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CS17 #370 Peggy-O


LennieG

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I took a step back in last 10 days instead of plowing ahead and rushing, and accomplished some things that will really pay off for me in future. I took the centerboard back to the millwork place and they took another 1/16" off and got it completely flat at 1 1/16" width. Also, I bought a few old stanley planes on eBay per advice here, learned how to restore and sharpen them right and also same with my drawknife and wow what a difference. I have used planes before but had never taken the time to really understand and learn them (like bevel up or down? on Stanley No 4 stuff etc).well, I spent two hours shaping the CB by hand today and what a pleasure! Both the drawknife and plane glides right thru the wood, taking a consistent and controllable slice off. Felt like a craftsman today. Very pleased. There will be mistakes but gained much knowledge and craft and that's what it is all about for me. Hopefully the "handle" is properly glued to the CB .......the pipe clamps didn't work as they kept sliding due to the angles and couldn't figure out good clamping system, so I used four inch screws sunk in the handle by inch. Wasnt seeing much squeeze out by that point. We'll see......post-3404-0-86642100-1386022526_thumb.jpg

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If yo try to explain what you just experienced to some one who has never really used hand shaping tools they will look at you like you are nuts.  They can't imagine that technology simply has not replaced everything.  BTW,  lay you plane on it's side when not using it, not resting on the iron.  Much less chance of damaging the edge you worked so hard to get, or even worse that you may ding it.

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Although there was a gap between CB handle and CB in places, the handle seemed to be secure. Removed the screws, drilled out holes and sunk and glued 6 dowels through handle into CB . Almost completely shaped and will be fiber glassing CB later today. Moving onto to seats. Will epoxy tanks today and fit seat tops. I assume best to butt block all seat tops away from cockpit then attach each side as one long unit, and can be done prior to trunk installation.......post-3404-0-35122400-1386164124_thumb.jpgpost-3404-0-93911000-1386164221_thumb.jpg

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I never had to butt join all my seat tops.. It came out perfect where all the "ends" where centered over framing. For the front seats/storage area that is supposed to be a solid piece with the side seats, I made the plywood two separate panels, so later I could unscrew them if I decided to put some clever device or container in like others do.

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Lennie: As you finish shaping the board, prior to glassing, keep in mind one of the most important rules in building foils, and that is the trailing edge needs to be sharp, with virtually no rounding of the edge. If there is any rounding at all, as water passes the trailing edge, it will try to wrap around the corner, and in doing so, create drag. Can't tell from your photo if that is the case for your board, just offering a reminder.

 

A consequence of the thin trailing edge (never a point), is that it can be a bit fragile and subject to dings and dents. One way to avoid that problem is to allow the glass cloth to lap past the trailing edge a bit. After it kicks off, you can back fill the gap between the cloth layers with epoxy. Once that kicks off, you can trim it back a bit, then plane the trailing edge square, straight and true. That way, your thin trailing edge is capped with epoxy to fend off any damage to the thin, sharp edge.

 

I've not seen the specs for your board, but from the photograph, the trailing edge appears to remain a little fat. I would think for that board, it would be no wider than 3/16 to 1/4 inch.

 

Looks like you did a good job on the lifting arm. The wood will probably give out before your joint does.

 

Don't know what your plans call for, but on the Princess, in areas like the decking that run the entire length of the boat, plans insist on using butt blocks on the underside to join panels and doing it well away from any support structures like bulkheads. It specifically says not to join panel ends over any support structures. You may want to check on that before you go too far down the road.

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Howard- thanks very much! I think I get what you are saying, and had no prior knowledge of your points.( we always said in business that part of the learning process was first knowing what you don't know......that is where you have brought me on these points) I did not get to the glassing yesterday, and thankful for that.......I will now proceed with improved understanding. thanks.

It always amazes me how we set plans for a week or even for a day with lofty ideas of the rate of accomplishment and they rarely turn out to happen. Yesterday I spent four hours and it is hard to account for the time versus what I thought I would get done, but I will say that every minute was enjoyable, relaxed and making forward progress- I wouldn't change a thing.

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I like to wrap the trailing edge, from each side with fabric, knowing this must be done over a well rounded edge, which beefs it up with more fabric (ditto the leading edge). After it's sheathed, I use thickened goo an mold a trailing edge, usually about a 1/4" wide on it's trailing edge and as mentioned ground flat, when cured. The leading edge can receive several treatments, such as the saturated rope trick, mentioned by many here, though a strip of metal or plastic can work too. One trick I've used recently is using stone dust (yep, rock) as the thickening agent on the leading edge. Decomposed granite, pulverized sandstone, etc., there are many choices and they're cheap. Mix it so it's a non-sagging batch and slather it on the leading edge. When it's nearly green, shape as best as you can, as grinding this stuff when cured will test your tools, so think diamond saw on an angle grinder, which works well. The stone edge is really tough and if impacted hard, might crack (really hard shot), but it remains in place and is easily repaired with more goo.

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To expand on Paul's comments, a durable and well shaped leading edge is every bit as important as the trailing edge. Of the two, shape of the leading edge probably being more important than what it is made of, but unless it is capped with something durable, it won't maintain it's shape, so both are important considerations. The best possible performance is going to be achieved with the theoretical perfect foils. Anything less than perfect foils will result in a performance drop off that will relate to how far from perfect they are. In hardcore racing fleets, where the skill level of the sailors is generally all the same, a guy trying to compete with less than perfect foils.......that is old or blown out sails, poorly shaped CB's and rudders, won't stand a chance.

 

Since most of us are recreational sailors and not hard core racers, this is not as critical, but if you want the best possible performance, doing a good job on your foils is an important issue. Would be a shame to turn what could be a really well performing boat into a dog simply because the builder didn't do a reasonably good job on the foils. This is one area where the extra effort to get it right will really pay off.

 

The good news is most boat plans outline the basic shape for CB's and rudders, and 3 dimensional measurements that allow you to build them. Bad news is unless you have a basic understanding of how foils function, as you start cutting and shaping, it is easy to unintentionally build in problems that are going to inhibit performance down the road.

 

Unless you are going with flat plates, CB's and rudders are shaped to resemble foils or wings. This is not a by guess or by golly shape developed by approximation. A foil represents a complex 3D shape that is developed from a set of mathematical computations.

 

I have attached a set of tables that could be used to build a rudder or CB. These are the mathematical constants that are used to develop the basic shapes. This is a 10% table, where the thickness of the foil is equal to 10% of it's length.  For example, a CB that is 10 inches from the leading edge, to trailing edge would be 1 inch thick. Offset x is the percent of distance from leading edge to trailing edge. So the .3  position would be centered 30% or 3 inches back from the leading edge on a board with a 10 inch chord. That is also the widest or fattest part of the board. Offset y is 1/2 the width of the board expressed as a percentage. So at the .3 position, 1/2 the width would be 5.002 or 5% of chord. So for our board with a 10 inch chord, it would be 5% x 2 = 10% or 1 inch at it's widest point. All other points work the same way. Loft out the points, connect them with a batten and that is your overall shape.

 

Because we already have a basic shape sketched out for us in the plans, none of this matters much, but there is one number on that table that does, and that is the L.E. radius = % of c. Translated, leading edge radius expressed as a percentage of chord length. For our board with a 10" chord, that would be 1.1% of 10 inches, or .11 inches. Twice that gives us the diameter of .22 inches, which in my book, is awfully close to .25 inches or 1/4 inch. So the leading edge is actually part of a circle.....more specifically, 1/4 quadrant of a circle.

 

So, if you wanted to build a perfect leading edge for that 10 inch board, you could glue onto the exact centerline of the leading edge of your blank prior to shaping, a 1/4" piece of epoxy impregnated rope. Perfect shape and durable to boot. Because the trailing edge of the foil that is calculated to intersect at only one point, which we have already stated is bad, if you trim also trim a quarter inch or so off the trailing edge, such that it leaves a thin, sharp trailing edge, the chord measurement pretty much stays the same, or close enough for our purposes not to matter.

 

Keep in mind, this is a 10% table, which it pretty typical for most CB's and rudders. For each % of chord, there is a corresponding table. For example 8%, 9%, 11%, 12%, etc. Not only are the offsets different, but so is the radius of the leading edge.  Thicker boards, such as one at 12% of chord, generate more lift, but create more drag as you pick up speed. Works similar to flaps on an airplane. For takeoff and landing, full flaps to generate maximum lift at slower speeds. Once airborne, the pilot will adjust the flaps to flatten the wings as the plane picks up speed. Sailors to the same thing when they adjust the draft of their sails to adapt to wind speed. Since we can't adjust the flaps on CB's and rudders, they are generally designed to give the best performance at average speeds. Fast boats like most of the B&B designs can use much thinner foils than slow fat tubs that are fighting weather helm when the wind pipes up. The downside is the thinner foils don't start to generate much lift until you get up some speed, so in a drifter, or coming out of a tack, the rudder may not be as responsive as it would be at speed.

 

If you are wondering what naca 00xx percent your board might be, it is easy to calculate. Simply look to the plans to see what the distance is from leading to trailing edge and that is the length of chord. Then look to see how wide the blank is supposed to be prior to shaping (about equal to 30% of chord) and that would allow you to calculate it. The rudder on my current boat has a 12" chord and is 1.5 inches thick, so is a 12.5% board (1.5 / 12 = .125)

 

If you didn't want to use the rope trick and wanted to use thickened epoxy as Paul suggests, that will work equally well, provided you have a means to shape it and good eye to match such that you don't end up with a sloppy job and bad performance that goes with it. I've never attempted to use it, but our local ACE Hardware sells a balsa cap that I believe is intended to be used on the leading edge of model airplane wings. If not for the fact it is made from balsa and is not durable, you could use it as it.  Or, if it was about the right size, you could use it to create a mold that could be filled with thickened epoxy and glue that onto the leading edge. Since all you need is a quadrant of a circle, there are lots of options, providing you can match up the size of the round object to the diameter you need. Stainless steel rods come to mind. Route in a shallow depression to keep the rod centered, then glue it in place. When ready to glass, pack in thickened epoxy on the sides, leaving on the leading edge exposed. Whatever you put up there, the key is to make sure it is straight and centered.

 

As for shaping the boards themselves, provided the board is going to be built from a rectangular blank, the method that Alan posted a link to which demonstrated using a router riding on foil shaped jigs is the best option I've seen. I can't see how home builders can improve on that. Simple and effective. The next best option I can think of is to cut out a shaping blank from thin plywood, using the foil outline provided in the plans as your guide. Cut that out to perfect shape, then use it to find your high and low spots as you start shaping the board by hand. A good shape and symmetry is the goal.

 

Tapered boards, on the other hand, are a different issue. Because the boards taper from top to bottom, no one router jig will work. The % chord is infinitely variable as you progress up and down the board. The foil shaped jigs don't work either as again, there are an infinite number of chord widths as your progress up and down the board. The best method here would be to use a CNC cutter, but those don't grow on trees. There are companies that will do that for you, but boards from them start at around $1,000 and go up from there. Hard to justify that, so the best option is do the best you can and try to live with it. If not, do it better the next time.

 

BTW, I was going to use Paul's suggestion to include rock in the epoxy bushings for my rudder cheeks, but got to thinking how hard it might be to drill through the rock for the bolt holes, so decided against it. Went with cabosil and wood flour instead.

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I wouldn't use stone dust on a bushing or bearing area, like a pivot, as it's hard to drill, but more importantly will likely eat up whatever you use as a pivot like a bolt. A diamond blade in an angle grinder is the tool to use shaping this stuff and it goes through like butter (or bathroom tile). In fact, I use this same style of blade for a lot of 'glass repairs or modifications, as it's far superior to a cutoff wheel, less dust too.

 

Foil sections and plan form shapes can get mind boggling very quickly. It's true a foil will do better than a radiused leading and tapered trailing edge shape, but not by much, unless racing identical boats all equally well handled. On a CS, the difference might be a 10th of a knot. The real trick is to use a set of shapes, that give you what you want at the speeds you'll be moving. The CS series can't go wrong with the 00 NACA sections, which will provide good lift and stall charistics across a fairly wide range of speeds and incidence angles. At the upper end of her performance envelop, the 00 series may be a bit more draggy then desirable and a 63A series might be better, but you'll pay for this at lower speeds and it'll stall sooner. Considering the CS's windward abilities, the slab sided foil shown on the plans will do just fine, with a 00 section offering just a wee bit more, which will be hard to tell from skipper error, sail set or plain old helm sensitivity, because your hands are cold from holding a beer. If you wanted to get real anal about foil sections, I'd use a surface piercing section at the root (H-105 maybe), transitioning through a few 00 sections in the middle of the blade, eventually ending with a 64A series on the tip. The average skipper wouldn't notice the difference between this and a straight up 00 section and possibly the slab sided section on the plans, but a good dinghy sailor would notice at the upper end of the performance envelop.

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I have not seen the CS plans, so assumed they were thinner foils in the 0008 range. If they are mostly slab sided, with rounded leading edge, then by all means, stick with the plans, which when you think about it, makes for a good mantra to follow anyway. :)

 

But even then, it is a good idea to strive for symmetry and to get them fair. If not, you will know it soon enough. It will vibrate on you something fierce.

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Man, wow. I definitely am learning what I don't know. My head is spinning. I really appreciate the time , effort and information provided.

I honestly think that what is practical for me is to proceed with a "fudged" foil, best effort without getting bogged down with precision, get the boat built, see if it floats, and then build the perfect foil later as a project unto itself. I have invested in my shop beyond a one boat project, and when Peggy-o is launched I will seek new projects. The perfect CB will be high on my list. I don't understand the intricacies of the CS17 at this point but assume the CB is removable and replaceable .

Thanks very much.

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Agreed. A good analogy is to think of a set of car tires. Two otherwise identical tires.......one is balanced and one is not. One is aligned and one is not. The driving experience of a thumping tire constantly pulling to one side is not a good one. But apply a few simple tweaks and everything changes. It is almost that simple, and yet the difference is almost that dramatic. They don't have to be fancy or perfect, but symmetry is important.

 

Probably the best test is when you are sailing are you even aware the part is there. When you drop your CB, the only thing you should notice is you are pointing higher and going faster. If some type of thumping or humming develops, something is not right. Same with the rudder. Ideally, your only contact with the rudder is through the tiller. You push or pull on the tiller and the direction changes. Beyond that, you shouldn't even know you have a rudder.  If you let go of tiller, nothing happens. On the other hand, if you constantly feel a shimmy or vibration, or when you let go of the tiller, it swings wildly to one side, something is not right and your sailing experience is not going to be a good one. Good symmetry will alleviate most of that.

 

The difference between foils with good symmetry and those without is as dramatic as black and white. The difference between those with good symmetry and those with good symmetry and perfect shape is shades of gray. At the very high end, shades of gray matters. For the rest of us, not so much.

 

And yes, you can always remove and replace either one, so don't fret over it. This could be one of many tweaks you may want to make once you splash the boat and get to see and enjoy what you have built.

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Appreciate all the help. Sloshing along at a snails pace, but making forward progress. Couple questions below. I've glued on four of six seat tops with drains. Plans call for PVC pipes but found those a bit rigid so went with a softer tube for easy installation. Bought drain adapters and tubing at West Marine ( good suggestion Steve) . Like the adapters as they have a nut on underside for easy installation and tightening and I like the finished looked of them. If the fact that they are raised causes a problem I can cut them flush with the multi-master. The nuts below will hold them firm.post-3404-0-17982100-1386883934_thumb.jpgpost-3404-0-98415200-1386883961_thumb.jpg

Working on shaping CB and assembling and gluing up components of the seat hatches. Little confused by the hatch puzzle.

In the attached photo it mentions "outside coaming Outboard". I cannot find any such part amongst my kit components, or numbered reference in the parts page on plans, nor dimensions to make my own. Anyone have a thought or can you point me to a thread that might have photos? The photos that came with the plans don't help.

Also, I went a bit deep in shaping the CB in a couple spots. What is best goop to fill in with? Peanut butter type fillet material, micro balloons or some kind of fairing compound?post-3404-0-59370300-1386884633_thumb.jpgpost-3404-0-54198000-1386884668_thumb.jpg

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When I got my combing parts on my CS-20 Mk-2, I was a bit confused too, but dry assembling the parts soon showed me what was what. Just look for little pieces that fit where the drawing says "outside combing outboard" and "inside combing outboard". The "outboard" in both cases refers to the side facing the outboard side of the boat. Could it be that these parts are missing from the kit? Maybe in the future, Graham could include an exploded view of this assembly.

 

I would just use micro-balloons or Q-cell and epoxy to fill those low spots. You don't need the strength of cabosil as a filler---it's too hard to sand to fair it in anyway.

 

I would definitely recess the drains on top of the seats. I like to epoxy a short section of pvc pipe to the backside of the top before it is installed on the boat, with a good fillet around it on the bottom. You can use a section of hose over that for your actual drain line. The pvc goes through the plywood seat top and is flush with the top. To me, that is easier than trying to recess a plastic drain fitting.

 

"Sloshing along" is fine. Better to do that and not get "burned out" trying to rush it. Take one step at a time and enjoy your project.

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ChuckA

I have been dry fitting but not all coming together yet. I am sure it will. I do think I am missing a couple things perhaps although the fact that that part is not on parts page throws me a twist. I have everything that is on the plan parts page, all numbered and understood. I have called Graham and emailed him and I know he will clear it up as he always does.

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Rather than drains in the cockpit seat tops, the traditional way to handle boarding water on the seats is a waterway. This is little more then a channel at the back of the seat, so water has a place to live and drain away when the boat is underway. It doesn't have to be especially deep, with a 1/2" being fairly common. When a boat is heeled the water tends to collect at the lowest point along the seat backs, which on a CS series will be about where the thwart lives. A shallow waterway "valley" there and one at each end of the seats will permit water to drain off, when you change tacks. No moving parts, no holes, no hardware, just a channel for water to escape through.

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Yes, now understand that well. Graham mentioned in an email that he wouldn't bother with seat drain when using the hatch on seats. That wasn't clear from plans to me, or that hatch was considered optional. It's common sense I guess but not on my first boat. Maybe he'll add that point on future plans. Also I have learned that the outside seat coaming is not ply wood but dimensional lumber....got it. Maybe reading this will help future builders.

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