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Permalink Reply by lhedrick on August 16, 2011 at 8:24pm

Everything about these boats is determined by the lines along the chine.  It's the only place we can make any changes.

 

Since I have my own requirements as to how I want the boat to move in the water it determines what I do to this line.

 

I started over 10 years ago with a 14 foot boat with modest rocker built from 4 sheets of plywood.  While it was a very good fishing boat it wasn't really ideal for big water but, it ran down the Green for years and then down the Grand Canyon before selling it and building a bigger boat.

 

What I liked was the 56 inch bottom so I kept that and used the same temporary frames to move up to 16 foot 6.  Since I was happy with the bottom width and I didn't want any more beam, it's all the same.  I just built with higher sides and changed the stem angel up front.  The 14 footer would spin a bit too fast in big water but  stretching it out to 16 6 turned out to be just right.  The bottom is flatter in the center and the extra 2 feet make the chine line longer so it doesn't want to turn as quickly but it's still quicker then a Briggs boat.  I have nothing against the Briggs boat, it's just a bit too long and slow to move for my taste.

 

To the point of dishing out the chine.  The bottom width and width at the oar locks kind of limit our options.  Since I like a wider bottom then the sides are not flared as much.  To get the same flair as the boats with 48 inch bottoms would make it too wide at the locks for me.

 

It really comes down to how flat we want the bottom to be and how wide.  I doubt many boats vary much up at the oar locks  Those 2 decisions will determine how a boat turns.  About all that is left is to determine how much we want the floor to curve up at the stem and transom.  While that might change how the boat climbs a big wave that's about all it does.

 

In 4 trips down the Grand Canyon, most of the boats I have seen there have been flat bottom, parallel chine Briggs boats.  It's what most people want in big water.  The McKenzie boats were the ones in our group.  My friend Jeremy has decided to move to the Briggs 48 inch bottom which he is building now  while I have moved to the stretched Mckenzie.  Once size doesn't fit all.

 

 

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Permalink Reply by Randy Dersham on August 17, 2011 at 3:07pm

The photo is working for me and it looks great.

There are two slight differences between the builders.  Asymetrical bottom and flat spot.

Most 16x48 actually row very similar.  The early Hindmans tend to be more symetrical than later boats, Willard Lucus tend toward even more asymmetrical.  The reason for the asymmetrical bottom with the widest spot in front of the rower toward the stem is to have more lift for the two passengers up front.  Any guide can quickly adapt from one boat to another so the differences are not large.

 

The one common thread today is that most guide boats are 16.5 to 17.5 with the largest majority very close to the 17x52 or 17x54 range.  Any larger or wider than that and the boat can be loaded heavy enough that you have to be a big strong rower to hold it in water all day long when fly fishing pocket water or faster current.

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Permalink Reply by Randy Dersham on August 17, 2011 at 2:54pm

McKenzies have flat spots and have had since the boats have been made at 16ft lengths.

McKenzies come in a variety of max beam at the shear because flair affects wet vs dry ride.

McKenzies have been made with over 48 inch bottom since the 1960s.

 

The difference between a McKenzie and a Rogue is not the flat spot but the shape of the chine when the side panel is flat.  It is easy to assume that a straight line alone the chine of a flat panel will cause a continuous curve but it does not have to.

 

Most McKenzie Boats have a flat spot on the bottom.  It is created by widening frames four and six on either side of five. It was true that the early boats of the 1940s had continuous rocker but once a boat went to 16ft a flat spot was the norm.  How you describe the McKenzie vs Rogue flat side panel is very true.  If you look at a Rogue boat you will see the concave chine line and the convex shear line on the panels while the McKenzie boats will have a straight line on the chine and on the shear. 

 

This is a very important distinction. When frames 4-5-6 are at or near the same width the affect is to lower the amount of rocker, add a flat spot, and add a couple of feet of flat straight chine .  Builders that like a bigger flat spot and more pronounced flat chine made frames 4-5-6 equal. Builders that wanted the curve to be more progressive and not quite as flat would make frame four and six not quite as long as five.  This caused the boats to row a little differently.  The flat spot boats turn a little slower and float a little higher.  The more continuous the bottom the the faster the boat turns with more rocker. This doesn't matter much to white water rowers.  It matters a lot to guides that row all day to hold water and go nowhere. 

 

McKenzie Drift Boats also have a wide range of max beam on the shear line.  Some fourteen footers as little as 70 inches with a sized up 18 footer at 80 or 82.  The flair is a very important decision in this size for guides because of the relationship to displacement (the more flair the more weight a boat can carry) and dry ride.  A boat with enough flair will have a dry ride while a boat with too much or to little flair will have a wet ride.  This is more important for fishermen than white water people because they are always trying to keep the flair wide to handle the big customers but not so much flair that the shear cuts the tops off of big waves.

 

We completely agree that words don't really do it. People should build a model, and then build another model, and then build another model.  When you're ready, build a boat and see how you like it.  Keep it fun and keep it safe.  Other than that there aren't really any rules.

 

If you can, row as many boats as you can get your hands on. 

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Permalink Reply by chris towles on August 17, 2011 at 4:03pm

What you have suggested is exactly what I have done the last few days. I have now built 4 models, all with differant characteristics. It's funny how these boats really do build and shape themselves once the panels have been cut. I have been messing mostly with stem and transom cuts as well as width with predetermined bulkheads. I am starting to get into the neighborhood, but there is much more to do. Seems like each model has something I like, but as soon as I play with one variable the others get thrown out of whack. I'll keep toting until I get what I like. I also went out and measured hull width and beam on the 9 stations in my roomates 16x48 which is either a tatman or don hill. That boat has a good flat spot on it, but it appears based on side panel height that it does not have a dished Chine. I added 6" width to all those numbers to get a guestimate of hypothetical stations for models. I'll prob build a model of that boat, and then see how it looks compared to my 17x54 models. This whole thing has been pretty fun Sofar so i think ive decided that plans are a waste of time. They were only going to be a reference anyhow, and I have a reference boat or two sitting out in the driveway. Heck, if Dutch doesn't sell that 17x54 sitting in front of Wilson gas station I may take a tape measurer to that too :) anyhow heres a shot of my fleet of tecate boats.

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Permalink Reply by Randy Dersham on August 17, 2011 at 4:15pm

Fantastic.  When you get close to one you like, double the size of the model.  That will surprise you a little.

 

I see the wide transom.  Here's a compromise to think about.  The more wide the transom the more displacement so the more weight you can carry in the back; however.  the more wide the transom the harder the river will push you if (or when) the boat dips into big water.  That push limits the amount of ferry maneuvering you can do.  Sanderson (my son and boat builder) loves wide transoms but we are not usually on more than a class IV river.  Notice the boats in the Grand Canyon have narrow transoms.  Being pushed around really makes you feel like you lose some control.  

 

There's no right or wrong, just what is best for the water you are on most often,

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Permalink Reply by chris towles on August 17, 2011 at 6:03pm

Well, as I said above, there is much more to do before I really get it dialed in. I'll probably make 10 more of these models. And I do plan to blow them up once I can find more cardboard than a 6pack holder.. Funny, seems there's always pbr cases around here until I'm ready to build models. As for the transom, that was mostly a guess. By scale It is roughly 1ft wide at the bottom, 2ft- 2'4" at the top and 2'6" tall. I just eyeballed it but I am not so convinced you need a wide transom to get more volume in the back of the boat anyhow. I've been working on evening the profile by adding with behind the rower, which has been giving me the nice stern rocker I have been looking for.. I need to do some more measuring and more models before I am ready to go much further. The displacement thing does makes sense, more surface area to be taken by water. However more surface area also means your boat is also less likely to be taken by the current anyhow. I'll also being messing with a curved stem and transom bottom. It will be interesting to see how this will effect the rocker.. The transome shouldn't have as much of an effect as the curved stem does. I made one model with a curved stem. It looks really nice and seems to pull a little kick rocker in to the end of the boat. It also makes it really hard to pull the stem together. Reminds me of pics of curved stem mbb boats being tortured into place..

At this point I'm just trying to get the width, stem and transom cuts, and rocker dialed. Once I do that I'll take that shape and build a bigger model with 1" of chine dish in the center 3' of the boat, and a 1-2" wedge dished out in the bow to give it a little kick rocker at the tip. I have tried experimenting with chine dish a little, but on these super small scale models it is hard to tell. I guess the bigger model should tell me alot more.

Thanks to all you boat designing folks for your insight

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Permalink Reply by lhedrick on August 18, 2011 at 7:35am

From everything you have posted to this point it's clear you have a handle on a lot of the issues related to hull shape, you also mention you had access to other boats.  This leads me to the following question I ask others who are thinking about a building.

 

I ask, of the boats you have rowed can you identify which you like and which you don't.  If you can identify the characteristics and map them to the hull shape and numbers you can also identfy what to change.

 

If a person said they had never rowed anything or can't feel any difference between the boats they have rowed thin it's more difficult to help.

 

The models are a big help but, they will not really identify the rowing behaviour.  They will show if the trim is good but how it turns will be a function of the curve at the chine.  If you can look at a model and say, well, it too straight for too long in the center then you are way ahead of most people.  

 

The question is to know how much of a flat spot and how much parellel section.  I have found what I like in relation to tracking and rocker but, others will want something different.  The key is being able to know how the changes to the chine will alter the movements when you pull one oar.  Will it rotate or will it resist.  Will it climb big waves or plow into them.  If it's for flat water then that might be fine but, it's good to be able to look at the model and have and idea how the shape will run in different conditons.  I wouldn't want to fish a Briggs boat with a 48 inch bottom on the Green when the Flow is 800 CFS but for running down the line at Hermit in the Grand Canyon it might be just the thing.

 

On some water I have been on we need to spin and move all over the place to row are way around rock gardens.  Other places we want to line up and power through.  We don't want a lateral to kick the bow around.

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Permalink Reply by Sandy Pittendrigh on August 17, 2011 at 8:44am

There is a how-to-do-it 'stitch and glue' design discussion at the following URI. But it doesn't have to be stitch and glue.  Dories are dories.  Some people like to use 3D design software.

I prefer to work with full-size models.  With computer images you still have to guess what the eventual hull will look like. With full-size models you get to see it first hand. And then you can make adjustments, as needed.

 

http://montana-riverboats.com/index.php?fpage=Driftboats/NewHullDesigns

 

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