More reading, more math, more fun!

First off, many thanks to Big Tom for extending his expertise and sharing his personal library of boatbuilding literature with me.  At this point I certainly can't say that I lack sufficient boatbuilding references to figure out what I need to.  The bigger problem is finding the information I need within the materials I have.  Easier said than done.

Current reading list

The biggest issue I am currently trying to solve is that I am having the mast stepped (installed) and all of the standing rigging made in July/Aug of this summer and there are a lot of preparations that need to be made to the boat between now and then.  The standing rigging is basically all of the "cables" (technically wire rope) that connect the mast to the hull and "ropes" (technically halyards) that allow you to raise the sails.  This is not to be confused with running rigging, which is all the other "ropes" (lines/sheets) that control the sails while underway. Since the mast has never been installed I need to figure out the exact placement for it, the keel step, the deck hole, and all of the chainplates.  I also need to calculate the strength required for each of these things as well as a number of other related things.  These sorts of things are typically calculated well before a boat is ever built, and indeed they likely were in this case as well.  The problem is that I don't have any of those calculations, all of which were made prior to my birth when the terms "Watergate" and "Reaganomics" were still in vogue.

On a brief side note, I apologize in advance for getting into nerdy boat terminology.  Maybe I will devote a page to boat vocabulary someday.  Until then, please continue to google terms or ask me for clarification.

Now that everyone has their boatbuilding terminology handbooks at the ready I'll dig a little deeper.  I currently know about 70-85% of the dimensions I need to calculate the placement and strength of all the chainplates that connect the standing rigging to the hull.  The frustrating part is that the remaining dimensions I need to figure out require an intimate understanding of the hull's displacement, righting moment, and other important design dimensions that can't be easily derived from other known dimensions.  This means that I have to go back to the drawing boards (literally) to fill in these gaps.

Fortunately I had a recent major breakthrough when I was able to get in touch with Lee Creekmore's wife Abby.  As the name implies, Lee is the son of Ray Creekmore who originally designed the hull of 'ol Creeky (and had the same nickname).  After some digging in their attic, Lee and Abby were able to find some original blueprints for the Creekmore 45'.  I can't tell you how exciting it was to lay hands on original drawings with various notes and scribbles from the design process.

Mast Step continued...

Where was I?  Mast step.  Right.  As I may have mentioned in prior posts Creeky came with a lot of important parts and loads of potential, but very little in the way of instructions.  Most of the time this is great because I get to use my imagination and come up with creative engineering solutions while double-checking my work with some trusted references.  However, designing and building a mast step is one of the handful of key components of boatbuilding that didn't really come up in the textbooks I have.  There weren't even many online arguments about the best way to build one in the forums I usually poke around in.  It's either assumed that this was already built into whatever structure sits below the floor or that the clever reader has the requisite knowledge to scratch something out on the back of an envelope without giving it much thought.

I took it to be slightly more complicated than that though, and decided to over-engineer it to a sufficient level of mental comfort.  Even now as I look at the mast sitting on top of the step I have that little itching question in the back of my mind.  "Could I have built it just a little bit stronger?"  What I think some people take for granted about the mast step is the amount of force it must withstand.  Even at rest the downward force on the mast step is tremendous.  Consider the following:

Approximate extruded aluminum mast section:
Dimensions: ~12in x 6in
Wall thickness: ~.3 in
Weight/ft: 15+ lbs (taking internal roller furling structure into account)
Length: 62 ft
Overall weight = 15 x 62 = 930 lbs

Now add in all nine 3/8in 1x19 stainless steel wire rope stays, each with a breaking strength of ~17,600lbs, driving the mast into the step like several giant compound bows all at once.  Assuming they are tensioned at 1/10 of their breaking strength (total guess), that would make:

9 x 17,600 = 158,400/10 = 15,840 lbs on top of the mast weight.

So at rest we may be looking at almost 17,000 lbs of force directly onto the mast step!  That doesn't even begin to take into account the myriad variables that can't be calculated or planned for, so there needs to be a considerable safety factor on top of that.  No problem...

The basic premise of a mast step is that it is a structure that distributes the load imparted by the mast to a larger section of the hull and keel.  I decided to build a step that would be strong enough to withstand the necessary loads but also allow for fore/aft adjustment of the mast foot on top of it.  This was primarily to give me a little room for error when cutting the hole in the deck for the mast, but could theoretically allow me to give the mast a little bit of rake if I wanted.  

Lining up height of mast step

The basic design of the step was to have four 2 x 6 in pieces of mahogany, each ~3 feet long going from port to starboard, with a 1/2 in thick, 6 in wide, 18 in long piece of 304L stainless steel going fore/aft.  This would be secured at either end and underneath to 1/4 in angle steel for extra sturdiness, and thoroughly bonded and fiberglassed to the top of the keel. 

Bonding

 I used a WWII era Bridgeport mill to fabricate the stainless pieces.  I could write about that machine for days, and I barely know how to use it...

Drilling

Milling

And more!

 Below you can see how the midsection of the stainless plate is attached to the mahogany bulkheads (I wanted to call these stringers, but my friend Nick corrected me and said that stringers go fore/aft and bulkheads go starrboard/port).

The bolts are counter-sunk so that the step plate can slide on top easily.

Almost done.

Finished product.

Still, could it be stronger???

Minor update - mast step

I had given up on the idea of being able to adjust the position of the mast step with the mast in place until Charlie suggested cutting a small access hole in the foot of the mast. I was nervous at first, but it seems like a solid move. 

Boom!

Chainplates start to take form

New dock lines

I bought new 3 strand nylon 3/4" dock line, which I had spliced by a guy at the store I bought it from. When I got it back I saw that he had finished the splices and cut ends with electrical tape. Not very yar...

I removed the electrical tape and melted the bejesus out of the splices and ends to ensure they would be extra rugged. 

Next, I needed to cover the melted parts. Since I didn't have the time or energy to learn how to properly whip the splices, I decided to use an easier alternative after seeing a product called dip-whip. On a nearby shelf was a similar product called plasti-dip that had three times the volume for a third of the price. Sold. 

Here I am masking off the places that I will apply the plasti-dip to. 

Here are the ends post dipping. 

And the finished product!  I applied 3 coats in total. 

I have to admit that i was pretty skeptical about the whole process and whether the plasti-dip was really sufficient for the application. However, after a few coats and sufficient drying time the stuff feels really tough. Overall I am very pleased with the results. Time will tell how well the stuff works though.