New Design / New Build - Opinions & Advice Requested

Discussion in 'Boat Design' started by gabenix, Sep 9, 2014.

  1. Mr Efficiency
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    Mr Efficiency Senior Member

    You are asking for trouble putting "style" before functionality ,imo, handsome is as handsome does. The boat appears to need fuller bows to balance the relatively flat and broad afterbody.
     
  2. gabenix
    Joined: Sep 2014
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    Location: Carolinas

    gabenix Junior Member

    Hey Gonzo and Mr. Efficiency, thanks for the input. Yea, I was having a hard time letting go of that swooping chine and was throwing ideas around, more or less brainstorming and treating the design more or less like how concept cars are where the initial designs are never meant to be practical but inspirational for a final product. As you both mention, the beam and area I require in the aft is mainly what I've been struggling with, not wanting to match it with the type of bow required.

    I've made some changes and toned it wayyy down, removing most of the chine resistance and adding more bow area and volume. I'm still incorporating the swooping curve, but have just incorporated it as a quasi spray rail.

    Oh, Mr Efficiency, I didn't mean for that post to come across as I was putting style before functionality, though I can see how it may come across that way.. I was merely stating that I don't want to lose sight of the "design" aspect by getting carried away with excessive functionality and protocol.

    Modified design is below (still a work in progress):
    [​IMG]
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    I should say designing a boat that will run well in broad, windswept, shallow bays is a tough essay, more exacting in many ways than operating on the open sea.
     
  4. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    I like the WL's now, but the double lower chine treatment looks like it'll ventilate the upper chine flat, which is self defeating and might lead to a "dry chine" situation and other undesirables at speed.

    Playing around with this area, will yield little but performance degrades, so self debate the need for folds and turns in the running surfaces, carefully. You could live without the lower chine entirely and this should be strongly considered. Of course this will alter quite a bit, so you'll have to ply with things again, especially forward. What's the deadrise at the transom now and how far forward are you able to carry this angle?
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    The latest configuration looks like it would slam like a lavatory lid. The shape is changing rapidly !
     
  6. SamSam
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    SamSam Senior Member

    Above deck those roof supports will be majorly in the way, plus they have a lean-to shed look to them. They should be eliminated entirely or replaced with a knee brace type support coming off the aft end of the side windows.

    That front prism type window might be hard to see through, especially with dried water /salt spray all over it. I can't imagine a practical way to put windshield wipers on it.
     
  7. gabenix
    Joined: Sep 2014
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    gabenix Junior Member

    Par - Chine is removed. Deadrise is 15 degrees and constant for about 9ft (LWL - 25.6). From there is varies / twists to bow.

    Mr. Efficiency - Slamming is not good. "Lavatory"... is now the word of the day.

    SamSam - The gnarly looking cockpit is just conceptual, I'm def not sold on it. Was borrowing some concepts from some of the wally yachts. The only wiper blades would be 3 coats of rainX.

    Modifications below... Removed a chine as Par suggested. Tweaked some other things. May shorten the beam in the rear a slight bit and widen a lil bit more mid-ship. Not sure yet. I don't the water lines near the bow right now, I'll will be working on cleaning those up later. The overall hull-form has ended up very similar to the VanDutch type of hulls though still distinctly different.

    [​IMG]

    [​IMG]
    [​IMG]
    [​IMG]
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    Your latest incarnation would ride a lot better, but how it will track with sea coming from behind, is what might concern me. And how "wet" are these things, with their plumb bows ?
     
  9. PAR
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    PAR Yacht Designer/Builder

    Plumb bows on high speed powerboats aren't really an issue. They're carrying the bow at running trim, so it's rake doesn't come to play. I think plumb bows are a waste of materials and added weight on high speed powerboats - they're really just styling exercises, unless the boat is big enough to need the accommodations volume.

    The removal of the lower chine has cleaned things up a bit, increasing deadrise forward, which will help her entry and wave cutting ability too. The slight hollow in the forward WL's isn't as objectionable with the increased deadrise either.

    15 degrees is a lot of deadrise for a semi protected waters boat, especially if being used as a fishing platform is desirable. On the other hand this deadrise will be helpful in the near shore ventures and when it gets rough.

    She'll turn better if you "tuck in" the chine in the aft quarters a bit. This will be better then making her wider amidship. Her current dead straight aft chine (in plan) will let her track nice, but will resist turning a little and creates unnecessary turbulence. All wide butted boats (and other half's) will have some difficulty in a following sea, if a typical plane hull shape.
     
  10. gabenix
    Joined: Sep 2014
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    gabenix Junior Member

    Hey, thanks for the input guys! I've thought about the plumb bow a bit and came to some conclusions, but I know nothing and am not sure how overall function is affected. Let me blurt out my thoughts to test if I'm on the right train of thought (boat design wise) and please chime in about it.

    READER DISCLAIMER: The following comments are completely subjective and my IQ on this is close to 0.

    * If it was a good design we'd see a lot of boats with plumb bows. Obviously the downside is greater than the upside.

    * It adds about 10% LWL to the boat. This probably comes with both pros and cons. More wetted surface and drag (which disappears while on plane).

    * (Maybe) less resistance if a following sea pitches the bow down into a swell. Bow will attempt to "cleave" into the swell. This scenario, if severe enough, would scoop water over the bow and into the boat. Otherwise, the looks are deceiving, and the upper tip of the bow is actually moved back and buoyancy will keep the bow high enough to keep complete immersion from happening unless you're in high seas with very short periods.

    * The boats in the photos by "VanDutch" are well known for comfortable sea keeping. Doubt this has anything to do with the bow though.

    * Probably wetter ride, but not as much as you'd initially think. I imagine windy days with a good chop would be bad.

    * Design is probably mostly cosmetic for power boats.

    Par - Thanks for all of the comments. Deadrise went from about 13.5 to 15 when I removed the chine on the last edit. Didn't move it back (yet). Still not sure what I want to do. I'm struggling with having a 27' boat (decently large boat for my standards) that can't handle a lil open water every now an again. Also, which part of the chine flat should be tucked in for turning, the inside or outside, or both?

    [​IMG]
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    The upper part of the bows certainly comes into play when you run into the back of a decent chop at any sort of speed. I would be getting ready to duck, to avoid a bath.
     
  12. PAR
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    PAR Yacht Designer/Builder

    The whole chine, not just elements of the flat, move in. This hunt and peck approach isn't the best way to get a good design. Maybe a set of plans, where you can add your reverse curved styling line in the topsides and deck structure, is a better way to go. I mention this because there are other considerations I have issues with, such as the chine sweep in elevation.
     
  13. Wayne Grabow
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    Wayne Grabow Senior Member

    http://www.frauscherboats.com/en

    This German boat company appears to have a concept similar to the VanDutch designs. It is nice to see something different but which still respects basic principles.
     
  14. gabenix
    Joined: Sep 2014
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    gabenix Junior Member

    Hey Wayne, Thanks for the link! I've haven't came across that builder before, but their boats are very similar to the VanDutch type, just with more angular geometry (similar to where my thought processes were going). I do like their boats, very edgy and modern, with a touch of vintage.

    Hey Par, thanks for the advice.. I realize the "hunt and peck approach" is not the most efficient and reliable, but honestly, I'm thoroughly enjoying the process of it. I have a lot of time on my hands before I can start, so I'm using this time to to really get a feel of the hydrodynamics aspect and how it affects everything else. And besides, I'm not nearly committed to any "one" design or concept to move ahead, just merely brainstorming... The construction and physical product are lower on my goal list, trailing the "design & engineering" part of the project, which to me is truly a delight. With that said, I do fear my weakness in this area is truly going to be revealed within the complexity and quantity of the components on a boat of this size. An area where wisdom and experience really play a role - consideration of all components, placement, and inclusion within the construction and framing plans of the project. I do feel your input has been very helpful, and I'm extremely grateful.

    Tomorrow, I'll post some modifications I made to the hull as well as some floor plan & seating arrangements I sketched - they're on a different computer so I don't have access to them at the moment...
     

  15. boatbuilder41
    Joined: Feb 2013
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    boatbuilder41 Senior Member

    great input from everyone... thats why i like this site. although i dont post often.... i like to listen and learn . kinda self educate from the input of professiomals. i design and build custom boats so no two boats i build are ever the same. i enjoy the comments of professionals here. although i design and build boats .... nobody knows it all...... i learn every day from these guys..... just expect some great comments and a little critism .... but take it with kindness. its just to help you and others build a better.... safer boat. and just remember....... you asked for it.... very nice start for a beginner..... these guys will help you get on track.
     
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