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Core Sound 20 Mk 3 -- #4 "Chessie" . .

Pete McCrary

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That's the plan. I have temporarily screwed the rubbing strake in place, but left 5mm (nearly 1/4") clear of the hull to help with the sheer strake placement. I appreciated the info regarding the inwales for the cabin roof/sheer strake intersect and also noting the extra supports or longerons for the cabin deckhead. Much appreciated. I love getting these extra little drawings from posts with measurements that I have never seen before, they are really helpful.

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For Core Sound 18 & 20 Mk 3 builders: Here's my concept for a multi-purpose Companionway Ladder. It will fit over the Group 27 battery in either of two positions. The most useful arrangement provides a 12" step. That's halfway to the bridge deck (although one's foot must be lifted over the 3" sill. But the "rise" is not uncomfortable and feels the same.


In this (12" step) position it also serves as a restraint to forward movement of the port-a-poti.


Here in this (~ 9" step) position it is also a platform at the same level as the port-a-poti shelf -- making it much easier to remove the PaP off its shelf. When the PaP is fully primed, it contains about 2 gal of water making its total weight almost 20 lbs. For me, that's not easy to lift, especially from an award position. The ~ 9" step isn't ideal, but the next ~ 15" step doesn't make me feel that I'm reaching a step that's uncomfortably too high.

I made the shape rectangular (on all sides) so that it could easily double (triple ??) as a cabin stool with heights of ~ 9", 12" and 18". It can also be used as a small table, or as a base for a larger table or game board.

The proof-of-concept was made of 3/4" cheap pine. I'll use prettier wood and try to lighten it somewhat. However, its weight could be an advantage for stability.


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Comments and suggestions would be appreciated.

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The RubRails have been milled to proper xsection. I only made the cuts required to provide a "raised" support under the "hollow-back" of the 3/4" half-oval -- which were the two off-center 30 degree cuts (c1 and c2) on the outboard side of each rail. Another builder suggested that there be a curf cut as a drip edge. But the two-cut xsection has a built in "drip" edge along Its bottom surface. Referring to my [previous] drawing you'll see that (without the third and fourth cuts, c3 and c4) the bottom surfaces (of the RRs) are perpendicular to the flairing topsides of the hull.

post-4915-0-53787200-1464117388_thumb.jpeg. The only cuts made were c1 and c2.

Notice, then, that the uncut part of the lower surface has an uphill slope to the lower corner of the RR (where it meets the hull side). I think that most of the drainage will spill off the RR at the cut's intersection with the RR's lower surface. The edge of that intersection will not be "rounded over" -- just blunted with sandpaper. The [cut's] edge on the RRs' top surface will be nicely roundedover with a block plane or spoke-shave.

To make these cuts required the help of my neighbor and friend, Henry Felber. The setup consisted of a step-ladder in the yard, table saw with an old "feather-board" clamped to it, an extension support, an open window, and multiple clamps. The following photos give a pretty good idea of how we did it. The feather-board kept the RRs pressed against the rip fence and my hands provided the down pressure and thrust. The fence, table-saw top, feather-board fingers, step-ladder top, extension support, and all four sides of the RR assembly were rubbed with bee's wax. Pushing it thru was fairly easy.

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post-4915-0-11771200-1464119272_thumb.jpeg post-4915-0-73295100-1464119307_thumb.jpeg

post-4915-0-05902700-1464119356_thumb.jpeg. Lines drawn for intended cuts.

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We think the cuts came out pretty good. The last two photos show how the underside of the hollow-back oval is supported by the shape of the RR. A little bedding compound will provide a resilient base and keep water out of the screw holes. The RRs will be attached with 1.25" x #10 SSWS from the outside and into the 1/4" hull and a 1/2" yellow pine inwale. The RRs will be bedded (not glued) in-place.

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Progress report -- Memorial Day 2016

The roof support is complete. It appears to be a nice cylinder (constant radius) or maybe a cone (radii slightly different at Blks 1 & 3). It also appears that at the corners Graham made the corners "drop" slightly. That would give it a softer or less "boxie" profile. Plywood can be stretched a little beyond perfect conic surfaces. I suppose Graham's CAD software can be programmed to allow for stretching depending on the material.

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Above: Both looking aft ...

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Above: Both looking forward ...

Next I started fabrication of the inwales to backup the [removable] rubrails. They are 1.25" x .5" xsection. The bottom edges are rounded over (r = 5/16") and the top has a bevel that's horizontal. Maybe so that it won't collect water or easier to use as a cable race. The next photo shows the first two inwales between the stem and Blk 1.


Of course the angle of the bevel changes from stem to stern. I easily measured it (from outside the boat) with a neat tool (by Stanley) that I found at Lowes. My father had a try-square like tool that had a level that could be rotated to any angle (shown on a scale). I've been looking for one for years. The Stanly "torpedo" level was pricy -- but it does the job.

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In the cockpit the inwales and cleats supporting the deck are in conflict. I'll have the inwales make way for the deck cleats. The underside of the roof panels will next be prepared and butt-joined on their centerline.

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Steve, thanks for the compliments. I've been messing with wood projects for 58 years -- boats for 53 years. That boat was an 11' 1" plywood sailing dingy from $5 plans published in "Popular Boating." That was before I ever heard of epoxy! "Chessie" is my 9th boat, 6th since retirement.

This forum is very helpful. I got pointers from Chick re the inwales and Graham and PAR for the rub rail design. Graham's build (on the forum) and the link to photos for "Carlita" have been very helpful. Especially his advice regarding the boat-length 1 x 2 fairing batten to guide the attachment of the sheer strakes. Alan and Graham are still working on the CS20.3 manual and detail plans for the hatches. And I'll totally rely on them regarding the yet-to-come details for the rigging. Also, PAR's links to his writings on hints and techniques have been very helpful.

Our boats are only the 3rd and 4th of this design and it's fairly obvious that many details are "works in progress." For example, the details for the hatches and the add'l longitudinals for the cabin roof. I'm sure those details and the boat-length fairing batten will be incorporated into the manual (and plans). When I get ahead of the present manual and have some questions, Alan and Graham have been helpful. I'm so glad that I chose B & B for this project.

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  • 3 weeks later...

Just before I was treated to a Fathers' Day luncheon -- I finished gluing [almost] all sections of the inwales that will backup the attachment of the rub rails. Wife & daughter picked up the check!! The two pieces remaining will go on top of the cockpit deck -- which won't be glued down until after the turnover.

ATTENTION new builders: Before assembling the cockpit module -- be sure to cut limber and vent holes in the two parts (#45, the longitudinal baffels) aft of the water ballast tank. Doing it later is a nasty job requiring a special "angle" drill. I'm pretty sure B & B will have them machine cut in future kits. Here are two photos showing my approach. The two limber holes were cut as close to the bottom and Blk 5 as possible. I cut 6 vent holes (d = 2.5").

post-4915-0-14704000-1466451985_thumb.jpeg post-4915-0-51438600-1466452013_thumb.jpeg. A very tight access!

While applying neat epoxy to the plywood exposed by the cuts I also installed the below-deck support for the mizzen (part ## 22 & 23):

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Now the mizzen below-footwell support and the limber & vent holes just need another coat or two of neat epoxy.

I'm going with a stepped mizzen w/o a tabernacle. My Chesapeake crusing waters seldom require lowering of any masts. So far, it's always been done at the ramp parking lot.

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Ah yes, the mizzen base. I'm not sure I have measurements since I am cutting sheet from scratch. Thanks for the reminder. My forard ballast tank is fully coated and the aft tank about to be, so now might be a good time to think about the mizzen. Seriously considering whether to put in a tabernacle for the mizzen mast.

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Hi Drew, not trying to hijack Pete's build thread, but after rigging and moving my CS 20.3 many times, a mizzen tabernacle is the only mod I would consider. We had to pass under a train bridge and lowered the main, piece of cake! Removing the mizzen not so much. Kinda awkward in a rolling boat! A tabernacle would be a mod I would seriously consider!

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MAST FOOT COVER -- Ever had birds and other critters make a long empty hole into the family homestead? It can be a mess (and kind'a heartless) to clear them out. So, with a 3" hole saw I cut into a scrap 3/4" piece of soft pine. The saw kerff was just about the right size to accommodate the wall thickness of the mast. With a little trimming, it makes a pretty good "press fit." Useful as well for trailer transport to keep out rain, bugs, etc.

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SOLUTION for wet footwell sole when extra friends are aboard. Try a couple of corks. So they won't get lost (when not in use) -- thread a couple of feet of whipping line thru their centers. True Value (hardware outlet) had a wide variety of corks. The clerk claimed they were from Portugal. Didn't Ferdinand, the sissy bull, sniff flowers under a cork tree?

Graham has suggested widening the drain tubes (using a heat gun) so that they would accept standard 1" plugs. But I had already installed "Chessie's" footwell drains -- so I had to find another solution. This will probably do the job.

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Reminds me of my "Honker," an antique Crocker 21' cruiser I had in 1964 at a marina in Beverly, Massachusetts. She had a "self-bailing" cockpit, a 12" keel, and the cockpit sole had a 4" sill (at the fwd end of the footwell) to the companionway. Arriving with a friend to sail one Sunday morning (after a spring tide) we found "Honker" floating with a new waterline at her sheer. Apparently, at low tide, her keel had bottomed and she was tilted (over) on her keel and chine. As the tide came slowly in, the low-side drain eventually allowed water into the cockpit and over the 4" sill and into the companionway. Instead of sailing, my friend and I bailed her out with buckets. It took us all day. She was carvel planked and the planks above the waterline weren't that tight -- so we had to bail faster than the topsides leaked. The tuition for that lesson was very had on us. Especially my friend, who didn't need the lesson.

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More progress to report. My local source for quality Southern White Pine closed down -- as a substitute I found a 13' x 3/4" x 7.25" cedar. Smooth on one side and slightly rough on the other. In New England this material was often used as siding. If they wanted a "stained" exterior, they would leave the rough side exposed. It's light and fairly strong. I'm hoping to use it for the sprit booms. Is anyone more familiar with the suitability of this wood for spars?

Just finished design & fabrication of the "stops" for the drawers that I made for access to the spaces under the cockpit seats between Blks 4 & 5. Photos show "locked" and "unlocked" positions.

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Now I think I'm prepare the roof panels for instillation.

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Examine the cedar carefully, it has a tendency to experience some crushing defects, which are hard to see to an untrained eye. As a rule it's not a good spar stock, because it doesn't hold fasteners well and is relatively weak. I depends on the actual cedar. Some are similar to Douglas fir, but others are quite weak. If it's Alaskan or Spanish cedar, I'd just use Douglas fir, as they're similar, but Douglas fir holds fasteners better and is slightly stiffer.

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Just finished "dry fitting" the aft deck in place. Next will be cutting, fitting, glueing all the deck support beams and cockpit hatch frames.

post-4915-0-65320200-1467473183_thumb.jpeg Beams located and marked.

post-4915-0-52245900-1467473285_thumb.jpeg Rough-cut motor well edge. Trim and roundover later.

The "cabin-step / battery box / table / stool" proof-of-concept NOW a reality. The battery will also have an "interior" cover just to protect the terminals and wiring from possible electric shorting when the cabin step is removed to serve some other purpose. The interior cover is made of skimpy 6 mm ply and will not support any weight. Notice the "NO STEP !" warning.

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Positioned for a 12" step. Hasps on each side provide stability and restraint for what may be on the shelf [aft] during transport or sailing.

post-4915-0-02902900-1467474036_thumb.jpeg Positioned for a 9.25" step.

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When in place as a "companionway step" it covers a "first-level" protective battery box.



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