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Dumas Big Swamp Buggy

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Old 11-15-2016, 06:09 AM
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Default Dumas Big Swamp Buggy

Has anyone bought a Dumas Big Swamp Buggy lately? Are the kits now laser cut or are they still the ungodly Die Crunched?
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Old 11-15-2016, 04:55 PM
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Don't know, but the one I built 30 years ago was "die cut", meaning smashed by a dull butter knife. Not sure why they would change, where they mention how the current kits are cut there is NO mention of laser cutting. Over the years I have built four Dumas boats, while they can look good they were heavy and the cutting was mediocre. How they justify $150 for a kit is amazing.....


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Old 11-18-2016, 07:18 AM
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I'm surprised anyone wants to still build the BSB anymore. The one I had ran and handled like crap as built from the kit except with lighter building materials. It ran better with the bottom converted to a flat bottom (1/8" Lexan covering the keel/rake), but it still didn't hold a candle to my Kamikaze flat bottom boat I scratch built. The Selph Inflicted tapered flat bottom .40 series boat is a nice running boat... I built one of those too (from scratch) - it handles great on water, but not as good on grass. No longer available as a kit, but the plans are available from some folks. Chris Selph is out of the RC airboat hobby now and his airboat forum is no longer running unfortunately.
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Old 11-18-2016, 07:38 AM
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I agree it performed like crap, I especially hated the fact that the "no trip chines" did not prevent a tip over. But...As you stated, I want to build another one with no tunnel hull. Mabe it would slide better on the turns. I plan to put an Enya 60 III on it. I would really like to build a Cajun Gator too, but sourcing nice hobby grade plywood is a drag.

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Old 11-18-2016, 08:07 AM
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Quote:
Originally Posted by controlliner View Post
I agree it performed like crap, I especially hated the fact that the "no trip chines" did not prevent a tip over. But...As you stated, I want to build another one with no tunnel hull. Mabe it would slide better on the turns. I plan to put an Enya 60 III on it. I would really like to build a Cajun Gator too, but sourcing nice hobby grade plywood is a drag.

The Cajun Gator boat is a drag - a friend of mine built one brushless/LiPo powered and couldn't get it balanced to run right. It would hopelessly spin out. If I were looking to build a flat bottom boat intended for water only, I would scale up the SI tapered flatty.
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Old 01-29-2017, 02:23 PM
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i like building mine if your up for the challeng - its maybe NOT for novices / i dont know. i built a .46 rv4 by great planes first. the hard part with the bsb is waterproofing the tunnels and using 150 dollars worth of epoxy... it is under appreciated because this is dumass best airboat and it is better with 4 stroke motors turning 3 blade props. however dumas should have made something for the speed demons looking for nonscale type performance.

passing 30mph out of the box needs a totaly different hull......or a smart builder. you could get flat bottomed dumas airboats that are nearly the same size as the bsb. its just a boat... pick one and face reality head on.

Last edited by sublunacy; 01-29-2017 at 02:26 PM.
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Old 01-29-2017, 04:27 PM
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Two-month-old thread, but I'll bite. I built one about 25 years ago, sealed it with 3/4 ounce cloth and thinned epoxy - not that expensive to do, not difficult and never leaks. I mounted a Fox .45 and a 10x6 prop, timed it at about 37 mph through the club's timing traps. When on plane the tunnel hulls will run faster and turn better than flatties.

I did change the motor mount to a monopod with zero angle with twin rudders. The CG position was also critical, mine ran best at 25%. The boat did not turn well until it got OB step, the it hauled...for the time. Prop choice was critical, a 11x7 just didn't cut it. It has to match the engine's power band.

Dumas kits are crude compared to many other makers, which is sad because many of their designs are very good. Wood quality is mediocre, and the die cutting is......terrible. But with patience they can be built into decent models.


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Old 01-29-2017, 05:10 PM
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cg at 25 percent sounds good. i here that if you make the engine level and move the prop forward an inch it will be a more neutral steering and slide in the corners more and less overpowered by the tunnel hull. an inch forward brings the prop to 50 percent of the flat bottom before the hull curves up towards the front.

reports are the hull can handle a 10cc gas or nitro engine if i have it right/ like a .91 maybe. that sounds like 10cc to me. the extra weight keeps it planted on the water for i believe / kick ass acceleration and respectable top speed
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Old 01-29-2017, 05:59 PM
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A tunnel does slide in a corner like a flatty does, it is designed to hook up tight around the buoys. There is very little weight difference between similar 7.5 and 11 cc engines, for example just 11 grams difference for OS engines. The advantage of the greater displacement is the ability to spin a larger diameter/higher pitch prop - but that means the larger engine has to be mounted higher. I think that either engine is a good choice for the careful builder, but the 11cc OS engine is $50 more than the 7.5.

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Old 01-29-2017, 06:39 PM
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As far as the cut, I'm sure they turned over the butter knife by now? I'd bet money it's still got rough edges and requires lots of filler and sanding. It's not like it's a big seller deserving upgrades in manufacturing. What masochistic experience building these boats were/are. Never liked the tunnel quirky feel, digging in and turning faster than I wanted it to, fearing a flip and water soaked engine. I never ever saw a tunnel ever slide, not on a Dumas.

I bought one here on RCU years ago and that was the only one that worked like no other. He filled the tunnel and made it flat bottom for a much more pleasurable feel, like the real thing. If you're set on doing this, I highly recommend that mod, and as always, keep your fishing rod handy.
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Old 01-30-2017, 07:48 AM
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hey genius. a flat bottom dumas bsb is called a dumas windy.
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Old 01-30-2017, 09:35 AM
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The Dumas I had took a .60, twin rudders. Not a puny .10 - .15 sized airboat for swimming pools. For more information, http://www3.towerhobbies.com/cgi-bin...P=ML#technotes \

The .19 Swamp Buggy that I started in RC back in 1977 with (2 channel radios were all I could afford as a teenager), also had a flat bottom. Removing the strakes on the hull really made it slide. It was more fun than the BSB, especially with a .32-.40 on it. Kept it until 2005 when I ditched my fins for wings.

Edit:
Pictures added of the .60 that was converted over to a better hull. I also covered the "bird bath" on the top deck as it serves no purpose but to catch more water, if you use a .60 that is. Height changes aren't needed with a 10X8 prop. As I recall raising the height of the rudders did a better job. I used a Webra Speed .60, today you'll just have to settle for O.S.
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Last edited by J330; 01-30-2017 at 10:31 AM. Reason: pics
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Old 01-30-2017, 12:34 PM
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maybe if you tried moving the prop forward 1 inch for water you could debate a boat designed to walk on land. im entitled to my critisism same as you seem to throw around. i like the hull limitations.

Last edited by Justaddwata; 01-30-2017 at 05:38 PM. Reason: argumentative
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Old 01-30-2017, 03:19 PM
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Here is a modified BSB on youtube with the tunnel filled and note the slide in turns that's perhaps a preferred behavior of the boat for many. https://www.youtube.com/watch?v=l12QLxWGrdU

Also note all the things immediately wrong with "moving the prop forward an inch" with the mod mounting, servo compartment, and not to mention the negative impact it would have on the rudder's effectiveness.

The flat bottom mod makes the boat much drier a ride for the prop too if you compare videos of the same model without the improved hull. He also enclosed the "bird bath" compartment as was the case with the big swamp buggy I had. No point in leaving anything open on these in the event of a flip which eventually will happen with speed and waves.

Last edited by J330; 01-30-2017 at 04:14 PM.
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Old 01-30-2017, 05:13 PM
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i apoligize/ if you need help with engines or whatever let me know. i have been the authority at many forums for 5 years running while i polish my diploma in the field. the best? no but whos going work for free? i cant find better on any continent. this avid bmx rider can tell you the bar is set very low.
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