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Tom Lathrop

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Everything posted by Tom Lathrop

  1. Here is a hint for saving labor, epoxy and getting a smoother job on surfaces. Sand the bare wood with about 220 grit. Vacuum. Spread on a THIN coat of epoxy with a spreader and force the epoxy into the wood as much as possible. The idea is to get the minimum amount of epoxy on and still fill the pores. I like a stiff rubber spreader for this job. After it sets up, sand with 220 grit. This will be a quick and easy job and should leave the surface very smooth. The idea is to get rid of surface fibers that always stick up through the epoxy and make sanding more work and wastes epoxy. :idea: This is a great time and labor saver. Give it a try. :idea: After this, you can put on more epoxy coats or epoxy paint. I don't know how the water resistance of the paint compares with epoxy resin, so I use epoxy base coats under the paint.
  2. I've been using this industrial epoxy paint on boats for 10 years and think it's great stuff. I use the Devoe brand but it is probably about the same as SH. They have one version for use in potable situations like inside water tanks and the chemical resistant type used on bridges, towers, water tanks and the like. Really durable and tough. I roll it on decks, soles and interiors with a short nap roller to get a fine pebbly finish that I like for these situations. I just sprayed the interior of my latest boat with it and got a satin finish. It's not high gloss no matter how you apply it. It does chalk but I am not bothered by that since I don't want glare on decks and soles anyway. I bought a quart of lampblack tint from Lowes for about $8 and tint the standard white to shades of grey. It will only get to dark grey starting with the highly pigmented white. Buying tints in small quantities is expensive. [attachment over 4 years old deleted by admin]
  3. John, There are a fair amount of lateral and longitudinal bulkheads in the forward area. Even without stringers or interior fabric reinforcement, the scantlings meet normal practice. The curvature of the bottom panels in this area create great rigidity. Belt and suspenders will help if your pants have a habit of falling down. The entire hull bottom is extremely strong as a result of the torsion box construction with longitudinal bulkheads on 7 1/2" centers bonded to both hull bottom and cabin/cockpit soles. The only issue is penetration of the hull by objects the boat may encounter. After looking at the beaches and marinas in Florida this morning, it appears that it may be impossible to guarantee against that. Gonna be some cheap boats down there. Adding 1/4" ply to the forward sections might be a difficult fairing job unless it is put on the inside. There, it might be a physical problem to fit in unless it were done in sections like cold molding. It would be impossible to layer it before the hull is formed up since it would never accept the curvature. If you did decide to add the layer, we will discuss a procedure later.
  4. John, I think your question is spot on the topic. A few weeks ago, we were cruising on Bay River at about 16mph when the boat hit a submerged something under the starboard side of the hull. Just a loud clunk and when the boat was taken out the next day I found some paint missing about 30% aft of the stem and further aft on the chine. No physical damage at all. In the Pacific Northwest, which we hear has quite a bit of debris in the water, this may happen more often. While I don
  5. Frank, I built the 8' Catspaw as a tender for the Bluejacket but find that I am getting too feeble to muscle it up on top of the pilothouse and don't care for any complicated lifting system. I looked at the Portaboat and had the dealer set one up for me. It was not a simple task and he was working on a concrete driveway. On the boat it would be impossibly awkward. Besides, the thing is heavy. I made up a few trial models of a folding plywood dinghy similar to the Micro but with solid ply transom inserts and a seat made to act as a central crossbrace. I just don't trust what looks like a pretty flimsy affair in the Micro. Also the size is just too small to be practical. One problem is getting it large enough for two adults and small and light enough to be easily assembled in the cockpit and lifted around. Placing the folded boat on top of the pilothouse would be no problem. I'm thinking about assembling on top of the pilothouse but refolding in the cockpit on the return trip.
  6. Jeff, A layer of glass on the inside will greatly increase resistance to hull rupture from impacts on the outside. Actually better in this regard than glass on the outside. Because of its toughness and high tensile strength, a layer of Kevlar on the inside might be the ultimate for this purpose. For abrasion resistance on the outside, an epoxy/fabric sheath of Xynole or Vectra polypropylene is excellent. A layer of 6 oz glass cloth in epoxy is about twice as good as epoxy alone and a single layer Xynole gives about 6 times the abrasion resistance of the glass cloth. These numbers are based on some objective tests I made a few years ago. On a light boat, such a sheath will stand dragging over sand, rocks and oyster shells with no more than minor scratches. The down side of these sheaths is extra money, time, labor and a bit more weight. If the boat is expected to see rough use as with a beach cruiser where the boat will be drug around in less than idea conditions, they are worth it.
  7. You don't want to go too far with the sandwich-strength thing. The stiffness of a beam or panel is much more a factor of the thickness than anything else. Given two same wood panels of the same wood and equal weight, the solid wood one will always be stiffer than one with fiberglass laminate on one or both surfaces. Wood is good stuff. When talking about strength, you have to define whether you are talking about breaking, impact, tensile, compression or some other factor. You have to get pretty high tech into fibers and cores (beyond glass) to beat wood as a boatbuilding material. I have built wood racing sailboats and had to add lead weights to meet the class minimum weight restrictions while fiberglass builders have to fight to keep the weight down to the minimum. Plywood is good stuff.
  8. Not poor seamanship but bad form nontheless. Like driving at 45 mph in the high speed lane, walking around with your shoes untied and laces flipping around, sailing with huge scallops in the jib luff, 2" of grass and barnicles on the waterline, etc., etc. If it's not a workboat and just out for a sunday sail with fenders hanging over the side, I certainly have a bad impression and tend to give the boat a wider berth than a shipshape one. It ain't the biggest social error, but it's an indication that all things MAY not be handled the best on that boat. On the other hand, if the skipper really needs the fenders to be hanging over the side when under sail, then I'm sure to give him a cable or two extra space. NO offence intended but that is my honest feeling.
  9. Now, now, Mike, Only one cup of coffee per morning.
  10. Mustang, If we back off and say that we are talking only about epoxy coating, then the question can be easily addressed. In that case epoxy becomes just another kind of paint. Many of us have found to our satisfaction that epoxy makes a tenacious, tougher and more waterproof coating than regular paint. If a fabric is added to the epoxy coating, the combination gets tougher still. It still needs protection from solar exposure and so we add some kind of paint or UV resistant varnish over the epoxy. The result is a superior sheath for things that live in or around the water. Taking emotional attitudes out of it, it's a simple enough proposition. Lots of boats were built with or without plywood long before epoxy was invented so you don't have to use it in order to get a good boat. My opinion is that epoxy is a great product that will almost always add to the life of a boat so I will continue to use it.
  11. Mike, First attempt at posting a photo of an epoxified boat. [attachment over 4 years old deleted by admin]
  12. In their day, the Herreshoff's were on the leading edge of boatbuilding technology. In fact, they introduced much of it. Does anyone truly believe that they would not be doing the same if they were around today :?: I'm a 3 digit member of the WB Forum and have gotten a lot of valuable information from it. There is much more acceptance of "our" methods now than several years ago. There are still luddites quick to pounce on epoxy if given the oportunity though and this thread contains several. Like most such topics, this thread will lead to no clear conclusion. As old Herreshoff was fond of saying, you "dear reader" will have to make your own conclusions. I have built about nine boats using epoxy as a ingredient for bonding and coating. All are doing well. Locally several hundred (mostly in Graham's Community College class) have been built with these techniques and there have been few problems. Almost all have been traceable to poor use of materials or technique. I have done major repairs on an epoxified boat that was poorly built though. Recently there was a large Piver trimaran in a local yard undergoing some major rot repair. In looking into the hulls, I saw that there were no (that's zero) limber holes in the frames and no (that's zero) provision for ventilation. I'm sure that some would pounce on this an example of epoxy failure. Draw your own conclusions. :roll: Sometime in the near future I want to build a small lapstrake boat using more traditional methods but there will likely still be some epoxy in it.
  13. Sam builds all of his boats with heavier scantlings than that recommended by most designers. I'd say that most are overbuilt for anyone who is performance minded. He describes his boats as solid, comfortable and quiet, all of which tend to increase with scantling dimensions. Different market. A power boat with power enough to punch into waves at more than twice sailboat speed experiences shock loads much higher than a slower boat and needs stronger scantlings. Around here, B&B's Core Sound boats run in water at least as rough and challenging as anything Narraganset Bay will toss at you. These boats are plenty strong enough as designed. Added weight is just more weight. If you plan on running into things more solid than water, then you should think about beefing up any possible point of contact. Otherwise, the boats are fine as is.
  14. Rob,, I detect a bit of understatement in your story. With somewhere in the neighborhood of 700lbs on the rail and a gusty blow, the mast was apparently loaded to a fair thee well. Oh well, at least now you know the limits of that particular set up and that the boat is strong. Hope that the repair works out well and you get back out soon. How fast do you suppose you were running? I remember the same thing hapening to me in a Thistle with five on the rail in a thunderstorm. Of course that is a stayed mast with double diamonds. Expensive thing too.
  15. Ah Mike, So you decided on cross planking. It's looking good! Do you plan on using the sprits'l rig with topsail? You know, some people actually know what kind of boat they are going to build BEFORE they start hammering nails. Julian would be proud. I've got to get down for a sail on one of your creations. Just now taking a break from preparing for Charley's visit later today. If the path doesn't change (ha!), you will likely get more surge in your area than us. Liz and I still plan to leave for a vacation at Brad Indicott's house in the Blue Ridge Mountains tomorrow. There's optimism for you. He and Debbie are in the NY state canal system somewhere. They are shipping Leah Ghent back to Oriental instead of making the offshore run around NJ.
  16. Fair enough Graham. I just thought that the trailer subject needed a little amplification.
  17. Boats of differing design and construction call for different "best" trailer solutions. I don't often dissagree with Graham but this may be one. :shock: In explanation, I'd say that Graham has far-far more experience in boat building and design than me but in trailering, it's likely the other way round. If the boat has a strong keel or keelson, then supporting most of the weight with the keel will work fine. Many stitch ane glue boats have neither a structural keel or a keelson. Supporting such a boat only with rollers on the keel can generate lots of point load under highway conditions, especially on rough roads. Over the 50 something years I've been trailering boats, I have seen some pretty deformed boat bottoms caused by inadequate trailer support. Possibly the strongest area under Graham's boats is the inside tank wall and the chine. I like to place fitted bunks under such a longitudinal bulkhead if one is available. Not to say that support under the keel is not good also. My current 2200 lb plywood boat has fitted bunks under such longitudinal bulkheads and has survived over 7000 trailering miles over all kinds of roads with zero deformation. However, the forward deeper V part of the hull is supported on a centerline pad under a transverse bulkhead. I also feel that the boat should be solidly attached to the trailer so that the boat and trailer move as one on the road.
  18. Scott, I looked at working self bailing into the CS 17 a while back. I was mainly interested in making the aft cockpit area drain through the transom in order to allow a beach cruising tent over the forward cockpit and not have water in the bilge in the morning. Even with this half length self draining attempt, the sole gets too high and takes up excessive volume so that the steps Graham mentions are necessary to make it work. To extend the slope of the cockpit sole all the way forward creates even more problems. It can be done, but the compromises to the highly workable interior that Graham designed make it undesirable in my view. Drainage is mainly a problem when the boat is not moving anyway. An Andersen automatic bailer next to the CB trunk will suck water out during the times that most water might get into the boat by spray or while on the trailer. That is the route most take in this area where many of these boats live.
  19. Mike, First, that is what I thought you might mean and it is now very clear. Second, I'm not in any way insulted when anyone questions anything. and I know that you have been working at the grass roots (or water level of small powerboats) more than I have. Wedges, motor bracket and hull -- I set the transom angle at the normal 11 degrees and that seems to be just fine at normal operating speed at all water and load conditions. Several things are at work here. First, there is the forward location of the CB relative to many other pwerboats. Second, there is the chine flats design which are set to a down (positive) angle of one degree relative to the hull bottom. this means that the width of the flats gradually increase toward the stern. The forward CB tends to hold the bow down and eliminates porpoising. The flats give extra lift to the stern without the drag of trim tabs and contribute to the level running attitude. Bluejacket has more than the normal longitudinal stability. Changing the motor trim angle has very little effect on boat trim. If I eliminated the chine flats, both hull trim angle and top speed would increase at the expense of low end planing and level running attitude. I sacrifice top end efficiency for low end efficiency. The big manufacturers could never sell many boats with that claim but then, I ain't trying to compete with anyone. Cheers, Tom
  20. One thing to remember about outboards is that they have only one gear ratio. If you use a too low pitch prop for low end acceleration, the engine will overspeed at WOT. Think of running your car in second gear at WOT. Using a too high pitch prop will be like taking off and running up hill in too high a gear. The engine will always be under stress. Manufacturers give a desirable RPM range for WOT. The prop pitch should be selected to put RPM in the range they give. This will vary with each boat. Cupping is a way to load a too low pitch prop to make it load like a higher pitch to the engine. Even a very small amount of cup (hardly noticeable) will drop RPM like about two inches of pitch increase will. Few people select props properly but everyone should. Like everything else in boat operation and design, it's a compromise. Not sure I understand what Mike means by changing the transom angle. The only adantage in putting trim tabs on Bluejacket would be to correct for lateral trim angle due to too much weight on one side. Easier to get the passengers to not congregate on one side. Otherwise, trim tabs are not needed and I would not consider them at all. The boat has high longitudinal stability as it is.
  21. Thanks for ringing my bell Frank. The issue of adding power to the Bluejacket comes fairly often but this is the first time anyone has specifically wanted to pull waterskiers. It was a very simple answer to use the 60hp Yamaha because it is just a souped up version of the 50. First, a couple of clarifications. Using an engine of 90hp will give no problem with trim or weight. I often operate with two adults sitting in the seats on either side of the engine and that is a lot more stern weight than the extra 130lbs of the larger engine. How much faster will the boat be? I'd expect speed in the low thirties. If the speed of the 50 or 60hp engine is fast enough, there is ample power to pull the skiers. Heck, I learned to ski behind a 10hp outboard. Most people will want more speed for skiing though. What are the issues? Weight -- Not a problem. Size -- May require some rearrangement / design of the stern area. The 50/60 just fits in the space allowed and gives room for the nice permanent seats. A wider engine will require narrowing or possible elimination of these very useful features or, perhaps reduction of the ttumblehome in the stern topsides. Use of a 2 stroke engine may make this problem moot, since their powerheads are quite a bit smaller than the 4 strokes. I
  22. I have always heard that Downeast in Maine referred to the northeasterly direction along the coast of Maine being downwind in the summer months. The area shown on the map by Oyster certainly qualifies as downeast by that definition. The prevailing southwest winds of the area usually mean a run to the northeast and a beat back. All sailors in the "Great Race" can testify to the reality of beating their way to Beaufort through Core Sound and around Harker's Island. Usually, only the occasion of a northeaster will change this pattern.
  23. I'm fairly certain that the Brits dropped support for the BS1088 & others several years ago. Therefore, no plywood now being produced is ever actually verified by the keepers of the standard. Of course, the standard is still there and some plywood makers still claim to adhere to it. Hopefully they are honest about the claim, but it is a matter of trust or experience with a given manufacturer.
  24. I managed to get rid of that awful Bolger Teal in a charity auction but still have the oars which get used now and again. By the way, Graham and I finished the boat in 2 hours and 18 minutes which was slower than some others. Anybody have a good safe method for removing Sikaflex from a mustache. I never learned not to store ring nails in my mouth when my fingers were coated with Sika.
  25. Alexander, The plywood does not look too bad to me. The outer ply is almost 1 mil and we often deal with stuff thinner than that. The batten I would use is about 1/2 " thick by 1 1/4" width (all approximate) and maybe 1/3 the length of the boat so that the bending is supported over a large area. I place the batten on the outside about 1" below the chine to give ample room to install the wire stitches. run screws from the inside through small pieces of scrap plywood to minimize scaring the panel. If there is a lot of panel edge curvature, you may need to decrease the width of the batten. I also like the thin epoxy coat on the outside like I mentioned above. Good luck.
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