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Tom Lathrop

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Everything posted by Tom Lathrop

  1. If you use expanding foam anywhere on the boat, make certain that it is of the waterproof, closed cell kind. Most home mixed expanding foams are not.
  2. I agree that 200hp sounds like a lot for 22'. These motors are very heavy and the placement will certainly have a large effect on the balance. It must be considered in the design of the boat to be properly balanced. Adding weight to the bow to compensate is a sure indication that the boat was not designed properly and further reduces performance in fuel economy, low speed planing and handling. The pods have some good points but I think they are mostly a fad and also have disadvantages. The transom must be built stronger (heavier) and the pod weight adds to that. They have a tendency to ventilate in waves more and take up more length docking, trailering and storing. The idea that they give more cockpit room is bogus. The real length of the boat has to include the engine so if it is on the transom, there will be more room in the cockpit than with a pod if the overall length is the same.
  3. And this is the same captain that ionce had a tooth broken by a sprits'l centerboard Maybe he has finally run afoul of one of the dragons he always promised were down there :twisted:
  4. Pipeman, Rot requires moisture and oxygen. Take either of these away and there will be no rot. That is why the term "dry rot" is an oxymoron and can not occur. All wood has voids within the cellular structure. Red oak has more than most and rots quicker than white oak which has blocking material in the veins. Balsa is full of air so it rots very quickly. However balsa core that is full of moisture gained by osmosis through a fiberglass skin but, is otherwise sealed from oxygen, is just wet and heavy, not rotted. So an enclosed void by itself is only a mechanical problem and not one of rot. Lots of boats have been built with Nomex, a honeycomb material that encloses mostly air between wood skins. Not saying that there have not been rot problems there though. A linear void that runs from edge to edge in plywood is the worse case since a breach anywhere along the void can let in both air and water. I don't like voids and try to a-void them but they are probably not the buggaboo that many assume,
  5. Ray, The main (maybe the only reasons) for rotary cutting plywood veneers are: It's much cheaper to produce, the veneers can make a full panel width without joins and there is less waste. The higher quality marine panels start out with equal thickness veneers of the same specie as Barry says and final sanding takes some away from the outer layers. This is less noticeable on high quality stuff. In lower quality plywood, the manufacturer skimps by using low quality stuff for the interior plies and a thinner outer ply where they have to use higher quality to fool the buyer. The worse will have one thick inner layer and two very thin outer plies. A lot of the common 3 ply lauan is like this. If you make a knife score lightly across grain on one outer layer, the whole thing breakes easily over your knee. The main dangers of the 1/2 thick outer layer is that it's easier to rupture. If you need to do a sanding repair, it's also easy to sand through the surface. Any one ever sand some teak or other expensive veneer? It's worth saying again that the BS plywood standards are no longer supported by the Brits. The "Standard" still exists on paper but we have to depend on the honesty of the supplier whether it's followed or not. Some of them hedge a lot but still might put the stamp on there even though there has been no inspection. I have never experienced checking on okoume and have no hesitation to leave it unsheathed unless there is a good reason for a sheath.
  6. The only plywood that is sliced flat (flitch cut) is furniture grade faces. All the rest is rotary cut and includes 1088 okoume. BS1088 ply should have even thickness plies. BS6566 sometimes has even thickness but often not. Face plies that are much thinner than cores should be avoided. If it's to be sheathed, then I guess it's acceptable. Quality, price and availability of marine plywood is a moving target.
  7. My comments on checking in meranti plywood was intended to be just a warning in that meranti has not been around in the plywood market very long and many have not ever seen or used it. It may be that it is unusual or common as in fir. Some lumber woods are prone to check and some are are not, whether soft or hard, from temperate or tropic sources. One thing that sets most of the plywood that we use in small boats apart is that it is all rotary cut from green or wet logs. This operation is very rough on the wood as there is a high pressure shoe just ahead of the slicing knife which curls the veneer off the log much like a hand plane makes curled shavings. The result is that much longitudinal cracking takes place in the veneer as it curls off the log. Some woods survive the slicing operation much better than others and do not show significant cracks (checking) later on. Some like fir are more prone to checking and so we downgrade it for boatbuilding for that reason. Since we use the veneer flat and it was originally wrapped around the tree, that also has some effect on it checking more than sawn timbers. I simply am warning that meranti, in addition to being heavier, may also, like fir, need to be looked at more carefuly as a boat building plywood. If others notice the same issue with meranti, we need to let it be known.
  8. I saw some sobering evidence in plywood this morning. A friend who was spending last week here from cooler lands brought a Bolger Lily electric launch along. We were looking it over and discovered that the plywood not covered with sheathing was checking extensively. I thought at first that it must be fir but it is meranti. I have not heard of that hapening to meranti before. All had been epoxy coated and painted and all horizontal surfaces had checked badly. Anyone have other experiences with meranti checking. It is bad enough to prevent me from using or suggesting meranti if this is a general fault.
  9. Dale, You just haven't gotten the latest issue yet. Since I built and sailed the boat in the article before selling it to John and Lynn Sperry, I have a proprietary interest in their travels and travails. "Loon" has to be one of the most active beach cruisers around. The Outer Banks, Maine, Canada and Great lakes while we had it and now the Great Salt Lake and Mexico. I marveled at the amount of gear they managed to cram into Loon for their latest adventure. Also sweated out the jibing entry into a downwind harbor with an overloaded boat in strong wind and waves. The Bay River Skiff 15 is a grand boat but was never intended to be pushed this hard. They would be much better off in a CS 17 or better yet, a CS 20.
  10. I got on yesterday but now. Graham's server (pinelink) is having the problem.
  11. I have used WEST, Chem Tech, System 3, MAS, Fiberglass Coatings, LBI, RAKA and a couple other less known industrial epoxies. For the home builder, there is little difference in performance among these. Some are lower viscosity which makes for easier wetting out of cloth. Some like the old Chem Tech adhesive were so viscous that it wore out my wrist to mix so I won't use them. WEST's 5 to 1 ratio makes mixing small batches iffy unless you have a WEST dispenser pump (expensive). The high ratios tend to be stronger in industrial use (controlled conditions and heat) but all the above epoxies are more than strong enough for use in boats. I and most in this area now use RAKA for economy, excellent packaging and service from the supplier. The commercial builders of sportfishermen on this coast and Outer Banks mostly use other brands that they get cheaper in very large quantities. If you are building high end boats (read expensive) where the cost of the epoxy is not a large fraction of the selling price and the customer can be impressed with the fact that you use the "best" (read most expensive) products, then it may be in your best interest to use those. If you are a home builder on a budget of ,say, $5000 and trying to keep cost down, it's a different story. The largest expenses in a composite wood boat are the wood and the epoxy, not counting the engine or sail & rigging. In this case where you might need 25 to 30 gallons of epoxy, you might save $1000 or more by choosing RAKA or FGCI over the high price brands. That is a big chunk of the budget for the home builder and if it takes a bit more effort or time to wet out some glass sheathing, so what. There are still some of the complexities brought out by the posters above to be considered but there is a personal learning curve to all boatbuilding.
  12. There are at least 2 different types of vibration in a rudder or center/dagger board. The one PAR is discussing occcurs when the foil is at or near stalling conditions and one side is experiencing the onset of heavy turbulence from separation of flow. This is generally a fairly low frequency vibration and is cured by not turning the rudder so far. The other kind which is more common in a centerboard or daggerboard is a high frequency vibration, humming or singing. This only occurs when the boat is moving fast like in planing. One of the worse foils for this problem in my experience has been the Laser daggerboard. This board is made in a good NACA section and is as symetrical as possible. What I am saying is that I believe that the more symetrical a foil is, the more likely it will hum or sing. This fits with other things in nature. If you want to stop a shroud from singing, hang someting on it to make it less symetrical and damp the oscillations. Want mess up a guitar or other string. Make it asymetrical. The cause is the alternate shedding of vortices from either side of the foil. These vortices are most effective in promoting the vibration if they are both of the same strength instead of one side dominating the other. In an asymetric foil one side will be stronger than the other and the oscillations will be of a lower frequency, more difficult to get started and usually of a lower amplitude. The same thing happens, whether it is a mast, a shroud, a flag on a pole, a radio antenna on your car or a foil on a sailboat. It's called simple harmonic oscillation and it also causes the washboard bumps in a dirt road which result from the suspension of a car being excited by a single bump and oscillating up and down. Good shock absorbers unbalance the suspension and damp out these oscillations. I know this runs counter to what many (maybe most) think, but it is what I believe. Got a singing daggerboard? Stick a piece of sandpaper on one side and see what happens.
  13. We should not miss the point that the second place boat is a G Cat. This is a fast boat. I once knew one to set a record from Wrightsville Beach to Atlantic Beach in North Carolina that AVERAGED over 17 knots for the 67 miles. Getting from here to there in a race like the Everglades Challenge is more than just speed. Congratulation to Graham and Fred.
  14. According to the tracking GPS, they got in at 1:27 this morning. That checks with their progress line. The 4:30 check in time is a puzzle. Don't know what happened there. The race organizers are doing a very sloppy job of keeping up with the racers. They deserve a lot better, especially considering the high entry fee..
  15. Green Heron is now about 10 miles west of Key largo. With an hour and a half to go before midnight, they will certainly break the existing record. The G Cat was 2 hours and 4 minutes behind at Flamingo. The winner will be the one that best navigates their way across the flats and mud to Key Largo. With 2 hours in hand, our guys should be OK but a lot depends on chance and finding the best channels. Gordy Hill will be there to pick them up. Go Go, you can sleep when you get there.
  16. Graham and Fred are carrying a GPS transmitter that periodically sends their position in the race. If I am following the correct boat, they were at the first check point about 10 miles south of Englewood. They had to sail and row quite a distance and pass under at least one low bridge to get to the check point. Here is the link to the website. I found it a little clunky to navigate but then I'm a bit clunky on the computer. I copied and pasted this so, who knows? The only boat that works for me is NavRes, which I hope is Graham. _____________________________________ Go to www.globalwave.com Click on
  17. No secret about the keel up dasher. It's a 20 foot center console sport fisherman. Designed by Graham Byrnes who lives a couple miles from the shop where this first one is being constructed. It has the classic Harker's Island flare and should be a nice addition to Graham's plan list. It's being built in the favored Outer Banks construction method of laminated occume ply and epoxy. Graham and crew are leaving in about 2 hours for this year's 300 mile Everglades Challenge taking off for Key Largo from St Petersburg. You can follow this very demanding endurance race for small boats at: http://www.watertribe.com/Default.aspx?Expand=7&ucPtr=Everglades/EvergladesTeaser.ascx
  18. Mike, Did you sneak a photo of Graham"s Offshore 20 in there??
  19. Just looked in on the forum this morning and saw this thread. This computer flunky is now taking a class at the local Community College in Microsoft Front Page. I will have a web site shortly if not later. I'm late to this game and boats are more fun than computers, especially for an old analog fart. I wonder what digital fart is like? Anyway, my email is harbinger@cconnect.net Good to see Mike has resurfaced. I do wonder where he gets all that porn though. When I type "porn" into my browser, I don't get anything like that
  20. Hi Jordyn, Ask your dad for some sandpaper for your birthday
  21. Quite a few years ago I joined Graham and a couple other guys in a project to build a racing trimaran. The first job he gave me was to build a 40 foot wing mast. This required scarfing five panels together in a school shop where the thing had to be put away each night. I used 3mm ply and rolled the completed sections up as they were completed. You can't roll 6mm as easily as that but you should be able to join the first two sheets and then bend them enough to have room to do the other joint. You can lay out the patterns and cut in partial sections the same way. Of course, the proper thing to do is move into a house with a bigger boatshop
  22. One of the main things you need to know about a boat is how much water it displaces in operating form. Only in this condition can the critical characteristics be evaluated. So what is needed is the weight of the hull plus whatever is needed to operate it under normal conditions. This includes engine, some fuel and water, some stores and normal crew. Too many give the hull weight and call that the displacement. The only way to know is to ask the right questions of the people with the knowlege. Sail area to displacement ratios mean nothing if these things are not included. In small boats, the extras often dominate the true displacement.
  23. Jeff, I was interested to see if anyone was going to take you to task for the way you set your hand planes down. :wink: I'm with you. Nice bench and it's good to see that it is not a show piece but that actual work is taking place. I just became the owner of a large and (very) heavy work bench about twice that size. It took four men to move it into my shop. It has a shoulder vise on one end and an old Emmert pattern maker's vise on the other. http://www.mprime.com/emmert/index.htm I already have a good bench I made many years ago but just could not turn that Emmert down. I have to do a bit of work on it but it's an awsome vise for clamping oddly shaped work in any orientation. Now, my problem is where it will fit in the shop. I will have to give the old bench to my neighbor and move my plywood storage to the boathouse to make enough space for it. Anyone familiar with the Emmert will cry but the bench and vises were given to me by a friend who is moving to small quarters. Now would be the proper for all to drool
  24. The particular boat that Mike is "rebuilding" was different from Simmon's regular designs and is between the 20 and 22 footers. He will use at least part of the deck and is able to scarf in the piece of the transom with the hull numbers carved in it. Otherwise it is as Dave said. The weather around here has been so warm lately that working outside is a pleasure although very wet the last two days.
  25. I received a complimentary copy of SCA a few days ago. It seems like a nice publication and the editor claims to be trying for the same kind of mag as the Small Boat Journal that was assasinated a few years ago. While I enjoyed reading it, it is not SBJ and does not cover a lot of the ground and not in the detail that SBJ did. For instance, not a single powerboat could be found in its pages and I like both bubba and blow types of small boats. Still, it is a nice magazine. Problem is, magazines are getting so bloody expensive. I can often find a good used book on the web (I like ABE books) for no more than a single issue and almost always less than an annual subscription. If magazines would offer a really good index search feature, they would be more valuable since digging through the stack can get to be a chore. Many offer indexes but they are not usually completely reliable. I agree with most comments on Practical Sailor. It's hard to justify either the cost or the filling space, unless you are in the process of fitting out a boat.
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