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Designer

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Everything posted by Designer

  1. Driving in a drywall or a self tapping screw with the modern cordless drill or driver is giving us all bad habits. Beside the obvious job of holding two parts together, the smooth shank of the wood screw allows you to draw the two parts together. The self tapping screw will thread its way into the work piece and thread its way into the main part leaving no way to draw them together without stripping one of the threads. If I am doing something quick and dirty like on the house and I can't be bothered getting the drill and drilling a clearance hole in the work piece, I will start the screw in the work piece and then hold it away from the house and run the screw all the way to the head and keep driving until I strip out the thread. I then put the work piece in place and drive it home. It can draw the work piece tight because there is no thread left. The other important job of the wood screw is to carry sheer loads. In carvel planking the screw gauge is unusually large. Nevens' rules for wooden yacht construction calls for 2" #14 screws for 1" planking. The reason for this is for the sheer loads. because the wood is relatively soft we need lots of bearing area to prevent the hull from wracking under load. While that might not be of much interest the modern boat builder we can learn from it. The Goejeon brothers came up with a clever way to spread the sheer loads in the wood for a self tapping screw when mounting hardware, yes it involves epoxy. If you are using a 1"# 8 screw,(I am ignoring the the thickness of the hardware in this example) drill a 3/8" hole 3/4" deep, fill hole with epoxy and hand drive the screw just snug. This increases the sheer carrying capacity and waterproofs the wood in one go. When using this method I wait as long as I can after filling the holes with epoxy before driving the screws because the epoxy sinks as it soaks into the wood the screw will displace some epoxy. Of course this can't used on vertical surfaces.
  2. Don, I think that you are way overthinking it. When I did my first EC, I was busy getting the my CS17 ready and the anchor was an afterthought. I scratched around and the lightest anchor I had was a 4# Danforth copy. As I was not planning on anchoring I dispensed with chain to save weight. I used 5/16" for the rode. I used that rig on all of my EC's and rode out a couple of wicked thunder squalls and never dragged. I think that the key was giving it lots of scope which is easy because we can anchor in very shallow water and using thin nylon. In the gusts it would stretch like a rubber band and absorb the shock load. Danforth used to say that you could go down one anchor size if you used thinner line. I got conservative and used an 8# Danforth and 3/8" nylon rode on Carlita. While visiting Gordie on Drummond Island he insisted on giving me his 11# Bruce because the Danforth fitted the bowsprit about as well as your Danforth fits your anchor sprit. I had never been a fan of the Bruce but when we tried it on Carlita, it fit like a glove. I gave him my danforth. I have had good success with both anchors and I am still not using chain. I know, if you live in New England you have to have a Herreshoff anchor. They are basically a fisherman with a bit more fluke area. The pull tests that I have seen show they drag much sooner than good modern anchors. As the only rocks that we have in our area have been carried here and there is no kelp and not much weed, I cannot think of any reason that I would want one.
  3. There is a reason why the halyard is led aft. The boat has single line reefing, if rigged properly. It is very convenient to be able to reef the boat from the helm in seconds. Don is correct, the left side in that picture is the leading edge. The reason that the top of the board is angled is to not foul the boom vang when the board is raised. While I prefer a centerboard, I put daggerboards in small boats because they take up less room. I have sailed daggerboards in shallow water a lot and the tips of my boards can prove it. While you have to pay a bit more attention with a daggerboard, I do not think that it is a big PITA. In dodgy water I sail with the board half up unless I am racing. I once won the around Carrot Island race in my Spindrift 10 doing that. There was a foul tide and light air. I was able to short tack in close behind a sand bank while the larger deeper boats struggled against the tide out in deeper water. Yes I made a bit more leeway but it was acceptable. You need to learn to get coordinated with that tiller extension. Unless you can hike out on the rail and move your weight forward, you will always be under performing.
  4. Yes you can modify the stern without hurting the boat structurally as long as you tie the critical parts into the boat properly. The aft bulkhead can be cut down to seat top height. You can cut out the middle of the lower part of the bulkhead but no more than Gira Gira did. The side stringers should go almost to the transom but you may have to add to them to support the new aft cockpit seat. You will need a support cleat across the transom to connect the seat to the transom. Because the aft seat area is too large for 6mmply you will have to add some support. This will depend on the hatch that you choose. I will stop here because the weather is looking really good for the long weekend and I have to get my boat ready. If you decide to go through with the project I will b happy to continue.
  5. That is a pretty picture, the boat and the big smile. Congratulations!!! Wheezer reminds me of granddaughter Marissa when she was that age. After sailing the Texas 200 in 09 while on the beach she instructed me to design a boat and name it after her, it became our center console power boat "Marissa". When it came time to paint the boat, I asked her what color should it be, she immediately said "pink". I said "no but I will meet you at red". I used up the end of that can of paint on Carlita. Unfortunately they grow up too quickly. Dr. Marissa has just started in practice and seeing patients. I do like the pink Spindrift. The only thing that I can see missing on your boat is the loop of light line (clew loop) that goes around the boom and thru the clew. It's purpose is keep the boom from drooping when you pull on the main sheet. The outhaul's job is control the draft of the lower portion of the sail. Without the clew loop it just flattens the lower part of the main. It will be more apparent in stronger winds. It is good that you are a good swimmer but I hope that you go thru some capsize drills so that you can self rescue when it happens. Good luck with your new boat .
  6. That is bad luck. The good news is that you built it and it is made out of wood, you can fix each problem piece by piece until it is as good as new. The Catspaw that we have kept on our dock for the last 20 years was on the stern of a power boat at the leeward end of a marina when an new owner of a 36' sloop got embayed in strong winds and crashed into the dinghy. The owner was well reimbursed by the insurance company, he left her with me. Her condition was similar to yours. No one knows that it has been crashed. I just cut out the damaged ply parts and spliced new parts back in. That vertical break in the side looks easy to repair with a butt block. I would use a 4" wide piece of 6mm ply. The reason for such a wide piece is force the hull back to it's original fair shape and to give plenty of gluing surface. Butt blocks do not have to look ugly if clean up the edges nicely. You would need to a pair of clamping blocks on each side of the repair to force the hull fair while the glue dried. If you do not have a deep reach clamp you can screw right through everything to clamp it in place. The gunwale is a bit trickier. It is impossible to get glue to completely fill the crack along the gunwale to hull joint. I solve that by running a handsaw down that crack so that I can glue in a sliver of wood that is well epoxied. If there is damage to the wood in the gunwales, you will have to cut out the bad bits and scarf in new wood. Just use an 8:1 taper on your scarfs. You can also do taped joints, just use the same tape as you used on your chine joints. You must tape both sides of a repaired joints. Tape won't force the patch into a fair shape but you can use clamping boards to force the taped joint fair while the epoxy dries. Don't forget the plastic release film. I would not sweat perfection, you need honest strong. This is just the beginning of her chequered history. Good luck with the repair.
  7. Yes, you interpreted correctly. The caveat is, I have not had the chance to verify the fuel burn yet. Those low speed numbers bothered me too. Evinrude claimed that with 2 strokes firing twice as often generate more torque at lower rpm than 4 strokes. I took those numbers from https://www.boat-fuel-economy.com/inboard-vs-outboard-fuel-consumption They show the Etech 50 burning .5g at 2000 rpm, Yamaha 50 .9g and Honda 50 .7g. and of course the performance was the best that could I tune in flat water but it gives some idea. The problem is interpreting apples with apples, we have to convert RPM to HP. The outboard makers do not release their torque/fuel burn curves like the diesel makers do. How much HP is each motor generating a 2000 rpm? I found a way to stretch the OK24 to 28 feet and keep the same properties and fairness without having to do a complete redesign, except for the volume. The stem and most of the frames stayed the same. LOA 30'5 with bracket, LWL 26' 2". Because the beam and height has not changed and displacement has not increased much,the scantlings do not change. There will be one new frame added and some readjustment of at least 1 frame. To run 6 knots gives a speed length ratio of 1.17 which does not take much effort. Here are a couple of screen shots of the stretched hull. I hope dust off our performance prediction program next week to see if we can get some realistic numbers. We have some real life numbers from a few OK 24's to help to dial it in.
  8. Dave, One of the advantages of building your own boat is that you understand how the boat was made and you are not afraid to get in and solve these little glitches rather than calling the dealer and waiting for him to get to it. If it was me I would keep the hole that you drilled. I would drill another hole through the trailing edge perpendicular or angled slightly to your hole so that the pennant goes down through the new hole and tie a stopper knot that is buried in your hole so that the pennant stays on the centerline of the board. It looks to me like your double line could get jammed between the trunk and the board. I would make a groove from the new hole to the top of the board to make sure that the pennant stays on center. This moves the pennant further from the pivot pin reducing the load on the pennant slightly. Looking at the plans, you should have enough height for a bimini. How are you connecting the halyard to the headboard? You may be able to raise the sail by reducing the distance between the halyard block and the headboard by tying a buntline hitch. I am using it on my boat, is a very reliable hitch and takes up the least space because it tightens down on the headboard.
  9. This is slightly off topic. Core Sound 17 Hull #1 was built out of aluminum and the last time I saw it was on the beach with the Panga's at Puerto Vallarta on the Mexican west coast. The builder resides there and is one of those guys who usually out-fishes everyone around him. He reaches out and back under sail and usually comes back in after burning no fuel with more fish than the big gas guzzlers. Here is the fuel burn curve that I made for my OB20 with an Etech 50 showing the hump. I trimmed the boat out as best as I could at each speed and took the lowest GPS reading in flat water. I took the fuel/RPM burn from Etech's web site and have not had a chance to verify it yet. You can see that I do not get any better mileage at 9 knots than 18 knots. For a large 20 footer, she is fairly economical due a small engine and accepting a comfortable planing speed as my cruising speed weather permitting. She does have trim tabs which I like but she jumps out of the hole quickly without them.
  10. Yes you just need to butt join those little triangles if you need them. They will later be covered by the centerline seam glass tape so there will be no loss of strength.
  11. Hi Dave, Congratulations on completing the Texas 200. I have done it twice and can appreciate why you are looking into a bimini. I would prefer that you do not reduce the size of the mizzen as you may have a lee helm problem. What is your hull # so that I can look at your rig? I thought that there was enough height under the mizzen, raised as high as it will go to sneak a bimini under the sail. The cheapest way to to raise the mast, if you need more height is to drill a new pivot hole lower down on the mast. This will raise the mast, you will have to move the the mast heel locking system up the tabernacle by the same amount.
  12. You have raised the age old dilemma, how to beat the hump. It is something that I have been struggling with for most of my working life. I do not think that we will ever see $2.50 a gallon gas again, so it is worth thinking about. The best approach is to go longer as you suggested and lighter. You can space out the framing to get longer. You can also add the outboard bracket. The bottom of the bracket sits a couple of inches above the transom and pitches up aft so that it does not drag while planing but lengthens the WL in displacement mode. It is hard to make the boat much lighter but you can pay attention during construction to not add anything unnecessary and choose okume ply over heavier species and not going above a 90 hp motor. Just by lengthening the boat and adding the extra structure you will end with a lower displacement to length ratio because it is a function of weight in long tons divided by .01 WL cubed, therefore it will be lighter for it's length. Trolling at 9 knots on the standard Ok20 with it's 16' 4" WL gives you a speed/ length ratio of 2.2. If you had an effective Wl of 25' your S/L R is 1.8. Is it worth it? If you spend enough time at this speed, it probably is.
  13. Hi Andy B. You are mostly right. There is no reason why the SR cannot be rowed. Alan and the Chief just rowed a 17 mk3 through the Harlow canal, you just have to set up the rowing station. I have not tried it yet but I believe I could fit a sliding seat in her if wanted. There is more stowage in the SR than the original because the seat lockers and under the foredeck are deeper but I never did use up all the stowage space on the mk1.
  14. Hi Viktor, It was always my intention to do a CS17 mk2. In fact I started designing the CS17 mk2 first when we got the order for the 20 mk2. My experience with the 20 mk2 confirmed the validity of the concept.
  15. The first four boats are home. Going by when the OK buttons were pressed on their Spot trackers, Skinny Genes was first on the Thistle. Heavily Laden was second on a class 1 kayak. Madmothist was third on a 49er and the Chief and SOS (Alan) came in fourth, one minute later. The rest of the field camped for the night. I am always impressed by anyone can paddle the whole course without sleeping and average over 3 knots, with most of the last 40 miles upwind.
  16. Ken, The nearest airport to us is Newbern. We can pick you up at Newbern and you can stay with us or you can sleep on one of the boats. I usually sleep on board over the weekend. There are two Hubs in NC served by the airlines with commuter service to Newbern, Charlotte and Raleigh. Charlotte is about a 6 hour drive and Raleigh RDU is about a three hour drive. Sometimes it is nearly as cheap to rent a car in Raleigh and drive down giving you a bit more independence and you get to see more of the area.
  17. The date for 2022 M&B Messabout is indeed October 21-23. There was some confusion when Marissa announced that date for her wedding day without realizing that it was already booked. She has changed her schedule and life will be back to normal.
  18. Ken, I m sorry to hear about your transmission issues. I am afraid that it was probably caused by you. Owners manuals usually say that when towing, take the car out of overdrive. The problem is that the cruise control locks the car at a constant speed, this causes rapid shifting on those rolling hills. The modern transmission has more gears to meet the demands of EPA for higher miles with smaller engines. It is a mechanical marvel but cannot be abused. Glad that you made it home. I look forward to Lula's next chapter.
  19. The console was moved a couple of inches forward after hull #1 because I expected everyone to use a larger motor. She is fairly stable longitudinally so she can take moving it further forward. Like everything, it is a trade off. The further you move the crew forward the harder the ride. I would prefer you to keep the move under 6 inches.
  20. On my trip out to Port Townsend with Carlita a few years ago I went through several zebra mussel inspection stations. I showed them the ballast tanks and the centerboard and trunk. They crawled under the boat with a flashlight and soon gave me the all clear.
  21. I am so sorry to hear this, I know that he has not been well for some time. I too enjoyed his company at the messabout's and the time he spent with us at the Mystic Wooden Boat Show.
  22. I do not usually disagree with Chic but I have piano hinges on the outboard edge my interior hatches and turn buttons on the inboard side. I always made sure that they were dogged down when underway in case of a knockdown. All exterior hatches are gasketed and dogged down.
  23. Frank, It took a while to find your boat's file and dig up an activation key for the old CAD program. Anyway it is now up to the current issue. I drew the Datum WL at 1470 # displacement. As has been discussed above, that there are always ripples on the surface and boats are rarely in perfect trim. I drew the painted WL 2" above the DWL Which works out at 12" below the chine at the stem and 3 1/2" below the chine at the transom. If you want to put on a boot top. It is 3" high at the bow, 1 1/2" amidships and 2" high at the transom. Remember all of these dimensions are measured vertically and not up the slope of the hull
  24. I remember my first employer telling me "the art of a craftsman is being able to disguise or work around your screw-ups. I have been where you are more times than I want to remember. I have not seen your problem but my instinct would be to trim some wood off one side and make it up on the other side with epoxy. A little adjustment with forward gunwales ends might be necessary. There may be some tweaking of paint edges. While you may not be able to eliminate the visual effect completely, reducing it will make invisible to most folk.
  25. I just want to clarify a couple points to avoid confusion. The sides of the Ocracoke and Outer Banks designs are planked with two layers thin plywood glued together after the 4 x 8 sheets are cut into narrower strips and fitted. This is done because the sides have compound curves (curved in two directions) to get the flare. This method is called cold molding. This is not to be confused with strip planking which is a very common construction method consisting of thin strips of solid wood edge glued over the hull. The term developable means that a flat sheet can be bent in one piece to the desired shape without stretching the edges or shrinking the middle. As an example you can take a sheet of paper and roll it into a cylinder or a cone. It can be heavily curved on one axis but must be straight on the other axis. Now try to wrap that sheet of paper over a globe and it will be instantly obvious that it cannot go without crumpling the edges or cutting darts. Developed panels are used in many of our designs and by carefully manipulating the surfaces you can get some excellent shapes, coupled with stitch and glue, makes for a good quick jigless build. The downside of jigless construction is lack of accuracy. On non planing hulls it is accurate enough. When designing Marissa, I attempted to build jigless and maintain the accuracy of a jig built boat. By using the boats structure as a jig you save the cost of cutting and purchasing disposable materials. The self draining cockpit sole set on a couple boards on a pair of saw horses became the jig base. To get the performance that I wanted necessitated keeping the hull light. To achieve a desired strength you can go with a thin skin with lots of internal structure or have a thicker skin and less internal support. The latter method will be heavier. The advantage of using the cockpit as the base, means that the boat cannot be out of square as both sides are identical, we proved this later when the cockpit was removed to finish the inside bottom, putting it back in the boat we deliberately put the port half in the starboard side and starboard into port, it made no difference (that had never happened to me before). While 9 mm ply can be a bit wavy, when the frames fit into their slots in the cockpit and the bottom stringers fit into the frame slots they straighten and true each up. I would not attempt to build a Marissa upright because you would never be able to get all of those pieces to fit without trimming after the fact, losing the methods main advantage. We design our boats to a resolution of one thousand of an inch which is also the resolution our CNC machine is set to. Do we get parts cut to within .001" (.025mm)? No, there is backlash and bit deflection to account for, but we get close. For example when we cut solid wood we cut the part .01" oversize and cut it again to size. This trim cut has very little bit loading, making a more accurate part. Our full size templates are printed from the same files that we use to toolpath our CNC files from. On larger boats like Marissa they are printed on mylar, while expensive, it is dimensionally stable and will not expand and contract with changes in humidity. Therefore a home builder can build just as fine a boat as the kit builder if he or she is a good and careful craft person and has a longer attention span.
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