Simple centerboard control pulleys

Here's our lord and savior and his mom admiring these really nice pulleys that I made to control the centerboards.  I used a british Boxford lathe to turn 3 in. stock delrin into pulleys. I then pressed bronze bearings in their centers to help distribute the loads of the lines. The mother and child are also impressed by the aluminum spacer which will prevent the two control lines from jumping ship onto the other pulley.  Both pulleys are home to a 1/2 x 8 inch 316 Stainless Steel bolt.

centerboard control

Here's a cross sectional view showing the pulleys and lines that control the centerboards.  The lower shot shows a side view in the board down position. ( blue line lowers the boards.....a pull on the red brings them up into the cases.) 

Flower pots, cardboard hatches and duct tape lines.

In preparation for a visit from expert builder / owner of  http://www.schoonercreek.com/ ; Steve Rander  AND the HARKEN rep,  I've turned 97 cent flower pots into thousand dollar winches.  These simulated winches will be used to study and optimize the sail handling gear locations.  Colored tape will also be used to trace line paths so that a comprehensive "picture" of a working deck can be modeled.  That's when Steve and the Harken rep can start building a frighteningly expensive bill of materials for things like travelers, line guides, deck pulleys,  hatches, etc. etc. ............

a day cleaning up

Here's a shot looking back towards the starboard cockpit area. .......a few things to notice: left side of photo shows the cabin top, right lower shows the storage openings along the aft  structural member, 3/4 record holding gravity bike (68 mph)  and........flower pots????

Trial fitting the cases and the boards

Before I bond the centerboard cases in place, I wanted to make sure all the pieces fit and that the boards  were going to move freely.  Here, you are looking at the trailing edge of the port side centerboard which  is partially down.  The 1 inch Stainless bolts fit beautifully and the spacing between the boards and the insides of the cases will allow me to shim the upper portion of the boards with the perfect thickness of Delrin sheet to insure good solid positioning when they are fully loaded under sail.

Don't worry, that big ugly gaping square opening will be faired over to provide a streamlined opening for trailing edge flow transition.  I may even see if I can configure gap seals like the first sailboard that I had.

OK....enough of this centerboard pivot scene...

So here they are......I TIG welded the flanges to the threaded pivot bolt receivers and then roughed them up a bit with a grinder so that they will hold tight once they are epoxy bonded and glassed into the outsides of the centerboard cases.

neonate silencer

 

Although it's taken a little while to gather and configure the board pivots, I'm now at the point where I can bond the receivers onto the back sides of these cases and get these things bonded into the boat. If you absolutely run out of places to look for items for a project, I recommend Mc Master Carr . They pretty much have everything on the planet. 

http://www.mcmaster.com/#orders/=5upyvk  

One note that I should mentione is that in order to obtain a 1 inch bolt that has a 6 inch long smooth shank, I had to order a 9" bolt.  For what ever reason, there doesn't seem to be an absolute standard as to how much thread they will include on any particular bolt.  I anticipated this knowing that I will need to chop a part of the threaded ends of these bolts off so that they will not "bottom out" and rupture the external shell of the hull.  Incidentally,  1" bolts 9 inchs long tend to have 6 inches of shank and 3 inches of threads.  Just for the heck of it, I chucked these bolts into the lathe and given them a nice polished shank. Perhaps that will prevent my centerboard pivot holes from wearing over time.  ( I machined two delrin liners and bonded them into the pivot holes of the boards.  Since that material is so slippery, I cut grooves into the outside of the delrin "tubes" used a table saw to cut small longitudinal grooves lengthwise to create a "checkerboard" pattern so that they wouldn't come out once I boned them in with epoxy.  All this may be overkill but i want to dispel the idea that centerboards require more maintenance.

However, like Ian Farrier says they are a heck of a lot more work and I'm beginning to agree with him..

Centerboard pivot bolts

These centerboard bolts are about the size of a small cowboy.  The tow receiver nuts will be welded onto a couple of 3 in. diameter stainless disks with a couple of screw holes in them so that they can be recessed and bonded into the "outer" sides of the centerboard cases.  This will allow the centerboards to be inserted and pinned in place from the inside while the receiver nuts will be permanently blind mounted into the cases. I'm not a big fan of stainless on stainless because it is horrible about "galling" and locking itself into place so I plan on using lots of anti cease paste when I mount the boards.

A little lathe work to create the centerboard pivot bolt receivers

A larger tool

Well........sometimes a larger tool makes all the difference.  After spending a while with the little pneumatic stripping wheel,  I realized that a large, manly twisted steel wire wheel mounted to a "widow- maker" would allow me to get the job done quick. 

Wham, bam,...... thank you mam

Removing a bit of hull core foam

In order to strengthen the area around the slot in the hull where the centerboard case will be joined, the core foam must be removed and replaced with a high density filler. The forward exterior portion of the centerboard slot can be seen here in yellow. This is the natural color of the Kevlar sheathing that runs the 3/4 length of the boat. You can also see the inner skin which is 24 0z. triaxial glass. 

To remove a portion of the hull core foam, I found that a 3M paint stripping wheel works fairly well.  It is aggressive enough to make short work of the foam yet tame enough to prevent the fiberglass skins from being damaged in the process.

 

Centerboard control lines

 The fiberglass tubes shown in the last post will be bonded in the locations that are pictured here in the drawing as blue and red dots.  The RED line is the pull up line and the BLUE line will be the pull down line.   The lines are guided upwards through two sheaves that are mounted inside the upper portion of the centerboard case. From there, they will continue upwards through the deck, through rope clutches to be managed by the turn of a winch.

fiberglass tubes liners ????

Since the centerboards will be controlled with ropes that will terminate with a knots inside fiberglass lined holes in the boards......Now where the heck do you find 1 1/2 in ID fiberglass tubes to line the holes?.  I looked around the shop and noticed that a standard florescent bulb was the perfect diameter.

TIP:  If you need to make some fiberglass tubes, wrap a section of an old florescent bulb with several layers of fiberglass and epoxy then wrap with peel ply. Once cured, a few whacks on the shop floor will shatter the bulb and you'll have perfect 1 and a quarter ID fiberglass tubes.  I then used a chop saw to cut them into the basic lengths that I needed.

After cutting holes in the boards with a hole saw, these tubes will be bonded in place then the small rope holes will be drilled from the edges of the boards into the sides of these now fiberglass lined holes.

ready-set-glass

One interesting reality about building a Cat is that you tend to learn a little bit each time you do something. Since cats have two of a lot of things, the second piece of work that you produce sometimes ends up being nicer than the first........of course, that's not always the case.

Here, the small tidbit of knowledge I learned about laminating the centerboards is that having the glass pre-cut and ready for layup should make the process go quicker.

So......the first board took a solid 8 to 10 hours of flittering about; cutting glass, mixing and rolling epoxy and donning numerous sets of gloves....... Tomorrow I plan on vac bagging the second board and we'll see how long it takes.

Upper center: 30 layers of uni
center: 1 glassed board 1 to go
lower left:  12 oz biaxial
lower right:  4 pieces of 24 oz tri.

The unfinished board

This photo shows a few details that are important to the workings of the centerboard system. 1) the upper flat part of the board 2) the unidirectional glass along the center 3) the taper on the trailing edge where the board will exit the slot and 4) the trailing edge indentation that allows the glass to bond together before the actual trailing edge. ( the groove will later be filled and tapered with micro balloon / epoxy mix )

Success

Opening the present.

ugly post cure oven

Improvised post cure oven......not too pretty but when the ends are covered the temp inside this simple enclosure tops 120 deg.

Board in the bag

Perfect vacuum from an imperfect vacuum pump.

glassing the port board

This is the beginning stages of what became a solid 8 hour session of laying glass, mixing and rolling epoxy, and vac bagging the port side centerboard.  Notice the kevlar insert along the leading edge......just in case. The schedule for the boards went like this: 

1) 24 oz tri axial glass over all
2) 15 layers 12 oz uni glass down the center line.
3) 24 oz tri axial glass over all
4) kevlar along the leading edge.
5) 12 oz. bi axial glass over all

Then the vac bag process......

6) laying peel ply over it all
7) covering the board with perf.
8) covering the entire board with breather
9) sealing the whole deal in the bag.
10) building an insulated "oven" around the bag with a 1500W heater to post cure.
11. Turning on the vacume pump and watching oil pour out of my very expensive Robin-Air Vacuum pump.@@$(^&#$*#&@*;;;!!!

YIKES.....!!!!!!..  Have no Idea why the pump blew a seal but all I could do was to place the pump over a barrel and spend the rest of the night adding oil as it leaked out..........

Uni for the boards

This is what 60 lbs of 12oz. Uni-directional glass looks like.