It's all about the set up right

A general, non-powerplant specific, discussion on airboat technology, ie., hulls, rigging, polymer, etc..
Basin_Runner355
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It's all about the set up right

Postby Basin_Runner355 » Thu Dec 08, 2016 5:38 am

Just got this boat and trying to get it set right. Boat does alright. It I think it should run better on the ground. I droped it off to a guy yesterday he's gonna change motoro mounts and drop the back a lil
Bit because my reduction was bout 1/2 higher the. Center of front motor mount Bolt He was telling me I have a higher engine stand then normal and that could hurt me because on the ground I'm not pushing against the ground to pick up the back. If this is true what could I do to get better ground preformace. I already checked the bottom the middle t bar is bout 3/16 lower than the outside ones already. I'm hoping that getting it closer to level will help but how do you measure to see what it need to be.
14ft diamond back zz4 350 sbc 2:1 belt drive reduction with a 80 inch whirlwind prop powershift hub pitched at 4850

jeepinocala1111
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Re: It's all about the set up right

Postby jeepinocala1111 » Thu Dec 08, 2016 8:01 am

Basin_Runner355 wrote:Just got this boat and trying to get it set right. Boat does alright. It I think it should run better on the ground. I droped it off to a guy yesterday he's gonna change motoro mounts and drop the back a lil
Bit because my reduction was bout 1/2 higher the. Center of front motor mount Bolt He was telling me I have a higher engine stand then normal and that could hurt me because on the ground I'm not pushing against the ground to pick up the back. If this is true what could I do to get better ground preformace. I already checked the bottom the middle t bar is bout 3/16 lower than the outside ones already. I'm hoping that getting it closer to level will help but how do you measure to see what it need to be.



Level your engine to the bottom of the hull. :cheers:

Basin_Runner355
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Re: It's all about the set up right

Postby Basin_Runner355 » Thu Dec 08, 2016 9:38 am

Kinda hard to get a measurement with the gas tank and shot in the way
14ft diamond back zz4 350 sbc 2:1 belt drive reduction with a 80 inch whirlwind prop powershift hub pitched at 4850

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Deano
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Re: It's all about the set up right

Postby Deano » Thu Dec 08, 2016 10:32 am

Basin_Runner355 wrote:. . . I have a higher engine stand then normal and that could hurt me because on the ground I'm not pushing against the ground to pick up the back. If this is true what could I do to get better ground preformace. . .
Here is an old thread that has an overview of how the engine thrust angle effects performance, both on the water and running dry:
http://www.southernairboat.com/phpBB3/viewtopic.php?f=85&t=28600

jeepinocala1111 wrote:
Basin_Runner355 wrote: . . . If this is true what could I do to get better ground preformace. . . .
Level your engine to the bottom of the hull. :cheers:
This is exactly correct. Level your stringers (fore and aft) and then level the motor. This will make the angle of thrust parallel to the bottom. Usually fine tuning can be done from that point with fender washers. If your engine was 1/2" inch higher in the rear, that is most likely to much. When close with a straight bottom, the width of 1 washer will make a difference.

Basin_Runner355 wrote:. . . I already checked the bottom the middle t bar is bout 3/16 lower than the outside ones already. . .
That is may be just fine. The premise there is that with a little bit of belly in it, it will decrease the contact area when it's sitting on hard, flat ground. The far bigger consideration is that it is flat and straight fore and aft (front to back). If the planning area is not straight and flat, it can and will create all kinds of unwanted side effects.

Basin_Runner355 wrote: . . . how do you measure [the bottom] to see what it need to be.
Upside down is the easiest, but seldom the most time effective. With it on the trailer (or on blocks if need be), the first option is to take a four or five foot level and place on the bottom from the transom forward. There should be no gaps. If there are, this is what's called a hook and will show you where the stringers need to be relocated to make it flat. While it is more work and might not be necessary, running a string line under the boat from the transom to the bow will allow you identify any and all imperfections in straightness of the entire bottom. Doing either under each stringer will show you exactly where any imperfections are. Naturally, if you need to install a jack you want to put it where the gap was the biggest.

Basin_Runner355 wrote:Kinda hard to get a measurement with the gas tank and shot in the way
If you pick up one of these, you'll also be able to use it later to set the blades on your prop:
http://www.ebay.com/itm/140636422546?hash=item20be958192
Last edited by Deano on Thu Dec 08, 2016 10:37 am, edited 1 time in total.
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mojoe
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Re: It's all about the set up right

Postby mojoe » Thu Dec 08, 2016 10:35 am

with the boat on the trailer, set a level on a stringer or have a buddy hold one underneath at the stern. Then jack it up or down till it's level.

Next set the level on the motor and shim up or down til it's level.

May need just a bit of tweaking after that, but that's where you start.


Basin_Runner355
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Re: It's all about the set up right

Postby Basin_Runner355 » Thu Dec 08, 2016 10:54 am

So like place a level on the the valve cover bojtnthe only place that is straight and nothing comming out to mess with it
14ft diamond back zz4 350 sbc 2:1 belt drive reduction with a 80 inch whirlwind prop powershift hub pitched at 4850

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90chevy396
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Re: It's all about the set up right

Postby 90chevy396 » Thu Dec 08, 2016 11:12 am

either valve cover or if the prop hub is flat on the back that will work also
13' LASER W/455 BUICK DD SINGLE FRONT DOUBLE REAR WHIRL WIND PROPELLER

Basin_Runner355
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Joined: Sun Nov 13, 2016 7:16 am
Location: St.martinville , Louisiana

Re: It's all about the set up right

Postby Basin_Runner355 » Thu Dec 08, 2016 1:08 pm

It's machined idk how true it is
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14ft diamond back zz4 350 sbc 2:1 belt drive reduction with a 80 inch whirlwind prop powershift hub pitched at 4850

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90chevy396
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Re: It's all about the set up right

Postby 90chevy396 » Thu Dec 08, 2016 3:17 pm

yeah that's not going to work
13' LASER W/455 BUICK DD SINGLE FRONT DOUBLE REAR WHIRL WIND PROPELLER

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90chevy396
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Re: It's all about the set up right

Postby 90chevy396 » Thu Dec 08, 2016 3:25 pm

so just use the valve covers because you cannot use the carb mounting location on the intake because it is sloped forward to accommodate the angle in which it was designed to be placed inside a car. set your 3' level on stringers and level the stringers using the jack on the front of the trailer and then set the engine parallel to that by placing level on valve cover and adjusting the rear of the engine.
lowest possible engine mounting location and parallel to the stringers gives better thrust line and with the engine setting higher it will want to push over on the nose and that might be why they have the rear of the box raised so high is to prevent hopping but get her parallel and run it and then adjust engine to best suit your running style.
13' LASER W/455 BUICK DD SINGLE FRONT DOUBLE REAR WHIRL WIND PROPELLER


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