Skipjack Kathryn by Mahuna - FINISHED - 1:32 - Based on HAER Drawings

[Mahuna]

Thanks Popeye.  The installation of the rails did go fairly quickly, mainly because of the shaping and drilling that had already been done in a prior step.  It would have been much more difficult and time consuming without that previous work.

[PETERPETER]

Frank,

Your completed hull is tres elegant! I have been fortunate to see your work close up, while learning many new things about modeling.

Looking forward to seeing Kathryn finished and hoping you may consider making a set of sails for her. It would not be that much extra work and would really bring her to life.

Peter

 

[GuntherMT]

Great solution for making the aft rail stanchions Frank.  Not only looks good, but functional!

[thibaultron]

Great work Frank!

[Omega1234]

Hi Frank

 

Brilliant as usual.

 

Also....Being able to see the full hull shots has made me think...”Low, squat and powerful”. There’s no doubt that these ships were powerful and hardy; befitting their role as working ships.  

 

Without a doubt, you’ve captured the essence of these ships beautifully.

 

Cheers. 

 

Patrick

 

 

[usedtosail]

Love those rails, Frank. They look great!

[Mahuna]

Thanks Peter.  Your models have been a major influence for me.   I'm still trying to decide on sails - but I'm leaning towards furled sails at this point.

 

Hi Brian - great to hear from you.  I originally thought about using styrene for the stanchions, but I'm glad I used brass - much stronger.

 

Thanks Ron and Tom for the kind words.

 

Hi Patrick.  Yeah, Kathryn is beautiful when seen in person.  She stands out from the other skipjacks still in use.  I'm sure she was powerful when dredging under sail, but now she depends on the power of the yawl boat when dredging.  I'd love to see her under sail during the annual skipjack races - maybe some day.....

[Jack12477]

30 minutes ago, Mahuna said:

 I'm still trying to decide on sails - but I'm leaning towards furled sails at this point.

Frank, that's what I did with my Willie Bennett skipjack - see here

 

Great job on the railings on your boat.  Been following along silently and learning a lot from your narrative.

[Mahuna]

Thanks Jack. Very nice job on your Willie Bennett. 

[EdT]

Wow.  Great work on those rails, Frank.

 

Ed

[Mahuna]

Thanks Ed.

[Mahuna]

Part 56 – Push Boat Bumper

 

When not under sail, skipjacks are maneuvered by a Yawl Boat, or Push Boat, pushing against a bumper located at the aft end of the skipjack. Since most skipjacks have an external rudder post the bumper needs to be located to the side of the transom. Kathryn, however, has an ‘inboard rudder’ with the rudder post located forward of the transom.  This allows the bumper to be located in the center of Kathryn’s transom.

 

Kathryn’s bumper is supported against the lower of the aft head rails by a curved ‘knee’, and is also mounted to the deck and to the transom below the deck.

 

                        

 

As can be seen in the above photo, there are three 1-inch iron bars mounted to the upper head rail in the center portion of Kathryn’s aft area, above the push boat bumper.  There are also single bars mounted on the port and starboard rear quarter.  These bars are used as belaying pins (but are not removable) for managing the ropes associated with the push boat.  On the model, these pins are represented by 1/32” brass rods inserted at the appropriate locations.

 

                        

 

The knee was fabricated from wood of the same thickness as the head rails and was glued in place.  A support was glued to the deck.

 

                        

 

The vertical main body of the bumper is a board with rails mounted at each side, so this was fabricated from appropriate stock.

 

                        

 

On Kathryn, the area between the vertical rails contains a strip from an old tire as a shock absorber.  A piece of paper-backed felt was painted flat black to simulate the texture of an old tire.

 

                        

 

The bumper’s main body was painted, and then a strip of the ‘tire’ was glued in place.

 

                        

 

The bumper was installed on Kathryn’s aft, and the support that connects to the transom was installed.

 

                        

 

                        

 

This was a relatively simple construction, but it added a nice feature to Kathryn’s aft area.

 

                        

 

Thanks everyone!

 

 

[Omega1234]

Very nice, Frank.  

 

That bumper-A nice feature, indeed, but then again, your whole boat is full of some very nice (dare I say, ‘masterful’) features.  Top job.

 

Cheers. 

 

Patrick

 

 

[Mahuna]

Thanks Patrick.  Can't wait to see your next build.

[Mahuna]

Part 57 – Cabin Exterior Details

 

My original intent was to construct Kathryn’s cabin so that the roof would be removable, allowing the interior of the cabin to be easily seen. After a lot of thought I decided against this for the following reasons:

 

1.    The boom will be very close to the cabin roof, and there would be a real danger of disturbing the boom if the cabin roof was not very carefully moved.

2.    Each cabin door consists of two parts, which allows the doors to be opened for the doghouse while leaving the lower parts closed.  Constructing these doors as two separate parts would make a very delicate part that could be damaged when the roof was removed.

3.    The Centerboard Hauling Lanyard is run over the main roof of the cabin, with pulleys, tackles, and a cleat for securing the lanyard.  Leaving the roof removable would eliminate this interesting detail.

 

The following HAER photo shows some of the detail of the Centerboard Hauling Lanyard.  Also note the controls for the Push Boat just behind the lanyard.

 

                        

 

There are two metal cleats on Kathryn: one that secures the hauling lanyard on the cabin roof, and one that is mounted on top of the bowsprit to secure the jib downhaul.  The other cleats are wooden cleats.

 

The metal cleats for the model were made from 3/64 brass rod and 1/8 x 1/32 brass strip.  The brass rod was flattened on one side using a file.  This would allow the strip to closely mate with the rod.

 

                        

 

A light groove was milled in a piece of Corian to hold the rod so that the strip could be centered on the rod for soldering.

 

                        

 

                        

 

The rod was then cut to the appropriate length with a razor saw. These metal cleats are 8” long (1/4” on the model).

 

                        

 

The strip was narrowed its final width, using a file and a rotary tool.

 

                        

 

The cleat was then ground to its final shape using a rotary tool with diamond cutters, and was polished using emery cloth.  The post for mounting the cleat was also cut into the strip.

 

                        

 

The cleat was then blackened using a well-diluted (5:1) mixture of the JAX Flemish Black, giving a steel-like color.  The following photo shows the jib downhaul cleat in place on the bowsprit.

 

                        

 

There are two open pulleys that service the Centerboard Hauling Lanyard. One is on the deck, with the lanyard running below the sheave.  The other is on the cabin roof, with the lanyard running over the sheave.

 

The sheaves on the model were made from 3/32” brass rod, which would equate to 3” diameter.

 

The rod was bored out for the axle using a center drill followed by a HHS drill.

 

                        

 

The width of the sheave on the model is .020.  A parting tool was used to cut partway through the rod so that this width was set off.  A very small round escapement file was then used to form the groove in the sheave, by carefully filing the shape as the lathe turned at a relatively slow speed.

 

                        

 

The sheave was then parted off using a jewelers saw while the lathe was turned by hand.

 

                        

 

                        

 

A HHS drill bit, reversed in the tailstock, was used to prevent the sheave from coming loose when it was parted (it would probably never be found again if it left of its own accord!).

 

The body of the pulley was made from a 1/16 strip of .010 brass sheet that had been cut using a paper cutter.  The strip was bent around a 1/32” thick piece of brass strip to get the appropriate shape, and was then bent around a sacrificial piece of wood for drilling.

 

                        

 

A mounting post was soldered to the hole drilled at its base.

 

                        

 

The shape of the body was then finished using a rotary tool and a diamond cylinder.

 

                        

 

The sheave was mounted in the body and soldered on one side of the axle. 

 

                        

 

The pulley was then cleaned up using files and emery paper.

 

The Centerboard Hauling Lanyard comes out of the deck under the dredge winder, with a wooden fairlead in place to keep the lanyard from fraying on the edge of the hole in the deck plank.

 

                        

 

The lanyard then runs under a pulley mounted at deck level just forward of the cabin.

 

                        

 

The lanyard then runs over a pulley on the cabin roof, through a double-block tackle, and is tied off to a cleat.

 

                        

 

The cabin doors are fairly plain, and seem to be made mostly from plywood. The hinges on the real Kathryn are piano hinges painted to match the doors, so they are virtually invisible. The outside of the doors have some strips to provide protection from weather for the separation between the upper and lower parts of each door, between the two doors when they are closed. The interior of the doors are plain and flat.

 

I wanted to leave the doors open so at least some of the cabin details could be seen, but I wasn’t thrilled with having plain flat doors being the only thing showing.  In addition, if the doors were fully opened then the rear windows of the doghouse would be blocked.  To resolve these issues I decided to have the doors propped partially open.

 

Thin pieces of wood strip were shaped so that one edge was angled. These strips were glued to the doors at that angled edge and served as a door jam.

 

                        

 

The door jams were glued to the inside of the door frames.

 

                        

 

 

So now the cabin exterior details are completed.  The only thing left on the cabin is to fabricate the column that contains the controls for the Push Boat.  This will probably be the subject of the next post.

 

Cheers everyone!

[cog]

After this extraordinary feat, Frank, those push boat controls will be a stroll in the park ... This is truely amazing detail ...

 

Cheers

[Mahuna]

Thanks Carl.  We'll find out pretty soon, I hope.

[Roger Pellett]

Frank,

A beautiful model of an interesting subject.  Well done!

A bit of a minor quibble.  I don’t understand the centerboard tackle.  With the pendant led through the two double bolcks both fixed to the cabin roof the mechanical advantage would be lost.  Shouldn’t the pendant be spliced into the end of the forward double block?

[popeye the sailor]

that bit of rigging is just way too cool Frank!     neat way to make metal cleats too.   very nice progress

[Mahuna]

11 hours ago, Roger Pellett said:

Frank,

A beautiful model of an interesting subject.  Well done!

A bit of a minor quibble.  I don’t understand the centerboard tackle.  With the pendant led through the two double bolcks both fixed to the cabin roof the mechanical advantage would be lost.  Shouldn’t the pendant be spliced into the end of the forward double block?

Hi Roger:

 

Thanks for the feedback and the comment on the tackle.  I don’t see it as a minor quibble – in fact you raise the same question I originally dealt with.  I originally intended to install the tackle as you described, having seen it in the plans for the Willie Bennett.  I changed my mind based on some other info, and I probably took the wrong approach, since I’m not all that familiar with the mechanics of tackles.  Let me explain why I took the approach that I did:

 

In Chapelle’s book “American Small Sailing Craft” (and in his short pamphlet on Skipjacks) he described how the centerboard would be treated when the boat was pulled out of the water for maintenance. The centerboard would be left in the water, and later (when the maintenance was completed and the boat was back in the water), the centerboard would be brought up into its case using the lanyard and a fore-end line.  It seems to me that the length of travel of the lanyard tackle would be limited to the length of the cabin roof that it sits on, so I had a hard time visualizing this operation.  

 

In addition, the lanyard travels under a pulley normally located on the deck or on the side of the aft hatch, as in the case of the Willie Bennett.  I found the following photo of the Kathryn’s deck pulley for the lanyard in the book “Working Skipjacks of Deal Island”.  

 

 

Since the lanyard runs under the pulley, I saw this as an additional limitation to how far the tackle could move.

 

I was also confused by the length of the coil shown in the HAER photo I included in my post.  It seemed to me that if the lanyard was spliced to the forward block there would be no need for the length of line shown in the coil.

 

Again, I’m not very knowledgeable on the mechanics of these tackles, so I probably was in error.  If you, or other readers, could help me understand how the issues I mention above would be addressed with the alternate tackle arrangement then I probably would re-do the tackle to make it more correct.

 

Thanks again for your feedback – to me, this is the real value of this forum.  Discussions like this are a valuable part of the learning process.

 

[Mahuna]

4 hours ago, popeye the sailor said:

that bit of rigging is just way too cool Frank!     neat way to make metal cleats too.   very nice progress

Thanks Popeye.  Yeah, the bit of rigging is cool, but it may be wrong (see my reply to Roger).  

[Roger Pellett]

Ok, I’ll try to explain.  The centerboard is under tension caused by the weight of the board trying to pivot it about its pivot pin.  We’ll call the tension T.  A rope transmits this tension along its length. By changing the direction of the rope a block or pulley fixed to the boat’s structure changes the direction of T but not it’s magnitude.  As rigged the force required to raise the centerboard is still T.  In fact it is somewhat more than T due to the friction in the pulleys and blocks.

 

Now, attach the block to the pendent so that it can move back and forth as the centerboard pivots up and down.  The force on the end of the block attached to the pendent is still T and while,the TOTAL force on the opposite end of the block must be equal and acting in the opposite direction, it is equally distributed between each of the “legs” of the tackle, in this case Five. The tension in each leg of the tackle including the leg that is secured to the cleat is therefore T/5. We would therefore say that this tackle has a mechanical advantage of 5.

 

There is however no free lunch.  Although the force to lift the board is now 1/5 of what it would have been without the tackle it now requires 5 times the length of pull (length of rope) as before.

 

I hope that all of this makes sense.

 

Roger

[cog]

Roger,

 

To get it clear for my layman's "brain", by increasing the length of the rope the required power is diminished, something like the leverage one gets from a longer pole vs a short one?

 

Cheers

[Mahuna]

Thanks Roger.  Yes, the explanation makes a lot of sense.  It also prompted me to do a little research on the topic and now I understand it a lot better.  I assume the lanyard would be removed from the tackle in the (rare) instances that the centerboard would need to be temporarily removed.  In normal operation it appears that the length of lanyard travel would only need to be 3 feet or so and there's enough room on the cabin roof to support that.

 

Thanks again for raising this subject.

[Maury S]

Frank,  I don't know how I missed this log.  You did a beautiful job.

Maury

[Mahuna]

Thanks Maury - and thanks for looking in.

[Mahuna]

Part 58 – Cabin Exterior Details Cont’d

 

The configuration of the tackle on the Centerboard Hauling Lanyard was incorrect, so the first step was to configure it properly. (Thanks again to Roger for catching this)

 

 

The remaining exterior detail for the cabin is the set of controls for the push boat, as seen in the following photo.

The controls are mounted on a column that is added to the aft wall of the cabin.  

 

                       

 

For the model, the column was made from a solid piece of 3/8” x ¼” hardwood. Moulding, made from 1/16 x 1/32 strip, was added to the top, and a notch was cut into the bottom of the column so that it fit over the cabin base moulding.  

 

                        

 

                        

 

                        

 

The control handles were made from .0155 brass rod, and the round knobs were made from Apoxy Sculpt – a self-hardening two-part epoxy modeling putty.  The knobs are approximately 1/16", and are as 'round' as I could get them.

 

                        

 

The two bases for the controls were made from 1/8” brass rod. It was first center-drilled, then the bottom was flattened by milling approximately ¼ of the diameter.  The rod was then turned in the vise and approximately 1/10 of the diameter was milled to represent the flat top of the base.

 

                        

 

The base was painted to match the cabin.  The control bases and handles were painted using aluminum color model enamel.  The knobs were painted using artists acrylic.  In the closeup photo it can be seen that the knobs are not perfectly round, but in normal viewing they give the appearance of round knobs.

 

                        

 

This completes the work on the exterior cabin detail.

 

Cheers, everyone! 

Edited April 20, 2018 by Mahuna

[GuntherMT]

Great detailing Frank, and good choice to change the rigging, even though I didn't notice it was wrong until Roger pointed it out. 

[Mahuna]

Thanks Brian - I'm glad I took the time to re-do.

[popeye the sailor]

I was having trouble wrapping my head around the problem at first........I kept coming to the solution that both blocks couldn't be fastened to the roof.   the way it looks now is much better....darned I didn't see it either.

 

     the picture you showed earlier with the center board  rope coming out from under the winch........the pulley on the deck really isn't doing much.   with the pulley in the upright position like that,  the rope would be rubbing on the pulley bracket.   now if the pulley was lying flat on the deck,  the the pulley would be more efficient...better pulley / rope contact.   true that it runs up to the second pulley......but look what it's doing as it runs through the deck pulley.

 

yours is better though,  because this pulley is closer to the cabin wall..........travels the deck.......goes through the pulley where you have it,  and then runs up to the second pulley,  where the rope is now attached to the double block.   there is better rope / pulley contact.