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Thread: Pilothouse Skiff - sketches

  1. #1
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    Default Pilothouse Skiff - sketches

    Sorry but I didn't sucessfully attach the drawings I wanted to share -
    Attached Images Attached Images

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    Default Re: Pilothouse Skiff - sketches

    Topheavy?

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    Default Re: Pilothouse Skiff - sketches

    Likely to ride bow up when planing and pounding in anything but flat calm.

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    Default Re: Pilothouse Skiff - sketches

    No way!
    Hull is way to small for that Cabin.
    Take a look at Downeast Bassboats. Standing Headroom under folding Bimini/Dodger.

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    Default Re: Pilothouse Skiff - sketches

    Thanks for all the comments! The hull bottom is actually flat in the aft bottom, from the just forward of Bmax back to the transom, with a slight rocker forward of only 5" or so. I built a scale model to work out this shape. It is not like the old "Brockway" styled skiff. which have dory-shaped rocker longitudinally throughout the run of the bottom. The flat-aft/rocker forward shape was achieved by cutting the side panels with a concavity in the bottom panel,which forces the bottom section flat in the aft section as the sides are bowed out when assembled. I'm probably not describing it adequately, but Walter Baron should be credited for this concept, and there are lots of his boats out there with happy owners using them.
    As for the fore/aft trim, that should be optimized by weight distribution (i.e. not too much heavy gear forward). FYI, there is a great short video by Mark Vickers on YouTube showing one of Walter's skiffs running at full speed WOT, in a light chop ("Building the Lumberyard Skiff - How it Performs on the Water").

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    Default Re: Pilothouse Skiff - sketches

    Looks like a nice dory-skiff to me. I image it would defy expectations as such dories always have.
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    Default Re: Pilothouse Skiff - sketches

    Quote Originally Posted by koederfischgriller View Post
    No way!
    Hull is way to small for that Cabin.
    Take a look at Downeast Bassboats. Standing Headroom under folding Bimini/Dodger.
    I actually did look at many small Downeast designs (including the Bass boat style) before I came up with this design.
    I am aware that conventional design wisdom says that a standing headroom pilothouse should not be used on any hull under 25 ft LOA, more or less, but, hey, I like thinking outside the box, and that's why I'm building it my way. I spent many hours drawing different profiles, and many spreadsheets calculating hull displacements, immersion values, surface areas, etc., before I came up with this design. If it doesn't look good in real life, then I'll take full responsibility for the results. But I'm just a student of all this stuff; not an expert.
    Thanks for your comments; that how we learn!!

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    Default Re: Pilothouse Skiff - sketches

    One of my previous builds. I co-designed this boat with Lee Creekmore, many years ago, and it was pretty successful in off-shore racing in Florida/Bahamas waters. Sorry for blasphamy; it was/is a solid fiberglass hull (but did have a wood interior!)
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    Last edited by CaptChap; 08-06-2022 at 08:05 AM.

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    Default Re: Pilothouse Skiff - sketches

    your design does not look dissimilar to

    https://www.boatbuildercentral.com/p...at-plans-hm19/

    Although the Harbor Master may have more of an upturned bow.
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    Default Re: Pilothouse Skiff - sketches

    Quote Originally Posted by CaptChap View Post
    One of my previous builds. I co-designed this boat with Lee Creekmore, many years ago, and it was pretty successful in off-shore racing in Florida/Bahamas waters. Sorry for blasphamy; it was/is a solid fiberglass hull (but did have a wood interior!)
    Quote Originally Posted by SKIP KILPATRICK View Post
    your design does not look dissimilar to

    https://www.boatbuildercentral.com/p...at-plans-hm19/

    Although the Harbor Master may have more of an upturned bow.
    Yes, you are correct, Skip... That was one of the many designs that influenced my thinking. I realize that it may not be for everybody, but the reasons I chose to go with the flat bottom is that (1) is is VERY easy, cheap, and fast to build; and (2) it doesn't require a big, expensive outboard motor to drive it, vs. a deep-vee hull of similar size.
    For several years in the Bahamas I had a nice 20 ft. Sea Hunt center console boat which I enjoyed very much. It was a dream to drive, even in heavy chop. It did, however, have a 115 HP 4-stroke engine to push it (the "experts" said it needed a 150). This little skiff should be quite happy with a 40-50 hp, motor, which is a LOT cheaper to buy & operate.

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    Default Re: Pilothouse Skiff - sketches

    Funny, I had a 20' Sea Hunt dual-console I loved that boat. And yes it had a 150 2-stroke and a 65 gal tank. That would be a beast at the gas pump even back then... now ugh!

    I am certainly happy to sacrifice speed for efficiency these days. My current boat has a 20hp Suzuki and can run all day on 3 gallons.
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    Default Re: Pilothouse Skiff - sketches

    Quote Originally Posted by CaptChap View Post
    I actually did look at many small Downeast designs (including the Bass boat style) before I came up with this design.
    I am aware that conventional design wisdom says that a standing headroom pilothouse should not be used on any hull under 25 ft LOA, more or less, but, hey, I like thinking outside the box, and that's why I'm building it my way. I spent many hours drawing different profiles, and many spreadsheets calculating hull displacements, immersion values, surface areas, etc., before I came up with this design. If it doesn't look good in real life, then I'll take full responsibility for the results. But I'm just a student of all this stuff; not an expert.
    Thanks for your comments; that how we learn!!
    Did you calculate the range of positive stability taking account of wind loading?
    Stability will reduce rapidly when a chine comes out of the water.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Pilothouse Skiff - sketches

    The flat Bottom is not a Dealbreaker at al to me. You might think of a Daggerboard for low speed manoverability and "counter Windage".There is a Youtuber who has one in his Power-Dory. Oregon Oldtimer is his Name i think

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    Default Re: Pilothouse Skiff - sketches

    To please the eye, it needs to be stretched at least 10% to lessen the visual impact of the house.
    If you are going to the effort and expense of building her, a small amount of V is only a couple percent more work.
    I had a 22' C-Dory with a warped bottom and 5 deadrise at the transom. It was still harsh in any kind of chop.
    I suggest you reconsider the flat bottom.
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    Default Re: Pilothouse Skiff - sketches

    Stay flat, or switch to a Tolman Skiff. Adding the slightest bit of V makes a big difference in terms of effort

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    Default Re: Pilothouse Skiff - sketches

    Quote Originally Posted by SKIP KILPATRICK View Post
    Funny, I had a 20' Sea Hunt dual-console I loved that boat. And yes it had a 150 2-stroke and a 65 gal tank. That would be a beast at the gas pump even back then... now ugh!

    I am certainly happy to sacrifice speed for efficiency these days. My current boat has a 20hp Suzuki and can run all day on 3 gallons.
    Skip - That's precisley why I'm going with this boat; I can't afford those expensive powerplants any more. I could actually use a 25 hp on this, if I didn't mind slower cruising speed. Even then it would be faster than an 18 ft. sailboat! And when the weather looks questionable, I'll stay in my recliner and read Wooden Boat Forum!

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    Default Re: Pilothouse Skiff - sketches

    Quote Originally Posted by koederfischgriller View Post
    The flat Bottom is not a Dealbreaker at al to me. You might think of a Daggerboard for low speed manoverability and "counter Windage".There is a Youtuber who has one in his Power-Dory. Oregon Oldtimer is his Name i think
    Interesting! I am actually putting an external keel running down the centerline, but more for grounding & trailer protection than for directional stability (however it may add a small amount of that, as well). It's a 2x6 CVG fir keel encapsulated in xynol/epoxy. That stuff is tough! (It's been dubbed "poor-man's kevlar). The hull is already encapsulated in that as well.

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    Default Re: Pilothouse Skiff - sketches

    Quote Originally Posted by Autonomous View Post
    To please the eye, it needs to be stretched at least 10% to lessen the visual impact of the house.
    If you are going to the effort and expense of building her, a small amount of V is only a couple percent more work.
    I had a 22' C-Dory with a warped bottom and 5 deadrise at the transom. It was still harsh in any kind of chop.
    I suggest you reconsider the flat bottom.
    I understand your comments, and am well aware of the performance constraints of my design. However, this hull is already built, and I'm looking forward to using it as built, limitations and all. If I had wanted to build a Vee-bottomed boat, or a deadrise boat, or a dutch double-ender, I would have, but this time I wanted to to build this design. I have a bit of experience at sea, both under power and sail, and some experience designing, building, and repairing boats. Thanks!

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    Default Re: Pilothouse Skiff - sketches

    Quote Originally Posted by Peerie Maa View Post
    Did you calculate the range of positive stability taking account of wind loading?
    Stability will reduce rapidly when a chine comes out of the water.
    Nick - A good idea, but, no I haven't done those calcs yet. Been too busy sanding & fairing! As soon as I get around to it, I'll post them. Based on my experience with similar-sized boats with large bimini tops, the biggest problem is when docking in a cross-breeze. I am however, installing built-in foam floatation to meet USCG regs. Thanks for the comment.

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    Default Re: Pilothouse Skiff - sketches

    Ah, the build is progressing, good for you. The fine bow will help, my C-Dory had a rather full bow.
    Docking in the wind is tricky with these boats, I could have used a daggerboard or leeboard a few times.
    ​​♦ During times of universal deceit, telling the truth becomes a revolutionary act
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    Default Re: Pilothouse Skiff - sketches

    I may well be wrong but I have a strong feeling that the curve of areas will be much fuller at the stern.Which makes me imagine a lot of green water climbing over the bow,unless a bit more flare is worked in.

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    Default Re: Pilothouse Skiff - sketches

    Quote Originally Posted by John Meachen View Post
    I may well be wrong but I have a strong feeling that the curve of areas will be much fuller at the stern.Which makes me imagine a lot of green water climbing over the bow,unless a bit more flare is worked in.
    Yes, John, the beam is carried much more aft than forward, and there is considerably less volume in the forward sections. Because of this, I will initially launch her without any house structure, and test (with weights) the optimum placement of any planned structures. Bear in mind that the weight of a 40-50 hp outboard, a 8" jackplate, 2 fuel tanks, and the batteries, will be aft of the longitudinal CL, and the crew (probably only me and an occasional friend) will be somewhat near the CL. I plan on positioning very little forward, and probably even stow the anchor in the cockpit, ranther than forward. Also, I plan on installing substantial sprayrails (not shown) on the forward bow, as well, to help with any spray.
    Since this is only a simple lumberyard skiff built of flat plywood panels, the addition of any topside hull flare forward (i.e. "Carolina flare") was way beyond the scope of this simple project. As I stated previouslly, I have owned (and enjoyed) a great 20 ft. center console (Sea Hunt 202 Triton) that had plenty of bow flare, and it was very dry, even in nasty seas. I also fished it many miles offshore in the Atlantic, off the Bahamas, and always felt safe. HOWEVER - this little skiff will never venture beyond the protected inshore bays & coves around Jonesport Maine, and only in the usually flat summer. Thanks for the comments... keep 'em coming!

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    Default Re: Pilothouse Skiff - sketches

    Quote Originally Posted by CaptChap View Post
    Yes, John, the beam is carried much more aft than forward, and there is considerably less volume in the forward sections. Because of this, I will initially launch her without any house structure, and test (with weights) the optimum placement of any planned structures. Bear in mind that the weight of a 40-50 hp outboard, a 8" jackplate, 2 fuel tanks, and the batteries, will be aft of the longitudinal CL, and the crew (probably only me and an occasional friend) will be somewhat near the CL. I plan on positioning very little forward, and probably even stow the anchor in the cockpit, ranther than forward. Also, I plan on installing substantial sprayrails (not shown) on the forward bow, as well, to help with any spray.
    Since this is only a simple lumberyard skiff built of flat plywood panels, the addition of any topside hull flare forward (i.e. "Carolina flare") was way beyond the scope of this simple project. As I stated previouslly, I have owned (and enjoyed) a great 20 ft. center console (Sea Hunt 202 Triton) that had plenty of bow flare, and it was very dry, even in nasty seas. I also fished it many miles offshore in the Atlantic, off the Bahamas, and always felt safe. HOWEVER - this little skiff will never venture beyond the protected inshore bays & coves around Jonesport Maine, and only in the usually flat summer. Thanks for the comments... keep 'em coming!
    CORRECTION: Sorry - I meant to say "longitudial center of buoyancy" above.

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    Default Re: Pilothouse Skiff - sketches

    Quote Originally Posted by Autonomous View Post
    Ah, the build is progressing, good for you. The fine bow will help, my C-Dory had a rather full bow.
    Docking in the wind is tricky with these boats, I could have used a daggerboard or leeboard a few times.
    Hey Autonomous, Thanks. Actually I quite liked the way the C-Dory fit a very usable pilothouse onto their hull, and it was one of the reasons I started looking into something similar on my little skiff. I understand the limitations on comfort in a chop, but still those boats have satisfied a lot of folks who cannot afford (or do not want) anything bigger. Cheers!

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    Default Re: Pilothouse Skiff - sketches

    I like your skiff design. It will probably be on the stiff side unless you get to about 2000# displacement. I ran some stability calcs based on the information you presented above. You might want to run the ultimate stability calcs as also stated above.

    Blowing off by the bow is a big pain in the rump for flat-bottom boats. I would run 4 full-length "lifting strakes" instead of the keel you stated above. They can be glued and screwed on outboard of the Xynole fabric. Not that these lifting strakes will solve the bow blow-off, but just be ready for it. I can't recommend a flat-bottom boat for choppy water, but if you slow down you can go without pounding. I just sold my 18' by 6' flat bottomed skiff, and I took it out in pretty bad conditions. It was a real workout when loaded below 1500#.

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    Default Re: Pilothouse Skiff - sketches

    Quote Originally Posted by Skiff Man View Post
    I like your skiff design. It will probably be on the stiff side unless you get to about 2000# displacement. I ran some stability calcs based on the information you presented above. You might want to run the ultimate stability calcs as also stated above.

    Blowing off by the bow is a big pain in the rump for flat-bottom boats. I would run 4 full-length "lifting strakes" instead of the keel you stated above. They can be glued and screwed on outboard of the Xynole fabric. Not that these lifting strakes will solve the bow blow-off, but just be ready for it. I can't recommend a flat-bottom boat for choppy water, but if you slow down you can go without pounding. I just sold my 18' by 6' flat bottomed skiff, and I took it out in pretty bad conditions. It was a real workout when loaded below 1500#.
    Hello Skiff Man -
    You are spot-on about the displacement numbers! during the design process I calculated the following:
    ESTIMATED DISPLACEMENT IMMERSION DATA
    WL DEPTH (IN) (FT) VOLUME (CU.FT.) WEIGHT (LB.)
    5.0 0.41667 28.5 1823
    5.5 0.45833 31.3 2005
    6.0 0.5 34.2 2188
    6.5 0.54167 37.0 2370
    7.0 0.58333 39.9 2552

    I am bringing the painted waterline (bottom coating in graphite/epoxy) up to 7" above the chine/bottom, thus allowing for the rare occasion when I am carrying a loaded disp. of 2500 lbs. I'll probably realistically be more around 2200 lbs, but you are right about the projected performance/displacement ratio.
    Also, you are right about the bottom "rails"; I have already cut to fit 2 additional "runners" to be glued & screwed on each side of the bottom, at 21" from & parallel to, the centerline "keel". These will also act as grounding & trailer protection for the bottom. I'll post pics when thery are installed. These will not actually be "lifting strakes" per se, but may help a bit with the side-drift in a cross-wind.
    You inspired another idea: I may install an external slot/bracket on the gunnel amidship, P&S, to slide a paddle down to temporarily act as a dagger-board, to help when needed (i.e. docking). Thanks for your very constructive comments!

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    Default Re: Pilothouse Skiff - sketches

    At 2200# I am calculating a metacentric height GM of about 54". GM for decent motion in rough water: 24" for the largest powercraft, 60" for the smallest powercraft. Too high GM gives too fast a motion to stand and work or fish, and too low does not give enough responsiveness to the waves for good seakeeping. You might want to create a GM column in your table in post #26.

    Not that you asked for it, but I calculated your nominal cruise speed using 30hp to be about 16 knots. So with S/L ratio of 3.93, your CG would be best at 61.2% of the at-rest waterline from the bow. I used the information posted by Tad Roberts to get this. Your boat, at 2200#, has a specific length of about 5.1. So pretty heavy on the waterline, and will make the bow rise when planing off. 6 to 6.5 is the usual range for semi-planing boats that don't have to jump the hump to plane off. But the pointy-bow skiff planes off much easier than the jon boat type given the same at-rest waterline.

    I like a clean hull bottom fore of the outboard to reduce the chance of ventilation in rough water. That is why I said 4 "lifting strakes." The trailer bunks are located between them. These strakes also improve boat control since the pointy bow hull likes to bow steer. They also catch and trap air, which improves speed, as can be easily heard in aluminum jon boats. Not sure about the daggerboard idea in a power boat. I always just got used to handling my boats with all their good and bad behaviors. 4 2x2 strakes will have better lateral grip than 2 2x2 plus 1 2x6 laid on the flat.

  28. #28
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    Default Re: Pilothouse Skiff - sketches

    The profile looks like a baby USCG 41 foot utility boat, which is the first thing that came to my mind when I saw it. Being retired CG, I'm inclined to like it, alot. I'm curious as to if the CG 41's had any influence in your skiff design here. There are plenty of under 25 foot pilothouse designs out there that are well proven, some including the C-dory's starting out with their 14 foot boat, up to their 22's. Devlin has a few, Phil Bolger. Glen L. Karl Stambaugh's RedWing series of flat bottomed skiffs. For what you plan on using it for; poking about in the quiet waters of your area, I think it'll be great! Looking forward to see how it finishes up!

    USCG_41UTB_outboard_profile-1536x937.jpg

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    Default Re: Pilothouse Skiff - sketches

    Quote Originally Posted by M. J. Notigan View Post
    The profile looks like a baby USCG 41 foot utility boat, which is the first thing that came to my mind when I saw it. Being retired CG, I'm inclined to like it, alot. I'm curious as to if the CG 41's had any influence in your skiff design here. There are plenty of under 25 foot pilothouse designs out there that are well proven, some including the C-dory's starting out with their 14 foot boat, up to their 22's. Devlin has a few, Phil Bolger. Glen L. Karl Stambaugh's RedWing series of flat bottomed skiffs. For what you plan on using it for; poking about in the quiet waters of your area, I think it'll be great! Looking forward to see how it finishes up!

    USCG_41UTB_outboard_profile-1536x937.jpg
    Thanks for the compliments! And, yes, the USCG 41 has always looked very "Salty" to me. Actually, my last paying gig was as a maritime security consultant to the DHS Port Security Grant Program, working closely with the USCG SAR Base Miami Beach, so I got to see several of their vessels, up close. I was fortunate to get a tour of the new (at that time) Sentinal-Class USCGC Bernard C. Webber; a very impressive vessel, indeed.
    I also studied the other small pilothouse designs you mentioned, and especially liked the Devlin and Redwing models, as well as the exellent Tolman skiffs. If I were younger, and had more time & money (and a much larger shop), I'd have designed & built a 22-24 ft. one with a modified Vee entry forward; sort of deadrise hull style, but that's for another lifetime.
    Many years ago, when I WAS younger, stronger, and much less wise, I co-designed and built a large (to me) 40 ft. sailboat; and after it was finally launched, my wife (who's incredably still with me) said empahtically, "...That's the LAST ONE!!"
    That's why I named this little bugger "LAST ONE II".


    USCG_41UTB_outboard_profile-1536x937.jpg[/QUOTE]

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    Default Re: Pilothouse Skiff - sketches

    JUst finished 2nd coat of EZPoxy painton topsides; next is the 2 -1/2" wide white boot stripe, then I'll flip her over.
    Attached Images Attached Images

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    Default Re: Pilothouse Skiff - sketches

    Very nice!
    I was born on a wooden boat that I built myself.
    Skiing is the next best thing to having wings.

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    Default Re: Pilothouse Skiff - sketches

    Looks good!
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    Default Re: Pilothouse Skiff - sketches

    Fine looking paint job!

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    Default Bar Island Skiff - Hull Painted

    Finally finished the hull painting; many delays due to weather up here on the bold coast. The bow-on photo looks distorted due to the camera angle... she's really not as narrow as the shot makes it look.
    Now I'm getting ready to rig it to flip it over inside this tiny shop. Will have about 7/8" clearance when I rotate it. Will try to post pics of the flip (if I do it without any loss of life!)
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    Default Re: Pilothouse Skiff - sketches

    First rate work Cap'n Chap! I look forward to following the rest of your build.

    I ran a few more numbers on your skiff that might help you make some decisions as you proceed. I scaled your waterline length at 15.5' (if LOD is truly 18.0'). Your specific length at 2200# displacement is only 4.77, i.e. 15.5ft/(2200#/64PCF)^(1/3). So don't under power this one. From the popular Resistance/Weight vs. Fn-Volume plot, your boat is just planing off at 15 knots. It takes about 30hp at the powerhead to sustain that speed. R/W doesn't increase until you get past 21 knots, so fuel mileage is the same from 15 to 21 knots at about 7.85 mpg.

    Rated HP=40, cruise HP=30, R/W=0.160, mpg=7.85, knots=15, S/L=3.81, CG from transom=6.05'
    Rated HP=50, cruise HP=38, R/W=0.160, mpg=7.85, knots=18, S/L=4.57, CG from transom=5.84'
    Rated HP=60, cruise HP=45, R/W=0.160, mpg=7.85, knots=21, S/L=5.33, CG from transom=5.66'

    The CG calculation is something to check yours against. I am interested to know why you want to use an 8" jackplate. I would think that this boat would more likely need the motor hung on the transom, and possibly use sponsons. This boat at lightship (say 1650#) would hit 30mph with the 60 HP outboard; much different performance than at 2200#.

    I see the Brockway-style 2x6 bottom frames laid on the flat in your drawings. Not a fan. The bottom/sole should be smooth and unobstructed, and drain to the transom. If it were my boat I would bond another layer of 3/4" plywood on the bottom (inside) to stiffen up the bottom. Keep up the good work!

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