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Relationship of Speed to Depth of Water
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MMT Member
Joined: Wed Aug 03, 2011 7:05 pm Posts: 10 
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 Relationship of Speed to Depth of WaterI have a Landau jon boat 16 ft ,it has a 70'' beam and is semi-v.the motor is a homemade mud motor using internet plans. It is 9hp. I do not understand why the boat goes faster in 1' of water. When I reach 4' of water or more we noticeably slow down. Can anyone explain this to me and perhaps provide a solution. The area we duck hunt limits us to 10hp.
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| Mon May 14, 2012 6:47 pm |
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MMT Elite Member  Joined: Tue Nov 23, 2010 6:33 pm Posts: 5603 Location: Corner of Hell an high water, La
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Re: Relationship of Speed to Depth of Water You draft more in deep water, stay in shallow water
_________________ You have your whole life to be an idiot, take a day off! |
| Mon May 14, 2012 6:48 pm |
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MMT Pro Member
Joined: Fri Sep 23, 2011 3:32 am Posts: 287
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Re: Relationship of Speed to Depth of Water the prop thrust hits the bottom, lifting the back of the boat and giving the prop a surface to push the water against. that push increases your speed. all mud motors do this. you will not gain any speed in deeper water without motor mods or a lighter boat. try shifting some weight around to get the perfect balance for your motor.
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| Mon May 14, 2012 8:45 pm |
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MMT Super Elite Member  Joined: Tue Jun 29, 2010 1:20 pm Posts: 11166 Location: Cecilia, LA
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Re: Relationship of Speed to Depth of Water _________________ Formerly:1648 Homemade Cypress Crawfish Skiff GTR23 Performance Cam and Heads; 17x46 Gator Tail with 35GTR and Hoyt's cam;s Currently: 17x48 Gator Tail with XD40 EFI. “Wisdom is not just expertise. It is knowing how much of various areas of expertise you need to know in order to make the decisions that the world needs and that you want to do,” Columbia University President Lee Bollinger. |
| Mon May 14, 2012 8:52 pm |
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MMT 1000 Club  Joined: Mon May 10, 2010 1:46 pm Posts: 1180 Location: Georgia
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Re: Relationship of Speed to Depth of Water _________________ 1854 Brother pulling a 36 PD viewtopic.php?f=5&t=12825 Brooks: "Tries masterbation and thank happy thots ...... purt near pulled mines off when I quit 'em ....." |
| Mon May 14, 2012 9:35 pm |
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MMT 1000 Club
Joined: Mon Sep 19, 2011 6:32 pm Posts: 1490 Location: south Florida
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Re: Relationship of Speed to Depth of Water I've noticed the same and suspected the same physics at play. I've also noted less chop and waves in the skinny, which is why I stay out of big water and hug the grass and veggie covered areas. When you run out of water, get out and mush with you waders on preferably.
 All right, so I'm being a shmart azz but it's contagious around here._________________ Sailing in the sawgrass /1648 grizzly and Swomp 26.5 EFI |
| Tue May 15, 2012 6:50 am |
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MMT Addict
Joined: Thu Jul 23, 2009 8:08 am Posts: 629
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Re: Relationship of Speed to Depth of Water mine goes faster due to my modified flux capacitating modulator....
_________________ cajun: its real simple, we live back hea', dis' is our home, an' nobody don' fuk wit' us! |
| Tue May 15, 2012 9:24 am |
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MMT Addict
Joined: Thu Jul 23, 2009 8:08 am Posts: 629
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Re: Relationship of Speed to Depth of Water _________________ cajun: its real simple, we live back hea', dis' is our home, an' nobody don' fuk wit' us! |
| Tue May 15, 2012 9:25 am |
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MMT 1000 Club
Joined: Mon Sep 19, 2011 6:32 pm Posts: 1490 Location: south Florida
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Re: Relationship of Speed to Depth of Water What, if any, is the effect of water depth, on a hovercraft? Just to stir the pot, and it is usually gumbo, so it needs
stirring._________________ Sailing in the sawgrass /1648 grizzly and Swomp 26.5 EFI |
| Tue May 15, 2012 9:33 am |
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MMT Super Elite Member Joined: Tue Jun 29, 2010 1:20 pm Posts: 11166 Location: Cecilia, LA
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Re: Relationship of Speed to Depth of Water The formula to calculate how much faster you will go in shallow water is very complex. The parameters are depth of water: dw
density of bottom: db salinity:Nacl prop pitch:degrees Horse power: HP beam: inches Lenght at water line: inches Type of motor: GT,MB,GD,PD Velocity in deep water: V Increase in speed: X X = (dw + db)Nacl/(Hp x Prop Pictch)+ Type of Motor(V + beam + length) I think I have that correct. _________________ Formerly:1648 Homemade Cypress Crawfish Skiff GTR23 Performance Cam and Heads; 17x46 Gator Tail with 35GTR and Hoyt's cam;s Currently: 17x48 Gator Tail with XD40 EFI. “Wisdom is not just expertise. It is knowing how much of various areas of expertise you need to know in order to make the decisions that the world needs and that you want to do,” Columbia University President Lee Bollinger. |
| Tue May 15, 2012 12:02 pm |
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MMT 1000 Club
Joined: Mon Sep 19, 2011 6:32 pm Posts: 1490 Location: south Florida
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Re: Relationship of Speed to Depth of Water Outliers being how much surfactant is in the water, how many cold ones in the cooler, flat bottom or ribbed, steelflex or frog spit, water temp.
 _________________ Sailing in the sawgrass /1648 grizzly and Swomp 26.5 EFI |
| Tue May 15, 2012 2:08 pm |
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MMT Super Elite Member Joined: Tue Jun 29, 2010 1:20 pm Posts: 11166 Location: Cecilia, LA
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Re: Relationship of Speed to Depth of Water _________________ Formerly:1648 Homemade Cypress Crawfish Skiff GTR23 Performance Cam and Heads; 17x46 Gator Tail with 35GTR and Hoyt's cam;s Currently: 17x48 Gator Tail with XD40 EFI. “Wisdom is not just expertise. It is knowing how much of various areas of expertise you need to know in order to make the decisions that the world needs and that you want to do,” Columbia University President Lee Bollinger. |
| Tue May 15, 2012 2:21 pm |
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MMT Elite Member  Joined: Tue Sep 13, 2011 11:46 am Posts: 5216 Location: Across the Bayou, LA
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Re: Relationship of Speed to Depth of Water _________________ 35 GTR - 1754 Extreme |
| Tue May 15, 2012 2:32 pm |
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MMT Elite Member
Joined: Fri Jul 08, 2011 1:54 pm Posts: 8133
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Re: Relationship of Speed to Depth of Water And all this time I thought the reason I went faster after drinking the beers is because the cooler was lighter
 _________________ Before the internet, the majority of the village idiots stayed in their villages. |
| Tue May 15, 2012 4:10 pm |
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MMT Member
Joined: Wed Aug 03, 2011 7:05 pm Posts: 10
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Re: Relationship of Speed to Depth of Water Holy Mackerel,
You all have given me plenty to think about, and some very interesting theories. The relationship of beers to speed? This will require much testing on my part. Do you think the brand of beer matters? The research alone may take months and no telling how many cases of beer will be required. I will start immediately. |
| Tue May 15, 2012 5:42 pm |
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MMT Elite Member Joined: Tue Nov 23, 2010 6:33 pm Posts: 5603 Location: Corner of Hell an high water, La
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Re: Relationship of Speed to Depth of Water _________________ You have your whole life to be an idiot, take a day off! |
| Tue May 15, 2012 5:47 pm |
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MMT Elite Member
Joined: Fri Jul 08, 2011 1:54 pm Posts: 8133
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Re: Relationship of Speed to Depth of Water Light beer weighs less...
_________________ Before the internet, the majority of the village idiots stayed in their villages. |
| Tue May 15, 2012 5:47 pm |
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MMT 1000 Club
Joined: Mon Sep 19, 2011 6:32 pm Posts: 1490 Location: south Florida
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Re: Relationship of Speed to Depth of Water I will use cheap beer, no telling how long this will take to address all parameters.
_________________ Sailing in the sawgrass /1648 grizzly and Swomp 26.5 EFI |
| Tue May 15, 2012 6:55 pm |
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