new hot oil system. Heat transfer oils will find leaks that aren't there!!! Started reading and digging, and determined most of the flanges weren't torqued anywhere close to right. Took 5-6 mechanics working around the clock 5 days to retorque the 700 flanges in the system. Didn't have another flange leak.

Cheers,

Bobby

Wow ...700 flanges!!!

[hokiefan]

Wow ...700 flanges!!!

Yep, 700. In pipe ranging from 1" to 10" in a 9 story structure. The system working volumn was 12,000 gallons, about $300,000 worth of heat transfer oil.

Cheers,

Bobby

[BBSebens]

The things I learn on the WoodenBoat Forum....

[Mrleft8]

... But really.... We've lost sight of the purpose of the thread here.... Is that bracket for holding up the framework for the fresh air return duct?

[Jim Ledger]

Thank you all for the tutorial on drilling for and the tightening of bolts. It was most enlightening.

To give an idea where this is going here is one floor sitting in position with two angles cut to fit. The angles are ready to be drilled and bolted to the floor, however, since there's fourteen floors to make we'll wait until there's a good batch ready to go before drilling any. The marking, drilling, countersinking and threading involve a lot of bit changing, so it would be best to work through the task in batches rather than do each floor individually.

To give some sort of reference to the photo, the blue tape is on the centerboard trunk bedlogs and coincides with the location of the floorboards. The floor timber on the left is at the rear of the centerboard trunk, an engine bed visible upper left.

[Jim Ledger]

This is the detail from the plans showing the cross section of the centerboard trunk and keel. The floor timbers and their angle clips and fastenings are shown. What is not clear is if there is one clip per timber or two. Two seemed right to me, although I have since seen a boat with one per timber. As I had already made enough clips for two each, than two it will be.

[beernd]

The craftsmanship of mr Ledger will never cease to amaze me (jealoooouuus)

[Sailor]

I see those plans have been "thumbed" on more than one occasion.

[Mrleft8]

If those screws are #14X1 1/2", then I'd guess that there's 1 clip per floor, unless the floors are 2 1/2" across.