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Thread: Sneakeasy - Modified Clam Skiff bottom shape choices for performance on Sneakeasy?

  1. #1
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    Default Sneakeasy - Modified Clam Skiff bottom shape choices for performance on Sneakeasy?

    I ordered plans for the Bolger Sneakeasy. Should arrive in a few days. I see 3 bottom design choices I could use. The flat bottom, wide Shoe and a narrow V wedge shape for the keel. My question is, what are the performance pluses and minuses of each of these bottoms for the Sneakeasy? It would be used to explore the waters around Vancouver/Portland and the various canals, slews, channels, lakes as well as the Columbia, conditions permitting. (I am a fair weather boater.) smooth to choppy water and dealing with boat wakes of all sizes. I was planning to build the box keel version, but I like the looks of the flat bottom version better. So I will probabably build that one. Plan to use a 20 to 30hp outboard. In Boating With An Open Mind, Bolger talks about the demonstrated performance of his various box bottom designs and why they work the way they do. I was intrigued by the wide shoe on the Clam Skiff. Finally found a good photo of one on a modified cabin version of that boat called 'Grinder'. Also a modified V wedge keel on another one called 'Grub'. The 1st photo is a Sneakeasy currently under construction, the 2nd is a photo of Grinder with the wide Shoe, and the last one is Grub with the V shaped keel.

    5/29/17:
    Phil Bolger talks about the tripping issue with these designs in various chapters in his book. These boats can go fast with modest power. In the years since this hull was designed, I was wondering if any tweaks have been developed to mitigate some of the negative aspects of this design that Phil points out.

    One of the big reasons I am looking at the different bottom designs is to try and incorporate some form of anti tripping feature. Problem is, I have not been able to find out what you have to do to properly incorporate one. I have seen some of the late 50's to mid 60's flat bottom runabouts with the beveled trip chines, but what and how much would I have to do on a Sneakeasy to make it work I do not know. My guess is the bevel acts as a lifting wedge so when the edge of the hull is moving sideways, it pushes the outside of the boat up banking it a bit more and reducing pressure build up on the side that causes the sudden stop to the slide and initiates the trip. The wide shoe and V wedge are intended to stiffen the bottom and help a bit in the ride in a chop, and lift the bow just a little when I hit the bigger waves and maybe make it bank a bit more in the hard turns.

    Another reason is I can add these features easily after the boat is built with just a flat bottom.



    Sneakeasy
    https://www.facebook.com/photo.php?f...9037007&type=3

    Grinder
    https://www.facebook.com/photo.php?f...size=320%2C240

    Grub
    https://www.facebook.com/photo.php?f...size=540%2C960
    Attached Images Attached Images
    Last edited by AmericanRambler; 05-29-2017 at 10:31 PM. Reason: Update description

  2. #2
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    Default Re: Sneakeasy - Modified Clam Skiff bottom shape choices for performance on Sneakeasy

    John Bartlett also did Loon, flat bottom. Nice boat . I saw it in 2007 at the Kingston Messabout and John let my son drive it . I have a video somewhere of Loon with 3 aboard planning with 9.9 hp.
    http://www.duckworksmagazine.com/06/...loon/index.htm

    I've built a couple similar boats and I suggest 10 hp and flat bottom with a 2x4 skeg.

  3. #3
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    Default Re: Sneakeasy - Modified Clam Skiff bottom shape choices for performance on Sneakeasy

    I'd want skiff like that with the wide shoe. It would deliver some directional stability, stiffen the bottom, and make it easier to push off a sandbar ( dead flat bottoms just suck in to the bottom).

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

  4. #4
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    Default Re: Sneakeasy - Modified Clam Skiff bottom shape choices for performance on Sneakeasy

    AmericanRambler, We are 'in the process' of moving to the greater Kalispell, MT area and I plan on building a Sneakeasy (maybe in the Fall of 2018). I cannot express how awesome it is to see your Build Photos on Facebook. I see some design mods that i think are great and the overall quality of the photos are great. Thanks for the Timeline and the Captions under the photos. These Photos and information that you have shared will speed up my build and i am sure create a better boat because of them....... MANY, MANY, MANY, THANKS !!!

    Please keep informing us of your experiences as you get the Sneakeasy in the water.

    Joe

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    Default Re: Sneakeasy - Modified Clam Skiff bottom shape choices for performance on Sneakeasy

    Hi Joe. These are not photos of my boat. The elegant one under construction is being built by Hans Rompa. He is a rowing crew instructor living in Holland. It will be a beautiful boat when done. There are a mix of other photos from different boats owned or being built by others mixed in. I have not started construction on mine yet. I have purchased plans and been researching Sneakeasy boats and others plus building materials in preparation of executing mine. I have been saving photos of Sneakeasys I have found on the web and Facebook and been adding them to my collection for future reference. I have been looking at doing some modifications to the design to meet some of my specific requirements for the water conditions in my area. I was seriously considering Phil Bolgers box keel version but have pretty much decided against that one for astetic reasons. I just do not like the way it looks on the front side profile. I am looking at the Clamskiff bottoms and other similar configurations for the ease of adding them to the bottom for it's strengthening capability plus the performance attributes they bring. Due to the square chines on the side and the flat bottom, I am looking at anti trip chine features to see what will or may work on a Sneakeasy. I have received feedback and read Phil Bolgers comments about the issue on this boat and others with similar configurations. This boat can be fast with modest power but as speeds rise, tripping will become an issue under certain conditions. I am looking to go faster than what 25 hp will bring, (I do not want to run wide open to do 17 mph.) but I am also not looking to run with the fast boats. I am thinking 25 to 35 mph maybe. 40+ not so much. Under 20 mph and I cannot go the distance in I want to cover and 35 plus will get too uncomfortable for the environment I will be in. My site distance is very close to the water in this boat so high speeds present to high of risk for available visibility to see the path ahead and avoid obstructions and debris. So my power will probably be in the 30hp to 40hp range. Based on scale weights of outboards, I may probably be looking at older 2 strokes because many of them have significantly superior power to weight ratios. I am less concerned about the poorer fuel economy of older outboards because the runtime hours will be fairly low overall. With the prices of new or newer 4 strokes, I can buy a lot of gas and perform the additional maintenance they require for a lot less than the procurement cost of a 4 stroke of the same power.
    Last edited by AmericanRambler; 08-12-2017 at 02:00 AM. Reason: grammer, spelling

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    Default Re: Sneakeasy - Modified Clam Skiff bottom shape choices for performance on Sneakeasy

    Hi AmericanRambler, Thank you for your reply! Hans Rompa is doing a great job of Photographing the Construction. I am sorry that I got mixed up with the Captions and Timeline, that is apparently from a Forum from Backwater.org. I have been going all over the web trying to find info on Building and Using the Sneakeasy and I got 'who said what' a little confused.

    I agree with you on the Box Keel design, it just does not look right. I think the Camskiff Bottom has a lot of promise. I think you my be talking about the one in the Boats with and Open Mind book? To me it appears that that kind of bottom would give a lot of strength to the hull.

    Please keep on this thread with anything you find on the tripping issue, that is of a lot of interest to me.

    Also, I plan to be boating on Hungry Horse Reservoir and Flathead Lake. Not much traffic on Hungry Horse Reservoir but Flathead gets busy. My boating is mostly hugging the shorelines in the early mornings and late evenings so there is not usually much traffic out there. We do a lot of Photography so we like the Early Mornings and Late Evenings for that reason. Hungry Horse has about 170 miles of shoreline so we do need some speed to get around the lake, but I think I will try to find an older 20hp motor for the same reason you gave for the older motors. (power v. weight, etc.)

    Thank you again, and I hope you are active on this Forum as you start your Build of the Sneakeasy, with lots and lots of Photos!!! I won't be able to start Construction on mine until Fall of 2018 at the earliest, so i am going to be collecting every scrap of info that i can locate on the Sneakeasy. Joe

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    Default Re: Sneakeasy - Modified Clam Skiff bottom shape choices for performance on Sneakeasy

    Hi Joe, I have been up and down US 93 a number of times by Flathead Lake in both summer and winter on runs to Kalispell. Had to look up where Hungry Horse reservoir was though. Those lakes can get pretty bumpy and windy. You will need the ability to scoot at a pretty good clip to deal with unforecasted weather changes. I myself would consider extra reserve flotation because much of that area is quite remote and if something does go wrong, you will still have a boat to protect you and not sunk down to the bottom by engine and gear weight. I suspect you will want to have a bigger fuel capacity than I am planning for mine as well.

    Two of the things I like about the Bolger Clamskiff wide shoe is the ease of installation and the extra strength it can bring. Plus I could install it and tweek the design easily if it does not meet my performance expectations. I was also thinking about the ability to incorporate a bit of a shallow V cutwater at the front of it for esthetic reasons. The plans use a 48 inch wide sheet of plywood for the bottom. If I find it necessary to widen the beam a little bit, to fit my wide body shoulders and permanently attached large area rear cushion comfortably, I could do that by incorporating a wide milled chine log which would accommodate the anti trip chine feature if I ever figure out a proper design. I have seen some early fiberglass runabouts with flat aft rockers and sharp cutwater stems from the md 1950s to the mid 1960s which have some interesting chine treatments that are a combination of rounded and squared chine edge. Until recently, I thought they were there because it made layup easier and strengthened the boat form. But I am seeing it on a number of different boats including performance models made in that period which are not splashed copies. I now suspect that the designers of the hulls had learned a thing or two about making these flat bottom boats corner without sliding, tripping and banking excessively with the modest horsepower then available. Part of my reason for that is some people have taken these old boats and put high hp jet ski motors and jets in them or rebuilt them to take double or more of the rated outboard power and they seem to run and turn pretty well with their original bottoms. There is a YouTube video of a guy with an early 1960's Hydrodyne runabout converted to a jet doing some major squirreling around and not flipping or tripping. I am thinking I can add 2 to 4 inches of beam with these special chines and get my anti trip chine, the extra cockpit elbow room I desire and still use my single sheet of plywood bottom. The extra couple of inches of beam would also help on the hp calculation which uses beam, transom width and depth, length and bottom type specifications to provide the power rating.

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    Default Re: Sneakeasy - Modified Clam Skiff bottom shape choices for performance on Sneakeasy

    Hi AmericanRambler, I am glad you know the area that we are going to be in. Flathead can get rough and there are some large boats on the lake that put up huge wakes. I plan to watch the weather closely when we get on Flathead. One of the main reasons I like the Sneakeasy is without too much power, is will have some speed to get us back to port and being that we plan to 'hug' the Shoreline a lot, we won't be creating much of a wake if we are speeding home. Hungry Horse is a bit different as it usually does not have many Large boats on it, mostly people fishing, etc. We know the Mountain Weather and we know gales can come down off those mountains around the Lake. We will just have to be really on our toes about the weather, otherwise, we may wind up stuck in a small cove for hours, not of interest to me.

    Yes I do plan to add some Flotation in the front as it is just open under there and I think I want to add Foam up there and I plan to install a Rear Seat with Foam Flotation secured under it.

    I do really like you idea on the Clamskiff wide shoe, it makes a lot of 'cents' to me. Hopefully you will get yours built first and let me know about the performance of the wide shoe. I am interested in what your thoughts are on the shallow V, that could look sharp. You have me now thinking of the Chine edge on boats that I have owned before. Like you, I was just thinking the style of the Chine on the Fiberglass Powerboats that I have had was mostly for manufacture and strength, but maybe there was a lot more to their performance. I am going to do some research on those Chine designs, don't have any idea what I will find, but I am going to look. I had a Fiberglass Runabout with a 40 hp Johnson on it in the early 60's that had an interesting chine as you are describing. Also, a later boat was a Tri-hull with a 250hp Ford/OMC IO that had the same type treatment to the Chine as I can remember and these boats were built many years apart.

    I like your idea of leaving the bottom a 4 foot sheet and adding a wide milled chine. The extra room would not be an issue in long lean design, it would not be noticeable as far as i am concerned, but it would be a little more comfortable.

    Think You for this Thread ! Joe Glacierboater

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    Default Re: Sneakeasy - Modified Clam Skiff bottom shape choices for performance on Sneakeasy

    Sounds like you are trying to change the original design function of the boat by quite a bit. I wouldn't think that the Sneakeazy is the type of boat where you would worry about chine tripping. The boat is long and thin and designed to go straight on low power. 25hp seems like plenty for the boat as-designed. You could stiffen the bottom by using 4 runners, and also double-plank it if you are planning to go above the 30mph design speed. I would think a good spray rail forward halfway up the topsides would be a great addition.

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    Default Re: Sneakeasy - Modified Clam Skiff bottom shape choices for performance on Sneakeasy

    Skiff Man, I am not really trying to change the design much, just that i have 'heard' on these Forums that the boat had some tripping issues. The 'Real' problem, is that I have not seen any Sneakeasy Boater write about any unpleasant experiences. That is what I would like to hear............ Someone that owns and uses a Sneakeasy and does the Tripping issue really raise it's ugly head or not........... If you see anything on this subject, PLEASE inform me......... I plan to power the Sneakeasy with a 20 hp, or maybe a little less hp. I think I will get plenty of speed for my interest and I am not a 'Performance' type person, I just love boats and boating SAFELY............

  11. #11
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    Default Re: Sneakeasy - Modified Clam Skiff bottom shape choices for performance on Sneakeasy

    Quote Originally Posted by openboater View Post
    John Bartlett also did Loon, flat bottom. Nice boat . I saw it in 2007 at the Kingston Messabout and John let my son drive it . I have a video somewhere of Loon with 3 aboard planning with 9.9 hp.
    http://www.duckworksmagazine.com/06/...loon/index.htm
    I have been thinking about a Sneakeasy for a future project. However, to my eye, the aesthetics of John Bartlett's Loon are superior to the Sneakeasy. Do you know if plans are available for the Loon adaptation, or would I be on my own to make similar changes?

  12. #12
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    Default Re: Sneakeasy - Modified Clam Skiff bottom shape choices for performance on Sneakeasy

    Quote Originally Posted by AmericanRambler View Post
    Phil Bolger talks about the tripping issue with these designs in various chapters in his book.
    My boating experience includes a lot of time in sailboats, human powered craft, and displacement boats, but perhaps only a couple hours in planing powerboats. So, please forgive the seeming newbie question. I am unfamiliar with the term "tripping". What is tripping, and how and why does it occur?

  13. #13
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    Default Re: Sneakeasy - Modified Clam Skiff bottom shape choices for performance on Sneakeasy

    Hello ThomRose, As I understand it, Tripping happens when a boat, particular flat bottom boats are in a turn and sliding. The 'Outboard' Chine may 'dig into the water' abruptly stopping the slide, sometimes violently. More so in choppy waters. A flat bottom boat going into a hard turn at high speed, if it has no or very little keel, may turn sideways but keep going straight, sliding with little Heeling as it is flat bottomed (leaning into the turn) so the 'Outboard' Chine is still Very Close to the Waterline and can be an issue if it 'digs in' and causes the Tripping that is talked about.

    There is quite a bit written about Tripping, it is just sometimes hard to find. Most Boat Manufactures that i know of that have had boats that exhibit this characteristic have made modifications to the Chine is some way to prevent this issue, sometime with quite a bit of difficulty........... And, most Manufactures that have experienced this try to keep it as quite as possible, for business sake.............

    I hope this helps, anyone feel free to correct me if they feel i am saying something wrong.

    Glacierboater

  14. #14
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    Default Re: Sneakeasy - Modified Clam Skiff bottom shape choices for performance on Sneakeasy

    One way to visualize tripping is to think of a car or SUV sliding sideways in a turn. When it hits a curb or a soft patch of ground, the outside sliding wheels abruptly stop and the momentum of the mass of the car keeps going and causes it to tip up on its side or roll over. The same thing can happen to a planing boat in a turn if the outside chine or side hits a wave or the water if it's sliding in a turn. (Most power boats turn by pushing the stern (back end) sideways instead of the bow (front) like a car does. It happened to me one time while I was waterskiing in a 16 foot outboard runabout. There were 4 of us on board and I was making a hard turn to starboard (right) to return to pick up my dropped skier to go back to him so I could place my boat between him and oncoming boats in case they did not see him in the water. The water was choppy with roller wakes from a lot of boats. As I came about, I came up over a roller just right and the right side came off of a roller just right and dropped into a trough just right so the chine and right side dug into the following roller and stopped the boat turn instantly. All 3 passengers were thrown out of their seats and into the left side of the boat on top of each other. They felt that. Fortunately, the boat itself remained stable and did not tip to the outside. That was the first time the boat ever did that. The next week I took it out by myself and repeated the turn under the same conditions and was able to duplicate the behavior. It was a specific combination of increasing turn rate, reducing engine power and speed plus the transition from planing to displacement mode in a chop where the bow dipped and the stern rose to where the boat started to pivot on the bow deep v and the flatter stern deadrise and pad skidded sideways until it caught the next wave and stopped the slide cold. Once I learned about it and what the boat would do, I would use that behavior when I wanted to make tight turns at certain speeds and conditions. It came in handy a few times later on. But if your not aware of that quirk, it can be an issue if it occurs unexpectedly. One time I did it while pulling a skier and drove by him to get behind him while he dropped. The rope was still pulling him the other way. The look on his face was priceless. I was following a 5 abrest line of boats and all 7 skiers suddenly dropped at the same time for an unknown reason so I whipped about in order to not pass through that suddenly very crowded patch of water with down skiers and boats turning everywhere. To much scrambled traffic in too small of a space because the skier I was pulling often would not watch what was in front of him and I did not want him to run over a down skier or into another boat.

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