Higher Cruise Speed! Need Help From The Pros....

A general, non-powerplant specific, discussion on airboat technology, ie., hulls, rigging, polymer, etc..
White Hawk
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Higher Cruise Speed! Need Help From The Pros....

Postby White Hawk » Wed Jul 11, 2018 8:45 am

What set up will allow an operator to enjoy a cruise speed in the 50's or even better 60's without burning up the power plant. I have been airboating for over twenty years in South Florida, I know some builders who like to ride fast. Free running hull, Hull Length, Deck Over, Prop type, Prop SIze, Tip Speed, Motor Angle, Etc..... I would like to put together a 14' free riding sled and slide close to 60 Mph all day long..... :florida: I know this is a formula, and I know it is out there....... Help... :angel4:

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John Fenner
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Re: Higher Cruise Speed! Need Help From The Pros....

Postby John Fenner » Wed Jul 11, 2018 10:45 am

Super light hull, set correctly, super light and simple rigging, a strong and big propped engine set up for what it's designed for. A PE 60 built up tight on the right hull will cruise 50/60 mph and sip fuel,,,, weight vs hp.
I never finish anyth,,,.

White Hawk
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Re: Higher Cruise Speed! Need Help From The Pros....

Postby White Hawk » Wed Jul 11, 2018 10:23 pm

So far my formula is deck over sled. Inline seating, one up top triple bench below. 600 plus hp light weight motor. Gearbox, 9 blade long prop, and motor set on a properly angled engine stand. Slick bottom on aircraft aluminum riveted hull.

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John Fenner
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Re: Higher Cruise Speed! Need Help From The Pros....

Postby John Fenner » Thu Jul 12, 2018 11:31 am

Good combination, I'd suggest a 7'6"×13' or 13'6" .090" bottom with .050" decks, 28" grassrake. Edit: saw your quote for 14"
I never finish anyth,,,.

White Hawk
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Re: Higher Cruise Speed! Need Help From The Pros....

Postby White Hawk » Fri Jul 13, 2018 7:51 am

John Fenner wrote:Good combination, I'd suggest a 7'6"×13' or 13'6" .090" bottom with .050" decks, 28" grassrake. Edit: saw your quote for 14"
I'm staying under 14'. Cruise speed will go down with every inch of transom dragging.

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John Fenner
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Re: Higher Cruise Speed! Need Help From The Pros....

Postby John Fenner » Fri Jul 13, 2018 8:36 am

Not if it is built correctly
I never finish anyth,,,.

Rich Andrews
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Re: Higher Cruise Speed! Need Help From The Pros....

Postby Rich Andrews » Fri Jul 13, 2018 10:25 am

crusing the glades at 60? really
I'll have my Manatee burger medium please...just say NObama

14x8 deckover FELBER 397ci.. HP ???..just stay back!!

LOHA is AHOL backwards

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Re: Higher Cruise Speed! Need Help From The Pros....

Postby White Hawk » Fri Jul 13, 2018 11:55 am

I Like to ride. I know 30-40 Mph is the average cruise speed. Many folks are concerned with running their boat like it is a small bulldozer,or even a drag racer, I want to ride and cover some ground. 50 slow cruise - 60 fast cruise is not asking for too much. I'm running 450HP now and at 4000 RPM i'm the low 40's, just not acceptable. I had a 180 wide deck on an old Don Davis and ran at 40 MPH all day. Now with twice the HP I feel like i''m walking backward. On any given ride I may cover 70 to 100 miles. South Glades easy 90 mile ride, Clewiston-Lakeport-Fisheating Creek easy 90 mile Ride, St. Johns easy 90 Mile ride I could go on. I am not just theorizing, I just want to make sure the sled I have built can cruise at 60 and not burn up in the process. 60 Really!

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Re: Higher Cruise Speed! Need Help From The Pros....

Postby White Hawk » Fri Jul 13, 2018 11:58 am

Rich Andrews wrote:crusing the glades at 60? really
I see a description of your sled, it sounds like it should have a nice cruise, what cruise speed are you getting out of your ride?

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John Fenner
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Re: Higher Cruise Speed! Need Help From The Pros....

Postby John Fenner » Fri Jul 13, 2018 12:02 pm

Definitely doable, I was apprentice for Don Davis @ 16 years of age, 28 years worked for him, I'm building hulls at my home shop, booked through October.
I never finish anyth,,,.

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Re: Higher Cruise Speed! Need Help From The Pros....

Postby Rich Andrews » Fri Jul 13, 2018 12:37 pm

30mph max cruise unless im gliding over real shallow waters, but my fast days are over
I'll have my Manatee burger medium please...just say NObama

14x8 deckover FELBER 397ci.. HP ???..just stay back!!

LOHA is AHOL backwards

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Re: Higher Cruise Speed! Need Help From The Pros....

Postby ladyblackwater » Fri Jul 13, 2018 3:21 pm

60 mph is sure not a cruise for an airboat no matter how you look at it. I'm not saying it can't be done. I'm saying it isn't safe. Good luck in your adventure.
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Re: Higher Cruise Speed! Need Help From The Pros....

Postby CarMotorBarge » Fri Jul 13, 2018 7:23 pm

White Hawk wrote:I Like to ride. I know 30-40 Mph is the average cruise speed. Many folks are concerned with running their boat like it is a small bulldozer,or even a drag racer, I want to ride and cover some ground. 50 slow cruise - 60 fast cruise is not asking for too much. I'm running 450HP now and at 4000 RPM i'm the low 40's, just not acceptable. I had a 180 wide deck on an old Don Davis and ran at 40 MPH all day. Now with twice the HP I feel like i''m walking backward. On any given ride I may cover 70 to 100 miles. South Glades easy 90 mile ride, Clewiston-Lakeport-Fisheating Creek easy 90 mile Ride, St. Johns easy 90 Mile ride I could go on. I am not just theorizing, I just want to make sure the sled I have built can cruise at 60 and not burn up in the process. 60 Really!


What type of engine are you planning to use?
14x7.5 Al David hull with 14 inch transom
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Re: Higher Cruise Speed! Need Help From The Pros....

Postby White Hawk » Mon Jul 16, 2018 9:09 am

CarMotorBarge wrote:
White Hawk wrote:I Like to ride. I know 30-40 Mph is the average cruise speed. Many folks are concerned with running their boat like it is a small bulldozer,or even a drag racer, I want to ride and cover some ground. 50 slow cruise - 60 fast cruise is not asking for too much. I'm running 450HP now and at 4000 RPM i'm the low 40's, just not acceptable. I had a 180 wide deck on an old Don Davis and ran at 40 MPH all day. Now with twice the HP I feel like i''m walking backward. On any given ride I may cover 70 to 100 miles. South Glades easy 90 mile ride, Clewiston-Lakeport-Fisheating Creek easy 90 mile Ride, St. Johns easy 90 Mile ride I could go on. I am not just theorizing, I just want to make sure the sled I have built can cruise at 60 and not burn up in the process. 60 Really!


What type of engine are you planning to use?


I have been planning on a Water Thunder 600+ Hp Motor. I've considered a variety of SBC and BBC as well as AC. I read the description of the boat you are running and I have got to ask what your cruise speed is. Can you run a constant 50-60 MPH without burning up the motor? I understand what I'm looking for can be attained by a combination of the right Hull, Rigging, Weight, Motor, Prop, all set up in the right configuration. Right now i'm running a built 383 in the 450 hp range (Steel Block), I understand it will never do what I want it to do, its like a drag racing bulldozer, I really want a machine to cover some ground with built for riding fast for a long period of time. I'm looking for motor suggestions, and gear ratio suggestions.

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Re: Higher Cruise Speed! Need Help From The Pros....

Postby mojoe » Mon Jul 16, 2018 12:26 pm

ladyblackwater wrote:60 mph is sure not a cruise for an airboat no matter how you look at it. I'm not saying it can't be done. I'm saying it isn't safe. Good luck in your adventure.


X2

Anywhere shallow enough (in Florida) to lend itself to the operation of an airboat, it will have vegetation and/or turns that limit visibility along with dynamic hazards. Combine that lack of visibility with a machine with a giant meat grinder on the back going 60mph with no brakes and you have a recepie for disaster. Please post when and where you will be riding so I can make sure my family and I are not there!!


Just wondering: What distance do you think an airboat traveling @ 60mph (88’/second) must cover before it has the ability to move itself over one boat width?

In a word problem: If this guy is traveling at 60mph in his sweet airboat and goes over vegetation to find a line of kayakers directly in his path. Each kayak is 10’ long paddling 5’ apart, how many kayakers will die before he is able to turn his boat?

I know the ignorant answer is some negative comment about kayakers.... unless one of them is you child on a scout trip.

Any reasonable person can see what I’m getting at here. Just because you can does not mean you should. If we cannot regulate ourselves reasonably our way, rest assured, they (anti-airboaters) will regulate us THEIR way.
Airboating is like marriage: There are unlimited ways a person can be right, and somehow still be wrong at the same time!!

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John Fenner
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Re: Higher Cruise Speed! Need Help From The Pros....

Postby John Fenner » Mon Jul 16, 2018 12:30 pm

8.6:1 GSIO 540, blueprinted cam advanced 10° with a 78 to 80" prop on a 7'x13'6" proper built hull will suit your needs!!
I never finish anyth,,,.

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Re: Higher Cruise Speed! Need Help From The Pros....

Postby Slidin Gator » Mon Jul 16, 2018 7:50 pm

In 1974 my dad bought a Buick Regal with all the crappy emissions controls they had back then. In 1975 he bought a book called "How Not To Disable Your Emissions Controls" with step by step instructions of what you should not do.

Do not do the following:

White Hawk wrote:I have been planning on a Water Thunder 600+ Hp Motor. I've considered a variety of SBC and BBC as well as AC.

understand what I'm looking for can be attained by a combination of the right Hull, Rigging, Weight, Motor, Prop, all set up in the right configuration. Right now i'm running a built 383 in the 450 hp range (Steel Block), I understand it will never do what I want it to do, its like a drag racing bulldozer, I really want a machine to cover some ground with built for riding fast for a long period of time. I'm looking for motor suggestions, and gear ratio suggestions.


98 mph is the fastest I have ever been, due west in area 2 covering pretty much half of the area in a matter of minutes. Had to stop so we didn't fly across the canal and 27. That was 1997, me playing navigator in the back seat with a new handheld GPS hoping that the throttle cable didn't break, otherwise the nose would lift and away we go. Mark that one off the bucket list, it would be nice to say 100, but not quite. I have no interest in that ride again, boat was probably 3-4 feet off the water riding the tops of the thick saw grass.

260 Hp O-540 Lycoming running a 6 blade prop that sounded like a herd of mad bees. Hull was 12 foot palm beach style, not even optimum for high speed.

It's all in the prop selection and set up to run boat loose without hop. You can get what you are after with an AV engine just fine if you get the airflow to keep it cool.

I disagree that a GSIO is the right answer, aviation gear drives and big props are for hauling loads and pushing ground. High speed calls for a smaller prop putting more power into less air to create higher velocity output over a smaller area. Basically a smaller prop at max RPM rating with a whole bunch of small blades (like you said, 9 blade prop, but forget the long part).

Depending on your present set up, a smaller prop and less gear may get you closer to your goal without too much coin.

I highly recommend that you don't do any of this.
1986 Airboat Engineering Inc., 14' Marsh Master. Refreshed narrow deck, SV O-540. A Bob Stossel original, still running strong.

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Re: Higher Cruise Speed! Need Help From The Pros....

Postby CarMotorBarge » Mon Jul 16, 2018 7:53 pm

Yes, I can run 50 to 60 MPH without burning up the motor. I even have poly. Dave builds a great motor. Tell him what you plan to do and he will point you in the proper direction. Expect to run 4,000 RPMs to maintain 60 MPH. This is assuming slick bottom with a free light hull and minimum wind drag. Don't go cheap on the valve train and make sure you have a good tune. LS motors are hard to beat.
14x7.5 Al David hull with 14 inch transom
419 CI Horsepower Barn LS3 with 2.68 Rotator soft drive swinging 4 blade 83.5" R
GTO Rigging and B&S Tilt Trailer
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