amax

Well first I want to say I'm not really an Air boat Guy I'm a Big Time Hydro Fan, but I have a friend that is building a Gas air boat. I have been searching around to give him different ideas on Hull set ups and such, and noticed all the Gas Air boats I have seen vids of they Don't use a Tuned Pipe they only use a Can Muffler.
In my years of 2 stroke engine building on Dirt Bikes and R\C Hydros I have learned that one of the Biggest Bolt on Performance Items you can get is a Good Tuned Pipe(Expansion Chamber) and a High RPM 2 Stroke Engine will never reach it's Full Potential without one.

So is there a Reason a Tuned Pipe is Not used on an Air boat??

71dartswinger

check out ptr34 video he has two with tuned pipes

amax

Got A Link?? Are you talking about the Step Hull Vids?? I Didn't see one with a tuned pipe.

Mr Cajun Gator

main reason is that the tuned piped does not really start working until it reaches 16,000+rpm all my gas airboat engine range from 10,500 - 11,400 rpms. With a true rc airboat (flat bottom and air rudders) anything after 30mph the boat starts to get out of control. If you are looking for speed go with the water prop race boat. In airboats its more about torque of the engine to spin the larger props, getting the boat to have good control. The main thing is having a good time. After running tuned pipes and can mufflers I find there is no where near enough gain in preformance to justify the cost.

amax

OK Thanks for the reply Mr. CG, I hadn't really considered That aspect of it. I'm a Speed Junkie and Always looking to make things Faster,, But it's not My project and He really wants to build an air boat, and he will need Plenty of Torque because he's building it from .060 aluminum so it's tough enough to run it around on the tall grass in his yard when he can't get time to go to the pond,,LOL.

Is it the prop torque and the lack of drag from skipping across the top of the water and not ridding In the water at high speeds that make in hard to control?? Just Curious.

Big Block Glock

First of all I must ask what kind and size of motor is being used for the application, and more importantly how big are the hull dimensions. If nito then yes a tuned pipe would be an ideal option. But with gassers some of the motors have limted rpm ranges due to the reed valve configuration, but could be modified to gain more power. I myself run a 50cc - 5.2 hp 2-stroke motor and it can push the 26 lbs boat like nothing, but I am also useing the recomended prop size as well ( 20" & 22" diameter )and nothing smaller.

Mr Cajun Gator

.063 is what I've built smaller airboats from. The next build I'm going to use .080 for the hull and .063 for the decking. I'm also interested in just what engine is planing to be used?

amax

Well I'm not sure hes completely decided on What engine he wants or dimensions, he keeps tryin to Go Cheap and put a weed eater or chainsaw engine on. I'm trying to talk him in to a Zenoah or CY(Sikk) maybe something in the 30cc range. He's still in the Planning Stage drawing the Hull up on "Solid Works" so he can cut as much as possible in one piece on a Water Jet to keep the number of welds to a minimum. Mr. Cajun Gator I know he watched a number of your vids and liked your set up A Lot, but didn't want to just Copy Somebody else's design, even though he's not trying to go into production or anything, just building something to play with.
I have absolutely No Experience with Air boats so ANY advice is appreciated.

rangerfredbob

My Feedback: (13)

if he's wanting to do it on the cheap, chainsaws have the most power stock and generally just need their mufflers opened up, for airboat use fancy ignitions don't offer much advantage other than ease of starting but that can be remedied by a contraption like this:


If he wants something smaller than a saw engine and still on the cheap, watch craigslist for Echo or Stihl weedeaters and blowers as they generally don't need modified either other than larger carbs and open exhaust. If he's stuck on a lesser engine, tear it apart and open the exhaust port timing to around 150 degrees exhaust duration, open the exhaust and put on a larger carb.

amax

yea that was kinda along the lines he was looking at, he's hunting a used Stihl Chain Saw for cheap,,LOL. Thanks for the info.