Centerboard Schooner C. Chase 1846 by Maury S - FINISHED - Scale 1:48

[Maury S]

The offending cant frame is replaced and the first eight frames are roughly faired on the inside.  Do I put the Hawse pieces in now or later???

Maury

 

[druxey]

It would make much more sense to add them now. This will help stabilize and solidify the framing so far.

[Maury S]

Hawse Pieces going in.  Translating Wayne's practum on lofting these pieces took a couple of iterations to get right.  Once done correctly, an "Ah ha".

They look pretty ragged because of the filler spacers between the hawse timbers, but they line up with the plan on the building board.

Once the glue has dried, I'll fair them and put in some additional support.

Maury

[Maury S]

There is a lot of sanding / fairing to do around the cants and hawse pieces.  It's a tight fit.  I wrapped a piece of 80 grit paper around the end of a riffler file and it gave me plenty of pressure to sand in the restricted space.

A lot of sanding ...

 

I've looked at dozens of photos and drawings of similar boats under construction and have not seen a deck hook or breast hook in any of them.  I'm thinking a deck hook might stabilize and simplify things for later.

Maury

Maury

[druxey]

There has to be at least a deck hook to support the ends of the deck planking!

[Maury S]

Thank you, I thought as much.

[Maury S]

Thank you, I thought as much.  A card profile was cut, transferred to some 9" stock and sanded to fit.  Simulated bolts added.  The height was carefully measured from the profile and transferred to the inside of the forward-most cant frame and stem.

That bow area is now very solid.

Maury

[Maury S]

Back from vacation.  Framing continues.  Frame 10 is being held level as the glue dries.  The section from Frame E to  Frame 5 is where the centerboard case goes.  The frames in that area require special handling.

Basically the same treatment as the square frames seated in the deadwood, one side at a time.  The frames on the port side butt into the centerboard case so will be sized to account for the case.

Maury

 

[druxey]

Starting to shape up nicely, Maury!

[Maury S]

While lofting and building the remaining frames at the stern, I've diverted to lining up the frames at the centerboard well.  Before the frames can be properly lofted, I need to know exactly how the CB well lines up.  The port side of the lowest plank of the well (where the ends of the frames seat) has been installed.

The well sits at the outer edge of the rising wood and has a slot 1" wider than the thickness of the centerboard.  There are rabetted logs at each end of the well that tie into the frames at the bottom and a deck beam at the top.  The tops of those logs are held in place with temporary spanners rather than the final beam.

I can now determine the difference from the centerline for the port-side frames.

Maury

[Maury S]

Installing Frame 12 against deadwood.  The jig described earlier...frame is clamped to the Plexiglas sheet glued to machinist square aligned with plan on building board and other square lining up top of frame. 

Slowly proceeding.

Maury

[Maury S]

The four half frames at the stern are installed and I've made some serious errors along the way.  They are not fair.  Not even close.  I went back to the original Chapelle drawing and compared the body plan with my framing plans and they do not line up.  Going back over the lofting instructions from Wayne Kempson's tutorial which I followed completely, I have determined that I probably chose the incorrect spline tool in projecting my body lines and the waterlines on the half-breadth.  I probably used the "spline by control points" tool rather than the "Spline by fit points" tool.  The difference shows up where there are sharper curves (like near the stern).  I've copied the body plans for the aft-most frames from the original plan (they correspond very closely to frames 11, 13 and 15) onto my body plan and I'm re-lofting the water lines aft of frame 9.  I'll have to replace the frames from 10 or 11 aft to 15.🙁

Maury

Edited September 1, 2018 by Maurys

[druxey]

Remember to run proof diagonals when you've done, to prove that your lines are all fair. Any wobbles in the lines will quickly act as tell-tales.

[Maury S]

I had to go over Admiralty Models' Drafting Workshop materials to understand how to use diagonals (complicated).  I expanded the stations to five since three will always result in a smooth line and ran checks.  The original lines are smooth.  Waterlines projected to the half breadth.  I then took care to determine exactly where the original station lines fell in relation to final frames and re-drew the waterlines on the half breadth.  From there I projected the center of the frames back to the body plan and the variations are as expected due to the width of the frames.  A whole afternoon of modifications to the plans.  I'll start removing the errant frames tomorrow.

Maury

[russ]

Maury:

Sorry to hear about the errors. I have been there. It taught me to never trust any drawing, but redraw and refair everything. I strongly support Druxey's advice on diagonals. Just when you think it looks right, draw out the diagonals and many hidden problems can be fixed.

 

On a centerboard hull, being shallow draft, I would advise, in addition to the horizontal waterlines, three or four buttock lines and the same number of diagonals. The buttocks will help fair the floor timbers down low in the middle of the hull. Without them, there is little to tell you anything useful below the lowest waterline. The diagonals in the body plan should run so that they cross the body sections at places in between where the waterlines and buttocks intersect the body sections. That will pick up those areas that the waterlines and buttocks do not address and give you several more points of intersections to ensure a fair drawing. It is a lot more work, but it will pay enormous dividends. 

 

One thing to remember about the diagonals, and you have probably already seen this, the diagonals, when projected in the halfbreadth, will appear as convex curves or perhaps in some areas close to straight. However, they will not show as concave or hollow curves. This is because they approach the body sections at, or nearly at, right angles whereas the waterlines intersect at all sorts of shallow angles. 

 

Good luck with the redrafting. 

 

Russ

 

 

 

[druxey]

Well stated, Russ!

[Maury S]

Thanks for the input!

Maury

[Maury S]

A lot of time since the last post...traveling, other commitments, etc. 

I finished frame #15 (second to most aft), which includes mortises for the post and horn timbers that support the transom.  Post timbers abut the stern post, the horn timbers are the ones further out.

A John Clayton photo from Dana Story's "Building the Blackfish" provides some insight:

To support the ends of the timbers, I built a jig to position them. It clamps to the square frames on the building board.  Now that they are temporarily in place, I can better fashion frame #16, as the timbers rest on it.

Maury

[Mahuna]

Great idea on the jig, Maury.

[Dowmer]

Great project and unique subject Maury.  Following along.

 

 

 

 

[Maury S]

Frame 16 is now installed and the post and horn timbers are temporarily in place to make sure everything glues up properly.  The outer two timbers butt against the aft side of the frame so the joint is inherently weak.  I'll put in some cross-framing to stabilize everything before removing the jig.

All pieces fit nicely...no major trimming necessary.  By the way, the jig has a crown (bend) in it to match the eventual tops of the timbers.  All I have to do is chisel / sand down to the top of the jig.

After that's done, I'm on to the remaining frames in the area of the centerboard well.  They are a series of half frames butting onto the lowest well plank (see photo) on one side and the keel / rising wood on the other.  I have to put in another CB plank pair and set the centerboard in place first so I can drill for the pivot pin.

Maury

[Maury S]

The first two planks of the centerboard well are in and the hole for the pivot pin aligned.  While I'm talking about the centerboard, let me throw out a question about the controlling (raising and lowering) the board.  It's rather large (5 - 6 feet by 15 - 16 feet) and would have been weighted.  I've found no drawings or photos showing this detail.  Some research has indicated that chain would have been used.  Might it have been cranked up on a drum or  connected to a simple pendant / gun tackle strung from the mast (which is just aft the aft part of the well)?

Any thoughts will be appreciated.

Maury

Edited September 30, 2018 by Maurys

[druxey]

I've seen models of centerboards showing a chain to a horizontal drum and two-handled winch. (Look for 'centreboards' on the RMG 'Collections/ models' site, but note the English spelling!

[russ]

Here on the Gulf Coast, there would have been a rod bolted to the upper aft end of the board and led through the deck. To the upper end of the rod was attached a block and tackle, the upper block of which was secured to a pendant that led to the main mast head. The tackle was handled from the deck. The centerboard tender would control the board per the captain's orders.

 

Here is a crop from a 1920s photograph that shows the typical centerboard arrangement.  

 

Russ

[Mark Pearse]

Hi Maury 

 

that's a very large centreboard, it would weight a lot. I like the sounds of the vertical tackle: having used some systems that are a tackle system laid horizontally on top of the case the angles are usually quite poor & to raise the board so you've got a mechanical disadvantage. I would think a tackle system has some advantages over a drum, the simplicity of using common hardware.

 

[Maury S]

It's been a while...Lofting and installation of frames continues.  The final frames are those that occur at the centerboard well.  That makes them all half-frames and the jig for those is the same as the half frames fore and aft. On the port side, the frames fit into the lowest plank of the centerboard well.

 

On the starboard side, the frames notch into the keel / rising wood and butt up against the CB well planking.

Multiple keelsons will go over the frames on both sides.  The hole for the CB pivot pin can be seen in the planking (right side).  Since the keelsons will cover it, they (the keelsons) will have to be bored out to allow for potential replacement.  The horizontal piece supporting the top of the CB well log is temporary.

Maury

 

 

 

[EdT]

Neat project, Maury.  I'll be trying to catch-up/keep-up.

 

Ed

[druxey]

Nice progress, Maury. Good thinking ahead re the pivot.

[Maury S]

The last (half) frame going in.  A beam held from the gantry puts pressure on the frame at the keel/rising wood while the glue dries.  A square lines up the outer edge of the frame to the waterline on the building board.  The temporary cross member supporting the CB log has been removed.  I don't know how I would have held parts in place without the gantry / building board setup.

 

All the frames are in.   While the spacers between the frames distort the fair line of the tops of the frames in the photo there is still a lot of fairing to do .  Right now I'm smoothing the tops of the frames at the keel for the keelsons.  The keelsons will add a lot of support.

Sanding block, straight on one edge, curved on the other can be seen on the right.

Maury

 

[EdT]

Looking really good, Maury - neat and clean.  Those spacers never look great but they do the job - and of course you will have the pleasure of removing them later.  The last picture shows wood in the CB well.  Is that a temporary spacer?  Maybe I missed something in an earlier post.  If so, it seems like a very good idea.

 

Ed