Lofting the Brewer catboat

[P.L.Lenihan]

Isn't there a famous rule that says,"a fair line always supersedes a given offset." or something to that effect..........As long as the rest of the lines line up and,most importantly, THE DIAGONALS....ooo...yippeee

Can't wait to see some nice pics of Marmalade all fresh in her Sunday-goin'-ta-meetin' cloths. Ought to give Mr.Ledger some pleasent inspiration!

Peter

[Jim Ledger]

Isn't there a famous rule that says,"a fair line always supersedes a given offset."

Yes, that is the rule. But sometimes it's difficult to chose which offset is the more nearly correct one.When the curve is pronounced the decision is easier. Four points may lay on the curve with one off by itself, so I ignore the loner.. The straighter the line gets the more ambiguous the curve becomes and the choice becomes less obvious.

The reason I laid down those three buttock lines first was to check the aft sections. in the drawing, the sections of the bottom, fron the transom forward, under the cockpit, appear as straight lines from the rabbet to the turn of the bilge. A simple straight deadrise. This seems right, yet the offsets aren't giving me a straight line or any reasonable curve. The buttocks seemed to work well on three stations..but there was one that wouldn't fall into line. No doubt the waterlines and diagonals will shed some more light on what should go where.

Ian, as I'm feeling my way along I'm being quite meticulous and checking things quite often. If I was more experienced I'd know what I could get away with and might be tempted to take short cuts. As that's clearly not the case, I'm taking it one careful step at a time.

[Bruce Taylor]

But sometimes it's difficult to chose which offset is the more nearly correct one.

No doubt this is obvious, but offsets taken from high-angle intersections do tend to be more accurate. The more nearly-perpendicular the lines of intersection, the more I am inclined to trust the offset lifted from that point (assuming no typos & transcription errors, of course).

Nice thread, Jim.

[Jim Ledger]

but offsets taken from high-angle intersections do tend to be more accurate. The more nearly-perpendicular the lines of intersection, the more I am inclined to trust the offset lifted from that point

In theory, yes. But what if the one you should trust the most is the one that appears out of line?

This is the reason for lofting those buttock lines. They should be giving me the most accurate reading of what should be happening in the deadrise portion of the bottom, the flat areas aft.

[Bruce Taylor]

In theory, yes. But what if the one you should trust the most is the one that appears out of line?

In that case, I trust Jim's judgment.

[Robmill0605]

The icepicks are an idea out of Alan Vaitses book "Lofting", a book which I'm finding a great help. The icepicks are quick and easy to use single handed, but they do get in the way a bit sighting down the battens.
posted by Jim Ledgebr /> .......
Thanks Jim, I have the book and have used this method of using icepicks myself. The tick sticks are a very accurate way of transfering mutiple marks with less error. Also advised in the book by Vaitses.

Looking great, enjoying looking over your shoulder......

[Jim Ledger]

The forward half of the waterline, showing a nice bit of hollow. The batten works well forward but won't make the bend aft, so a more flexible one will have to be used there, running the curves into each other.

[outofthenorm]

This is cool. Every line looks better than the last. Great shot Jim.

[paladin]

Oh...Helll.....now my arthritic knees is hurtin' all over agin'......

[Frank E. Price]

Very interesting thread. I just looked at the plan on Brewer's web site. 10,100 lb, 12' beam, 522 sq ft SA all in one sail; uffdah! That's one big little boat. What a piece of work. Thanks for putting it out here. That shop is going to be chock full, isn't it?

Frank

[Jim Ledger]

That shop is going to be chock full, isn't it?

Frank

It's the way of all shops, everywhere.

The waterlines are drawn on the plan view and there was a bit of minor fussing with some of the after sections, getting the tumblehome right. Nothing major, though.

Here, the forward end of a buttock line is being drawn on the profile view. Because the waterlines were already drawn on the plan, they gave a lot of additional points on the profile, one on each waterline, to help nail down the actual curve this lines should take. Without the points on the waterlines, there would only be points on the stations, thirty inches apart, which would only give a vague idea of the curve.

[P.L.Lenihan]

Judging by the presence of a hammer in the picture, I would imagine Mr.Ledger, that your palms have just about had it with pounding in those pesky ice-picks. I once duct-taped a hockey puck onto the palm of my hand when I could no longer take it Careful with the hammer though, you might drive the ice pick in too deep and have to wrestle the darn things out afterward.......risking the handle coming loose in your hand and the pick staying on the lofting table.

Happy pounding and take care of your knees

Peter_

[Jim Ledger]

Judging by the presence of a hammer in the picture, I would imagine that your palms have just about had it with pounding in those pesky ice-picks.

Peter_

Naaaah, the ice pick are easy to use and work quite well, in addition to being faster. If you look closely at the picture, you'll see two 8d finishing nails where the batten takes a sharp bend. The nails hold better in this situation.

That's all.

Jim

[P.L.Lenihan]

Thanks for the reminder for me to get my eyes checked Mr.Ledger...
Continued success with the lofting!

Peter

[Bill Perkins]

Just to pick up on something Ian mentioned : my boat 's plans had "keel scuppers" spec'ed . These are just a couple of good sized holes , one forward , one aft , drilled through the keel right down by the bearding line . I lined mine with hard copper plumbing pipe . These allow bilge water to drain from one side of a big keel to the other . You can then use one pump ,though I choose to have two for redundancy . I'm thinking about adding a tiny diaphram pump , rigged to a manual switch and intended to clear the last few gallons out of the boat when putting her away .

[Jim Ledger]

my boat 's plans had "keel scuppers" spec'ed . These are just a couple of good sized holes , one forward , one aft , drilled through the keel right down by the bearding line . I lined mine with hard copper plumbing pipe . These allow bilge water to drain from one side of a big keel to the other .

That's an excellent suggestion, Bill. Even pumping one side dry would still leave 2 or 3 inches of water on the other. I've never heard of this being done and I would suppose that attention must be paid to keeping the line clear, but it would certainly help the drainage.

I'm going to look into the possibility of using a Black Locust knee for the stem and forefoot, which would also incorporate the mast step, rather than using several smaller, straight grained pieces. Here is a rough pattern to bring to the sawmill to explore the possibility. The timber would have to have a sided thickness of 7". It's a long shot, I know, but there's no better way to build a catboat stem.

The outer edge is the stem profile. The inner is just a quickly marked off curve. There's no point in refining this without an actual timber to consider.

[Ian McColgin]

I'd not worry much about scuppers side to side. No good place with the CB in the way for the whole length of the deeper parts of the bilges. Have two bilge pumps one per side each in the bay just under the companion bulkhead - lowest point so each side will drain to there. Under weigh, pump the weather side as on the lee side the water will have traveled away from the pump in that shallow bilge.

G'luck

[Frank E. Price]

Does anyone use docking plugs on a boat that's hauled out for extended periods? I'm thinking of the bronze plugs with a square head that are accessed from below the boat, presumably one each side of the keel.

Frank

[Jim Ledger]

Larry, a white oak crook would be an excellent alternative.

Frank, the catboat I'm sailing now was built in 1916 and the garboard drain plugs were two tapered wooden plugs, driven into holes in the garboard, nothing more. The current ones are bronze.

The fairing is complete and I'm satisfied with the result. It wasn't without a bit of erasing and redoing but the final lines are very pretty to look at and, most importantly, the different views agree with each other.

These are the body plan sections, penciled in dark red and ready to make molds.

[Jim Ledger]

Isn't finding a good White Oak crook that large is another problem?

Larry, if it was up to me, finding and buying and harvesting a knee like that would be just about impossible. Fortunately, there are a few sawyers who can still provide this kind of piece, given a bit of time to look around. One of them has my stem on his list of pieces to watch out for.

Meanwhile, the lofting has slowed down a lot these past few weeks. After ordering the backbone timber, the urgency went out of the task, as there will be somewhat of a wait for the timber. In addition, everything else that I usually do around the ranch has been literally piling up and much needs attending to. Forget about going sailing. The cover only just came off the boat, but the frame still needs to be removed and the sail and spars need a bit of attention.

Just to keep things interesting. though, is the sudden appearance of the future engine for the boat, a 1969 Sabb G10, with 1 1/2 hours on the clock, never been in a boat yet.

[Paul Girouard]

Just to keep things interesting. though, is the sudden appearance of the future engine for the boat, a 1969 Sabb G10, with 1 1/2 hours on the clock, never been in a boat yet.

Nice find Who had that stashed away? Spendy $$ ?? Looks sweet either way.

And I hear ya on the work around the house , jeesh it never ends does it! Mow the grass, trim the trees , P/W the driveway , etc ,etc.

[P.L.Lenihan]

I envy your machinery Mr.Ledger! Once summer gets underway(if it already hasn't down your way), what are the temperatures like in your bowshed? Is beer an integral part of the cooling system?
Love this thread and look forward to the process as it occurs.

Best of luck!

Peter

[Jim Ledger]

that engine look well suited for catboat.. who needs to go fast anyway..
Bandsaw in the background is huge... what is throat height on that?

That engine will be very well suited for the boat. Although it's only rated at 10 horsepower it has a tremendous amount of torque working through a 19" variable pitch wheel. It'll push the boat at hull speed at a sedate 1800 RPM while burning through 3 quarts of diesel an hour. It's also hand-startable, a nice feature in a marine engine.

The bandsaw is a 20" Powermatic, an ex-high school shop machine from the 60's. When I bought it, about 18 years ago, it was in pieces. I sandblasted all the parts to bare metal and put in a 3 HP single phase motor and recently installed Carter guides. It's actually a metal cutting machine with two speed ranges and a variable speed transmission and can be dialed down to run very slowly, if needed.

[Jim Ledger]

[quote=boylesboats;1861951

So will that bandsaw able to re-saw planks?[/quote]

You bet, Larry.

Here's a good thing. Forumite and fellow catboater Doug B PM'd me to ask if I could use a gaff for the new boat. Maybe a bit early, yet, but one day it'll come in handy, sure. Says he's coming down my way from Nantucket this weekend and he'd bring it with him.

So, this afternoon he shows up at my shop with the gaff and dropped it off. We took the Sea Rover for a spin up and down the Patchogue River. Just motored, sails not on yet.

Here it is, it's absolutely beautiful. Solid sitka spruce, twenty four feet long. I'd have driven up there to pick it up if I had to. A gorgeous piece of wood.

Thank you, Doug. That was most generous.

[outofthenorm]

Ah Jim, she's a lucky boat already - and you haven't even cut wood!

- Norm

[Mrleft8]

Bandsaw in the background is huge... what is throat height on that?

Nah....That's just a lil' bitty thing.....
It's all looking good Jim! I'm still amazed at your ability to banish dust and debris from your work enviroment.... Do you have super powers that you're not telling us about? (Super duper dustpan man! )

[Jim Ledger]

The pattern of the inside face of the transom.

[Ian McColgin]

That tumblehome is so sausy.

[Jim Ledger]

That tumblehome is so sausy.

Look about right, Ian? I sure hope so.

Ian, on your boat, are the transom planks glued up solid, or is there caulking seams in between?

[Jon Agne]

Hi Jim,

That engine looks great in your shop!!!

SURPRISE's transom is oak and is caulked because , as you know, it moves. I think that with a much more stable wood, like mahogany, you could glue it up.

Jon

PS: Launching tomorrow on the tide.

[Jim Ledger]

Hi Jim,

That engine looks great in your shop!!!

.

Wait till you see it sitting on the keel. Those little Sabbs just drip personality, don't they?

BTW, Jon was the former caretaker of the little diesel in the picture, who kindly let me have a turn looking after it for a bit.

My knees have about had it, I'm fed up with lofting and I'm itching to stick one bit of wood to another and get going.

So, here goes...

[Jim Ledger]

Oh com'on Jim, quit teasin' me here...

How do you like that, Larry?

Mmmmmm, looks gooooood, don't it?

[P.L.Lenihan]

My knees have about had it, I'm fed up with lofting and I'm itching to stick one bit of wood to another and get going.

So, here goes...

Now the fun really begins! Can't wait to see some of your detail construction techniques Mr.Ledger.....I'm a veritable sponge when it comes to learning-through-viewing and your pictures are aces!!
How are the temps in your bowshed?


Peter

[Jim Ledger]

How are the temps in your bowshed?

Peter

The cloudy days are best in the Summer. Even with the shade cloth on and the fan running it can get a bit uncomfortable during the middle of the day. The best thing would be two large sliding doors that opened up one end almost entirely, allowing a free passage of air.

Here's the transom, glued up, trimmed to size and sanded, and ready for beveling the edges.

[Eric D]

What material and thickness is that transom?

looks great.

Epoxy for glue or ????

Keep them coming!!!