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Tom Lathrop

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Everything posted by Tom Lathrop

  1. If the glass seems to be "floating", you have put on too much resin and need to squeegee it around. It is too dificult to roll epoxy on without getting too much on in some areas so a squeegee (a rubber one is best) should be used to put on the minimum required to completely wet the cloth and the surface below. There is way too much concern about bubbles in the resin. I defy anyone to mix epoxy and apply it without creating air bubbles. The only time they are a concern to me is if they are in the finish coat. Think about it. Lots of boat construction materials are purposely full of air. Foam, Nomex, microbaloons, balsa, etc., etc. Air ok, water bad! Protect it and seal it and it will be fine. Keeping epoxy in a box that is heated with a small light bulb is a good idea in colder times. Makes pouring or mixing easier and prevents crystalization of the resin. I store the containers of epoxy in use in a wooden cabinet with a 40 watt bulb. Smoothing out the dry glass cloth over the hull is best done with a wide soft brush to avoid the snags that happen when you try to move it around with your hands. I have a draftsmans brush that works great.
  2. John, Put "knife suppies" in google and lots of sources will show up. Koval has finished blanks for sale. I looked for someone (internet, magazines, knife shows, etc) who would make custom unfinished blanks for quite some time but never found anyone who would do that. I did find one really fine knife at: http://www.knifecenter.com/kc_new/store_detail.html?s=lin4970 Liz bought this one for me for my birthday. One main thing I wanted is the straight cutting edge. This is a real heavyweight, can go through an old 1/2" nylon line in a single swipe and comes with its own marlinspike in the sheath. I don't like the sheath it comes with and plan to make my own. I am never without such a knife on my belt unless the social occasion demands it. I made the one I now use (along with a couple of kitchen knives) from an old table saw blade. It works great but will not hold an edge very well since it is not properly hardened, a process I have not yet learned.
  3. Andersen bailers are great for slurping the water out, usually even on a beat. One word of caution. If you leave them open on the trailer, Make sure that you close them before launching or sliding on the trailer. If you jam the aft end of the bailer into something solid, the bailer will distort and it may leak a bit forever. In a pinch, axle grease from the wheel bearings will help seal a leaking bailer.
  4. Bubbles is not a result of the brand of epoxy. To attempt an answer to your problem we need to know what the application is (coating or filet) and whether the epoxy is thick or thin, fast or slow hardener, whether any filler is involved and how you mix it. Large bubbles should not exist in cured thin epoxy but are difficult to keep out of thickened epoxy like that used in filets.
  5. Most store bought furniture has a sprayed lacquer finish since it so easy for a manufacturer to apply. Laquer thinner works well. One caution is that you absolutely must do this with ventilation, preferably outdoors. A vapor mask is highly recommended. Laquer thinner is highly volatile so it will evaporate rapidly. With volatile removers like methyl chloride and others, I like to use a plastic sheet wrapped around over the piece as soon as possible after slppping the stuff on. This delays the drying for hours and allows the finish to soften much better. Same thing with oven cleaner on table saw blades, cooking grills, etc. A remover like Formbys is also available from comercial paint supplier Parks.
  6. Frank, Brent, John, I built the 8' Catspaw but I did the new extended beam version which was probably a mistake because of the extra bulk. I used 4mm occume and the final weight came out to 52 lbs. That is very light for such a big boat. The weight is not the real issue although I'm not getting younger. It is just too awkward to manually lift up to the pilothouse top for me. I don't think I want the bother of a mast and boom system for lifting either. Truth is, up to now I have felt no real need for a tender. Only thing that I would have used it for is rowing around at an anchorage or visiting other boats. Those are nice things but we have managed to do them with "Liz" instead. I can tow the dinghy which my birder wife named "Chirp" at 14mph in good weather. A tender can be a hassle with any size boat and on one as small as Bluejacket, it may just not be worth the trouble. This is one of those problems without a good solution. I have spent a couple hours fashioning a model of a folding dinghy that I may build. It would be both lighter and much easier to handle. If I were only to tow a dinghy, I would build another of Graham's Spindrift 10's which I consider to be the best boat of that size ever. Wonderful little sailboat for an adult.
  7. Barry, First, I like fat rudders because they are more resistant to stall than thin ones. Yours looks great although the experts call for a squared off trailing edge rather than a rounded one. I do have a couple of other comments. Such a rudder seems out of place on a boat like the Weekender. A highly efficient rudder to steer a boat with an inefficient lateral resistance spread out along the keel. Unless the stock rudder is very bad, I doubt that you will notice a great improvement. Also, the maximum stress on the rudder is just at the point where you have it necked down in width and thickness with a couple of large holes to further weaken it. Since it probably doesn't have much lateral resistance or sail area to work against, there should be no breakage though. Not meant to be negative but perhaps useful.
  8. Jeff, I made the first raising floorboards for Graham's boats and they were installed on the BRS 15 "Loon" as on the website. There are two plywood floorboards aft of the center thwart split on the centerline. When raised, they rest on 3/4" sq. ledgers all around the aft cockpit. There is a folding leg hinged to the underside near the center to add support. Only one folding leg was needed as there was a lip on that side to support the other floorboard. With some ribs on the underside to stiffen them, the floorboards were made of 1/4" ply but anything larger should be 3/8". On Loon, these made a berth about 7' by 5' and left room for both side lockers to be opened with the berths made up. When lowered, the boards were locked in place by a simple rotating wooden latch. Worked great. Something similar can be done forward on each side of the CB trunk if desired.
  9. I have no real problem with meranti except for the extra weight. I recently used some (3/8") that I got from Graham on a runabout. I thought the surface was rougher than most occoume I've used but that caused no problem. It is stiffer and probably stronger. Some of the floatation I put in was an afterthought.
  10. Tom Lathrop


    I don't understand sime of the answers to this question. My experience has been quite different. The problem with cutting Lexan, acrylics or other plastics is heat. Keep the cut cool and there is no problem. Both tablesaws and bandsaws run pretty cool when the blade has a fair amount of set and the workpiece is run through in a smooth motion without hesitation. Any reciprocating saw like a jigsaw has a small blade that gets hot enough to melt the plastic behind the cut. First choice - bandsaw and for straight cuts - tablesaw. In those instances when you are forced to use a jigsaw, use a medium coarse blade that will work well on the thickness at hand and use a slow speed. All in the effort to keep the cut cool. I recently cut out 1/4" Lexan windshield panels on a bandsaw and there was absolutely no problem. This was on a small 12" bandsaw and a larger one would have run even cooler since the longer blade would have more time to cool between cuts..
  11. Do I recognize the docks at the Port Townsend festival? And yeah, where is the sailing shot?
  12. The CS boats are designed with kick-up rudders to make sailing in and from shallow water easier and more controlable. It also protects the rudder from damage in a grounding. The rudder blade is fitted within two cheek plates and is held securely by a pivot bolt through both. It is held down by a line to a cleat which can be released to allow the rudder to swing up. A kick-up daggerboard is a tricky way of mounting the board within the case which is also claimed to allow it to release if the board hits something. I have no direct experience with these. In any event the board must be lifted vertically to clear the bottom in shallow water or when launching from a beach. Unless the area above the DB case is free of all rigging there can/will be fouling on a tack. Trouble is, when you run aground on a shore line, a tack is almost always called for. I own and have sailed many daggerboard boats and while they are great for some uses, a beach cruiser is not one of them. I have had a lot of experience in sailing daggerboard boats to and away form a beach and have had my fair share of problems caused by the daggerboard sticking up high above the case. All said, a centerboard like those found in the CS boats is, in most every way, far superior. Some go for the daggerboard since it is somewhat easier to build and takes up less room in the boat. For me the price is right for the centerboard. On an equal sail area basis, I would expect the sloop rig to be superior upwind. Off the wind, it is probably an even situation.
  13. The CS 17 is still a pretty big day sailer and not at all "unreliable", assuming you mean seaworthy by that term. I'd consider the CS17 very capable of handling any waters a reasonable day sailor should be out in. Since I "discovered" the cat-ketch rig, it has become my favorite for all the reasons listed in Graham's article. The sloop is certainly not a step up in rig quality, just different. In our experience, the sloop is only marginally superior in performance to the cat ketch and not on all courses at that. In my biased opinion, the CK17 looks like a knock-off of the CS17. All the differences I could spot come off in favor of the CS. For one point, your need to sail off-of and on-to a beach makes the daggerboard of the CK17 a big liability. The claim of a kick-up feature on the daggerboard doesn't make this much easier. The claimed building time of 60 hours for the basic CK17 hull and 60 more to complete the boat and rig should set anyone to laughing who has ever built a boat.
  14. Charlie, The Princess looks just great. Sorry that Graham was too loaded (work) to get down to see it. Have you gotten to sail it? I sailed in the first one several years ago and it proved to be a fine handling boat, as I would expect from one of Graham's designs. Travis is lucky to find someone willing to share this kind of work (soul) with him. When one of my creations leaves, a part of me goes with it. I'm sure you feel that way even though it was to be someone elses boat from the beginning.
  15. Graham's second sentence should be re-read several times until the meaning sinks in. Otherwise what happens in the next sentence is sure to occur. Epoxy just not bond well with a cured epoxy coating that has been poorly prepared or, in this case, not treated at all. Pre coating panels is fine but later bonding joints MUST be agressively sanded to get decent strength.
  16. I copied this from the Woodenboat forum. - ------------------------------------------------------------------------------- Since I designed the Bluejacket 24 I guess it is time that I got into this problem after just talking with Hugh. The break was caused by stress concentration caused by the assembly sequence. The fact that the bottom panels were opened and took their design shape indicates that there was no undue stress up to that point. When the port topside panel was stitched in place and the fairing blocks screwed in, the hull undoubtedly warped a bit and put more stress on the starboard side bottom panel. Hugh then attempted to fit the starboard topside panel in place and screw the fairing blocks down BEFORE tightening the wire ties. this combination put a stress concentration on the already stressed bottom panel just in front of the block as seen in the photo and the panel failed. The fact that Hugh is using 9 ply plywood may also have contributed since it is said to be stiffer than 7 or 5 ply. The proper sequence to install a panel that needs bend and/or twist is to start at the end with the most severe bend or twist. This is almost always at the bow. All wire ties should be put in from this point and tightened snug. This will help prevent stress concentration by allowing some transfer of stress to adjacent areas as the panel is gradually bent into shape. The fairing blocks should not be put in until all the panels are in place and wires tightened. The purpose of these blocks is to force the panels to make a fair intersection at the chine near the bow, which they may not like to do. In severe cases, installing a batten an inch or two below the chine and on the outside will be even more effective in preventing stress concentration. Another help is to squegee on a thin coat of epoxy on the outside (tension) side of the curvature which will delay local fiber failure by spreading the stress. Sometimes water and/or heat can help but on thick plywood, it may not work too well. There are limits to which plywood can be bent without fracture but using these techniques will enable you to reach that limit. Some more stuff to be added to the plans I guess since not everone is familiar with these problems or solutions and they are not in any of the books I know of. At least that is fairly easy for me to do since I make my plans in a loose leaf format that is not too much work to add to or modify. ------------------------------------------------------------------------------- Adding a batten to the edge of the plywood will not intoduce flat spots provided the batten is long enough to extend well past the area of severe bend. In fact the batten will make the curve more fair by eliminating the "edge effect" of the plywood. Try bending any sheet of material and notice that the center part does not take the same curve as the edges. This is caused by any point in the center being supported by other points on either side while the edge is supported on only one side. Some materials won't work because you gotta get at least near the elastic limit of the material in the bend. I don't necessarily understand this stuff since I'm an electrical engineer but I'm told it is so and it sounds reasonable since we have the same phenomena (nearly) in physics.
  17. >>>Also look in the back of the galley ( I hope I mentioned that) and don't forget the ice box, which gives about 800 lbs. It's a w-e-l-l insulated ice box.<<<<
  18. John, Who is it that had a panel fracture? It has happened to many people, including me, when twisting a sheet of plywood, especially if the plywood has any flaws. Lower quality plywood is much more apt to have this problem. I need to tell him about a cure for that problem which I assume ocurred near the bow in the bottom panels. A good fix is to screw a batten on the outside of the panel about 1 1/2" to 2'' below the chine. The batten should be about 1" thick by 1 1/2" wide by 6' to 8' long and the screws should be through plywood washers from the inside. This will prevent stress concentrations from causing failure at a weak point by spreading the load through the batten. The reason for having the batten away from the chine line is to allow wire ties and some epoxy reinforcement before removing the batten to finish the joint. Ray, Jake is not waiting to ask questions.
  19. I recently ingested several ounces of DHMO and had some to splash on my skin. Should I be concerned? Is there no antidote effective on humans? I have seen dogs roll vigorusly in dirt after coming in contact with HDMO. Would this work for humans?
  20. Frank & John, I have been away for a while and went to the Annapolis boatshow while visiting #1 son. Real crowded and pretty much a waste of time and money unless you are interested in big expensive fiberglass or aluminum boats. Anything under 30' was stuffed away behind the tents. Some interesting stuff in the tents but not enough to get me there again. I do think the risk of hitting submerged objects may be creating a bit more concern than it warants. Just how much impact would be experienced by hitting a log in the bow area is unknown. There are just too many variables like speed, size and weight of the deadhead, just where and at what angle the impact occurs, etc., etc. In the PNW or flooding inland rivers where semi-submerged trees and logs are sometimes found, some extra caution in both cnstruction and boat operation may be called for. The hull of the BJ24 is very strong but any hull can be penetrated, given the right conditions. Looking at photos of boats following the Florida hurricanes should be enough to convince anyone that no boat is immune from such damage. I think the best route is to use the normal construction in most areas and to put a layer of Kevlar on the inside of the bottom from the stem back to the forward bulkhead of the pilothouse in areas where there is much concern with debris. I have used 18 oz biaxial cloth which might be as good but I have no comparative data. Kevlar has extremely high tensile strength which would prevent penetration by all but the most sharp and heavy blows. I would prefer this to just making the skin thicker since it would allow some flexing under impact but would be very hard to actually penetrate. Some tests I have seen of this kind of sandwich show that the plywood can fracture while the structure remains intact. The Xynole on the hull exterior is tough and flexible which will also help maintain an intact skin even though the plywood is fractured. "Liz" has over 1500 lbs of positive floatation in the form of blue waterproof styrofoam in addition to the natural buoyancy of the wood so sinking is out of the question.
  21. John, Marine ply can be difficult to come by in most places. There are alternatives other than lauan . There is nothing wrong with lauan except that much of it uses glue that is not even fog resistant. Lauan is actually more durable than okoume. I do find the 52 lbs a bit much. My two Birders finished out at 34 lbs with 4mm okoume. The boats would be fine with 3mm ply instead of 4mm and might come in at 28 lbs. There are manufacturers of cored home doors almost every where. Even with no suppliers of the ply facing in your area, you should be able to buy some from local door builders. Get the exterior kind which has waterproof glue. It is often okoume but can be anything from birtch to walnut. It comes in sheets 3' by 7' and is inexpensive (relatively). As said though, the experience of having a project that interests your offspring overpowers all other considerations.
  22. 3/4" plywood will not take the bend in the bow, John. The required bend is near the limit for 1/2" material. I suggest fabric on the inside as the easiest solution, if you think that reinforcement is necessary for higher impact resistance. That is what I did on my new runabout, Scamp. I had to reduce the forward bottom thickness to 1/4" for the curvature on this boat.
  23. There are several areas on the North Carolina part of the ICW that have silted to teh point that many boats have to wait on high tide for passage. I saw an item a few weeks ago that the Corps of engineers have been allocated some money for dredging these. Many of these areas require dredging pretty often to keep them clear. Of course, the driving force is likely to be mainly commerce and not pleasure boating.
  24. It's been on the decks and cockpit sole of this Bluejacket 24 for five summers in the south. Protected most of the time but still exposed a considerable amount of time. It's fairly dull, which I like, and some will come off with rubbing. Looks like it will still be several years before it needs recoating. [attachment over 4 years old deleted by admin]
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