New Design / New Build - Opinions & Advice Requested

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

  1. gabenix
    Joined: Sep 2014
    Posts: 9
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Carolinas

    gabenix Junior Member

    Hello to everyone! I'm a first time poster with a new boat project I want to start.

    I plan on constructing a boat that I just designed and welcome your opinions and advice. The plans I made are attached.

    Please go easy on me, this is the first time I've ever designed a boat.

    To begin, I know some topics can be a very opinionated. Understanding that, I want to state that this will be a single I/O boat with a bow thruster. Please don't provide opinions on why I should have two engines (i.e redundancy, power, handling, etc.) This does not need to be discussed.

    Okay, let's begin. The aesthetics of the boat design is based on a simple modern fusion of angles and curves. I used Wally Yachts as inspiration for much of my design. I wanted to design a boat small enough to trailer, yet large enough to retain some yacht style conveniences. This turned out to be a difficult process on such a small vessel without compromising aesthetics or usable space (my first concept started to look like a lobster boat).

    Things I wanted to incorporate:
    • Cockpit that is Protected from the Elements
    • Standing Room in Cockpit
    • Wrap Around Deck (avoid seating and other structures that impede access to the perimeter of the boat; this is good for docking, fishing, etc.)
    • Full Length Sunning Areas (6ft +) That can be accessed and utilized while under power.
    • Shallow Draft & Easy Planing
    • Stitch & Glue Type Construction of Hull
    • Hull Panels no wider than 4ft

    What I ended up with meets all of my design criteria. There is also additional room forward of the cockpit for a berth, head, and cook prep area with standing room at entry (entry hatch must be raised for standing area in berth). All hull panels are developable with no convex or concave surfaces (note the "plan view" that is green (green is good, red is bad.)

    The only software I had access to was Free!ship which is old and outdated, but it served it's purpose.

    Hull panels will be stitched together around permanent (and temporary) bulkheads and frames. After the hull panels are stitched and glassed, I plan on generously incorporating a good amount of longitudinal frames, stringers, and bulkheads with special attention to weak spots where taller bulkheads are not possible.

    Design length : 27.000 [ft]
    Length over all : 29.638 [ft] (with rear sun deck)
    Design beam : 8.500 [ft]
    Design draft : 1.500 [ft]
    Volume properties:
    Displaced volume : 106.86 [ft3]
    Displacement : 3.053 [tons]
    Total length of submerged body : 23.145 [ft]
    Total beam of submerged body : 8.430 [ft]
    Block coefficient : 0.3651
    Prismatic coefficient : 0.6821
    Vert. prismatic coefficient : 0.5157
    Wetted surface area : 166.77 [ft2]
    Longitudinal center of buoyancy : 8.633 [ft]
    Longitudinal center of buoyancy : 11.375 [%]
    Vertical center of buoyancy : 1.042 [ft]
    Waterplane properties:
    Length on waterline : 23.145 [ft]
    Beam on waterline : 8.430 [ft]
    Waterplane area : 138.14 [ft2]
    Waterplane coefficient : 0.7080
    Waterplane center of floatation : 8.764 [ft]
    Entrance angle : 10.468 [degr.]
    Transverse moment of inertia : 651.68 [ft4]
    Longitudinal moment of inertia : 4004.7 [ft4]
    Initial stability:
    Transverse metacentric height : 7.141 [ft]
    Longitudinal metacentric height : 38.520 [ft]
    Lateral plane:
    Lateral area : 29.874 [ft2]
    Longitudinal center of effort : 11.515 [ft]
    Vertical center of effort : 0.828 [ft]

    Last edited: Sep 11, 2014
  2. Petros
    Joined: Oct 2007
    Posts: 2,936
    Likes: 148, Points: 63, Legacy Rep: 1593
    Location: Arlington, WA-USA

    Petros Senior Member

    welcome to the forum!

    that is quite an ambitious project for an amateur design, very attractive. Do you have experiance or special education in the marine industry, particularly exposure to design?

    My first thought when I saw it is that swooping downward side strake would cause a slot of drag until you come up on plane. I imagine your thought is that it would help you come up on plane faster, which it might do, but below planning speed it would be like a drag brake. Perhaps if you fethered the narrow surface it backwards some it could retain the styling element of it and not be so costly at lower speeds.

    If you do not have someone experienced to help you with the design details, it might worth spending a little money with an experienced navel architect to assist you in executing the design. this would be money well spent rather than to go to the trouble of building it and find out it has some serous flaws, or mistakes you will have to fix later. It would save you money in the long run, and get you to where you want to be with this design that much faster.

    Good luck.
  3. Ad Hoc
    Joined: Oct 2008
    Posts: 7,659
    Likes: 1,538, Points: 113, Legacy Rep: 2488
    Location: Japan

    Ad Hoc Naval Architect

    Welcome gabenix to the forum.

    First question...have you defined a proper SOR..i.e the purpose and intent of the design..where it will go, how far how long etc etc? Second, have you a general arrangement drawing?...if not you need one. Without a GA dwg it is all just lots of meaningless numbers. Thirdly, you need to write a brief specification based upon your SOR and GA, and lastly you'll need to do a weight estimate based upon #1-3.

    Unless you do this and in this sequence, what you have drawn may well up in the bin. The point is, you don't know. So focusing upon minutiae of details such as the lines, drag missing the point of your objective, and that is to design a boat. You know nothing until the boat is designed, then you can see if it satisfies your SOR.
  4. gabenix
    Joined: Sep 2014
    Posts: 9
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Carolinas

    gabenix Junior Member

    Hey Petros and Ad Hoc, thanks for the welcome...

    Petros - Thank you for your thoughts, that is exactly the kind of response I'm looking for. Initially I had the strake more narrow nearer the bow area, but later widened it for appearances. Your thoughts do seem founded, and I initially was just thinking of the relative position and angle of the strake at the waterline at rest. I can definitely see it causing drag in a finite range of speed and it certainly needs to be considered, though I'm not sure if it deserves alot of attention. Generally, with a planing hull, you're either idling slowly, or moving on plane.. otherwise your wasting fuel while plowing through water between 10 - 20 knots which is avoided anyways...
    As far as boat design experience, I have none, and I wouldn't attempt to move into a commercial arena in boat design or even want to attempt designing multiple boats. But I do feel as though I have a good feel of the concept (enough to rely upon for a one-time project).

    Ad Hoc - I listed some of my requirements in the initial post. As far as the general use of the boat and it's main purposes: Mostly bay area pleasure use. The boat will spend most of it's time cruising intercoastal waterways and resting at local sandbars socializing. Perhaps a brief stent a few miles offshore occasionally (though I may not want to modify the transom for that.) Perhaps the greatest purpose of the boat is to give myself another project to tackle and complete. Another bucket list item. Initial rough weight estimate is 5,000 - 5,500 lbs including materials (ply, epoxy, fiberglass, acrylic, etc. , 800 lbs cargo / people, fuel, engine, beer..... At this point, I'm giving myself 500lbs extra, I'm sure it will get used somewhere. The final measurements and plans for construction will not be a problem, I'm extremely proficient in autocad as well as multiple design and 3D modeling cad systems.
  5. Petros
    Joined: Oct 2007
    Posts: 2,936
    Likes: 148, Points: 63, Legacy Rep: 1593
    Location: Arlington, WA-USA

    Petros Senior Member

    There are many excellent designs done by amateurs, and yours might be one of them. but considering the cost of materials and the investment in time and effort, once you have your lines worked out, it would be money well spent to have an a professional with experience in exactly the type and size of boat you want to build, to go over the plans with you to work out any overlooked details and considerations. Although I agree with your motivations, and often find many "professionally" designed boats not to my liking at all, there is still a lot of value in the opinion of someone that has done it a number of times before. Someone who has seen big mistakes before, and can point out areas that you may have overlooked. Interview several local naval architects and find one you like his approach and philosophy and see if you can work out a fee for service to consult on your design. Make it clear that you need him to excute your design ideas. What you spend with a competent designer to review all of your design details and assumptions could easily save you many times over in mistakes. And likely save you a lot of time too, since he or she would know all of the regulations and requirements that you must also meet.

    You will end up with a better boat, and something that would have more resale value as well for later, having a well known NA assist you in achieving your goals.

    Good luck and post your progress here so we can all enjoy it.
  6. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,401
    Likes: 1,039, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    I worry that boat may be broach-prone. Then again, I may be wrong ! But you don't want to find out the hard way.
  7. Wayne Grabow
    Joined: Aug 2003
    Posts: 251
    Likes: 17, Points: 18, Legacy Rep: 297
    Location: Colorado

    Wayne Grabow Senior Member

    Yesterday, my wife and I were boating when we had to pull a friend's boat off the rocks due to strong winds (and mismanagement). Skipping the details, it required us to approach the lee shore bow first to pick up a tow line with 2-3 foot waves breaking against our stern. I would hate to do that with your stern design. Bad weather can happen quickly.

    Overall, I am impressed with your design, especially for a first effort. You are getting excellent advice from some of our resident professionals.
  8. gabenix
    Joined: Sep 2014
    Posts: 9
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Carolinas

    gabenix Junior Member

    Hey Petros - Yes, don't get me wrong, I will definitely have a more finalized set of plans reviewed by a navel architect before starting, but I'm not close to that point yet. I'm most interested in the design and structural engineering part of this project of which I'll get more satisfaction from executing and learning rather than the construction process which will be mostly comprised of cursing, annoyance, and impatience lol. With that said, my next steps after feeling comfortable that the hull design will not change too much, will be structural framing plans. I'm considering making a 10/1 scale model of the hull and superstructure as a next step...

    Mr Efficiency - I do see the greater risk of broaching, especially with the combination of the BWL in the aft, combined with the sharp entry and lack of buoyancy nearer the bow, but I'm leaning more heavily towards design over function with this concept. The good news is this is designed to be a bay boat and not a rough water fishing or utility boat where the aesthetics would take more of a backseat to the function and fitness of the vessel.

    Wayne - Are you referring to transom height? If so, I completely agree! I've actually been on a boat that sank offshore because of that exact same situation and ended up treading water for 4hrs (exhausting). And if that wasn't enough, the boat that rescued us nearly diced me to pieces with their props, I was literally bear-hugging an outboard with the prop wirring away inches from my goods. There will definitely be an inset transom that will be about 1.5ft taller than what is pictured in that hull concept. Everything in those concept images besides the hull lines are included for visual reference only. The only thing I'm trying to solidify right now are the hull lines. Everything else including the transom design will be drawn in AutoCad after I feel comfortable with the hull form.
  9. JosephT
    Joined: Jun 2009
    Posts: 859
    Likes: 107, Points: 43, Legacy Rep: 218
    Location: Roaring Forties

    JosephT Senior Member

    gabenix, good looking loft, and if I do say so myself your rescue story about the prop "wirring away inches from my goods" was one of the most hilarious things I've ever read. I do realize it was a dangerous situation though and we're glad you're determined to build a safer boat.

    Good luck with your project and keep us posted.
  10. JSL
    Joined: Nov 2012
    Posts: 811
    Likes: 64, Points: 28, Legacy Rep: 41
    Location: Delta BC

    JSL Senior Member

    some observations:
    - Broaching (following or quartering seas) could be a problem.
    -could be a candidate for 'chine walking' (progressive heeling)
    -could be a wet, noisy,(slapping), ride.
    - Visibility from the helm (which window are you looking through???) looks a bit 'dodgy'. and could challenge the ColRegs.

    I would agree with others, get a professional to review the design.
  11. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 497, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I too see a number of issues and some professional guidance, will help in this regard. I'd consider much less hollow in the WL's forward and taking the warp out of the bottom, particularly for those envisioned, if occasional off shore blasts, will become more frequent. The chine is difficult to justify and just as difficult to design properly. This is a bit of black magic in design, with only some experience being the real guide, in where they go and how they should be shaped. You'd be best advised to not get too radical with this aspect. Though stylish, I don't see the need to split it either.
  12. Petros
    Joined: Oct 2007
    Posts: 2,936
    Likes: 148, Points: 63, Legacy Rep: 1593
    Location: Arlington, WA-USA

    Petros Senior Member

    I thought some more about this design, and something else occured to me. there is not much detail but it looks like it could be top heavy as well, it may not be, and some professional guidance, and deterniming the CG height would reveal is this is a problem or not, but it is something else to keep in mind.

    Also, if that hard chine is going to create issues, you can could reduce the size of it and flare it aft so it becomes more of a styling line than something that will alter the water flow. It does serve a useful purpose however, it should deflect spray away from the sides of the hull to give a more dry ride, so I would not eliminate it.
  13. gabenix
    Joined: Sep 2014
    Posts: 9
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Carolinas

    gabenix Junior Member

    Hey Everyone, there's a lot of good input here and I want to let everyone know I'm very grateful for your opinions and advice. Thank you.

    I've made some alterations to the hull form based on the critiques above. They're in the attached image.

    Joseph - Ha yea slightly traumatic situation, that one moment sticks out in my memory more than anything else from that ordeal. Fortunately everything was left intact and I've had 3 kids since then lol.

    JSL - I've made some changes to the hull and gave it a slightly deeper V. What do you think of the alterations? View from the helm should be good with wrap around windows. Helm position to be determined, could be in the center or to one side, depends on if I use the space forward of helm for a berth. Not sure if that's the way I want to go, to be decided later. Adding a berth would create a much trickier engineering issue with the structural integrity of that portion of the boat.

    Par - Thanks for chiming in. I took what you said about removing the warp to mean make the hull more of a monohedron style hull with a constant deadrise. I made alterations to that effect. The forward part of the bow still retains a slight concave shape, do you see that as a problem? I also increased the deadrise at transom slightly.

    Petros - That strake / hard chine is definitely something I want to keep as part of the aesthetic appeal of the design. I'm not sure what I'm going to do with it, but I did make some alterations by reducing the width and tapering it to have a vertical entry angle until it gets more aft where it needs to be more horizontal. Part of the reason why I beveled it vertically is to keep it as a focal point visually. It's something I want to be pronounced, but i feel if stays horizontal and narrow, it will end up disappearing visually. Hmmm... I'm not sure if I like it the way it is, still pondering what to do with it.

  14. gabenix
    Joined: Sep 2014
    Posts: 9
    Likes: 0, Points: 1, Legacy Rep: 10
    Location: Carolinas

    gabenix Junior Member

    So... I was thinking about my previous post with the updated alterations and I feel like the hull design was starting to lose most of it's character and began to look like every other planing hull out there, ordinary and mundane (exactly what I don't want to happen). I don't want to lose site of my fundamental goal which is to design a hull and boat that is unique with distinct styling. Obviously she needs to be fit for use, but I don't want the boat to be merely shaped by necessity of efficiency, speed, stability, etc. Rather, it needs to be an artistic impression that meets certain required criteria, not a mere quest to be the most efficient of all criteria, some sacrifice must be made.

    With that said, I'm back at the chopping block hoping to forge a design that is seaworthy, yet markedly different and unique. I've been messing with the lines and made a couple radical changes which yields another concept for consideration. The strake/chine has changed to actually twist and become a part of the hull. The bow line has most of the taper removed (more like a Vandutch). I've kept the deeper V which has increased the draft slighty. The displacement remains very close to expected. The sides of the hull start to slope inward near the aft similar to a runabout.



  15. gonzo
    Joined: Aug 2002
    Posts: 16,565
    Likes: 1,555, Points: 123, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    The rather extreme hollow forward in combination with the very wide chine flats will produce a very fast pitching movement. The little floatation reserve on the bow will bury and then the chines will slam. You should spend more time in the operational characteristics. Computer programs can be a drawback because they produce really pretty graphics that distract you from the actual designing.
Similar Threads
  1. Thomas F.
  2. Rasponov
  3. rony2014
  4. Chris Harding
  5. RCB Designs
  6. David L. Dodd II
  7. cluttonfred
  8. Adam Smalley
  9. KoruCaptain
  10. Biscuit
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.