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Thread: "Toe-In" for powered cata-rafts?

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    Member BluNosDav's Avatar
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    Question "Toe-In" for powered cata-rafts?

    When building a cata-canoe, everyone suggests that the canoes should be lashed together with the bows "tow-in". It is said that this will enhance performance and decrease splashing between the hulls. I know that almost all cata-raft frames are built to hold the sponsons parallel to each other and that motors are only used on an occasional basis. So, I doubt anyone would go to all the effort to reconfigure their frame every time they started the motor. But, maybe someone motors their cata-raft A LOT, and uses it more like a sport-boat than a raft.

    Has anyone ever experimented with building a frame for a dedicated motorized cata-raft and used a "toe-in" design?
    If so, how did it work out for you? Any downside when drifting downstream and using the oars?

    Secondary question:
    What kinda speed have ya'll been able to achieve with your motorized cata-rafts (either parrallel or tow-in)?
    (please include your specific: raft model, engine model, approximate load, etc.)

    Thanx, Dave.

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    webmaster Michael Strahan's Avatar
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    I don't know who "everyone" is, but I've never heard of rigging this way. Seems to me that it would create additional drag along the outside edges on both sides. Yes, it would result in less splashing between the tubes, but at what cost? More drag and poorer tracking.

    In my experience you control the spray with a spray shield; something that seals against the tubes on each side and covers the floor area. The shield can compress the aerated wake between the tubes and duct it right to your outdrive. This generates lift and allows you to run the motor shallower than normal.

    The largest one I ever ran was a 22' custom boat from AIRE. It had remote steering, a complete flooring system and seats everywhere. It was for a lodge. The outboard was an 88-horse Yamaha.

    -Mike
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    Member BluNosDav's Avatar
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    Well, I usually try not to use words that are so restrictive that there is no wiggle room. But, I did say "everyone". My apologies.

    What I meant to infer, was that during my research on the canoeing forum, most of the time, when someone asked about making a cata-canoe, there was usually someone with experience, that recommended setting up the two hulls with a bit of "toe-in". The only numerical amount specified exactly was about 8". Which is not much, when considering canoes of about 16-18 feet in length.

    Now "toe-in" is not a new concept when it comes to improved handling. Almost all of our cars & trucks have their tires "toe-in", and many power-catamaran manufacturers use a similar technique with their hull molds. So, while there probably is some slight increase in drag, there surely must be some increase in performance that makes the trade-off worthwhile. At least at higher speeds.

    I suppose that at rowing speeds, or just drifting along with the current, the advantages of "toe-in" are probably negligible? And given the relatively small scale of cata-raft frame manufacturing, it's probably easier to just set things up at right-angles and parallel. Plus, given the need to often row upstream while floating downstream, a symetrical "double-ender" design, is probably better.

    But, since I tend to be a tinkerer at heart, and as Admiral Gorshkov used to say, "Better, is the enemy of good enough". I just wondered if anyone, who mostly used their cata-raft as a powerboat, might have experimented with a little bit of "toe-in" and found that it helped?

    Thanx, Dave.

    PS - I would almost certainly use a spray shield with or without "toe-in".

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    i had a aire couger that i hung a 35 hp outboard prop with a lift, as well as a go devil from. any toe in or out was like dragging a anchor, nor did it stop water from being pushed up between the tubes. set up that way i could only haul a half of a moose up river in stiff current and it was slow going.i would not want to go far that way.

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    BluNos,
    ...ain't never heard any rafters talk 'bout any "toe-in" while riggin any catarafts. Not ever. Not when they were sober. Not when they were impaired. Parallel tubes for proper trackin in current, in wind, flatwater.
    Talk to the guys in the Anchorage stores. Or call the "outside" manufacturers. Neither will suggest any intentional "toe-stuff".
    And while running a motor, I definately want the tubes perfectly parallel and equally inflated.
    Listen to Mikey and Oyster, above.

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    Agree with ya there ATA.

    "Everyone" (oops) involved in rafting, has "not ever" talked about toeing-in the sponsons.
    Makes sense, because . . .
    Most cata-rafters started out drifting downstream with a relative water-speed of 0 kts.
    Then, they started rowing upstream to avoid rocks, and downstream through slow pools and lakes.
    Next, they attached a small outboard motor to get across the same lakes just a little bit faster.
    And later on, they tried a slightly larger outboard on their cata-rafts in order to run upstream a little ways.
    But they "always" (ouch) planned to turn off that motor relatively soon, and get back to drifting downstream.
    Under these circumstances, I will concede that parrellel sponsons are probably the better way to go.

    It may also be that the more bulbous, double-ended-tear-drop-shape of two canoes, causes much different
    hydrodynamics and wave compression, than the relatively straight-sided sponsons of inflatable cata-rafts.

    I honestly don't know. That's why I asked this question.

    Ya know, once upon a time, "everyone" (there I go again) thought the world was flat.
    For those who always stayed within sight of land, that theory worked well for them.
    They also warned against anyone thinking otherwise. But, that didn't make it so!

    I still have a nagging hunch, that if I wanted to build a fleet of powered inflatable cata-rafts,
    the primary purpose of which, was to spend alot of time motoring at high-speed under power,
    and relatively little time drifting with the current, they might just be improved by a little bit of toe-in?
    Probably never know . . . . . .

    Thanx for everyone's input,
    Dave.

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    Interesting idea. From the little I know about toe-in on autos (from accidental experimentation), it improves tracking. Cars that I've used, start to wander around when there is little or no toe-in. There might be a similar effect on catarafts, although I've not tried it. I haven't had a serious motor on my cataraft in years, but I never found my quad tubed Cougar to be a very power efficient hull design. Besides all the water blasting around everywhere was discouraging to my riders. I doubt that adding toe-in would have changed that effect.

    I have, however, experimented with toe-in while rowing the cat. This also was not intentional but merely the result of having mismatched frame sections on each end of the raft. In any case, I could not tell a difference in tracking while rowing. In fact, I couldn't tell any difference at all. There might have been some indeterminate difference in hull speed, but it would have had to have been so slight as not to be noticed. Rafts slip and slide through the water anyway. Half the time drifting sideways to the left and the other half drifting sideways to the right. Who can tell if there is any effect? I think it's a non issue until you're going fast enough for details in tracking to matter.

    It should be an easy matter to design a tube frame that allows for adjustable toe-in. You ought to try it. I no longer have a motor bigger than 2.5hp, but it would be interesting to know.

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    hey dave,
    i tried to make a aire couger a viable upriver craft. i had what i thought was limited success, poor performance and fuel economy. i also tried it with a bi-yak, which is a poly hard shelled cataraft evan going so far as putting a uhmw bottom on it. it had enough rocker in it so when you poured the power to it would stand on end. the only one i saw that worked well had a aluminum floor frame and transom with uhmw floor. it was essentially a rib i thought. i know that plenty of people have been tinkering with the concept for many moons, so it is not new ground. i myself love to mess with boats so i never let that stop me. you will never know how deep the water is till you jump in. have fun

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    Consider that a frame and cataraft tube combination that is purposely rigged to "toe-in" effectively acts like the start of a skiers plow maneuver to reduce speed and stop.
    So like a skier who desires greater speed, keep the cataraft tubes parallel and with equal weight distributions.
    Control the conditions that are controllable.
    ...and the next whippin goes to...?

    Onward and upward.....AlaskaTrue

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    And one more gem.....

    When spending "alot of time motoring at high-speed under power", when using either a 9.9 or a 30 horsepower motor, the best water speed I can get is around 12 or 13 miles per hour using either a AIRE Leopard, Cougar, or a Cata-Canoe rig.

    Them critters just are not designed for high speed motoring. Actually they were not designed for motors at all. Call AIRE in Idaho and they will act completely surprised at the concept of putting a motor on a cataraft, which really is an Alaskan concept. Of course by now they have fielded a thousand questions on the motorized deal, they just will not recommend it. Go ahead and ask Mike S about that. He and the crew he rafts with were on the leading edge of the motorized cataraft thingy about 12 (?) years ago.

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    Member BluNosDav's Avatar
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    ATA,

    ...and the next whippin goes to...?
    &
    And one more gem.....
    I'm not sure how to respond to such statements, but, I'll try:
    For some reason you have fixated exclusively on speed? While I have asked about improved handling/performance.
    I never proposed building a cata-raft dragster, since rivers are usually winding and often contain obstacles.

    In almost every advanced/refined form of transportation (boats, planes, cars, etc), perfectly parallel surfaces are rarely used. Instead, small twists and tweaks, control the forces of speed & steering to improve the vehicle's handling/performance.

    Using your own example; skiing. Take a look at a modern pair of skis. They are not straight slats. They taper in and flare back out to improve control/handling/performance. Just for fun, let's both go to the top of a long mountain with varied terrain along it's slopes. You can use a frame that holds your skis perfectly parallel, and I will toe-in my skis to some degree. Who will get to the bottom with the least number of collisions into rocks & trees? Who will even make it to the bottom at all? I'm sure that you will go faster, for awhile anyway . . .

    Before this thread turns into a mud-wrestling match, I'll stop trying to explain.
    I was just curious about building a better mouse-trap.
    Thanx to all who contributed to this discussion, Dave.

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    webmaster Michael Strahan's Avatar
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    Quote Originally Posted by AlaskaTrueAdventure View Post
    And one more gem.....

    When spending "alot of time motoring at high-speed under power", when using either a 9.9 or a 30 horsepower motor, the best water speed I can get is around 12 or 13 miles per hour using either a AIRE Leopard, Cougar, or a Cata-Canoe rig.

    Them critters just are not designed for high speed motoring. Actually they were not designed for motors at all. Call AIRE in Idaho and they will act completely surprised at the concept of putting a motor on a cataraft, which really is an Alaskan concept. Of course by now they have fielded a thousand questions on the motorized deal, they just will not recommend it. Go ahead and ask Mike S about that. He and the crew he rafts with were on the leading edge of the motorized cataraft thingy about 12 (?) years ago.
    Dennis,

    I haven't been involved in this in years, but I remember we tried all sorts of combinations in an effort to make it work. In the end there was some foundational disagreement over rigging, with my associate opting for ever more complex flooring systems that required a lot of custom fabrication and aluminum welding. They were prohibitively expensive and far from the portable systems I was hoping for. But it was on his dime, so that's the direction it went.

    I remain convinced that there is a way to make this work very well, but some things remain untried. For example, why not make an inflatable floor system that secures to the tubes and is braced by a frame similar to those we are currently using? I know it would work, and it could be laced on or off as needed.

    I am sure there are other ideas out there as well. It will happen. But it might take a while.

    -Mike
    LOST CREEK COMPANY: Specializing in Alaska hunt consultation and planning for do-it-yourself hunts, fully outfitted hunts, and guided hunts.
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    hey mike and blunosdav
    i, like you feel there is a way to make it work. the trick will be to do it in a simple cost effective way. my motivation for trying was to make something that could be put on plane and be good for upriver travel with a load. metzler used to make a raft with a inflatable transom that had a hard transom that strapped in above the floor level, so you would not tear the bottom out where it meets the transom. it would handle a fair sized engine. might be a good design concept / start. under a rock out there is the better mousetrap, so do not let up on turning over rocks because it is fun and keeps us all young at least in heart

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    Post Putting my Right foot in... Tip to Tail - NO Toe.

    Hello Dave,

    Cat-a-canoes (as cat-a-rafts go) are not all that practical, more expenditure overall, lack in most areas --- particulars being performance as well as versatility. The only viable reasons for consideration should be that you already have one or two inflatable canoes of suitable make/model/design... additionally that you are seeking more load capacity and/or stability given likelihood of only one driver at oars (sometimes a low HP motor), or up to 4 paddlers (or poles).

    This raises the next two questions... What are we talking - hard-shell or inflatable? Make/model/design features including accessorizing/outfitting/powering of boats you may be considering?

    Frame-wise, it is not sensible to tow-in the bows --- Yet I know it can be creatively done:
    A.)
    Unless you go fully custom (think like a bike frame builder geometry) you will not easily or effectively alter a component-type frame construction with the exception being shimming tube surfaces from the frame rigging. In other words, component frames like to fit at right angles and the other stuff that allows variances is not trustworthy enough in my opinion. (This is coming from a guy ie. me that have moved ahead of the component race of speed-rail, speed-rail import copies, old school NRS cast fittings or the likes modernizing with much nicer/stronger/lighter CNC custom machining)
    B.)
    Versatility of Cat-a-raft design favors tubes of some symmetry... this means not only running in parallel at some given beam/width apart, but also in the shape/transition of the hull in vs. out the water. Upset this to some degree of tow and/or canting --- you'll most often feel the change by way of negative performance. There are boats having asymmetry for specialized boating or handling... just not applicable here regarding a cat-a-canoe --- already touched on poor performance characteristics.

    Most river-based Cat-a-Rafts are lousy motorboats!!!
    I have first hand used (given my fair-minded shake to countless design applications) several top brands/models/designs including the lesser names. True to form... no matter how and how much you dink around, it will not meet your expectations of even middle of the road quality Zodiac-type sport-boats. The only thing you get in the labor-searching for any beneficial return is remarkably good gas mileage and the versatility factors. Put it this way... an 18' top of the line AIRE Leopard Cat gives you 11 mph using a 15HP prop -- while a 35HP gets you the occasional 13-15 mph. A 15'-18' Zodiac with 25-35HP will get you 21-24 knots every day. To me this makes it a no-brainer... get two or more boats! Now try to draw comparisons/conclusions looking at even further reduction in performance from a cat-a-canoe --- no matter what ya do.

    I feel any tow-in variation will be more expensive, extra to mess with, and not make a licks-worth of positive difference in handling given any rationale.

    Hope this lends a hand, (or a toe)
    Brian


    Quote Originally Posted by BluNosDav View Post
    When building a cata-canoe, everyone suggests that the canoes should be lashed together with the bows "tow-in". It is said that this will enhance performance and decrease splashing between the hulls. I know that almost all cata-raft frames are built to hold the sponsons parallel to each other and that motors are only used on an occasional basis. So, I doubt anyone would go to all the effort to reconfigure their frame every time they started the motor. But, maybe someone motors their cata-raft A LOT, and uses it more like a sport-boat than a raft.

    Has anyone ever experimented with building a frame for a dedicated motorized cata-raft and used a "toe-in" design?
    If so, how did it work out for you? Any downside when drifting downstream and using the oars?

    Secondary question:
    What kinda speed have ya'll been able to achieve with your motorized cata-rafts (either parrallel or tow-in)?
    (please include your specific: raft model, engine model, approximate load, etc.)

    Thanx, Dave.

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    webmaster Michael Strahan's Avatar
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    Quote Originally Posted by oyster View Post
    hey mike and blunosdav
    i, like you feel there is a way to make it work. the trick will be to do it in a simple cost effective way. my motivation for trying was to make something that could be put on plane and be good for upriver travel with a load. metzler used to make a raft with a inflatable transom that had a hard transom that strapped in above the floor level, so you would not tear the bottom out where it meets the transom. it would handle a fair sized engine. might be a good design concept / start. under a rock out there is the better mousetrap, so do not let up on turning over rocks because it is fun and keeps us all young at least in heart
    oyster,

    I applaud your vision, and I share your belief that there is a way. Here are some of the ideas that we tossed around "back in the day"...

    1. Catacanoe. Two inflatable canoes of similar configuration, secured to each other with a simple frame an transom setup. It worked as a paddle rig for people who needed to float headwater areas that could not accommodate the width of a cat. So you start with the canoes and a paddler in each one, with the frame divided between the two, stowed in each boat. When you get to the lower end where you have more water, assemble the frame, put on the motor and scoot. This boat was used for downstream travel on all but the slowest streams, where some upstream travel was possible (it usually was not). It was never intended as a rig you would get up on step with or waterski behind. The catacanoe has certain limitations, especially if the canoes are self bailers (as the AIRE Travelers are).

    2. Power Cataraft. We never rigged the 14-footers, and I think we only did a handful of the 16-footers (mostly AIRE Jaguarundis). We played around with getting them up on step (the dream was to create an 18-foot jet boat that packed up to load into an airplane). But getting upriver with them proved problematic because of the spray issue. You have to control that spray or it's not going to work. I remember running one on Skilak Lake, where I had a huge plume of water flying over my head. I was soaked. It ran really fast, but I was soaked. Sooo... the challenge of making a really good flooring system is out there. I wish someone would make an inflatable floor to attach firmly to the tubes. If you braced it with a properly-constructed frame, it would be a really good performer.

    Another problem with power cats is that it doesn't take a lot of weight before performance is severely impacted. Zodiac-style sport boats don't have this problem so much, because of displacement. But cats have no floor, and the deeper you push those tubes into the water (by adding more weight), the poorer the performance becomes. The inflatable floor system could cure this dramatically.

    Okay. The Metzler boat you refer to is still around. Jim King, of Alaska Series Inflatable Boats, makes a boat that is quite similar; the "Jet Ranger". The transom sits atop the inflatable floor as you described. Jim has copied many Metzler designs quite effectively; it's worth your time to have a look at them. He is usually at the Great Alaska Sportsman Show, which is held the last weekend in March this year.

    Okay there's a lot to write on this, but I better quit before I end up here for an hour.

    Hope it helps!

    -Mike
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    hey mike,
    one thing i did not try that i thought had some prospect was to put 4 cat tubes tight together. i am past this particular mouse trap so you guys will have to forge on without me as i have other ventures to keep the rocks turning. do not forget to have fun.

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    Member BluNosDav's Avatar
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    Just when I was ready to take Brian's advice, and shift my search to an inflatable sportboat . . . .
    Mike & Oyster come along and reignite my imagination for a jet-powered cata-raft!

    (the dream was to create an 18-foot jet boat that packed up to load into an airplane)
    Sooo... the challenge of making a really good flooring system is out there. I wish someone would make an inflatable floor to attach firmly to the tubes. If you braced it with a properly-constructed frame, it would be a really good performer.
    one thing i did not try that i thought had some prospect was to put 4 cat tubes tight together
    Last summer, I took the family on a long-weekend camping/fishing float, down the Little Sue using an 18' Aire Leopard cata-raft. I wanted as much room as possible for our 3 kids to move around and cast for fish. So, I took along my 17' Old Town Tripper (hard shell) canoe, to use for additional cargo capacity. I loaded almost all of the camping gear in the canoe, and slid it underneath the frame, between the sponsons, and then tied all 3 bows and all 3 sterns together. The Tripper had a couple of inches of room along the sides, but was displacing upward slightly against the frame. With the whole family aboard, it stayed very steady and carried at least it's share of the total load. As a result it reduced the average draft for all 3 hulls. Our hybrid cata-raft-tri-canoe-maran was a success! Which got me to thinking . . . . if I still had my former Old Town 15' Sport Canoe with it's shorter length, wider beam, and square-stern. I could have made an easily motorized hybrid (some might say hill-billy) tri-hull vessel.

    Now, that doesn't solve the "load into an airplane" requirement, but it just goes to show, that there is more than one way to skin a cat-a-raft!

    I should probably start this all over as a new thread, since it goes way beyond "toe-in".
    Thanx for reading, Dave.
    "Luckily, enforcement reads these forums, and likely will peruse this one...Especially after a link of it is forwarded to them....." - AlaskaHippie.

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    dave,
    a few thoughts, worth less than you payed for them.
    thinking is cheap,acting on those thoughts aint.
    i feel Brians advice is by far the most prudent,functional and cost effective.
    us dreamers got nobody to blame but ourselves.
    do you know where i might find some help with my boat addiction?
    have fun

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    Default toe-which or none

    Quote Originally Posted by Jim Strutz View Post
    Interesting idea. From the little I know about toe-in on autos (from accidental experimentation), it improves tracking. Cars that I've used, start to wander around when there is little or no toe-in. There might be a similar effect on catarafts, although I've not tried it.
    I'm also not sure that there's any correlation possible between a normal stationwagon's toe-in and cata-raft rigging. But no one has mentioned that on real race cars, they never toe them in. They give them toe out. It makes for more responsive turning. (I used to race sports cars, just at the amateur level, and every last competitor used toe out.)

    I doubt either analogy has anything to do with boating, but I'd like to proven wrong if anyone knows better. I'm here to learn.

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