Wooden Boat People
By McKenzieDriftBoat.com
Building for big water and looking for options.
For some background on white water take a look at the images at the following site. Some of the images are from Joe Hutch rapid on the Green at a flow of 25000 CFS a class IV run.
http://www.inskeepimages.com/g/highwaterdeso
People with GPS units on their boats have reported boat speeds through the rapid at over 20 MPH.
The dory images are of Linclon Frye, Ryan Pearl and Dave Inskeep. Each built the boat they are rowing. Ray Bloxham is running my boat which I built about 8 years ago.
Dave Inskeep runs a 16 foot all wood Tatman design modified for whitewater. The boat is over 10 years old, has run the Grand Canyon twice and has never had a hole in it. It makes it's third trip down the Grand next March.
We are not talking about fly fishing drift boats here. As we all know wooden drift boats are more then up to the task for class III water. We may need to fix a dig now and then but these boats will last a lifetime. However, I wouldn't advise running a Hyde or Tatman open fishing rig through Joe Hutch at 25000 or Lava at 10000 if you don't want it swamped and pinned on the rocks at the bottom of the river. This is not to imply there is anything wrong with either boat. I don't like fishing from my decked white water boat, the right tool as they say.
Who cares? Well, In the last 4 years I have been on 3 trips where there have been dories which could not continue until repairs were make. I also know of 3 other events on trips I was not able to make. All of this carnage happened to highly skilled boaters. It's just part of the deal. Being and old weak dude I look for the anti-carnage line whenever possible. One boater I know likes to say “go big or go home”. Well, he does and sometimes with a hole in his boat. We have fun and do what we can.
Lets try to apply some number to this. With the added weigh of bulkheads and decks let's say a 16 foot whitewater boat will be around 500 pounds. Add 2 adults, safely gear, cooler, food, camping equipment, water etc. Just call it 1000 pounds for a loaded boat. A large 17 foot Briggs boat will be more.
Now think about riding up a wave at 15 MPH and going down the back side into the trough and coming down onto a rock. 1000 pounds of force plus some added component with the boat moving downward. This isn't a math class (F=MA and all that stuff) so we will call it some number of pounds of force well above 1000 pounds. The rock is around 6 inches square or 36 square inches. 1000 pounds of boat and gear being dropped onto a 6 X 6 inch square. We also know from basic chemistry that liquids and solids are not compressible. So, when we hit the rock were does the 1500 pound impact energy go?
Options
We could crush the rock,,,,,, or not
The bottom of the boat could bend or not if we have bulkheads or frames.
If the rock doesn't crumble and the boat bottom can't bend then it will be the bottom of the boat which will brake. The energy will be converted into heat as it brakes the wood fibers and fiberglass as it folds inward.
How thick would the plywood and frames/bulkheads need to be to prevent this breakage? I don't know how thick it would be but it's too thick for a boat and the boat becomes 500 pounds heavier. If you want to build from wood that's fine but then you must live with the properties of the material and be willing to fix some things when you get pushed off line and take a big hit. There is no way around it and we have been doing just that for a long time.
What else can we do?
1 --
Make the bottom flexible. This sends some of the impact load to the surrounding material as it flexes. Like old time bridging of floor joist. Step on one floor joist and as it bends downward we send some of the load to the joist on each side of us. The impact now loads 200 square inches instead of 36. Unfortunately this is not an option when frames or bulkheads are being used.
2 --
make the bottom stronger so we can prevent the impact from braking the plywood by sending the load through more wood fibers to the material around the impact. Less psi on a bigger area to bring the load down to what the material can handle. Much thicker plywood. This would send the impact load down the fibers of the wood and with more plywood layers at some point the wood becomes strong enough not to brake if we make it think enough. This option is not practical beyond ½ inch plywood due to the added weight.
3--
Different materials.
Honeycomb, some of us have already started using this.
If you are building a wood white water boat the only option is to go with ½ inch plywood and cover it with kevlar which brakes at a much high load then glass fiber. I don't know of any other way. This will make a fine boat and over the years we will just need to fix it when we put a hole in the bottom. Not the end of the world. We pull the boat out of the river and thank the person who needs to mix up some epoxy for the patch for giving us a layover day. We can point to the fixes and toast the past which is nice. We can fix anything the river throws at us given enough time, beer and epoxy.
Now if we use ¾ or 1 inch honeycomb in place of the plywood we have a much lighter material since most of it is hollow. When the load of the impact is applied to the 6 X 6 inch area the inside of the honeycomb will start to deform dissipating much of the energy before it gets to the inside surface. If the impact load is high enough it will also brake the fiberglass on the outside as it crushes the honeycomb material just like with plywood. Now replace the fiberglass with Kevlar. Since the Kevlar is mush stronger then glass and does not want to stretch, the impact will try to stretch the fibers sending the load to a much larger area. This sends the impact energy into lets say 200 square inches of honeycomb taking away enough of the energy to prevent the rock from punching through. The thicker the honeycomb the more it can crush without getting all the way through and the kevlar sends the force to more of the honeycomb. Like stretching a trampoline over the outside of the boat so it can bounce off rocks.
Lets say the rock hits right next to the frame/bulkhead and the impact load is so high that the honeycomb just can't absorb it all. Then just like with plywood it folds inward and we have a hole in our boat. How could we stop this one? If we all agree that the honeycomb with kevlar is stronger then plywood what do we do now? What if the bottom could flex? What if the frames or bulkheads were not their? Then the entire bottom could bend inward sending the impact load to many square feet not just a few inches. Now we can take a much larger impact. How can we do this with a frame? I have no idea but we can do it with a bulk head. If the bulkhead does not go all the way to the bottom then the entire bottom can flex up and down. The bulkhead would only attach to the sides.
Some possible solutions.
Make bulkheads out of foam which can crush. We have damage but just not as much and we don't get water in the boat. My current boat has 2 foam bulkheads which go all the way to the floor. There are also 2 plywood bulkheads at each end of the boat where impact will not be as severe. Haven't take a big enough hit yet to damage any of them. Not all sheet foam is suitable for this.
Keep the bulkhead up off the floor by 2 inches and fill the space with a soft foam filler piece. Epoxy over the foam cells to keep water out then glue it in place with 3M5200 or 3M101. Now the floor can flex. If we take a hard hit right next to a bulkhead the bottom can flex upward instead of folding the material inward. I don't think it's reasonable to try to build a boat which can't be damaged. It's not worth the time or money. But maybe we can find some simple ways to lessen the damage to an amount which will allow us to float on and do the repairs in our shop instead of camp.
As for Kevlar, there has been an on-going debate about where Kevlar is best applied. Inside our out? Lets call it even and say we are going to use it inside and out. At any rate it is strong stuff but a bit harder to work with. The sky is the limit. At this point we are only constrained by cost. Honeycomb is available in polypropylene, aluminum, aramid, polycarbonate, stainless steel etc. Carbon fiber, while it is strong and light it is also brittle and will not work in our application other then possibley in sandwich construction here and there but, I haven't any spots on a dory where it makes sense at 50 dollars a yard.
The decked Tatman whitewater boat I mentioned is very solid but it is also very heavy. I believe I can build the same boat entirely out of plascore and drop the weight by 150 – 200 pounds (or 200 cans of Dale's pale Ale). Now that's motivation. Some people like heavy boats and feel they are more stable and less likely to flip. I do not share this view. To me lighter is always better if we can maintain strength and durability. About a framed boat. If we have frames which are strong as hell then the only thing a bulkhead does is support the deck and seal a chamber. It doesn't need to be ¼ or even 1/8 inch plywood. We could make it out of polypropylene sheet only a few mills thick. Then again get rid of the frames at the bulkhead locations and use a plywood or honeycomb bulkhead. We don't need both.
The whitewater boats made by Boulder where mentioned. While they have their place, the material is not something which will work in our 1 off construction. It's more of a factory material. It is also not practical in that it must go back to the factory for a patch. I have a plastic roto-molded boat which has a crack in it and nothing will close it. I have been able to keep water out of it using 3M5200. If I can't patch the boat on the river it's not for me.
The ideas are the same for wood or plascore. The materials work the same way and no lines are altered based on the material we chose. So this isn't really a statement of one material over another but rather getting the most flexibility out of whatever material we use.
This subject came up a here a week ago and I went back to some past discussions about the subject to put this together. I posted it here to see if others can add to the descussion and contribute some new ideas. Since famed construction has evolved to it's current state after many years of work it look to be mature. The boats running the Grand Canyon have proven their durability. The only change I can see would be to replace wood bottoms with newer composits. I don't see any other options with framed design.
This is a wood boat forum and wood boats are classic and nothing looks like them. If the desire is to build an all wood boat by all means do it. Tom's project of building a new version of Fulmer's GEM demonstrates how far we can go with wood construction and a 50 year old design still works. It will run the 100 rapids from Lee's Ferry to Lake Mead just like original did. We just need to keep in perspective what the materials can do. The last boat I completed was wood with a honeycomb bottom. I have lots of different hardwoods built into it. It needs to be oiled from time to time and that's ok. Painted honeycomb will never look like a handcrafted wood boat. What will I build next? Not sure, I just like to keep building but, I need to sell something to make room.
Looking for the views of other builder.
Larry
http://www.inskeepimages.com/g/highwaterdeso
People with GPS units on their boats have reported boat speeds through the rapid at over 20 MPH.
The dory images are of Linclon Frye, Ryan Pearl and Dave Inskeep. Each built the boat they are rowing. Ray Bloxham is running my boat which I built about 8 years ago.
Dave Inskeep runs a 16 foot all wood Tatman design modified for whitewater. The boat is over 10 years old, has run the Grand Canyon twice and has never had a hole in it. It makes it's third trip down the Grand next March.
We are not talking about fly fishing drift boats here. As we all know wooden drift boats are more then up to the task for class III water. We may need to fix a dig now and then but these boats will last a lifetime. However, I wouldn't advise running a Hyde or Tatman open fishing rig through Joe Hutch at 25000 or Lava at 10000 if you don't want it swamped and pinned on the rocks at the bottom of the river. This is not to imply there is anything wrong with either boat. I don't like fishing from my decked white water boat, the right tool as they say.
Who cares? Well, In the last 4 years I have been on 3 trips where there have been dories which could not continue until repairs were make. I also know of 3 other events on trips I was not able to make. All of this carnage happened to highly skilled boaters. It's just part of the deal. Being and old weak dude I look for the anti-carnage line whenever possible. One boater I know likes to say “go big or go home”. Well, he does and sometimes with a hole in his boat. We have fun and do what we can.
Lets try to apply some number to this. With the added weigh of bulkheads and decks let's say a 16 foot whitewater boat will be around 500 pounds. Add 2 adults, safely gear, cooler, food, camping equipment, water etc. Just call it 1000 pounds for a loaded boat. A large 17 foot Briggs boat will be more.
Now think about riding up a wave at 15 MPH and going down the back side into the trough and coming down onto a rock. 1000 pounds of force plus some added component with the boat moving downward. This isn't a math class (F=MA and all that stuff) so we will call it some number of pounds of force well above 1000 pounds. The rock is around 6 inches square or 36 square inches. 1000 pounds of boat and gear being dropped onto a 6 X 6 inch square. We also know from basic chemistry that liquids and solids are not compressible. So, when we hit the rock were does the 1500 pound impact energy go?
Options
We could crush the rock,,,,,, or not
The bottom of the boat could bend or not if we have bulkheads or frames.
If the rock doesn't crumble and the boat bottom can't bend then it will be the bottom of the boat which will brake. The energy will be converted into heat as it brakes the wood fibers and fiberglass as it folds inward.
How thick would the plywood and frames/bulkheads need to be to prevent this breakage? I don't know how thick it would be but it's too thick for a boat and the boat becomes 500 pounds heavier. If you want to build from wood that's fine but then you must live with the properties of the material and be willing to fix some things when you get pushed off line and take a big hit. There is no way around it and we have been doing just that for a long time.
What else can we do?
1 --
Make the bottom flexible. This sends some of the impact load to the surrounding material as it flexes. Like old time bridging of floor joist. Step on one floor joist and as it bends downward we send some of the load to the joist on each side of us. The impact now loads 200 square inches instead of 36. Unfortunately this is not an option when frames or bulkheads are being used.
2 --
make the bottom stronger so we can prevent the impact from braking the plywood by sending the load through more wood fibers to the material around the impact. Less psi on a bigger area to bring the load down to what the material can handle. Much thicker plywood. This would send the impact load down the fibers of the wood and with more plywood layers at some point the wood becomes strong enough not to brake if we make it think enough. This option is not practical beyond ½ inch plywood due to the added weight.
3--
Different materials.
Honeycomb, some of us have already started using this.
If you are building a wood white water boat the only option is to go with ½ inch plywood and cover it with kevlar which brakes at a much high load then glass fiber. I don't know of any other way. This will make a fine boat and over the years we will just need to fix it when we put a hole in the bottom. Not the end of the world. We pull the boat out of the river and thank the person who needs to mix up some epoxy for the patch for giving us a layover day. We can point to the fixes and toast the past which is nice. We can fix anything the river throws at us given enough time, beer and epoxy.
Now if we use ¾ or 1 inch honeycomb in place of the plywood we have a much lighter material since most of it is hollow. When the load of the impact is applied to the 6 X 6 inch area the inside of the honeycomb will start to deform dissipating much of the energy before it gets to the inside surface. If the impact load is high enough it will also brake the fiberglass on the outside as it crushes the honeycomb material just like with plywood. Now replace the fiberglass with Kevlar. Since the Kevlar is mush stronger then glass and does not want to stretch, the impact will try to stretch the fibers sending the load to a much larger area. This sends the impact energy into lets say 200 square inches of honeycomb taking away enough of the energy to prevent the rock from punching through. The thicker the honeycomb the more it can crush without getting all the way through and the kevlar sends the force to more of the honeycomb. Like stretching a trampoline over the outside of the boat so it can bounce off rocks.
Lets say the rock hits right next to the frame/bulkhead and the impact load is so high that the honeycomb just can't absorb it all. Then just like with plywood it folds inward and we have a hole in our boat. How could we stop this one? If we all agree that the honeycomb with kevlar is stronger then plywood what do we do now? What if the bottom could flex? What if the frames or bulkheads were not their? Then the entire bottom could bend inward sending the impact load to many square feet not just a few inches. Now we can take a much larger impact. How can we do this with a frame? I have no idea but we can do it with a bulk head. If the bulkhead does not go all the way to the bottom then the entire bottom can flex up and down. The bulkhead would only attach to the sides.
Some possible solutions.
Make bulkheads out of foam which can crush. We have damage but just not as much and we don't get water in the boat. My current boat has 2 foam bulkheads which go all the way to the floor. There are also 2 plywood bulkheads at each end of the boat where impact will not be as severe. Haven't take a big enough hit yet to damage any of them. Not all sheet foam is suitable for this.
Keep the bulkhead up off the floor by 2 inches and fill the space with a soft foam filler piece. Epoxy over the foam cells to keep water out then glue it in place with 3M5200 or 3M101. Now the floor can flex. If we take a hard hit right next to a bulkhead the bottom can flex upward instead of folding the material inward. I don't think it's reasonable to try to build a boat which can't be damaged. It's not worth the time or money. But maybe we can find some simple ways to lessen the damage to an amount which will allow us to float on and do the repairs in our shop instead of camp.
As for Kevlar, there has been an on-going debate about where Kevlar is best applied. Inside our out? Lets call it even and say we are going to use it inside and out. At any rate it is strong stuff but a bit harder to work with. The sky is the limit. At this point we are only constrained by cost. Honeycomb is available in polypropylene, aluminum, aramid, polycarbonate, stainless steel etc. Carbon fiber, while it is strong and light it is also brittle and will not work in our application other then possibley in sandwich construction here and there but, I haven't any spots on a dory where it makes sense at 50 dollars a yard.
The decked Tatman whitewater boat I mentioned is very solid but it is also very heavy. I believe I can build the same boat entirely out of plascore and drop the weight by 150 – 200 pounds (or 200 cans of Dale's pale Ale). Now that's motivation. Some people like heavy boats and feel they are more stable and less likely to flip. I do not share this view. To me lighter is always better if we can maintain strength and durability. About a framed boat. If we have frames which are strong as hell then the only thing a bulkhead does is support the deck and seal a chamber. It doesn't need to be ¼ or even 1/8 inch plywood. We could make it out of polypropylene sheet only a few mills thick. Then again get rid of the frames at the bulkhead locations and use a plywood or honeycomb bulkhead. We don't need both.
The whitewater boats made by Boulder where mentioned. While they have their place, the material is not something which will work in our 1 off construction. It's more of a factory material. It is also not practical in that it must go back to the factory for a patch. I have a plastic roto-molded boat which has a crack in it and nothing will close it. I have been able to keep water out of it using 3M5200. If I can't patch the boat on the river it's not for me.
The ideas are the same for wood or plascore. The materials work the same way and no lines are altered based on the material we chose. So this isn't really a statement of one material over another but rather getting the most flexibility out of whatever material we use.
This subject came up a here a week ago and I went back to some past discussions about the subject to put this together. I posted it here to see if others can add to the descussion and contribute some new ideas. Since famed construction has evolved to it's current state after many years of work it look to be mature. The boats running the Grand Canyon have proven their durability. The only change I can see would be to replace wood bottoms with newer composits. I don't see any other options with framed design.
This is a wood boat forum and wood boats are classic and nothing looks like them. If the desire is to build an all wood boat by all means do it. Tom's project of building a new version of Fulmer's GEM demonstrates how far we can go with wood construction and a 50 year old design still works. It will run the 100 rapids from Lee's Ferry to Lake Mead just like original did. We just need to keep in perspective what the materials can do. The last boat I completed was wood with a honeycomb bottom. I have lots of different hardwoods built into it. It needs to be oiled from time to time and that's ok. Painted honeycomb will never look like a handcrafted wood boat. What will I build next? Not sure, I just like to keep building but, I need to sell something to make room.
Looking for the views of other builder.
Larry
Views: 585
Replies to This Discussion
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Permalink Reply by Jeremy Christensen on
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"Sure we all get the thrill from the "BIG WATER" but you also have to use a little sense. You do not have to be going 15 mph in a rapid if you do not want to. That is what the oars are for some times. They help to slow you down."
Herb, this may be true for low volume rivers, but with the power of the water at higher volumes, you can pull on your oars all you want, they aren't going to slow you down. When you hit the tongue sliding into Lava Falls, you better hope you are on the right line, because you aren't getting off it. This is not about finicky rock-dodge lines through rock gardens at 2-3000 cfs. In truly BIG water, you get set up on the right line, and you can pretty much ship the oars and hold on. The power of the river is more than anyone or any oar can overcome. Lining your boat is not always an option.
Still, I agree with your basic point: don't hit rocks. Duh. But why not prepare for the eventuality by designing a boat able to withstand what you are going to subject it to? As Larry asks, should we still be using hide glue instead of epoxy just because our fore bearers did? I use the Grand Canyon as the ultimate example. This is, as far as I know, the most committing river trip you can undertake in the 48 states. When you push away from Lees Ferry in a wood boat, you have 230 miles and 160 named rapids to class IV awaiting you. Some of the unnamed rapids in the Grand will put named rapids on other rivers to shame. The average oar-powered trip length is 16-21 days. How many people do you know that could row 225 miles, 160 rapids, without making a single mistake? Crabbing an oar? Missing a stroke? Mis-reading the water or mis-gauging the setup? Obviously a much better boatman than I.
I would rather do everything I can to minimize the inconvenience when the eventuality occurs, while still doing everything I can to prevent it once I'm on the water. The point for ALL boaters, raft or hard hull, should be to have clean runs and not hit rocks. Rafts make lazy boaters, as you can get away with a lot more. The people I know that row wood boats are the most skillful. But we all still hit rocks.
all the best, Jeremy
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Permalink Reply by Randy Dersham on
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There are a few things that are critical to make a white water boat handle and maneuver it's best.
A low center of gravity
Enough rocker to keep each end of the boat up and out of the water you are running
Enough width to be laterally stable; however, the more width the more energy it takes to change directional momentum
Stiff enough to efficiently transfer energy from the oars
Enough flair to prevent the boat from diving deep when downward momentum is coming your way
Strong enough to handle the expected collisions that come from being on the water that you are building the boat for
Last: no matter what the design or materials are, once in the water the boat must be trimmed for even weight distribution front to back and side to side. Lots of jokes about where to put the beer, but ignoring this fact can turn a fantastic boat into a poor performer in almost any white water.
These are the basic characteristics of the river dory. We can change whatever design and materials we want as long as we understand the compromises and are willing to live with them. At McKenzie River Drift Boats we sell over ten double ended drift boat designs because each one is best in a specific type of water with a planned load. My point is that there is no best boat, but it is likely there is a best set of compromises for a specific type of water.
I recommend that you start with the characteristics of the water you plan to run, then the load you want in the boat. After that you can use the above list as a measure to gauge the compromises made by the new changes you have planned.
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