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Thread: Downsides to flat-bottomed skiffs?

  1. #1
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    Default Downsides to flat-bottomed skiffs?

    I am thinking about this in relation to the Lumber Yard Skiff, but the question applies to all the hulls in this family. I know they are recommended for inland and or protected waters, and they will pound in chop. What are the conditions in which they become dangerous and how do they fail? I have mostly just owned and used light aluminum V or semi-V hulled fishing boats on inland waters, so I am just trying to understand these hulls and gain some wisdom from those with more experience.

  2. #2
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    Default Re: Downsides to flat-bottomed skiffs?

    There are flatties and there are flatties. At one extreme are the narrow hulls with a bit of rocker that move quite easily at displacement speed. Very efficient under oar of low power at their designed speed but pretty much stupid if over-powered. At the other are boats that from above look like a triangle. No rocker. Gread wide stern to hold up a lot of horsepower. They plane easily on flat water and can go dangerously airborne at really high speed.

    In between are modest beam flat bottom boats of good seakeeping ability that can be throttled back for heavy going and can plane at moderate planing speeds, like twenty knots, fairly easily. And then there are specialty boats for both facing or running in steep and breaking seas, like the Oregon dory.

    So, it all depends.

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    Default Re: Downsides to flat-bottomed skiffs?

    Thanks Ian. The Lumber Yard Sport Skiff has a beam of 5' 10", a length of 15' 6" and a bit more rocker than the standard skiff. It planes quickly and easily with 20-25 horses, so I am thinking it is the second type of boat you describe. Living just a bit over an hour from Cape Kiwanda/Pacific City, the home of the Oregon dory fleet, I am very familiar with the surf dories. Amazing boats -- as are their skippers.

  4. #4
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    Default Re: Downsides to flat-bottomed skiffs?

    The lumber yard skiff will take you where you want to go. Outside of heavy plunging surf it's perfectly able. She will pound if you try to blast into steep head seas but that's when you should slow down anyway. She's fast enough that you can get on the back of a wave, just ahead of the trough, and ride with a following sea.

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    Default Re: Downsides to flat-bottomed skiffs?

    "Living just a bit over an hour from Cape Kiwanda/Pacific City, the home of the Oregon dory fleet, I am very familiar with the surf dories. Amazing boats -- as are their skippers."

    Build what works in you area! The LYS skiff is an East coast design & not suited to coastal Oregon - except the bays & calmer rivers. Plus the materials & build times are similar so why not? Although the Oregon dorys are longer so likely a somewhat bigger project...but they are larger for a reason!
    There are many variations on the power dory theme from a narrow 19ft Carolina dory to the wider Oregon dory types. They all pound...but for the $$ they can't be beat for utility & safety. Moe

  6. #6
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    Default Re: Downsides to flat-bottomed skiffs?

    It does not sound to me like the Oregon dory would fill Bill's bill. It's heavy and takes a big rig to launch. Very few come from inland and they are boats that are not really happy about general boating. There are estuaries and bays along the Oregon coast that are worth exploring by a lighter boat and there are plenty of calm days when one could put in at one of the little ports at river's mouth and have a nice day after crossing the bar. And then if one were to trailer up to the Columbia there's many miles of interest that can call forth the abilities of the LYS.

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    Default Re: Downsides to flat-bottomed skiffs?

    Moe, I am not an open ocean guy. Never was able to treat my severe motion sickness. I think the LYS would do just fine on our lakes and in our bays for fishing and crabbing, and the build is straightforward.
    I was just trying get a sense of how the various skiff hull designs perform in different marine conditions.
    Ian, you know exactly the sort of water I am looking at.

  8. #8
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    Default Re: Downsides to flat-bottomed skiffs?

    Been there. I can imagine few finer days that puttering the Columbia's Prairie Channels just up-river from Astoria. Sailing and kayaking, eagle watching and catching illegal dredge spoil dumping, it's all good up there. And puttering up the Columbia past Rooster (nee Cock) Rock . . .

    My ideal LYS would have a nice long tiller arm on the outboard for easy handling while standing and for sitting a bit forward. Rather than thwarts, I'd go for purpose built latch down boxes with perhaps cushions atop. Simple. Versatile. Open.

    And maybe a really cool Quonset hut shaped tent so's a night's tie-up in some slough against a log raft . . .

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    Default Re: Downsides to flat-bottomed skiffs?

    "Moe, I am not an open ocean guy." Ok...all back full! The LYS is a great stable platform for anything short of the Oregon bars & ocean & Ian is right. Be perfect for bay crabbing - stand up & haul! Moe

  10. #10

    Default Re: Downsides to flat-bottomed skiffs?

    Surfed many following seas in a flat-bottom dory. No more flat-bottom girls fer me.
    http://boatladyc.blogspot.com/2016/0...dy-c-2016.html
    Last edited by Mo 'Poxy; 04-11-2017 at 10:56 PM.

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    Default Re: Downsides to flat-bottomed skiffs?

    This may or may not apply to you so much for a powered skiff, but I sailed a Goat Island Skiff a little bit, and while trying to dry the sail out, I had it tied up at the dock with the sail up. It broached, and with such a hard chine, it was fairly difficult to right. So back to your original post and trying to understand how the hulls perform, if you capsize and need to right the boat, a flat bottom skiff with one very hard chine could be extremely difficult to stand back up. It was much easier for me since this boat was tied to the dock. I was on the dock and stood on the gunnel, but someone else came over and did the same thing. I'm only 150 pounds and could not right the boat by myself while standing on the gunnel. I have no idea how I would have done it if I were in the water and couldn't touch bottom. So that's something to think about.

  12. #12
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    Default Re: Downsides to flat-bottomed skiffs?

    Firstly, Train, "broaching" is when a boat running with the seas slews due to the stern essentially falling down the wave faster than the bow. That may or may not result in a capsize, which is what happened to your boat when you set her up in a way where she'd be unable to respond to any breeze.

    Your recovery problem has nothing to do with flat bottom and everything to do with your having no capsize plan. With sail boats, the standard method is to use the centerboard or keel as your lever. If the boat's lying on her side, you just swim around to the bottom, reach up to the board, and haul yourself up on that. Sometimes you complete the righting standing on the centerboard with hands on the gunnel and butt as far out as you can get it. If the boat's truly upsidedown, you might start by depressing one side so that you can grab the centerboard after it's about 45 degrees from vertical. Conditions vary. Practice.

    One is very unlikely to capsize a boat like the LYS except through some very unfortunate combination of steep waves on the beam coupled with massive incompetence. But swamping the boat, which hard, is possible. I'd consider some floatation. Enough enclosed buoyancy to float her level with the gunnels above the water is much harder than for a light sail or row boat, given the engine weight. Many boats simply provide bow floatation so that at least something is sticking up to hang on to. Making an outboard suitable for self-rescue is very difficult and often counter to the full use of the boat.

    Anyway, those issues have nothing even remotely to do with hard chines per se. More to do with beam and metacentric.

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    Default Re: Downsides to flat-bottomed skiffs?

    Around here we typically have short steep waves though they never become nearly as big as ocean waves. In our conditions flat bottomed skiffs are considered safe only on our small inland lakes and on the protected waters between the reed beds in river deltas.

    The reason for this is that when a flat bottomed hull takes a steep wave from the side or on the bow or quarter the flat bottom will make it roll over and often capsize.

    Traditional boats used on the coast were various forms of round bottomed doubleenders. Theese days V-bottomed square sterned hulls are the new norm.
    Amateur living on the western coast of Finland

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    Default Re: Downsides to flat-bottomed skiffs?

    Heimlaga raises a fair point. Safety aside, in chop, and especially a beam sea, flat bottom boats are not as comfortable as V- or round-bottom craft, IMO. They follow the shape of the wave rather than first leaning into it and then heeling away from it. V- and round bottom boats are sort of self leveling in a beam sea.



    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  15. #15
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    Default Re: Downsides to flat-bottomed skiffs?

    Yep. Keep flat bottom boats on flat water . . . .


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    Default Re: Downsides to flat-bottomed skiffs?

    I have no experience of flat bottomed power skiffs but I have used a 3.5 HP engine on my 15 foot banks dory and when travelling in a following sea above rowing speed it's awful - she surfs and wants to broach. Going into a short head sea she pounds hard at any speed. The upside of the design is that when I'm scared and tired and stop the boat for a rest, she feels totally safe, bobbing over the steepest waves without taking water. Totally different kettle of fish to the LYS but my gut feeling is that I won't build another flat bottomed boat after building 4. I was charmed by Bolger and folks on the net into thinking they were the bees knees but now I'm skeptical. I still think building and using at least one dory type hull is an invaluable lesson in understanding boat design, though.

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    Default Re: Downsides to flat-bottomed skiffs?

    Just to clarify my previous post, I know light banks dories and transom outboards don't mix! But this boat is very similar to a lot of flat bottom power skiffs in the front third, where the pounding and forefoot plunging happens.

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    Default Re: Downsides to flat-bottomed skiffs?

    Quote Originally Posted by Ian McColgin View Post
    Yep. Keep flat bottom boats on flat water . . . .

    Flat bottomed?


    Nah
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Downsides to flat-bottomed skiffs?

    I think--and that means its just my opinion--that dories and dory-derived boats are an attempt to replicate round-bottom shaped boats with a less laborious construction method. Sure they are meant for stacking on deck and, perhaps, other "missions" as well. But the great flare to their sides, coupled with their narrow flat bottom allows them to behave more like a round-bottomed boat than other, wider-bottomed, straighter-sided small boats.

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

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    Default Re: Downsides to flat-bottomed skiffs?

    Quote Originally Posted by Breakaway View Post
    I think--and that means its just my opinion--that dories and dory-derived boats are an attempt to replicate round-bottom shaped boats with a less laborious construction method. Sure they are meant for stacking on deck and, perhaps, other "missions" as well. But the great flare to their sides, coupled with their narrow flat bottom allows them to behave more like a round-bottomed boat than other, wider-bottomed, straighter-sided small boats.

    Kevin
    Just so.
    I heard somewhere that they behave better with some weight in them as well.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: Downsides to flat-bottomed skiffs?

    Dories predate stacking on deck by centuries. Earliest evidence goes back to the 1300's. Seem to have come along when sawmills started happening so wide boards could be produced. Have a look at the first chapter of the Dory Book. Some of these dory built boats are quite wide bottom e.g. Arnold's bateaus. Might be better to think of dory as a construction method that involves lining up some planks, putting cleats across to hold them then putting sides on with crooks to hold them. One could see how this could be developed out of rafts, whereas cross planking with short stuff was a way of repairing a dugout bottom and we have hard evidence that this was the case.
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  22. #22
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    Default Re: Downsides to flat-bottomed skiffs?

    I'll admit to have some fun at the expense of ill-informed prejudice and extrapolation from limited experience.

    By the way, I admit to a little cheating by showing the McKenzie River dory. A very specialized boat that positively sucks on a long open water row.

    The hard chine of a flattie does not by itself force the boat to trip sideways in a beam sea any more than happens to any other boat. Some boat really do slide nicely sideways along the face of a wave. My gunning dory did. My round bottomed dink does. The unprepossessing Dunbar flattie skiff does. It's the total boat, not beam alone and certainly not a hard chine, that set you up for a roll.

    Same with broaching in a following sea. Any boat will at least want to broach in a following sea. The stern is higher than the bow and free in the water while the bow is more or less buried and held in place. Of course the stern will try to fall past the bow. Many factors but especially strong steering and nice drag can overcome a broach. A round bottom will broach every bit as fast as a flat or a V unless she has good drag and/or very positive steering.

    Boats are designed for various conditions, excelling in some and not in others. And some boats respond more to handling skill than others. Learn your conditions. Improve your skills on as many different boats as you can. And have fun.

    G'luck

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    Default Re: Downsides to flat-bottomed skiffs?

    Quote Originally Posted by Ian McColgin View Post

    Same with broaching in a following sea. Any boat will at least want to broach in a following sea. The stern is higher than the bow and free in the water while the bow is more or less buried and held in place. Of course the stern will try to fall past the bow. Many factors but especially strong steering and nice drag can overcome a broach. A round bottom will broach every bit as fast as a flat or a V unless she has good drag and/or very positive steering.

    Boats are designed for various conditions, excelling in some and not in others. And some boats respond more to handling skill than others. Learn your conditions. Improve your skills on as many different boats as you can. And have fun.

    G'luck
    In regards to broaching and its causes, here's a good video worth watching.
    It was made by a mate of mine who was the Chief Nav Arch at Tom Fexas Yacht Designs, where we worked together for a number of years. We actually desiged quite a few vessels for Kadey Krogan. The vessel you see in the video is just one of these vessels that we designed as a team
    https://www.youtube.com/watch?v=FtbXfOzD-_k
    Last edited by Mark Bowdidge; 04-12-2017 at 08:02 PM.

  24. #24
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    Default Re: Downsides to flat-bottomed skiffs?

    Thank you Mark. A good insight into how to make a docile easily steered displacement boat in normal conditions. It introduces some of the very important differences between these and light motor, human, and sail powered boats.

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    Default Re: Downsides to flat-bottomed skiffs?

    Mark, I appreciate that video. Very clear explanation of hulls in following seas.

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    Default Re: Downsides to flat-bottomed skiffs?

    Glad to hear it explains things more clearly.

    We find even with our deep v hulls when driven at slow speeds (displacement of semi displacement speeds) in down wind or in a following seas (when trolling, crossing bars and more), the same principle principle applies and broaching does not occur. (A comment made time and time again by our clients).

    Sometimes the opposite will occur, where the boat will bank outwards (instead of inwards) due to the upwards force being on the "inside" instead of the outside. As the boat goes down the wave, this outward banking can result in the boat rolling, pending the steepness of the wave face.

    So all in all, deadrise is a very important part of the overall efficiency and safety of the hull
    Hope this helps

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    Default Re: Downsides to flat-bottomed skiffs?

    A skiff is a super simple shape. Quick and easy and cheap to build. And. . . . .well, that's about sums up its best qualities. All the other things that go into making a great boat are typically more likely achieved with a more sophisticated hullform.

    Nothing wrong with a skiff if you're content to live inside its limitations. But don't fool yourself that it's not constrained by its very nature.

  28. #28
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    Default Re: Downsides to flat-bottomed skiffs?

    James, I agree. Almost the opposite of the LYS is a hull form with narrow planing bottom, broad deadrise surface in the second plank and mostly parallel in the third. I 'm thinking of Bolger's Diablo. Guessing it would be fine in a following sea, but I would sure hate to try to pull a crab pot from it!

  29. #29
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    Default Re: Downsides to flat-bottomed skiffs?

    Another bit of explanation on one of the issues about skiffs: stability.... if you want to get geeky -- http://www.cruisingonstrider.us/Stability.htm
    David G
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    Default Re: Downsides to flat-bottomed skiffs?

    Flat bottomed power skiffs excel for their stability, capacity and shallow draft, and the shape is ideal for planing with modest power. This makes them excellent as inshore family boats.

    There are several downsides.

    (1) One derives from the need to have the bottom of the bow of the skiff rockered up, to keep the bow from burying in a wave. This is taken to an extreme in the Pacific beach dories which must ride over waves as they are launched. The rockered bow has a major consequence: it creates a wave under the bow which must be surmounted by adequate power. When the boat planes, there is a dramatic decrease in both wave making and frictional resistance, and an increase in speed. The problem with the raised bow is that it pounds, and the boat porpoises. Any boat with a bow wave is also not very welcome in harbors and rivers...

    (2) The second most common problem with a flat bottom is that it can slide sideways. Bolger found that skiffs could be stabilized at modest planing speeds by a longitudinal "shoe" under the bottom. The long keels of lobster boats have the same function, and also help to protect the propeller. In general, lobster boats don't bury their high bows or broach in a following sea. Of course a keel increases the draft of a small boat, and makes it less suitable for beaching.

    (3) Offshore waves present a difficult problem for all small boats. A boat with a wide flat bottom does fine at slow speeds, but it is hard to stay on an efficient plane among waves. Hunt found that a boat bottom with a deep V was ideal for pounding through waves at high speeds. Unfortunately the deep V hull is sadly lacking in stability, capacity, shallow draft and efficiency compared to a flat bottom.

    So by all means use boats like the lumber yard skiff for suitable waters, and something else for waves.

  31. #31
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    Default Re: Downsides to flat-bottomed skiffs?

    Great thread but too much emphasis on the negative (naturally, given the OP's thread title...) so here's some flat bottomed love...

    They take the least power to reach planing speeds.
    Flat bottoms are easy to haul up a beach.
    Rigging a trailer for one is...easy.
    They draw less water for their displacement than any thing else.
    You can sleep on the floor & it's generally wide enough for two...
    For a given length they have the greatest initial stability.
    Bolger once designed a flat bottomed hull with vertical sides for transporting sled dogs - the dogs won't flip the boat when they all jump to one side to bark at seals...(never heard if it was built...)
    If you carry idiots (ok boat ignorant but otherwise fine folks) they won't flip the boat when they all jump to one side to gawk at seals...

    I designed & built a 21'x 6' round sided skiff with a 4' wide flat bottom - so a hybrid of sorts - 18kts with a 30hp Yamaha - think planing Swampscott dory. I could launch & retrieve it with 8" of water, never getting my trailer hubs wet. It pounds when you have to run straight into a chop but it was fine quartering & following. It was great for British Columbia & now lives with my brother on the Chesapeake, (we went out the Golden Gate 3 times, got scared & then I built my 27ft Bolger...) I could standup pull shrimp pots (in BC they were 350' - 400' down...) but if it were 16ft in length I couldn't (stability increasing with length), so there are many kinds of flat bottomed skiffs & make generalizations at your peril. But no question about one thing...in the "right" conditions they pound like hell.


    Spirit makes some good general points but I'll quibble with these two -
    "The problem with the raised bow is that it pounds, and the boat porpoises." No...some do but it's not inherent to the breed.
    "A boat with a wide flat bottom does fine at slow speeds, but it is hard to stay on an efficient plane among waves." Actually it's usually easy to stay on plane - but the teeth of the occupants tend to loosen...Also they plane at lower speeds & power inputs than any other bottom type so often you can maintain an efficient, maybe even comfortable plane in conditions that are brutal for v hulls that don't plane till 13 kts or so.Moe

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    Default Re: Downsides to flat-bottomed skiffs?

    I love flat bottomed skiffs. I built the Bluegill 15.5' and the Nez Perce 13.5'. Nez Perce is the nearly perfect boat for my purpose. It Usually attracts a lot of attention; It's pretty. I am in the process of restoring a year 1946, 5 HP, Johnson Sea Horse, with built-in gas tank, to use on it. Don't ask how much I have spent on that motor. I am currently using a late model, 6 HP Tohatsu, 4-cycle. I use my boat on the TN River for fishing in North Alabama. A wooden skiff reminds me when my Dad and I went fishing on Mobile Bay when I was young. Plastic boats have no soul.
    Last edited by Bluegill; 04-17-2017 at 10:27 AM.

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    Default Re: Downsides to flat-bottomed skiffs?

    Bluegill, I have Ken Swan's catalog. Agree the Nez Perce boats are charming.

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    Default Re: Downsides to flat-bottomed skiffs?

    My main complaints about my flat bottomed 18'x6' skiff (aside from the pounding underway) are that the bow blows off too readily, and that the shallow draft and deep heel of the stem make launching and recovering a pain. A V-hull with well-rounded forefoot would solve these issues.

    But I have had it out in 3 ft short period chop numerous times, and even 5 ft swell in the middle of the Chesapeake, without incident. The boat has 18" of freeboard amidships, and has 1/7th of the boat length in freeboard at the bow. Sides are fairly plumb at 7 degrees which I like alot (with sprayrails).

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