Tabu

Been in my shop a lot lately and have some images of my progress.

First image is the mast frame stretched across my bench and table saw.

Second image is the mast with one side covered (half mast?)

Third image is the mast construction finished BS (before shellac) with diamond stays in place

 

Just for interest's sake, what does the mast as rigged weigh? If it weighs dramatically more than 20 pounds, you might want to consider a used aluminum mast lying unused in the grass at a local sailing club. Weight aloft is a huge factor in sail-ability and capsize recovery, and the complexity of the rigging shown will be a huge factor in tuning the boat for speed.

Aerodynamically, the mast you've built is a fencepost (albeit a nice one built by a craftsman). This was accepted back in the day, as materials were what they were, and aluminum tubes were very expensive. You could buy a used Thistle, Flying Scot (or whatever) aerodynamic aluminum mast lying unused for next to nothing and have far better performance potential and far less rigging & wires aloft.

This one change in your design could make a huge difference in your enjoyment of your Tabu. (And you would already have a spare mast). I bought a couple used 505 masts for under $100 each, and they would be perfect for your boat. I'm sure there are folks in Arkansas that could help you make your rocket ship really fly.

Don't be afraid to diverge from the 1972 build plans you've got, especially if the change will make orders of magnitude improvement in the fun you have sailing the boat. I'd also consider finding a used mainsail of the appropriate size that is designed for purpose. A five year old used sail available for next to nothing will typically outperform one you can make yourself dramatically. If I were in your end of the world, I'd sell/give you a 505 main for your project. I'm sure there are folks locally who would contribute to the project.

I live in Canada, so cross border shipping isn't worth it.

 

Bistros
Thanks for your input! The mast weighs 25 puonds fully stayad and presents only 1 3/4" frontal area and 4 5/8" depth, tapered to 3/4" aft. Comparitively it may be a fence post but one of my main objectives is to build the boat in its entirety by myself. If when finished I find the desire to improve performance, I will surely investigate your suggestions. One modification I will be making to the plans is to seal off all but the cockpit into water tight chambers so that WHEN I capsize, the boat will float high and retain a minimum of water when uprighted that will be attacked with a 4 stroke per gallon manual bilge pump kept handy in the cockpit. My father has a friend working as a research chemist at Dupont who throws away carloads of mylar type substances I can use to experiment with as sail material. Thanks again!
David

 

I completely understand and support the 100% built-it-yourself concept.

In regards to capsize flotation, it is entirely possible to have too much flotation - making the boat hard to right and easy to turtle. If the boat floats too high on it's side, the daggerboard is really hard to grab from in the water, and again really hard to pull yourself out of the water to climb on the board to right the boat. I'd also consider testing the daggerboard for adequate strength by putting it in a horizontal clamp and then standing on it. The daggerboard design pictures from the site don't look extremely strong.

Remember that enclosed air chambers MUST have a tiny pressure relief hole of some kind, or changing ambient temperatures could cause your boat to blow out a chamber as temperatures climb. Air tight inspection ports aren't enough.

A clever guy like you could make automatic bailers that could empty the cockpit just by normal sailing, so the manual pump may not be necessary.

Have you found a source for the "Dynel" fabric? It looks to be discontinued and not commercially available. Are you just using glass or polyester cloth?

My "fencepost" metaphor was referring more to the stiffness of the mast than the profile. Masts generally implement controlled bend, allowing them to de-power sails in windy conditions. Bend control is dependent on direction of bend as well - you don't want a mast inverting under spinnaker, but you may want some side to side tip bend and certainly do want the mast to be able to bend aft so the the cunningham pressure can flatten the sail by induced mast bend without closing the leech.

Cheers,

Bill

 

And what is that thing sticking out of the wall in your shop? Air conditioning?I doubt I've got enough points with my wife to have that! By all means you look really well equipped and better yet organized.

I noticed a local product built here in Ottawa, Canada in your shop as well - the Veritas wood vice. I'm lucky to have Leonard Lee's head office/store and tool making facility for Lee Valley tools and Veritas design manufacture locally. I spend a lot on tools there.

 

You guys are just too good to be true in sheparding a beginner in building a sailboat - you are all welcome to go for a ride next spring! To reduce costs by almost 50%, I plan on not placing Dynel or any other fabric on the boat. That will reduce hull weight by about 50 pounds. Second generation Dynel is available from several sources. As far as mast stiffness goes, it will bend quite a lot in all directions without stays and I suppose that it will take a bit of tuning the turnbuckles to reach the best flexibility factor once in the water. The daggerboard does seem a bit delicate and may need to be rebuilt - thanks for that tip! My thought on flotation chambers is that when it capsizes, if the boat floats high it will retain less water when righted than if it rides low on its side. Air chamber relief is another thing that skipped my mind. I can install one way valves topside. I was presuming that because the mast is mostly hollow it will float and thereby avoid turtling??? Would it be possible to climb on the boat from topside (sideside while on its side) and climb over to the daggerboard? I've done a lot of Laser sailing and like the self bailing there but that requires the floor of the cockpit to be above the waterline - is there another way? I would like to sit in the boat at times instead of always sitting on the boat and cockpit depth is mighty shallow as is. And, last but certainly not least in the subject of sail track. All plastic sail track that I have found comes from overseas. C-Tech in New Zealand has 9 meters of it for $40 and freight is the same totaling $80 delivered. Is there a domestic supplier? And yes, that twin screw vice is a dream.

Thanks for all your help!!!!
David

 

Thoughts:

1) I'd really consider adding at least a very light layer of fiberglass cloth to the outside of the hull - 4 ounce e-glass is about as light as it gets for a hull, and cover it with epoxy resin. Plywood alone, especially unpainted will not last, and the slightest bump/scratch will quickly cause hull failure. A light layer of glass with a very light epoxy coating, may add 5 to 10 pounds weight, but 5 to 10 years of life to your boat.

In addition to the surface protection, the glass layer will add stiffness to the hull, making it far more likely to perform well. Hulls that deform by hydrodynamic pressure ("oil-canning") are slow and have trouble maintaining a plane - soft hulls are slow hulls. You may pay a slight weight penalty by adding a glass layer but you will get a big performance boost.

2) Do build the daggerboard to sustain your weight standing on it. If the board can't hold your weight when clamped in a fixture that simulates the daggerboard box in your hull, it won't work on the water and you'll be effectively needing a chase boat to help in event of a capsize. Basic safety rules demand that this MUST work.

3) One way valves are not the right way to go. A little one sixteenth of an inch hole (or smaller) is all that is needed. Each chamber should have an inspection hatch to allow you to use a sponge to dry any water that enters. Each tank must be coated inside with epoxy resin or the like to waterproof it, else you will be rotting within the season. Most folks advocate for transom drain plugs in hulls, but I think they are more of a water ingress point than egress. Remember to drill & epoxy lowest point limber holes allowing water to flow to the lowest point in each chamber for sponge removal.

The 1/16 hole is needed for pressure changes in both directions - up and down. A little hole like this will not effectively be a problem in a capsize.

4) Automatic bailers like the Elvstrom bailer operate below the waterline when the boat is moving fast enough to cause a vacuum behind the bailer opening. Google "Elvstrom Bailer" for a diagram. You do not need bailers to be above the waterline (effectively scuppers). All dinghies from the era of the Tabu used these bailers, and all had sit in, not sit on cockpits.

5) I've heard of folks running a thin kerf saw blade down one side of a plastic pipe to create a sail track, and then s.s. screw/epoxying the pipe to the mast. Given your cost objectives, I'd think about innovate ways to solve the problem outside the traditional marine supply route.

6) As far as capsize recovery goes, a hollow mast MAY provide enough buoyancy to prevent turtling, but it may not provide enough buoyancy to allow climbing on the hull from the inside. It really depends on the amount of buoyancy provided by the mast. The lower the boat floats on it's side, the easier it is to climb on and right. If your cockpit is fully enclosed, water shipped is limited.

7) If your daggerboard strength is suspect, adding righting lines that allow you to stand on the board close to the hull, while leaning out further on the lines may be if use. You just do not want your board to break on the water, or you will be flagging down a power boat for help.

Hope this helps!

--
Bill

 

Bill

For all the reasons you mentioned I've decided to add fiberglass to the hull. Fibrtglass as opposed to Dynel because it is stiffer and poly resin instead of epoxy for the same reason, its stiffer, not to mention less expensive.

Your concern about the daggerboard's structural integrity prompted me to do some testing. I clamped it to my workbench and from a stepladder gingerly stepped on it where it projected from the bench - no signs of trouble. Then, holding tight to the ladder, I moved my other foot onto the test subject with no signs of failure. I hesitantly moved out to the tip and still no problem. I bounced on the tip then jumped up and down and it passed the Bill test with flying colors. I had my doubts but now i can build the well without having to rebuild it to accommodate a stronger dagger.

Now that I Know the principle of an automatic bailer, it seems a simple pipe from the cockpit that sweeps down and aft with the end cut nearly parelell to the bottom of the boat, sealed in the cockpit with a plumbing waste cleanout plug might work.

The PVC pipe as a sail track is genius - simple, inexpensive, effective.

As far as righting lines go, I have always thought a trapeeze would be soooo cool on the boat. I spent a little time on a Star and found trapeeze work to be really exciting. Yes, I will add righting lines for sure!

The image is the first layout of the structural bits and pieces on my shop floor. Where did all the room I used to have go?

 

Lots of progress and all of it good. You could experiment with the bailer designs a little to figure out what works and moves the greatest volume of water at various speeds -an excuse to get out on a motor boat as well.

I really think you won't regret the glass layer on the boat.

There is no reason in the world you can't rig a trapeze up for fun. I sail a single hand trapeze boat with a big asymmetrical spinnaker and you CAN do it. Lots of people may think a trapeze is too complicated for single handing, but it isn't. Longer tiller extensions made from bamboo (one for each side) is all that is really needed. A trapeze will greatly increase the wind you can sail in, and greatly increase the speed potential of the boat.

Great to hear the board is strong. That's the kind of question you want answered before you leave the shore. You might want to glass the board as well - cheap protection from damage, and it won't affect appearance at all.

--
Bill

 

Progress

Some Progress has been made on Tabu. She is in false assembly now (assembled with screws but no glue) for fit and fair operations.

 

Thank you one and all (especially Bill) for all of your comments and suggestions. After reading Bill's comment on "oil canning" I did some research about that quirk and found the best way to aviod it is to have a very stiff bottom to resist deflection. Luckily Tabu is in false assembly and easy to take apart so taking apart is what happened. The plans call for a keelson that is fragmented by the dagger well and assocoated supports in addition to the mast step. A bed log is called for that spans the fragmentation. The original keelson and bed log was made of white pine for minimum weight but seems to be inviting the oil can. In reconstruction, the original keelson has been replaced with tight grain, quarter-sawn southern yellow pine. Married to both sides of the assembly is now a pair of 3/4" strips of similar yellow pine from stem to stern. Just for good measure another pair of those 3/4" strips widen the keelson within the cockpit. Additionally the fore and aft enclosed sections are cross braced with small diameter bamboo poles to stiffen the entire boat. The cockpit flanks are also bamboo braced. I am hopeing to forstall any major oilcanning. The new spine is a heave one and may improve the righting moment

I have reversed my intention of fiberglassing. Instead, I will laminate heartwood strips of eastern red cedar to the 1/4" mahogany plywood then cover it with 6 coats or spar poly waiting 2 weeks between coats. This will eliminate the stringy look of clear fiberglass coatings (I do want the wood to show through)

Being thoroughly convinced that Tabu will not be the fastest boat on the water, I want to make it one of the prettiest. After all, I have always chosen pretty gals over fast ones if the chioce had to be made.

 

Sawdust;
Light weight is good for go fast stuff. Drilling all those holes in the frames will not save much weight unless you are measuring in ounces. I do agree that the perforated panels are sexy looking. I might have done that myself were I building such a boat.

I love scows (I have owned M20s and Es) but I do not have any delusions about their ability to best more sophisticated types. I think you are safe enough with what you are doing because there are probably not many 49ers, I14s, Aussie 18s, or FDs to contend with in Arkansas. Keep on making sawdust.

 

The boat looks like a sweet project. Put a trapeze on it and a big assym spinnaker and do speed runs down the lake!!!

 

Thanks messabout and the future. The holes are sexy but the stiff keel has added more weight than the holes took away and will probably add more speed and stability. Bicycles, cars, airplane wings are always performance and response enhanced through stiffness. Tabu will be mighty stiff! Cant wait to show the bamboo bacing i'm now installing to that end. So much bamoo it looks like a panda farm. Maybe I should call her Panda Paradise? Even if it doesn't perform as intended, it will add the the holes as a cool factor and promote lots of questions at the dock.

I'm particularly happy with the rudder appendage - all wood including the pintles and gudgeons. Better get out to the shop and make some sawdest so I can turn all this talk into pictures to show yall

The future, i do intend to have a trapeeze or 2 but my biggest thrill is as Bob Seeger says "runnin against the wind" - i do love to point, hiked over with my back splashing across the water. Might not be going as fast as the other guys but the "sense" of speed is a rush!

 

The fine craftsmanship on your project is apparent. All of us respect that ability. Building boats is a labor of love and you are creating a real sweetheart. Never mind that it may not defeat a 49er, that is not the point. It will certainly give you some satisfaction to build and ultimately great joy to sail.

About the mast....You can make the mast with two halves joined down the fore and aft centerlines. Half an inch forward of the trailing edge, on the interior surface, rout out a groove about 5/8 inch diameter (5/16 per side) the entire length of each half. Now plane or rout a little of the trailing edge so that a slot is formed when the halves are joined. The bolt rope of the sail luff will fit into the round grooves and the sail will exit through the slot. At or near the base of the mast, cut away part of the trailing edge, a bit forward of the grooves, to get an entrance to the bolt rope slot. Judging from the pictures of your work, you can sure enough build a fine mast without resorting to hokey stuff like PVC pipe or sail slides. Plane some shape into the outside surfaces after joining the two halves. It can have a streamlined section that will be worth a little bit of speed. You will have installed a round rod in the base of the mast so that about an inch and a half protrudes from the base. The mast is now capable of rotating. The pin will fit into a base plank on the keeson that has several holes fore and aft to accept the pin. With this arrangement you can select the appropriate hole in which to step the mast. That will be handy when tuning for helm balance. Attach the shrouds at a point on the mast that is forward of the pin location. The mast will now auto rotate. Rotating masts will add some more speed, I promise. You will have to arrange some kind of stop mechanism so that the mast does not over rotate. Over rotation will cost speed. If there are some Hobies in your neck of the woods take a look at how the standing rigging is done.

Masts made in the way described are, or at least were, the standard way to go before aluminum masts became the norm. Controlled rotation is well worth the effort it takes to make it happen.

Forgive me if I have laboriously described things with which you are already familiar. Keep up the good work.