1st R/C Airboat build
#51
Thread Starter
The way my hydrofoils balance the bow ends up being lighter for speed. Hold by the prop nut. If it hangs level, it should be good to go. If its bow heavy, it's gonna hop (porpoise). It will probably porpoise if its too light in the bow and consequently blow over. This boat has always been bow heavy and it's almost always porpoised. With the right amount of weight in the right spot it will balance out. I started this R120 install with the prop's centerline (thrust line/balance point/CoG) at 1/3 total hull length +1/2". Something like 10 3/4" from the transom on a 32" length hull. The Lowrance GPS adds 8oz of weight to the boat with Alkaline batteries (2). There are MUCH lighter options like the little Garmins. So to recap - bow heavy = move engine forward. Bow light = move engine back.
#52
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A airboat with a rudder in the water is not what a airboat is about. A airboat is designed to go over weeds and wet grass and even on the bank if your engine is powerful enough, its not ment to have a rudder in the water its supose to have air rudders.If you want a rudder in the water build a v bottem or something and you can go realy fast and turn realy sharp. If you want better control put 2 slats on the bottom of the hull about 6 inches long on each side and make the rudders the same higth as the prop to get full forse of the air over them. I have 4 air boats electric and nitro and they run fine and turn good ,better in the direction that the prop is turning but ok the outher direction too.I have a 51 inch airboat with a 140 nitro turning a 18 inch pusher 3 blade prop and it goes where ever it wants to go and runns in the 40 mph...Bob
#54
Thread Starter
I don't mean to be rude, but if your boats went as fast as mine do, you'd need a wet rudder too. They steer like they're on rails most of the time much like a car. Try running 50mph with an air rudder and see what happens. Once you get over 25mph, they're just too hard to control. Sorry. There isn't a soul on this Earth that will convince me to dump the wet rudder in favor of an air rudder on water. Not gonna happen. If crispyspa catches this, I hope he will chime in. He has more experience than any of us, but I'm sure he will agree with me. For speed, wet rudder is the way to go. If you want to be able to slide, drift, spinout, or whatever... Then the air rudder is the go-to. I don't care for the sliding and wide turns. I like having tight control of the steering. I just do. Aside from preference, the hull sides have such a shallow angle, it's much easier to catch a wake and have a lot of water come over the side. Getting a bunch of water in the prop arc usually kills the engine.
So do you guys have some pictures of your GPS readings of your boats with air rudders?
So do you guys have some pictures of your GPS readings of your boats with air rudders?
Last edited by 1QwkSport2.5r; 12-23-2013 at 09:13 AM.
#55
Join Date: Oct 2004
Location: Coshocton, OH
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A real airboat is air rudder controlled, not controlled with a water rudder and are not speed boats. It is arrogant of you to say one person knows more than another, not trying to be rude. The speed you speak of 50mph, yes I would recommend a water rudder.
#56
Thread Starter
If I was building for the "scale" look or wanted to be the most "realistic" then I'd build differently. But I am not a scale of realistic builder. My boats are built to look good, be fast, and be fun. I think its ignorant of you to come into my thread and tell me I cannot have a wet rudder on MY boat built by ME to MY liking. A toy airboat is not a "real" airboat anyway and I don't care.
One more thing; prop cages are for wusses.
Last edited by 1QwkSport2.5r; 12-23-2013 at 04:36 PM.
#58
Thread Starter
Perhaps instead of being an ignorant jerk, you should think about the fact that some of us want to build airboats for speed. Speed and air rudders don't mix. You can't use electric starters with cages and they create too much drag. The slats on the keel like the other guy mentioned adds unnecessary drag to an already draggy design. Why make it slower? Man that sounds stupid.
So you can take your advice elsewhere. It serves no practical purpose in my threads.
So you can take your advice elsewhere. It serves no practical purpose in my threads.
Last edited by 1QwkSport2.5r; 12-23-2013 at 06:54 PM.
#59
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A airboat with a rudder in the water is not what a airboat is about. A airboat is designed to go over weeds and wet grass and even on the bank if your engine is powerful enough, its not ment to have a rudder in the water its supose to have air rudders.If you want a rudder in the water build a v bottem or something and you can go realy fast and turn realy sharp. If you want better control put 2 slats on the bottom of the hull about 6 inches long on each side and make the rudders the same higth as the prop to get full forse of the air over them. I have 4 air boats electric and nitro and they run fine and turn good ,better in the direction that the prop is turning but ok the outher direction too.I have a 51 inch airboat with a 140 nitro turning a 18 inch pusher 3 blade prop and it goes where ever it wants to go and runns in the 40 mph...Bob
#60
Thread Starter
In the real world people have choices. I don't appreciate your attitude telling me I can't use this or I have to do that. That's BS. I highly suggest you come back to reality. Now please, start your own thread to preach your beliefs there instead of jacking my thread.
Common Sense Warning: spinning props will cut you. DUH. If you stick your hands in the prop arc, you will get hurt. DUH. Paint the tips of your props with bright colored paint to make it easier to see.
Common Sense Warning: spinning props will cut you. DUH. If you stick your hands in the prop arc, you will get hurt. DUH. Paint the tips of your props with bright colored paint to make it easier to see.
Last edited by 1QwkSport2.5r; 12-24-2013 at 07:04 AM. Reason: Added common sense warning.
#63
Thread Starter
Now that we have wasted these last posts dealing with something that should come as common sense, let's move on.
#64
Thread Starter
http://www.rcairboats.net/phpBB/view...php?f=15&t=168
#65
Thread Starter
It's been awhile since this baby has been run, so I felt like a good day to go out and run some fuel through it. The carb was a little sticky, but once freed up, she ran like she always does. This boat is a real failsafe.. Almost always runs great. https://youtu.be/6KGEXRVP5js
#67
Thread Starter
It's pretty fast with the big 20cc 4-stroke on it - so much power it's been hard to get it to balance perfect and not porpoise at speed. It runs dead flat with a 10-15cc 2-stroke though. I use a wet rudder on it on water, so it turns and drives like its on rails. I think I have a video of it running on water with this engine... I'll post a link if I still have the video online.
#69
Thread Starter
It will flip over by 45mph with this engine. I'd need to go back to a 2-stroke on a smaller prop to lower the CG and get more rpm. But really - this is not a speed machine. It's fun the way it is. I wanted to tune up the 4-stroke so I can clean it up and oil it. I have some other engines I want to try on it. I might even go crazy and stick my Jett .56LX on it for an experiment. We've already swapped the Jett onto another boat previously... May as well keep moving the $495 slug around.
http://www.rcuniverse.com/forum/rc-a...hull-swap.html
http://www.rcuniverse.com/forum/rc-a...hull-swap.html
Last edited by 1QwkSport2.5r; 07-19-2016 at 03:06 AM.
#70
Thread Starter
Here's a decent video of this boat with an Enya .60 four stroke engine on it with wet rudder and I think 12x6 prop. I've never been able to get it to not hop in the turns. The porpoising can be cured if I had spent the time to balance the boat (move the engine forward) better. https://youtu.be/fVadTr40eQw
Heres a short video on the water with the 1.20 four stroke engine: https://youtu.be/dUUC1GWJfgQ
Heres a short video on the water with the 1.20 four stroke engine: https://youtu.be/dUUC1GWJfgQ