Blackrock 24 (Build)

Well, here is my new boat....well pieces of it. Some old cedar I've been dragging around for an unknown number of years and some freshly purchased planks from the lumber yard yesterday. Also some SYP OHSA certified scaffold planks. The SYP will be my keel dead wood.

Here is the design thread that covers those aspects of the boat.

http://www.boatdesign.net/forums/boat-design/blackrock-24-a-46525.html

It's my own design and I'm extremely eager to start building. Today, I only made dust and smaller boards. I rough cut about half of the cedar into strip planks to be stacked for drying. I'm hoping a couple of monthe in the airing stack will pull their moisture content down to acceptable levels.

This will be a slow thread in the beginning, but I hope things will pick up when the time is right.

I also want to convey a special word of thanks to Paul Riccelli for all of his assistance in getting my design to this stage. He has been extremely generous with his time and knowledge in helping to guide me through this boat design. Thanks, Paul.

 

LP, Good on you for starting a new boat. You are a gentleman for acknowledging Pars help. He is sometimes pretty blunt but is certainly knowledgeable and generous.

If you run into some sort of building puzzlement you could get in touch with Roger Allen , head honcho at the Buffalo maritime museum and boat house. Roger is a a very knowledgeable, and experienced builder and restorer. He is a good guy that is pleased to help fellow boat builders.

 

Thanks for the heads up about Roger. Sorry for the delay in responding. I've been in the throes of a major redesign. I think that Paul doesn't suffer any fools. He tells it like it is, but I think that is great because He won't lead you down the wrong path. He is also very generous with his knowledge.

That being said, this is pretty much my design with input from Paul and if there is any "funkiness" any where in the design, most likely, I'll have to take the credit/blame for it.

Anyway, I've done more than make little pieces of wood from big ones. One part of the redesign was the removal of the keel and the addition of a centerboard. Making the design work with a centerboard took a lot of head scratching and designing and redesigning, but I've finally settled on the configuration as shown. It's an offset, slice o' pie type of board that should perform well with the type of rig that I have.


I've started building some accessory components so that when the hull is complete, there will be fewer items to knock out before finishing.

A short run down of the centerboard assembly... so far.

The drawing.
View attachment BlackRock24CBTSCenterboardDWG.pdf

Drawing out a pattern to assist with cutting individual pieces.


One set of components.


The second set of component pieces.


Milled to thickness and edged for gluing.


Two boards set up for gluing. I used furniture dowels to help align adjoining boards during glue up. It worked out nice as all I had to do was apply clamping pressure without concerning my self with alignment issues. The doweling also backs up the glue joint during the assembly process. The next layer boards will be glued to first with drywall screws applying the clamping force and the first layer providing alignment.


First joint all glued up.


The second joint being prepared.


All seams were wetted out thoroughly before thickened epoxy was applied. One of the key elements here is the fact that all surfaces were freshly planed and given an acetone whip before any epoxy was applied. I've used a lot of SWP and never had a problem, but it doesn't hurt to do all that you can to insure a good bond.


Glued and clamped.


Cured and flipped.


Initial trim to final profile. Also feeding the beast. I took the opportunity to feed the freshly open wood grain with lots of epoxy. I'm some what concerned over the dimension and thickness of the boards and I'm eager to get them sealed up to stabilize moisture content. They will eventually get a layer of 18 oz. cloth all of the way around and down the middle, but for now, I'll just feed the hungry little suckers all they want. It's encouraging to see the amount of epoxy that is soaking into the boards. It should provide for a good bond base when I start stacking them up. I've also be feeding the second layer of boards so they be ready when stack-up time comes.

 

Looks like you are on the way LP.

Keep on keeping on and best of luck with all those little boards that will become shapely big ones.

 

I cut and fit the second layer of SWP and have it all pre-assembled. This sucker is HEAVY. Who needs ballast? For all of it's heaviness, I find it amazing that it is still lighter than water....so far. I calculated it's weight at about 42 lbs. per cubic foot. I think I erred on the light side. Right now, the board is at a stand still until some materials arrive. There is a bit of a warp in the lower glued portion so I have it weighted and supported to pull it flat. On glue up day, I'll have to reweight it this way so the glue will "set it straight" when it cures.



With the cenerboard on hold and a few free days available, I was eager to keep things rolling. I sourced some white oak locally and purchased my rudder materials. Some 4/4 stock that that cleaned up at about .93".



Lastly, my centerboard isn't moving off of this bench until I'm ready to set it aside to wait for installation so it became my drawing board for my rudder full size patterns. Note the tablet on the board. I've found a great use for my tablet in the shop. I save my drawings in PDF format and import them to my tablet and now all of the detail that is in my CAD drawing is now available on my tablet in the shop. I've saved drawings as BMP's and JPG's in the past, but they loose detail when zoomed. With the PDF file, it redraws itself as you zoom and even the slightest detail is still maintained, regardless of the enlargement. I also like it because dust access is limited when compared to a PC. I wouldn't think of taking my PC to the shop, but I'm completely comfortable with my tablet being there.

 

LP looks like you are well on your way. It also appears that you are a thinking craftsman. Keep on keeping on.

 

Good to see the pivot has been moved down.

 

More photos

While waiting for materials to arrive, I started working on the rudder blank. The plans are to have an 0012 foil and give about a 2.5" total thickness on the blade. The structural portion of the blade will be two thicknesses of white oak with additional thickness made up of cheeks of doug fir, yellow pine or even white pine or cedar. I plan to have an epoxy soak piece of cord embedded in the leading and lower edges of the blade. I preparation for this, I took a square(dado?) router bit and put a recess in these locations prior to glue up.



The blade will eventually be wrapped with glass, but I add some cross grain strength to the build up. I took my bag of glass cut offs and laid out a couple of over lapping layers of glass to be sandwiched between the blade halves. A secondary purpose for the glass was to hold an additional amount of epoxy between the blade halves to ensure a good glue up. Kind of a thickened epoxy without a thickening agent. The small pieces of glass were a pain to wet out, but I believe I achieved the desired results.



Glued up and curing.



I used a similar technique in the centerboard glue up. The primary laminate was a single piece of 18 oz. glass cloth. Again, I wanted to build cross grain strength and avoid mixing horrendous amounts of thickened epoxy. This thickness of cloth held a nice amount of epoxy and it kept it in a nice uniform layer. I thick that if I wasn't looking for the added cross grain strength, I could have use some CSM as an alternative to thickened epoxy. Also to note in this photo, I had some left over 4 oz. S-glass from an old build so I added multiple layers of this at key locations to spread stress concentrations throughout the board. Specifically, at the pivot location and the board lift location.



I was able to wet out the glass at each board location and was able to keep a "wetted edge" going though the whole build up. Start to finish, it took about three hours. This photo shows a preliminary glue up test. Only the glass was wetted, the attaching board was screwed dry and removed to check for glue transfer. Transfer was almost complete, but there were very minor areas of dryness. I made sure to thoroughly wet out of the glass cloth and then pre-wetted the attaching boards to give adequate epoxy to the bond.



A typical glue up of a board:

Wetting the cloth, thickened epoxy at the joints and pre-wetting of the attaching board (not shown).



Board placed and screwed down.



Squeeze out at the edges indicating a thoroughly wetted bond.



The excess unthickened epoxy is squeegeed (sic) out across the glass cloth and the thickened epoxy is scraped up, rethickened and used on the next board.

The end product with weights and supports at strategic locations to pull the board flat.



The following day I went to pull screws and had great difficulty. The first two screws, I snapped the heads out using a power drill and bit set-up. I stepped back and used a screw driver and proceeded to break off three bits. So much for using Harbor Freight bits. Finally, I broke out the plumbers torch and a US made screw driver bit and a 1/4" wrench. The screw driver with bit went in the screw, the torch went on the bit for about 30 seconds and the bit was torqued with the wrench until the epoxy let go. I think I have a good bond on my board.

 

I have a few screw drivers that are blued and scorched from this very technique. Press the driver into the screwhead, apply heat from the torch until you get a reasonable dull glow, then apply some torque. Don't touch the damn driver shank. You'll learn this lesson after you do.

Another method I've used to provide space for the epoxy, when clamping pieces together is fishing string. I'll weave a light weight monofiliment near the edge and back and forth in the center sections of the piece to be joined. The monofiliment will space the two apart, just enough to prevent a glue starved joint.

 

Yup and my cheapo magnetic tip holder lost it's magnetism just as soon as it got warm. Very tempting to reach down and pick up the hot tip that kept falling out of it's holder.


Shaping the trailing edge:

I opted to go with a circular profile for the centerboard taper profile. The trailing edge thickness is going to be left at 1/4" and the length of the taper is 12". Using these parameters, I calculated a "depth of cut" at 2" intervals concentric to the hinge pin.

Here you can the concentric lines that coincide with cut locations. From here it looks like a jumble of random cuts.


From here though, it starts to make sense. Once the initial depth cut is made, I made three more on the back side of the first cut to help in material removal.


Excess material chiseled and knocked out of the deeper cuts. The shallower cuts were left for the power planer. Fairing progression. The first passes were along the cut direction and as the final shape neared, the passes turned to across the cuts. With the right depth set, the planer did a great job of following the desired profile. The final passes went back to the same direction as the initial cuts with a very shallow depth setting. Finally, a belt sander and then a sanding block, both with 36 grit, were used to bring it to this level of fairness.



The profile:

 

The latest exertions.

I had made a couple of bird's mouth spars a while back and never finished them. I set to make end plugs for both of them. Yesterday I glued up a whole stack of douglas fir that I could rip all of the plugs from at once instead of gluing up four separate pieces. Each was ripped from the mother block and squared and octoganel'd. Four inches from one end of each was kerf'd down to mate with the spar. Lastly, the small end of each plug was tapered a bit and the spar was rasped out to create a short taper there also. The idea being that when the inner spar and the inner portion of the plug are slathered with thickened epoxy, the epoxy will feed into the joint rather than be scraped off by square cornered parts. As far as I can tell it worked to plan. I pulled one partially assemble piece apart and it looked like it was getting full epoxy coverage.



Glued up spars with packing tape clamps.



Another ongoing project over the last few days has been the build up of the rudder head cheeks. These are made of white oak. I used joiner biscuits for board alignment. It sure eases glue up to have the boards self align. I trimmed them to shape yesterday and laid on an 18 oz. layer of cloth on what will be the inside surfaces of the rudder head. The cloth here plays a multi-function role here. It build epoxy thickness quickly, it provides abrasion resistance to rudder movement and also provides needed support for the torsion loads produced by the rudder. In the photo, I've filled the majority of the weave with wood flour thickened epoxy and have applied a coat of straight epoxy. Tomorrow it will get hit with a heavy sanding and some more epoxy. Note the filler/spacer pieces between the two cheeks. These will translate over the left hand cheek and the right side cheek will flip over to the left.



The last item today was a little work on the rudder blank. I had cleaned up it's exterior edges a day or two ago. I realized though that I had made a square inside corner where the balanced portion extends forward. I took some left thickened epoxy and built up a radius there and will eventually glass the area also. This may or may not be necessary, but it's an easy enough fix/change. I little tape and an old Ziploc bag and the fillet is form able until set.

 

I've found for birdsmouth plugs, it's best to just use a hole saw and drive it as deep as necessary, then shape the plug to the diameter of the hole, rather then 8 side a plug.

 

Goings on.

The rudder components roughly assemble for fit.



The rudder head and a couple of yards. The bowsprit and boomkin are all sealed up and will be put away until final fit out.



The rudder blank with it's leading and lower edges filled colloidal silica mix. One side is pre-fit with filler pieces to bring the rudder to full thickness. The opposite side will get matching pieces.



The centerboard pin bearing. The board is a massive unit and I thought a beefy pin support would be recommended. This photo is the initial lay-up of the pin bearing. I took a dowel and built up it's diameter with masking tape until the desired bearing size was acquired. I wrapped the masking tape with packing tape as a release agent. A length of fiberglass tape was cut that would wrap the dowel ten times. Some straight epoxy was mixed with a little bit of colloidal silica the thicken the mixture some, but not so much that it would loose it's wet-out abilities for the glass tape. The epoxy mix was applied to the glass tape as it was rolled around the dowel.



The bearing removed and cleaned up.



Pre-assembly: The hole was cut to accept the bearing. The hole edge were radiused and a layer of clothe was cut and positioned so that pin loads would be carried across the board.



Fully assembled: Both sides were done together. The glass cloth was applied first and worked down into radius. The hole and the bearing were coated with colloidal thickened epoxy and the bearing was placed in the hole. The excess epoxy was worked into the radiused hole and smoothed.



Installed and cleaned up.

 

One side of the board is finished except for final sanding and paint. Most likely, when both sides are done, I'll give a good primer finish and put it away until installation time. Note extra layer of cloth at the hinge bearing.



Filling screw holes. I have insights during the build that I miss in the design phase. On this side of the board, the planks are running in two directions. for ease of construction, I chose a simple 45 deg. transition. In retrospect, a longer, more scarf like cut would have been a more sound plan with two or more pie shaped planks to reorient the grain direction. Ultimately, a balanced board lay-up (plywood term) would be the best option. The point of all of this is to highlight my attempt to negate the stress riser that will no doubt develop at 45 deg. transition. I am tying the two layer together at this juncture with nothing other than some trunnels. Specifically, 1/4" diameter bamboo skewers that I found at the grocery store one day. I bought a couple of packs and regret not buying the whole lot. Anyways, I drilled corresponding holes for the trunnels to tie the plankends to the opposite side of the board.



Holes and trunnels wetted with epoxy, ready to be pushed in.



Preliminary fairing and sealing coats applied.



Both sides of the board's trailing edge are shaped and faired.



Lastly, a hard edge for the trailing edge. I left the glass sheathing from the other side long so that it could capture the thickened epoxy to make a hard trailing edge. It was a bit of an after thought so I will have to do the same when I sheath this side to get a consistent extension along the entire trailing edge. The first side needs a little more compound for fairing purposes so it should all work out well.

 

This was kind of a fun little adventure for me. I had thrown together these spars as an experience building exercise and had just roughly estimated the length requirements for the spars. Rechecking my calculations, I saw that I was short on at least one of the spars. In building these plugs, I was also sneaking a little more length into the spars. On your spars, I'm sure your planning is a little more in depth and you would never build a spar that was too short. I suspect your plugs slide entirely into your spars.

In my case it was a fun excuse to make a lot of saw dust. I made square blanks for each end of a spar, held it up to the end, marked the 45's and set a my table saw at a single dimension for all cuts on each block. That gave me the octagon and using the miter index, I made the depth cuts on each face to define the inner dimension. I knocked off the remaining bits and cleaned it up. The eight sided plug helped to align plug faces to the spar faces also. If I decide to shorten the spars, I have plenty solid material that can be removed.