Hobbyhorsing - Wharram Builders and Friends2024-03-29T13:23:35Zhttp://wharrambuilders.ning.com/forum/topics/hobbyhorsing?commentId=2195841%3AComment%3A169527&xg_source=activity&feed=yes&xn_auth=no Ditto the Merry Christm…tag:wharrambuilders.ning.com,2019-12-23:2195841:Comment:1705642019-12-23T15:56:56.171ZDean Wilkersonhttp://wharrambuilders.ning.com/profile/DeanWilkerson
<p> Ditto the Merry Christmas to all!! I will be spending it alone as I have for many years. Family is 800 miles away, but I prefer a quiet Christmas. I'll call my mother (87) and brother, and I'll light up my Komodo grill and smoke cook a special treat. Making up some mini pecan pie tarts with my own sort of puff pastry shells....... a creme cheese layer that settles in the middle. Pie filling made with real maple syrup instead of corn syrup, and bits of crystal ginger in…</p>
<p> Ditto the Merry Christmas to all!! I will be spending it alone as I have for many years. Family is 800 miles away, but I prefer a quiet Christmas. I'll call my mother (87) and brother, and I'll light up my Komodo grill and smoke cook a special treat. Making up some mini pecan pie tarts with my own sort of puff pastry shells....... a creme cheese layer that settles in the middle. Pie filling made with real maple syrup instead of corn syrup, and bits of crystal ginger in it. Sound good?? Sounds really good to me, as I will be coming off the second of my annual winter fasts on Christmas Eve. 5 days of water fast, following a single eating day after a 3 day water fast....... It's hard not to obsess about food under the circumstances ;-) </p>
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<p>I don't think most cats are designed to have a submerged transom...... rather they are overloaded. I totally agree with framing back during the build rather than chopping a finished hull off. The big benefit of the transom stern is more space where it would do the most good.... a decent aft berth.......... where a berth should be....... widen the aft portion of the hull rather than sucking it together for a Vee. Boats have been cut off and spiced back together many times, but that is an extreme solution. Here is a Utube of someone adding 5 feet in the middle of a <a rel="nofollow noopener" href="https://www.youtube.com/watch?v=_0sHe4q613s" target="_blank">Woods Gypsy Catamaran</a>. I'm not advocating anything like this, but it's a very impressive project. As this is about hobbyhorsing, I think displacement pods, fins, and foils are far more viable solutions. The chopped hull wouldn't do much if anything in and of itself. It really calls for a rounded or flat bottom and more aft displacement to do the job I think. </p>
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<p> DW</p> Immersed transoms are only a…tag:wharrambuilders.ning.com,2019-12-23:2195841:Comment:1705632019-12-23T03:33:33.143ZReuben Filsellhttp://wharrambuilders.ning.com/profile/ReubenFilsell
<p>Immersed transoms are only a penalty at very low speed, if the boat is moving quick enough and the flow breaks away then there is no consequence. What that speed is for various hull forms I'm not so sure about. From my observations of a few local cats if there is enough breeze to press the hull in, there is enough speed to free the transom. If it was a serious liability why would the majority of designs use it ?</p>
<p>My thoughts on transom mods for a Wharram would not be to cut it off but…</p>
<p>Immersed transoms are only a penalty at very low speed, if the boat is moving quick enough and the flow breaks away then there is no consequence. What that speed is for various hull forms I'm not so sure about. From my observations of a few local cats if there is enough breeze to press the hull in, there is enough speed to free the transom. If it was a serious liability why would the majority of designs use it ?</p>
<p>My thoughts on transom mods for a Wharram would not be to cut it off but to bring a more forward frame back which of course can only realistically happen on a new build.</p>
<p>Wharram has actually done this on the Tiki 25 "race" boat here. <a href="http://pca.colegarner.com/SeaPeople-001.pdf" target="_blank">http://pca.colegarner.com/SeaPeople-001.pdf</a></p>
<p>I agree with Dean, that foil hasn't had much thought put into it. But I do like the idea for a stock Wharram, I would have gone a bit bigger with a swept back foil section rather than a Delta, and deeper, on the bottom of the skeg. However on that boat the situation is complicated by the shaft and prop.</p>
<p>Anyway, I have already mentioned these thoughts on page one.</p>
<p>Merry Christmas people.</p> I agree that chopping the ste…tag:wharrambuilders.ning.com,2019-12-23:2195841:Comment:1706092019-12-23T00:41:47.990ZDean Wilkersonhttp://wharrambuilders.ning.com/profile/DeanWilkerson
<p>I agree that chopping the stern for a transom wouldn't work well........... But that's because you will have a dragging transom. For a mod like that to work, it would have to be recontoured so the transom was at or slightly above waterline... I disagree about the "slippery nature"........ I think that's absurd. Being open deck, they tend to be lighter than many other cats. A properly designed cat with a transom should allow the water flow to rejoin at the stern just as well as a double…</p>
<p>I agree that chopping the stern for a transom wouldn't work well........... But that's because you will have a dragging transom. For a mod like that to work, it would have to be recontoured so the transom was at or slightly above waterline... I disagree about the "slippery nature"........ I think that's absurd. Being open deck, they tend to be lighter than many other cats. A properly designed cat with a transom should allow the water flow to rejoin at the stern just as well as a double ender so long as the transom is not dragging. The problem with cats in general is that they have little load capacity, and are often if not usually overloaded. This results in a dragging transom, which would be a huge liability in terms of streamlining. It's pretty difficult to compare Wharrams to other cats as a generalization. The deep V hull if anything is a liability in terms of performance. It has long ago been abandoned by virtually every other designer of cruising multihulls...... for good reason. I think you would find that a Richard Woods catamaran with open deck, comparable length, and loaded weight would outperform a Wharram with the same sail area. He uses mostly round bottoms for just this reason. He does retain some deep V designs just for simplicity of build. How many people want to strip plank a round bottom hull with a chine??</p>
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<p>Has the lateral fin shown in the photos been sailed yet? What effect does it have? I can see where if the AOA is neutral with the boat level, as the stern pitches down or the bow up, it will get some positive angle and provide some lift....... I'm wondering why the trailing edge isn't feathered like an airfoil? Seems to me that an airfoil shape would probably be worth the effort unless it's just an experiment.......but having an aviation background, I tend to think this way. </p>
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<p> Dean</p> https://drive.google.com/open…tag:wharrambuilders.ning.com,2019-12-22:2195841:Comment:1704862019-12-22T21:49:54.473Zboatsmithhttp://wharrambuilders.ning.com/profile/qe0j3ojqb10
<p><a href="https://drive.google.com/open?id=1Nr49NPWi6LW2FkIwm-P-nQrQxzPcYoXv" rel="nofollow noopener" target="_blank">https://drive.google.com/open?id=1Nr49NPWi6LW2FkIwm-P-nQrQxzPcYoXv </a></p>
<p><a href="https://drive.google.com/open?id=1ikgKUNCytENwhfPX8hvf996DOo-KDBYr" rel="noopener" target="_blank">https://drive.google.com/open?id=1ikgKUNCytENwhfPX8hvf996DOo-KDBYr…</a></p>
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<p><a rel="nofollow noopener" href="https://drive.google.com/open?id=1Nr49NPWi6LW2FkIwm-P-nQrQxzPcYoXv" target="_blank">https://drive.google.com/open?id=1Nr49NPWi6LW2FkIwm-P-nQrQxzPcYoXv </a></p>
<p><a href="https://drive.google.com/open?id=1ikgKUNCytENwhfPX8hvf996DOo-KDBYr" target="_blank" rel="noopener">https://drive.google.com/open?id=1ikgKUNCytENwhfPX8hvf996DOo-KDBYr</a></p>
<p><a href="https://drive.google.com/open?id=1EUN2Yg24xcE1V919CIOuYhnSpL2eyGym" target="_blank" rel="noopener">https://drive.google.com/open?id=1EUN2Yg24xcE1V919CIOuYhnSpL2eyGym</a></p> If you chop off the stern of…tag:wharrambuilders.ning.com,2019-12-22:2195841:Comment:1706062019-12-22T21:02:59.316Zboatsmithhttp://wharrambuilders.ning.com/profile/qe0j3ojqb10
<p>If you chop off the stern of a Wharram and install a transom you will have a bastard child of no value. The boats do pitch more than many other designs. It also won't get shoved into a broach by large following seas as easily as a transomed boat. The double ended design also adds to the slippery nature of these boats which move quite well considering the tiny rigs. Like others have said, don't try and build an orange from apple plans</p>
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<p>If you chop off the stern of a Wharram and install a transom you will have a bastard child of no value. The boats do pitch more than many other designs. It also won't get shoved into a broach by large following seas as easily as a transomed boat. The double ended design also adds to the slippery nature of these boats which move quite well considering the tiny rigs. Like others have said, don't try and build an orange from apple plans</p>
<p></p> Dean have you seen this threa…tag:wharrambuilders.ning.com,2019-10-21:2195841:Comment:1694642019-10-21T22:27:54.841ZAllen Boselyhttp://wharrambuilders.ning.com/profile/AllenBosely
<p>Dean have you seen this thread? <br/><br/></p>
<p><a href="http://wharrambuilders.ning.com/forum/topics/adding-winglets-to-my-tiki-26" target="_blank">http://wharrambuilders.ning.com/forum/topics/adding-winglets-to-my-tiki-26</a></p>
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<p>Cheers, Allen </p>
<p>Dean have you seen this thread? <br/><br/></p>
<p><a href="http://wharrambuilders.ning.com/forum/topics/adding-winglets-to-my-tiki-26" target="_blank">http://wharrambuilders.ning.com/forum/topics/adding-winglets-to-my-tiki-26</a></p>
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<p>Cheers, Allen </p> And it could possibly be used…tag:wharrambuilders.ning.com,2019-10-10:2195841:Comment:1696332019-10-10T09:26:43.465ZReuben Filsellhttp://wharrambuilders.ning.com/profile/ReubenFilsell
And it could possibly be used as a step for swimmers. Win win win.
And it could possibly be used as a step for swimmers. Win win win. Ruben:
I like the foil co…tag:wharrambuilders.ning.com,2019-10-10:2195841:Comment:1694452019-10-10T02:00:28.405ZDean Wilkersonhttp://wharrambuilders.ning.com/profile/DeanWilkerson
<p>Ruben:</p>
<p> I like the foil concept... I've toyed with the idea before. The useful range of angles of attack for the foil you are using, if I read the chart right is about 8 deg either side of being in line with the fluid flow, after which the drag rapidly increases, and the foil will stall.... that's fairly significant in the real world, especially as water has a very high Reynolds number compared to air, and a fairly small foil will create considerable force. If the foil is…</p>
<p>Ruben:</p>
<p> I like the foil concept... I've toyed with the idea before. The useful range of angles of attack for the foil you are using, if I read the chart right is about 8 deg either side of being in line with the fluid flow, after which the drag rapidly increases, and the foil will stall.... that's fairly significant in the real world, especially as water has a very high Reynolds number compared to air, and a fairly small foil will create considerable force. If the foil is aligned with the static water line, then when the boat is moving forward the aft mounted foil will produce a lifting force when the stern drops, and a downward force when the stern lifts, which is exactly what you want. If it has enough authority, it will considerably dampen pitching, and if the foil projects outboard it should also dampen roll, which though roll is hardly an issue, would also be a positive contribution. The airfoil should actually be a symmetrical foil, and if I were doing this, I would use the top profile on both top and bottom. The further aft the foil is, the better, and an endplate / foil on the rudder would be pretty ideal, as the foil would have the max authority there, and at the same time increase rudder authority by blocking the flow around the bottom of the rudder.</p>
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<p> Hobby horsing seems to be a problem only in very specific conditions, but foils would seem to be beneficial all the time, and even lowering the outboard nacelles would probably have a useful dampening effect... far more than the drag they create.</p> Hi Dean,
My understanding of…tag:wharrambuilders.ning.com,2019-10-10:2195841:Comment:1697092019-10-10T00:57:13.685ZReuben Filsellhttp://wharrambuilders.ning.com/profile/ReubenFilsell
<p>Hi Dean,</p>
<p>My understanding of the rationale behind the canoe sterns is that these designs are primarily for tradewinds sailing, i.e., downwind, as I understand it the idea is that the canoe stern sinks into the following wave rather than be lifted by it which could then stuff the bow in. </p>
<p>It's my observation that as soon as modern cats increased transom volume to avoid pitching they then went rapidly to plumb bows and higher prismatics to stop the bows digging in, this now…</p>
<p>Hi Dean,</p>
<p>My understanding of the rationale behind the canoe sterns is that these designs are primarily for tradewinds sailing, i.e., downwind, as I understand it the idea is that the canoe stern sinks into the following wave rather than be lifted by it which could then stuff the bow in. </p>
<p>It's my observation that as soon as modern cats increased transom volume to avoid pitching they then went rapidly to plumb bows and higher prismatics to stop the bows digging in, this now creates more volumous shapes and higher building complexity.</p>
<p>Back to Wharrams, if your going to add volume to the stern you might need to plumb the bow and now your back to building from scratch and it is really no longer a Wharram.</p>
<p>As for the canoe stern it's not entirely useless, it adds waterline length and lowers hull beam ratio which decreases wave making, I'm sure you know all this.</p>
<p>Boat designs are an assemblage of compromises so I guess it's up to each individual to work out which design fits the bill.</p>
<p>I crew on a Corsair trimaran, as a yacht its a beauty to sail, fast, nimble, exciting, but no load capacity, flops from side to side at rest, probably over canvassed, especially the asymmetric so not relaxing.</p>
<p>I'm not a rich man, just a humble handyman, I may, if I'm lucky, get a small used Wharram to potter up the coast in, every style of catamaran I have looked at, Wharram, Woods, Simpson etc gets a mental redesign, thinner ply to torture some extra volume maybe, Paulownia timbers, better foils. At the end of the day, without doing a boat design course, its better to just accept the compromises.</p>
<p>And hence why I suggested the horizontal foils. KISS.</p>
<p>Reuben</p> Ruben:
The sponson adde…tag:wharrambuilders.ning.com,2019-10-09:2195841:Comment:1694442019-10-09T17:06:41.778ZDean Wilkersonhttp://wharrambuilders.ning.com/profile/DeanWilkerson
<p>Ruben:</p>
<p> The sponson added to the inboard side of the hull could incorporate boarding steps, functioning like a transom with steps. It's main function being to add displacement above the WL, and secondary function to facilitate boarding. It would be faired into the hull forward at least half way between the two bulkheads forward of the sternpost. </p>
<p> IMHO, the stern compartments offer very little of value, so if you were to chop the boat there during construction you…</p>
<p>Ruben:</p>
<p> The sponson added to the inboard side of the hull could incorporate boarding steps, functioning like a transom with steps. It's main function being to add displacement above the WL, and secondary function to facilitate boarding. It would be faired into the hull forward at least half way between the two bulkheads forward of the sternpost. </p>
<p> IMHO, the stern compartments offer very little of value, so if you were to chop the boat there during construction you would be gaining more than you would be losing......... except for one factor. If you put a transom in.... say at the aft bulkhead, or slightly behind it, your transom would drag, and proper transoms should be above the WL at rest. That's a standard bit of engineering on modern cats. So adding a transom would involve putting triangular bottom piece of ply in to transition from the deep V to a flat or rounded bottom........ Not a big deal, but something to remember if you contemplate doing this. To do this on an existing boat would be a challenge to say the least!! One would have to remove the last too bulkheads and the stern post in order to achieve a smooth shape transition for a more full stern, as well as adding freeboard, though that could be done as part of the coach roof. All of these considerations apply to a new build. I see zero real benefit to the canoe stern personally.... it's a styling statement IMHO and not much more than that. </p>
<p> Here is a photo of some rather elegant inward facing transom steps...... I like the idea.... Obviously is is not directly applicable. The general idea of adding to the inboard side right at WL makes more sense to me in terms of the simplicity of being able to keep the canoe sterns. This is by no means what I have in mind, but it was the inspiration...... Nothing says the steps have to be right at the transom.</p>
<p>DW</p>
<p><a href="https://www.epoxyworks.com/wp-content/uploads/2014/07/transom-and-aft-steps.jpg" target="_blank" rel="noopener"><img src="https://www.epoxyworks.com/wp-content/uploads/2014/07/transom-and-aft-steps.jpg?profile=RESIZE_710x" class="align-full"/></a></p>