Is there any advantage to making the bow more narrow on an airboat?;stir;
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Is there any advantage to making the bow more narrow on an airboat?;stir;
I moved this post into the Hulls section.
There may be a slight advantage to making it smaller than the rest of the boat. You have less area contacting the water when breaking over(getting on plane) and less area as far as wind. You also save a bit of weight. It's mainly a balance between the room you need on your front deck and the look of the boat. If you stay full width they tend to look boxy.
I think the front should be a little narrower because it makes it easier to turn and as papee said itll be lighter and get up on plain easier. Both my boats and most boats that im aware of are narrower in the bow then in the back. My dads boat is 7' or 84" at the top of the transom in the back and has a 65" wide bow.
And what I've been finding during my scale model mock-ups are if you have the sides made from one piece and pull them in for a narrower bow it also raises the deck/bow area of the boat in an arch to the front of the hull..Something I've seen on a few lifesized hulls no matter how big or small they are..
I'm not sure what you are saying Corky. If I lay my boat upside down it will touch the ground evenly. The curve in the front makes the sides bow out. Do you have any markings at the river that I would notice going by? I'm going to run down that way this weekend depending on the rain.
Sorry I did'nt check back on here until now.....I see your boat is flat along the gunwales...What I'm running into is depending on how hard you pull the bow in it seems to curve it upward at the nose...And I've noticed the bow out you're describing also.... The old red airboat is in the water...I'm about a mile below the clarks ferry bridge on our side of the river...Red airboat and there's a white vinyl fence around the inground pool that can be seen from the river...The white house/green shutters is very visible as you come down the river...Stop on by if you get down this far...
Let me see if I can explain this where it isnt goobly gook.
The curving up on the front of the boat ,we call it rocker in building kayaks is governed by how far you lean the sides out,the farther you lean them the more the nose will come up.
If you use a 5 ft sheet on the bottom and a six inch flare on the sides at the back then where your bottom sheet starts turning up you drop to a 2 inch flare then no flare at the front . This will give you a pretty flat boat, the bottom will be the same all the way but the top will go from 72 inches to 60 inches. Go back and look at the tank11 build and you will see what I am talking about.
Hope that is clear as mud lol
Ron
Thanks for explaining that I couldn't get it right in my head. I have the information in there but getting it out into speak that can be understood is my big problem. I've been writing a book on this stuff for the past three years and every time I try to get something down what I'm writing always leads to other thoughts so I just have about 120 pages of "notes". I'm going to have to figure out a way to get it organized at some point.
And that answers alot of secondary questions regarding the "rocker" effect....Now I see why the sides get progressively flatter on some builds...To keep the bow from raising up in relation to the stern as it gets narrower... I wonder if there's any advantage to leaving the flare throughout the sides and simply trimming the height if needed...I'd think the water would be directed under the boat quicker{and plane faster/easier} with the flared sides at the bow...
I see the hulls built both ways with the bigger airboats but I'm not sure how effective it comes into play with the mini...
Yeah, that is what I am trying to determine. Which design is better and what are the advantages. As most airboats are running in skinny water, it may serve for better control as well as getting on top faster. [?]
The narrow bow really has little affect other than a little less weight and I think they look better. There are a few advantages though. Putting the curve in helps strengthen the gunnels a bit. When getting on plane the front of the boat raises slightly and you are pushing on the wide part of the boat any way. The narrower bow also helps when you are idling, there is not as much width there to push water. When on plane there again is not as much width to trap air, not much of a difference but there is some.
Thanks Papee, I can buy that.Quote:
Originally Posted by Papee
On my hull bottom will be 5 ft front to back
top at back will be 6 ft
where the front starts rolling up the top will be 5 ft 8 in
at the very front top will be 5 ft.
My thinking on these measurements
The 6 inch flair should work like a modified chine if your sliding.
More inches of displacement at rest and decreasing displacement as you plane out as the bottom gets narrower.
Front will be curved up a small amount ,this will make me put the front deck in at an angle which should leave the pipe across the front as a kick rail, plus the high bow will work like a mini grass rake and also bust waves in rough water better.
Ron
Airboats just arent aerodynamic so the shape above the water doesn't have much effect on performance
I think I get what you're saying. By "flair" do you mean the angle of the gunnel? When on plane, if a boat is set up right, you are only running on the back 1/3 or less of the bottom. If your boat is running free there is no part of the side in the water on a hard chined boat. A chined boat will always have part of the chine in the water.