Mckenzie design differances

So I am in the planning stages of my next boat. It will be a 17x54 decked mckenzie with a few modifications. I plan on higher sides 26" ish at the locks. I also want a flat spot 3'ish under the rower. I want gradual stern rocker. Bow rocker will start gradual but I would like a little kick rocker right at the very front to keep the bow climbing over by waves instead of smashing into them. The sides will probably have a decent bit of flair. I'll probably also experiment with the slightly curved stem and transom bottom.

Obviously there is no design out that fits all these characteristics , so I'll most likely design my own. Doesnt seem too hard given that there are only 2 sets of sides and 1 bottom to deal with. But I need a place to start. first thought was to "blow up" a 16x48 double ender w transom and then work the numbers from there. I could also start similarly with a 17x54 fishing boat and then add higher sides and tweak the rocker profile. I could also go in with no numbers, start from scratch with models and work from there.

Sounds like the easiest way is to start with a design and work it to what I want. So in looking around I notice there are quite a few 16ft designs out there. What are the general characteristics of each designs. What makes a tatman 16x48 differant from a don hill 16x48? How are either of those designs differant from a ray heater, woody handyman, or Keith steele design? Does a don hill have more side flair and less rocker than say a tatman? Do any of the designs have a dished Chine and flat spot. Any of them have more symmetrical hull design and less pear shape than the others.how does the stem angle of each design compare. I am just wondering what are some of the more distinguishing characteristics of each design are and any differences between shapes. If I do end up ponying up for a set of plans which wont even really get used, I would like to get as close as possible so that I have less to modify. Also like to make sure I get the right shape for when I do want go build a quick and cheap fishin boat someday.

Anyone got anything to add? What makes each boat design differant from the next?

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Permalink Reply by Dave Z on August 15, 2011 at 6:20pm

Framed or S&G

 

I designed the "flyfisher skiff" in the foll0owing manner...This method can work for you.  Build a model or several models.

 

1. get a few manilla folders or posterboard.  I wanted to make use of the materials so what I did was make a 1" = 1 foot scale side panel.  I wanted a 11'9" side panel by 4'. 

2. I did my boat from scratch, but the easier way would be to take the plan form a boat close to what you want, say a Briggs dory or a 17x54.  make the side panels tall, decide whetre you want the stations to be=- can be planned or arbitrary.  In my boat I wanted them roughly 24" apart.  In real life, they ended up at 23-25"

 

3. Build trapezoid "frames" with the flare and bottom width you want and fit them in the model. tape that baby all together.

4. you will find that you will tweak on the design until you get it right.  Probably build three or four models.

5.  then re-measure it all right off the model.

6. then build a new model off the measurements. massage the measurements so that you get maximum use of the materials/'side panel/bottom width.

7. then build a wood scale model if you choose.

8. tweak on the numbers and build it real size.

 

you can see pictures on my blog here...http://thtchronicles.blogspot.com/2010/12/drift-pram-10.html

when I design the flyfisher skiff.  you can see what I did.

It's not all that hard. its alot of fun.

 

You can also build a scaled 'plug'  which involves a scaled block of wood, carved to the profile you want.  then use it to extract the side panel and measurements. 

Permalink Reply by chris towles on August 16, 2011 at 12:06am
I'll be building s&g with as much foam and honeycomb as I can find a use for. The sides may still be 1/4 or 3/8 ply but the chine area will be reinforced with honeycomb. At very least. I thought about trying to add the 2" to the panel with the core material in the Chine area. However, I decided wood reinforced with foam or honey would make the strongest joint in that area.

Back to the design front. I like to draw. I have done plenty of drawings Sofar. Today I went out and got some graph paper so I can draw better to scale. My first project was to try and make side panels work with 3 sheets of plywood. I think it can be done. Just doing some rough guestimating the panels should be 17' long and the side cut should taper from 30" to 22" front to back , being 26" at the locks in the center of the panel at 8.5' along the gunnel line. If I make the big bow cuts out of 2 sheets, I'll have just about unusable bottom pieces. I could then take the third sheet and make that taper from 26" to 22"ish Leaving me about a foot short but with two end cut pieces which could be scarfed onto the transom end to make up the length. I'll need to play with the numbers more to figure it out, but it seems to work ok with my paper templates. I may have to lose a little height(.5") to make it work this way, but that should be fine. Not trying to build a boat for the grand canyon here. More looking for a boat that will easily handle our class III canyon run on the snake, as well as possibly handling some easier multidays like the main salmon, deso, cat, etc. Small and manueverable.. Big enough to run some easy desert big water, not so big as to be a barge for everyday use.

Im just wondering where the best place to start is. I'll Definatly be building some models, just wondering what my best starting point, and if certain designs might have characteristics I am looking for already designed in. I've also always been curious about design differences. Would really like to know what some of the more distinguishing characteristics of each design are.
Permalink Reply by lhedrick on August 16, 2011 at 7:21am

Chris,

 

I just completed the type of build you are describing.  It was not built of wood but the build would be the same with plywood.

 

You can look at the build process at the following web site

mountaindogs.net/plascorehull

 

Just pretend you are looking at plywood and not composite.

 

When I started I was looking for what you describe.  I have all my panel build notes on file but I have not gotten around to putting them on the web site.  To address the bow rocker as you described it (lifting instead of plowing into big waves) I increased the front stem angle to make it more like the Briggs boat.  This pulled up the front floor quite a bit.

 

If you have any specfic questions about my project you can email me directly since it was a not a wood build:

 

lhedrick at mountaindogs.net

 

 

Permalink Reply by Randy Dersham on August 16, 2011 at 11:38am

Chris, the very easiest way to decide on the boat shape that you like is to buy some hobby shop balsa and think birch panels and build a model. 

You have already made your most important decision which is the general size of 17x54.  This is a very popular size because it is big enough for big water and still not so big that it becomes the huge multi person expedition boat.

 

Cut the birch panels to scale so the shear line is 17ft at scale.  Make a guess at the angle of the transom and the stem.  Cut a transom and stem to scale and glue them to the side panels.  Now you have a scale model of a 17ft boat with no bottom.  You can pull the sides away from each other which will cause rocker, pull flair into the sides which will cause more rocker, etc. 

 

Once you have done that you have three ways to tame the rocker caused by the flair and the wider bottom.  All methods create a flat spot on the bottom of the boat. 

 

1. place a bottom frame in the center of your model that sets the bottom at the width you desire.  Then set a frame on either side of that center frame that is the same length.  At a constant flair this will create a flat spot and pull down the rocker just a bit.

 

2. set the model on a flat surface and mark where you want your flat spot to start and end.  Match that on either side and cut a smooth convex curve between you two marks.  A couple of inches is usually enough, three inches is a lot. 

 

3.  Use both methods together.  The late Prichett boats on the Rogue did this and have a HUGE flat spot.  They have a concave curve in the side panel from stem to transom and they widen frames 4 and 6 on either side of 5  to tame the rocker even more.  The reason is they start out with radical rocker generated by the very wide flair of those designs.

 

Once you get a length of shear and the bottom shape you want then you can go back and mess with the height and angle of your transom and stem, or stem and stem if you decide to do a double-ender.

Permalink Reply by Stephen Markley on August 16, 2011 at 12:50pm

I am still waiting to hear some comments on this:

Quote from Chris: What makes a tatman 16x48 differant from a don hill 16x48? How are either of those designs differant from a ray heater, woody handyman, or Keith steele design?

 

One thing I have noticed is that Tatman's, Ray Heater's, and Don Hill's have a little wider bottom by an inch or so, as compared to the Woody Hindman (in Roger's book), I am not sure about Steele's boats..

 

But what are the differences in how all these boats row? Or trim? Or is it minute and this a dumb question?

 

Thanks

Permalink Reply by Randy Dersham on August 16, 2011 at 1:36pm

The real answer is that each of these builders made many boats.  I have one collector here on the river that has five Keith Steele styles.  Most of Keith's changes were to the angle or height of the sheer line.

 

The early boat by Woody in Roger's book is narrow as many of the early boats were; however, the later Woody Hindman boats had the same 48inch bottom that quickly became a standard because of the minimum draft for the most efficient use of materials.  Post 1960s the bottoms started to widen out if user requested it.  The 17x52, 17x54, and 17.5x54 are all very popular by the mid 1980s.  At 18ft and above at the sheerline the boat becomes large enough that it wears out a rower to hold water at 3mph or so.  If a boat is used for West Coast flyfishing it is most often under 18ft.

 

As a general rule most of the West Coast boats had a asymmetrical bottom that put a little more bottom width in front of the rower to help lift the two people in front.  

 

 

Permalink Reply by lhedrick on August 16, 2011 at 5:25pm

What's the difference?  Well, not much.  Why are all the McKenzie boats about the same?

 

Because plywood only comes in  4X8.  

If

2 sheets yield 1 pair of sides 

and

2 sheets yield 1 bottom

then

we get about a 14 foot boat with a 48 inch bottom and that's the end of it.

 

For 16 foot we need to add 2 feet more plywood starting with 18 feet.  I build 56 inch bottoms and the finished length will be about 93 percent of the flat side panel length finishing about 16 6.

 

Since most use 48 inch bottoms lets stick with that.

 

If the bottom is 48 and the beam is 78 at the locks them all the boats will be about the same.

If the bottom goes to 56 and the beam stays at 78 then the side flair must be different.

 

I can go on and on about all this but, words don't really do it.  Any new builder will learn a ton by studying Rogers Fletches book about dories and drift boats.  When you look at the flat side panel of the Grand Canyon Briggs boat compared to the McKenzie you will instantly see the difference.

 

Start there and build upon what is the book.  The only issue with the book is that everything is 48 inch bottom width.

 

So is there a difference between a Tatman, Heater or Hill or Hedrick (me) dory?  Not much but, there is a bit difference between these and a Briggs or Rogue boat.  When you see the flat panel layout you will know why the Briggs has a flat bottom and the McKenzie has continuous rocker.

 

Hope it helps but I still think you should get Rogers book and see for yourself.

Permalink Reply by chris towles on August 16, 2011 at 6:21pm
Well, I guess most misunderstood what I was really asking here. While I do not own the book, I am well aware of side panel layouts and the effects of dishing rocker out at the bow and stern to add rocker, dishing it out in the center to reduce rocker, straight cuts on the bottom for Continuous rocker. Those concepts are not new to me. I feel like I have a pretty good idea on how the rocker profile of the boat is created, and what you can do to effect it. I was mostly curious as to the differant designs differences between 16x48 mackenzies. X has a wider beam at the center and more bow rocker than y, w is wider throughout the center section than v, etc etc. Just wondering if one design might be better to start with than another. My roomate has either a don hill or tatman 16x48 and I will likely pull some measurements on hull and beam width to use as a referance. I've been making models today as I have been feeling a little under the weather. The models do make obvious the effects of messing with width and flair also. Here's some shots of my first model. I started with my 17' panels cut to scale, I put in a 54" hull width, 82" beam station in the center and have been messing with the width to try and get that right, trying to get a little more width in the back of the boat that the standard mckenzie. It is amazing how pulling the chines flat and parallel immediately gives this boat a Briggs like profile.. I'll keep messing with it, but I think I am just gonna keep working from models because that will get me close. My best friend is also an architect and cad wizard. Ill probably enlist his help once i get my numbers closer. I'll also be building this boat right side up s and g so the stations can be fairly arbitrary anyhow. I'll just torture the boat to shape as I build it.

[url=http://www.flickr.com/photos/55830476@N04/6050914747/][img]http://farm7.static.flickr.com/6083/6050914747_fe9a10d3fa.jpg[/img][/url]
Permalink Reply by chris towles on August 16, 2011 at 6:29pm
Sorry, cant figure out how to make the pic work. Wbp doesn't run so good on my iPhone, and I can't upload directly. Can't figure out how to make the link work either. Oh well
Permalink Reply by Stephen Markley on August 16, 2011 at 6:50pm

I could see 'em... had to copy and paste one of them.

 

Looks good. Could you add 2 or 3 about the same size ribs to the middle to make a flatter spot?

Permalink Reply by lhedrick on August 16, 2011 at 6:54pm

Sounds to me like you have this all nailed down really well.  

 

I too have made the boat wider at the transom.  Since it lowers the floor I cut the chine up a bit starting 24 inches before transom to get the bottom of the transom backup.

 

Many really like the 48 inch bottom, I don't.  I also don't like a boat which tracks in a straight line.  There really is no way to build one of these things and get just what we are after.  We really need to row a few to decide what we like.  Then tune the lines a bit to drill down to what we are after.  After we build a few we get there.  If you row a few and are lucky enough to find one you really like then you can take some measurements and try to build close to the same thing. One thing for certain is that what I like others won't and for good reason.  As far as a 16X48 all we can really do is add some rocker or take some away and torture the center a bit to get the chine parallel (that is if you want a boat to go straight).  I for one find no reason to try and get all I want by minimizing plywood usage.  It makes more sense to me to build what you really want and purchase as many sheets as needed.  Left over plywood never gets wasted.

 

I think the model idea you are working with is the best shot and getting the lines you want.  I worked with a CAD system once and on the screen in 3D mode hulls looked okay but when I had the system flatten out the panels the boat had way too much rocker.  A model would have really showed the problem.

 

A model will also be a big help in finding how much of an arched cut to make to the chine while it's flat to remove rocker.

 

On last item.  My last 3 boats were 16 foot 6 boats which were stretched out from a 14 foot design.  Pulling them out to 16 foot 6 and using the same bottom width really flattened them out the amount I was looking for.

Permalink Reply by Stephen Markley on August 16, 2011 at 7:09pm
Did you still have to Dish the Chines on the 16ft 6in boats?

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