Alita is a Sparkman & Stephens yawl (design #1245-S), built in 1962 by Astillero Bottini in Montevideo, Uruguay. She is 39' 7.5" long, with a keel/centerboard. She is a sistership of the famous Finisterre, 3-time winner of the Newport-Bermuda race.
Although Alita was built to impecable stardards, she was in sorry shape when I took possession of her in 2009. Having been out of the water for a number of years, she suffered from a dried out hull, severly checked cabin sides, a deteriorated cockpit, lifting toe rails, a "frozen" engine, and many other ailements too numerous to mention.
With some luck, I hope to restore Alita to her former beauty.
12/10/2014: Here is the promised writeup on installing the transition plank Installing the transition plank S8 and the first inner plank ID1.
11/23/2014: The transition plank S8 along with the first inner plank of the double planking are now installed. I will provide a summary of this process shortly. In the mean time here are my thoughts on the right sealant for this job ( Choosing the Right Sealant for Double Planking ).
10/21/2014: Repairing the Double Planking
I have now replaced or repaired the first 7 planks on both port and starboard. Plank number 8 is a transition plank that marks the beginning of the double planking. The double planking requires a significantly different approach than what I've dealt with thus far. So I'll begin by discussing the issues associated with this phase of the project. I'll then describe what I've accomplished thus far.
Work Top Down or Bottom Up?
The overall goal with regards to the planking is to reduce that chance of serious leaks below the waterline. Hence, I am not planning on disturbing planking above the waterline. So the first question is whether to start the repairs at the waterline and work downward or to work bottom-up. The decision is largely governed by the location of the shutter plank. The shutter plank is the last plank to be installed, so consequently it cannot be easily clamped into place. So it is best to choose the location of the shutter in an area of minimal twist and bow. That happens to be in the area of planks 9 or 10 - basically just above the transition plank. This suggests that I need to work top-down.
Repair or Replace Double Planks:
The next question is whether to repair of replace the existing planking. Unlike the lower planks, where planks can be removed and replaced individually, double planking consists of overlapping inner and outer planks that are effectively glued together. So removing an outer plank results in irreparable damage to the inner plank. Although repairs are more difficult, it might be possible to replace sections of planking rather than entire planks. For planks at or near the waterline, this is important because only a short section of the plank is actually under water. It would be wasteful to replace a 40' plank when only a 5' section is bad. The question is how to make this repair? Maybe the section of the outer plank can be removed with a router and the repair scarfed in place - not an easy task. Replacing sections between existing butt blocks might help.
Regardless of the adopted method (repair or replace), at the top-most plank one must devise a way to tie into the original planking. The idea is to remove all or part of the outer plank while leaving the inner plank undisturbed. At this point, the favored approach is to use a router to cut a dado in the middle of the outer plank not deep enough to touch the inner planking. This dado would follow the seam (using a batten nailed to the hull) between the two inner planks below it. One could then remove the remaining part of the inner and outer plank below the dado, leaving a nice clean interface to continue with the new planking.
What Wood to Use?
The original double planking is Spanish Cedar for both the inner and outer planks. The availability of quality Spanish Cedar is questionable, so I've decided to use Alaskan Yellow Cedar for the inner planking and Wana (recommend by Nat Benjamin) for the outer planking. Wana is tougher than cedar, which is an asset for outer planks, although it is about 1/3 heavier. Yellow Cedar is available in lengths to 17' and Wana is available in lengths to 30'. Although using long stock helps to reduce the number of butt blocks, dealing with long stock is unwieldy - at least in my shop working alone. Also, to make good use of long stock, it also needs to be quite wide. Most planks have considerable curvature over their length, so even a 10" wide board isn't wide enough to get out a 17' plank. Even if you are fortunate enough to have full-length planks, fitting the plank can be difficult, especially if you have hood ends that must fit into a rabbet at both ends. With planks consisting of two or more sections, you can fit the ends and then trim the butt ends with saw kerf or plane to get the desired length.
To fill the gap between the inner and outer planking, some form of sealant/adhesive is required. Traditionally, shellac was used with or without a thin cloth membrane. More recently, modern sealants/adhesives have been used, although it is not clear what's best. In principle, the sealant/adhesive performs two functions: (1) it prevents water from migrating from the outer planking seams, along the inner/outer plank interface, through the inner planking seams, and into the boat, and (2) it increases the stiffness of the planking by bonding the inner and outer planks together. Certainly an epoxy or resorcinol (Nevin's Rule) would work, although expensive. Some recommend an elastomeric sealant like a polyurethane or polysulfide, because of their flexibility (as much as 700% elongation). Flexibility might actually be more important than stiffness in that it can better accommodate the differential shrinkage between the inner and outer planks. Although double planking (both planks running longitudinally) is inherently water tight, if the boat is left to dry out, the accompanying shrinkage will tend to split the inner planks along the outer planks seams, defeating the water-tightness. To be effective, however, one must insure that sufficient sealant thickness is applied.
One must also consider the workability of the sealant/adhesive. It must have low viscosity so that you can apply it to large surfaces quickly, but also be thixotropic to stay in place on vertical surfaces. It must also have an adequate pot life.
So although there are numerous unanswered questions, I am moving forward. Starting with the starboard side, the first step is making the transition plank S8. This is for the most part completed and is described in ( Making Plank S8 ). Then we make the first inner plank, which is described in ( Making the First Inner Plank ). When these planks have been installed, I'll begin work on planks near the waterline.
In the meantime, there are a few other projects that need attention: Replacing one of the main bulkheads ( Replacing one of the major Bulkheads ) and repairing a crack near one of the fasteners in plank S7 ( Repairing the Crack in Plank S7 ).
8/21/2014: S7 is now finished S7 Plank Repair .
In repairing S7, I had to replace some stopwaters More Stopwaters
With the completion of the repairs to the single planking, I'll be headed into "uncharted waters" - the double planking.
8/3/2014: Well the repair/replacement of the single planking is almost complete. I've finished with the seventh plank on the port side (P7) and the sixth plank on the starboard side (S6). The aft section of plank S7 is nearly complete, leaving only the shorter forward section to be done. I'm going to replace this section with a new plank, so I'm off to the lumber yard tomorrow to buy some more H. Mahogany.
I've included the following PDF files describing my experiences with S6 and P7
I've also include a file describing my approach to plugging old fastener holes Plugging Fastener Holes
The next planks up (P8 & S8) will require special treatment. Although these planks are still 1" Mahogany, a lap joint must be cut into the edge to overlap the 3/8" cedar inner planking. So at least one course of 3/8" cedar will have to be fitted before installing the eighth plank. At this point I'm still uncertain how to proceed.
6/3/2014: I've reached an interesting point in the restoration. I've progressed to the point where I'm now having to deal with the double-planked part of the boat. In addition to the new challenges that this presents, I've found a frame that is severely rotted. You can read all about the frame repair as well as a planking update in Planking Update 6-3-2014 .
5/13/2014: Two months since my last update! I really would like to post at least once per month. It's not that don't have anything to say, quite the contrary. I'm working but not writing.
This latest installment is a long one Hanging P6, working on P7 and the double planking section of the boat . I hope you find it informative.
I've also taken a week off to build a small table for my daughter.
3/15/14: The fifth plank on the starboard side is now fastened to the boat. A summary can be found at Hanging the fifth plank on the starboard side .
On to the sixth planks É!
2/27/14: The fifth plank on the port side is now fastened to the boat. A summary can be found at Hanging the fifth plank on the port side .
I'm now starting the repairs to S5.
I've also made substantial revisions to the description of Planking a Carvel planked boat.
1/10/14: I finished installing the fourth plank on the starboard side (S4), and I've updated the writeup on making S4. Making the fourth plank on the starboard side .
I've also been straying the stern with water in an attempt to close up the gap between the stern post and rudder post so that I can insert a new stopwater. The original stopwater was 1/2" in diameter. Before starting the spray, the hole for the stopwater was oval shaped having a major diameter of over 5/8". My goal was to swell the timbers so that the hole was closer to 1/2" so that I could drill for a 5/8" stopwater. After about 1 month of spraying (about 8 hrs/day), the hole had shrunk to just over 0.600". At that point, I drilled the new hole, inserted a cedar stopwater, and trimmed it flush.
The next step is to fasten P5.
12/4/2013: After installing the fourth plank on the port side (P4), I decided to fit the fifth plank on the same side (P5) instead of working on the fourth plank on the starboard side (S4). The fit between P4 and P5 is rather tricky, so I wanted to see what I was up against before moving to starboard.
I completed the fitting of P5 but have not yet installed it. As it turns out, P5 covers a stopwater that needs replaced, but it spans a seam that has opened up. You can see the hole for that stopwater in the pic below under 6/18/2013 (upper left-hand corner). So I'm trying to close up the seam using a water spray. While I'm waiting, it's worthwhile to reflect on the mistakes made and lessons learned so far. This is summarized in Reflections on installing the fourth the fifth plank on the port side .
With greater insight (and still waiting on the seam to close), I'm starting to make S4. See Making the fourth plank on the starboard side .
9/23/2013: The fourth plank is now complete on the port side. Read about it at Plank #4 on the Port Side .
9/10/2013: I've completed the first three planks on port and starboard and have started the fourth plank on port. The problem with this plank is that it is (1) over 12 ft. long, and (2) requires considerably more twist and bow than any of the previous planks - so much so that I'm having trouble checking the fit. In addition, since I plan to reuse old plank #5, I have to bevel both top and bottom edges of plank #4. When I finally get plank 4 in place, I'll update this site with all the details. In the mean time, I've prepared a rather lengthy article on planking based on what I've learned so far: Planking a Carvel planked boat . Happy reading!
8/3/2013: Here is the info on stopwaters that I promised. Stopwaters .
8/2/2013: Well it's been over a month since my last post. Since then, I've made considerable progress in planking the boat. That's the good news. The bad news is that it's taking me forever to write about. That's what IÕve been doing for the past few days. You can read about it under Planking the Hull . I also plan to add a short section on replacing the stopwaters - hopefully soon.
6/18/2013: It's time to start replanking the boat. Before I do so, however, I'm concerned about how much the boat has dried out since I bought it. For example, the following pic shows a gap of about 1/4" between the stern post and the rudder post.
I've tried to control the humidity in the garage using a small humidifier, but it just hasn't done the job. In the winter, I couldn't get the RH above about 50%. So before I start fitting planks, I want to increase the moisture content of the backbone timbers (at least those aft) so that they are closer to their working dimension. To accomplish this, I decided to wet the backbone timbers. Here is the setup.
I'm using components for a garden misting system from Lee Valley. The pic above shows the port side. The pic below shows the starboard side. (The beige piping is just a support frame for the misting nozzles.)
The water from the misting nozzles is captured by the plastic sheeting and directed to a bucket. Inside the bucket is a sump pump the feeds the misting system.
This system not only wet down the timbers but it also increased the relative humidity in the garage to over 85%. I had to add about 2 gal. of water to the system every day. After about 20 days of this, the gap between stern post and rudder post decreased to about .095". Here is the gap now.
I also noticed that the gaps between planking all over the boat decreased.
I don't see any point in continuing the misting. Additional changes should be small, and I don't want to encourage rot. (I considered circulating a borate solution but I was afraid it might cause problems for the pump.) So I've dismantled the misting system and I'm preparing to fit planks.
5/27/2013: I've plugged the holes in the ballast that were created when I decided to pull two additional keel bolts. See the following link for details: Plugging the Ballast Galleries.
5/9/2013: I'm finally just about finished with installing the centerboard trunk assembly. See my update to the link Installing the Centerboard Trunk Assembly.
4/20/2013: For the past month or so I've been busy installing the centerboard trunk assembly. If ever there was an example of something that's easier to remove than install, the centerboard trunk assembly has to be it. Not that it was that easy to remove, mind you, it's just that reversing the process was so much harder. In fact, I've been working on this aspect of the project for over a month now and I'm still not done. For details see Installing the Centerboard Trunk Assembly.
3/11/2013: It has been a busy month, but I thought I'd take a break to update this web site. So what's been happening?
First, I discovered that the rudder gudgeon cannot be installed without the rudder. I discovered this when I tried to temporarily install the rudder to check the fit. The problem is that there is not enough clearance for the rudder pintle to enter the hole in the gudgeon. This actually make sense, since otherwise it is possible that the rudder could become dislodged at sea - not good! In any case, the installation of the gudgeon will have to wait until I repair/replace the rudder, which won't be any time soon.
My previous post discussed installing the rudder gudgeon, but I neglected to describe how I drilled the holes for the rivets. So I've now updated the link Fitting the Gudgeon to describe that process.
IÃve now plugged all the screw holes on the starboard side where IÃve removed two more planks. This turned out to be quite a job. For this batch of holes, I decided to plug all of them with 1/4" plugs that I cut myself using a Fuller plug cutter. The problem is that this cutter produces plugs that are only about 3/4" long. The holes to be filled were occupied by #12 bronze screws 2" (into the frames) and 2.5" long into the keel plank. So the holes for the long screws required up to 5 plugs to fill the hole. Overall I needed almost 500 plugs for just 2 planks! This experience leads me to provide yet another update to the Plugging Holes link.
I've also repaired the frames on the starboard side and painted the bilge are in preparation for installing the centerboard trunk. See my update to the Frame Repair link.
Finally, I've installed the centerboard. See Installing the Centerboard
2/9/2013: I've finished all the prep work for installing the rudder gudgeon. I've temporarily bolted the gudgeon in place so that I can check the rudder fit before I install the rivets. I'm just waiting on help lifting the rudder.
I've also finished making the 5 rivets.
These rivet were made using the die shown under Fitting the Gudgeon . In making the rivet heads, I heated the rivet end to red hot and then let it cool. This served to anneal the bronze. I then used a ball peen hammer to form the heads. You form the heads starting with light blows, which mushroom the head. Heavier blows are required to drive the bronze into the die. Note that I did not reheat the bronze while forming the head. It's easier if you frequently reheat, but I wanted to practice what I needed to do on the boat, where reheating is not an option.
After checking the rudder fit, I will bolt the gudgeon in place, using Boatlife caulk (polysulfide) as a bedding compound. Then, removing each bolt individually, I'll replace it with a rivet (end annealed). I'll need someone to back up the opposite end of the rivet with a heavy iron weight as I peen the head.
While waiting for help with the rudder, I decided to remove two additional planks from the starboard side. I did this to gain access to some of the frame ends that needed repair. The frames were steam bent, but at the turn of the bilge were the bend was excessive additional wood was glued to the frame the cut, rather then bent, to shape.
Over the years, the glue failed. So these appendages are now loose. As I have already done on the port side, I will glue these appendage back in place. I plan to use a 50/50 blend of West System G-Flex epoxy and 105/205 epoxy as the adhesive.
The choice of adhesive is always a question that is hotly debated, but I think an epoxy blend is the right choice here. If the application involved a critical structural component or the frame ends were to experience large swings in moisture content, I would use resorcinol. But in this case, I favor an epoxy, with its better gap filling ability. I choose the G-Flex blend over straight 105/205 to provide a more flexible bond, which is better for absorbing the stresses of expansion/contraction.
In removing the two planks, I learned something new about removing stubborn screws. You can read about it at the end of Plugging Holes
1/17/2013: Well it's taken me this long to shape the deadwood to accept the rudder gudgeon. Yes the holidays cut into my work time a bit and we also took a weeks vacation, but still ... ! You can read all about it at Fitting the Gudgeon .
During the past month I also sent the centerboard lift tube out to have the deteriorated chrome plating stripped. Rather than have it re-chromed, I decided to paint it white. Since then I've learned that chrome plating does not hold up well in a salt-water environment unless it done with great care and plated with sufficient thickness. Forget those shops that specialize in auto parts - it just won't hold up, and even the auto-chrome is very expensive.
12/3/2012: Some additional progress on the deadwood ... Progress on Finishing the Deadwood .
11/28/2012: With the ballast and new deadwood installed, the next big project is installing the centerboard. Before I get to that, however, there are numerous mini-projects that should be done first. For example:
... well you get the idea!
I decided to tackle the worm shoes first. The worm shoes consist of three bronze plates about .2" thick, which are fastened to the deadwood with bronze wood screws. Although conceptually a simple task, execution is often another matter. Read about it under Installing the Worm Shoes .
11/22/2012: I apologize for the long delay since my last post. Unfortunately, there has been little to report while I've been waiting for the keel plank to swell. Well the keel plank has swelled, and I'm happy to report that I was finally able to install the new deadwood and the ballast without having to enlarge the keel-bolt holes. Details can be found at Installing the New Deadwood and Ballast .
During this long wait, I have not been idle. Instead I've been doing a lot of reading and experimenting, primarily to try to understand the effect of moisture on wood and the resulting effect on the various adhesives used in boatbuilding. I've also looked at the various coatings that attempt to mitigate these moisture problems. I've summarized these findings under Moisture & Adhesives in Boatbuilding .
Based on this research, I've looked back on my approach to replacing the deadwood. This is summarized under Reflections on the Construction of the New Deadwood .
8/15/2012: Testing feasibility of enlarging the keel-bolt holes
In anticipation of having to enlarge the holes in the keel plank to make it easier to install the ballast, I ran a test to see if I could effectively fill the annulus around the bolts with epoxy. The details of this test can be found at Filling Keel-bolt Annulus . The bottom line is that yes the annulus can be easily filled with epoxy and the keel bolt can be removed afterwards.
8/6/2012: Swelling the boat (yet again)
Well the keel plank has now been underwater for about 3 months. I've been measuring the bolt hole spacing at regular intervals and the results are quite curious. First let's review the situation ... All but four of the keel bolts are embedded in the ballast, and are quite inflexible. The embedded ones (12 of them) are arranged in pairs. Of these 6 pairs I can only accurately measure the transverse spacing of the aft most 4 of these pairs (the mast step prevents me from measuring the others). The bolt holes that I can measure are shown below. The pair between the two floors are the forward most.
The aft most bolts are 12-3/16" apart. Back in May when this process began, the hole spacing was 12-1/16". In just shy of 2 months, these bolt holes expanded to 12-3/16", which is the desired result. Unfortunately, the other holes have not been as cooperative. The worse case is the forward most pair, after 2-1/2 months I could detect no increase in hole spacing - 12-5/8" in May and still 12-5/8 at the end of July, and the target is 12-25/32"! At that point, I began to wonder if it would ever change. Maybe the two substantial floors near these holes was preventing the keel from moving. Then on Aug. 5, I measured a 1/16" increase in spacing for the two forward most pairs. Maybe is just takes a loooong time for water to infiltrate such a large timber? So, I've decided to prolong the soaking for at least another 2 weeks.
While doing all this waiting, it occurred to me that even if the holes line up exactly with the keel bolts, it might still be very difficult to insert the ballast. Even if I lubricate the bolts, it's very likely that the bolts will bind in the holes. I raised this issue with a number of professional boatbuilders at the recent WoodenBoat show. The options appear to be ...
I tend to favor this last solution because of its simplicy and because it make it easier for me to fit the ballast to the new deadwood.
Now all this business of swelling and drying out has me worried ... once I get the keel saturated, how do I keep it from drying out again. This is an issue not just for the keel but for the boat in general. Coating the wood with some type of finish, seems to be called for, but what finish? After reading what has been published about this topic, I decided that I needed to do some experimenting. The study is ongoing, but preliminary results can be found at Moisture Exclusion Test . Unfortuanely, the raw data from Excel isn't legible. I'll try to correct that soon.
6/12/2012: Swelling the boat (cont.)
The keel plank has now been (almost completely) submerged in water for about 6 weeks; however, the bolt- hole spacing has only increased by about 1/16"! I'm concerned about introducing rot with this procedure, so I've strayed borate solution on those areas were the wood is only intermittently under water. I hope this is sufficient. I guess I'll continue for another 6 weeks and see were I stand.
5/5/2012: Swelling the boat - finally!!!
Well after two attempts, I've finally succeeded in building a water trough that doesn't leak (much). Now I can attempt to swell the keel plank so that the ballast and deadwood can be installed (I hope!).
Unfortunately, the first attempt was pretty much a disaster. I didn't put much thought into the original design since it's just a temporary structure. That was a mistake - it not only leaked like a sieve but it started to come apart soon after I started filling it with water. The problem was that I didn't consider the weight of the water and I under estimated the difficulty in making the trough water tight. I put much more thought into the second design, which is described under Swelling the Keel Plank .3/10/2012: Swelling the boat, continued.
I've completed the task of removing the bottom paint - at least all the heavy buildup collected over the years. Some residual paint remains, but I should be able to paint over this easily, since it's well bonded to the wood. I might, however, have to use a chemical stripper to remove the residual in spots where I need to apply epoxy filler.
I also removed the head and associated cabinetry to provide better access to the hull interior. I then vacuumed and washed the hull on the inside to remove as much of the bilge grime as possible.
Since several planks have been removed, I needed to devise a way to contain the mess, while I hosed down the interior. See the link Cleaning the Hull for details.
I'm still undecided as to what do about the hull. So I've decided to postpone the decision until I've replaced the deadwood and re-installed the ballast.
To this end, I've decided not to swell the entire boat at this time, but just swell the backbond - In particular, the keel plank, so that the keel bolt holes align. My plan is to build a shallow wooden trough under the boat that surrounds the keel. I'll fill it with water and let the keel soak.
2/6/2012: Progress towards swelling the boat ...
1/6/2012: My recent plan was to complete installation of the new deadwood and ballast by summer. Unfortunately, I've encountered a major set back that will certainly delay this goal. Here is the problem ...
I finished coating the faying surfaces of the deadwood with epoxy, and so I was ready to position the deadwood under the keel plank and drill for the mouning bolts, using the existing holes in the keel plank as guides. The four most forward bolts are embedded in the ballast, so it's very important that the hole spacing in the deadwood matches the bolt spacing of the ballast.
Well after drilling the holes, I decided to check to be sure that the spacing was right, although I expected them to be close since I was using the holes in the keel plank as guides. To my dismay, the hole spacing (laterally) was almost 1/4" narrower than the bolts in the ballast! How could this be?!!! Then it dawned on me ... keel shrinkage due to drying out.
This explains alot ... for instance, it explains why it was so difficult to remove the ballast, and it explains why there is a big check down the center of the keel plank. The keel shrunk (about 2%) while the ballast didn't.
More importantly, it means that I cannot install the deadwood/ballast until the boat has been swelled. It probably also means that the holes that I drilled in the deadwood will not be correct. Oh well, I didn't think that this project would be easy!
So the goal now is to swell the boat. Exactly how, I'm not sure. I'll probably try to wrap the boat in plastic with a humidifier inside and see if that works. But first, I have to complete a bunch of smaller projects, including:
12/15/2011: I've been progressing on a number of fronts over the past month with the goal of installing the new deadwood, ballast keel, centerboard trunk, and centerboard. First, I removed the scale and old deteriorated paint from the ballast and coated the surfaces with epoxy. See the Ballast Keel link for details. Second, I repaired the damaged frames. See Frame Repair for details. Third, I'm in the process of coating the faying surfaces of the deadwood in preparation for bolting in place under the keel plank. See Replacing the Deadwood . Finally, I think the questions about the check in the keel plank have been resolved. See A Check in the Keel .
11/14/2011: Questions arise with regard to a large check in the keel plank. See the "A Check in the Keel" link.
11/3/2011: The repair to the port keel rabbet is now complete. See the link above for details. This was probably the most challenging woodworking project to date. So with the keel repaired, I can now progress with installing the new deadwood.
10/19/2011: Additional work done on the deadwood (see "Replacing the Deadwood"), and undertaking the repair of the port side keel rabbet (see "Repairing the port keel rabbet").
9/15/2011: Added commentary to the pics under Replacing the Deadwood.
9/12/2011: I've been working hard on replacing the deadwood. I finally have something to say about it. See Replacing the Deadwood.
8/19/2011: I'm still working on replacing the deadwood. I've also done additional repairs to the sternpost. Check progress under Sternpost Repair (Part II).
7/25/2011: I'm continuing the work on replacing the deadwood and repairing the sternpost. I've also decided to reorganize this commentary page, moving the detailed discussions to separte links. Hopefully, this will be better for readers with limited bandwidth. You can read about my progress with the sterpost under the "sternpost repair" link above.
An update on the deadwood replacement will appear shortly.
7/7/2011: Well I've been out of commission for over a month with appedicitis, but I'm back at it now.
At this point, I believe that I've "turned the corner," from disassembly to repair. To "get my feet wet" I'll tackle the repair to the stern post. Follow the "Sternpost Repair" link above for details.
5/23/2011: Ballast removed
The "Ballast Keel" link has been updated.
5/12/2011: Removing the ballast keel (cont.)
See the "Ballast Keel" link for additional progess with this project.
5/2/2011: Ballast keel
It's time to remove the ballast keel. See the "Ballast Keel" link for details.
4/26/2011: Understanding ghost lines and tangent curves.
In replacing the deadwood, I find it helpful to build a 3D graphical model of the piece. That way I can experiment with different construction options before I cut wood. To do this, I use an inexpensive (but powerful) CAD program called Rhino. To build the model, I have to redraw the boat's lines - just that portion the defines the deadwood - in Rhino. This is equivalent to manually lofting the lines, except that the drawing is done on a computer.
The process of lofting is treated in any number of books on boat building or yacht design; however, most of these books only cover the main points. Some of the more subtle points, like ghost lines and tangent curves, aren't covered in most books. So in an attempt to fill that gap, I provide a brief discussion here.
When drawing the body plan of a traditional keeled sailboat, the lines undergo an abrupt transition from the classic hourglass shape of the hull to the flat at the bottom of the keel. Defining this shape using a single curve is difficult, especially by hand, due to the radical change in curvature. Instead, the line is produced in three segments - a fair curve defining the hull, a straight line segment for the flat keel bottom, and a parabola connecting the other two.
To produce a fair hull curve, the architect draws the hull curve as if the keel were perfectly flat (no radius); i.e., the hull curve terminates on an extension of the flat at the bottom of the keel. The locus of points defining these hull-curve terminations is called the profile ghost line (ghost in the sense that it is not actually a line of the boat, but rather a drawing artifact). The ghost line follows the bottom of the keel in the profile plan and appears as a fair curve in the half-breadth plan.
The width of the flat at the bottom of the keel is defined by a keel-flat line in the half-breadth plan.
The parabola is uniquely defined as follows: (1) It terminates at the end of the keel-flat line and is also tangent to it; (2) It is also tangent to the hull curve and the point of intersection is specified by what is called the tangent curve in the profile plan.
This parabola can be constructed in a CAD program using a 3rd order B-spline with 3 control points - one control point at each termination point and the third at the point of intersection of the two tangents.
4/19/2011: I was able to remove the two aft-most keel bolts, which were through bolted. They looked as good as new, so I don't think that I've got a keel-bolt problem. I was also able to remove most of the deadwood, but the presence of the ballast keel is hampering my efforts. It appears that most of the remaining keel bolts were cast in place and two of these penetrate the deadwood. So removing/replacing the deadwood will probably requring dropping the ballast keel - oh goodie! See "Deadwood/Keel" for the details of this "memorable" experience.
4/5/2011: I've now removed the centerboard trunk, exposing the top of the keel. This will allow me to pull and inspect a few ballast keel bolts. See the link "Deadwood/Keel."
3/29/2011: The centerboard has been removed. Another big project. Read about it at Centerboard (revisited) - second half. It's now on to repairing/replacing the deadwood.
3/3/2011: Finally was able to remove the centerboard pivot pin. It turned out to be a rather involved project. Read about it at Centerboard (revisited).
2/25/2011: For some time now I've worried that, after spending a lot of time/money on cosmetic repairs, the boat planking will not swell shut. To me, this would be a disaster. The last thing I want is a leaky boat, and repairing, or even just locating, a leak in a double planked boat with all the furniture in place, would be nearly impossible. So on the advice of several experts, the current plan is to try to swell the boat in place. This is done by building a plastic tent around the boat and using one or more humidifiers to raise the relative humidity to 90% or better. This, in addition to wetting the inside of the planking (most of the interior is now removed), should approxiate the conditions the boat would experience after launching.
Before I can do this, however, I need to replace the bad planks that I've already removed, and repair the damaged keel and deadwood. The keel has several problems: (1) a large check down the middle on the inside which intersects with the centerboard trunk, which is a potential source for a leak; (2) evidence of a large shake on the port side; (3) split keel rabbet. Assessing the extent of damage and affecting repairs would be easier if the centerboard trunk and deadwood were removed. The deadwood itself is suspect, so this is additional motivation for removing it.
To begin, I need to first remove the centerboard. So, that's what I'm doing. See the Centerboard (revisited) link to read about it.
12/13/2010: Just added some pics of the interior, as it was when I took delivery.
11/27/2010: The rudder has now been removed. Check the details at the "Rudder" link.
10/28/2010: The engine is now operational. Check out link "Engine (cont. III)." Also, I've included the work I've done on the propeller shaft and other parts of the drive train.
9/17/2010: Today I've updated what I've done with the cabin sides. See "Cabin (cont.)" for the latest.
9/3/2010: Another month has gone bye. Lots of work done on the engine. The engine has been total rebuilt; however, the first test run failed. I've traced the problem to incorrect fuel injection timing. Now the question is why? Details under the "Engine (cont. II)" link. I still have to update the info on the hull and cabin sides.
8/9/2010: Well I've been neglegent in keeping up this web site; however, I've made substantial progress in the last two months. The engine is almost completely rebuilt. Details can be found under the "Engine (cont.)" link. Because I've been devoting much of my time to the engine, only modest progress has been made on the cabin sides and the hull. You can see (in the next couple of days, I hope)what's new by following the "Hull" and "Cabin (cont.)" links.
6/7/2010: Starboard cabin side has been removed - ready for repair work.
6/1/2010: Prelimiary engine work is now complete. The cylinder walls cleaned up after removing .5mm, so we can use oversize pistons. I ordered $1300 worth or parts, some of which have to come from Japan, so it will be awhile. I continue to work on removing the cabin sides.
5/26/2010: Well it's been awhile since I've added content to this site. I guess I've been too busy working on the boat. I'm currently working on several fronts:
1) Engine: The block is still at DL Automotive to be be rebored and the head reconditioned. I've located a source for parts, so when the block's done, I'll start rebuilding.
2) Hull: I removed five planks on port side from the garboard up. See the 'Hull' link for details.
3) Cabin trunk: I've decided to remove the cabin trunk and repair/replace the sides. See the 'Cabin' link for details.
4) Toe rails: Force from the genoa track has lifted the toe rails, so they need to be repaired. I started to remove the port toe rail to see what's involved. See the 'Toe rails' link for details.
5) Centerboard: See the 'Centerboard' link for my progress on inspecting the centerboard.