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Prop powered iceboat

Old 09-18-2011, 02:24 AM
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CDC120602
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Default Prop powered iceboat

I'm a newb and if this is in the wrong section, please let me know or (if you're a mod reading this) feel free to move it to the proper section.

This will be my first venture into building any RC vehicle. I've had numerous cheapo Wal-Mart RCs and a nitro Thunder Tiger Challenger Pro nitro buggy. I know a little about this stuff, but I know better than to think I know it all and would like to benefit from the experience of the internet masses by asking questions here.

I live right next to Lake Erie and it's getting close to winter. I got to thinking that I'd like to build a prop powered iceboat. I plan on using a nitro plane engine and 1/8" roundstainless steelstock for the frame. Since I'm making the frame to suit my needs, I can set this up any way I need to.

I would like to use the spoiler or wing (not sure of the proper terminology) from a buggy for the front and rear instead of springs/shocks to keep the runners in contact with the ice. Am I going overboard here? I don't want to put so much downforce on the boat that higher sppeds are unattainable, but I want to maintain positive control at all times.

I plan on using as little stock as possible, but I know stainless has some weight to it. I'd like to make this about3' long and2' wide. Am I going to be able to use a smaller sized (and priced) plane engine on this or should I upgrade everything and start looking into weedeater engines? The plan is to do this as cheaply as possible.

I understand that there will be a lot of stress on the front runner during turns. Should I look into a 1/4 scale servo for steering?

I'm wide open for any suggestions you might be able to give. Thank you all for your time in advance!
Old 09-18-2011, 03:12 AM
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Default RE: Prop powered iceboat

Some thing like this ?

http://www.youtube.com/watch?v=yaUmStOtJ6Y

(go to 27 seconds)

For a vehicle like this, you should just be able to use a very simple "T" shape to your frame.

If you keep the weight down, i don't think you'll need to get up to a 1/4 scale servo..... you're not going to need to turn it much.

As you have posted in the airboat section of the forum, I've got to ask if you have thought of a flat bottomed airboat to run on the ice ?

http://www.youtube.com/watch?v=as1QiNalMO4

my flatty is 39x18, pulled by a .60 2 stroke Enya..... Your choice of engine is entirely up to you, gas or glow, both have their advantages

Old 09-18-2011, 03:57 AM
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Default RE: Prop powered iceboat

Thanks, Altered.  I entertained the idea of a flat bottom for a little while.  Runners offer a little better control, though, and with ice fishermen to contend with for space, I need that.  lol  I have a nifty idea for brakes, as well.  It involves levers, a servo, and reciprocating saw blades.  Now I guess I need to take a trip to a local hobby shop to see what they have to offer.
Old 09-18-2011, 05:17 AM
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Default RE: Prop powered iceboat


ORIGINAL: CDC120602

Thanks, Altered. I entertained the idea of a flat bottom for a little while. Runners offer a little better control, though, and with ice fishermen to contend with for space, I need that. lol I have a nifty idea for brakes, as well. It involves levers, a servo, and reciprocating saw blades. Now I guess I need to take a trip to a local hobby shop to see what they have to offer.
Metal runners probably would scoot pretty good since there would be less of the hulls surface contacting the ice however dealing with metal is a catch-22 because the heavier it is the more power you need. The bigger the engine means it needs to spin a bigger prop so you have to keep that in mind. On water, a .65 glow engine will move my flat bottom boat at 30mph or better but on snow its a lot faster but its hollow and made of balsa and birch plywood. If it were metal, it would barely move.

Neat idea, and I like it but you will want to use aluminum instead of stainless to save huge amounts of weight. I'd also suggest only using metal for engine mounts and the runners. I'd use wood for as much as possible only for the weight savings. I'd sharpen the runners, too. Less likely to slide in turns.
Old 09-18-2011, 06:00 AM
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Default RE: Prop powered iceboat

Here's what I drew up whilst bored at work.  I plan on making it about 3' long and 2' wide.  I don't think it'll be super heavy.  I also only plan on reinforcing the frame as much as necessary.  Considering the minimalist construction, I don't think it should have too much of a problem moving right along.  After looking at the classified section, I'm also wondering about a dual prop setup.  Smaller engines are available on the cheap and I could possibly get more power per dollar.  Any wise words on this idea?
Old 09-18-2011, 09:22 AM
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Default RE: Prop powered iceboat

In my eyes, the weight of the craft needs to be taken into account to decide on which powerplant to use. Also, are you looking at straight line running or are you going to want to be able to turn at speed? For just straight line speed, you can get any good revving engine (probably under .50ci displacement) to turn up good rpm on smaller props but if its too heavy, the prop pitch will need to be lower and diameter larger. 3 feet long and 2 feet wide is a pretty big craft so if you came in at 3-4lbs or so on the hull weight minus engine I would think a .40-.50 would do the trick.

Being that the engine will be used in winter, you're going to want to use a ballraced engine, not a bushed engine. Bushed engines (and lapped iron piston/steel liner) need a high volume of castor oil to run properly and castor oil gets quite thick when its cold. The synthetics are better in the colder weather but are not recommended in high doses in bushed engines because there arent bearings supporting the crankshaft - the castor because its thicker acts as a barrier to "float" the crankshaft. Bushed engines are cheaper, but the trade-off is the fuel that should be used.

You can find decent ballraced aero engines in the .40-.50 range for $50-$100. Thunder Tiger makes the Pro .46 which is ballraced, turns a small prop pretty nice and benefits from tuned mufflers very nicely. I have one and it will turn a 9x7 prop at 16,700rpm with a Jettstream muffler. I paid $45 for the engine NIB from a guy on craigslist and the Jett muffler cost $65. The Jett muffler gives 1000-1500rpm more over the stock muffler.
Old 09-19-2011, 05:32 PM
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Default RE: Prop powered iceboat

When I lived in Alaska I built a three-foot "T" shaped .45 nitro-powered ice boat - with wheels in the summer and blades in the winter. Weight doesn't matter much, with the power to weight ratio of the boat the speed will be very very fast. Once it is up to speed there is little friction, the boat is easy to move. Stopping is a real problem, just like it is with full scale ice boats - but worse. Turning - another problem and a strong servo isn't needed as it's tough to get the front runner to bite on bare ice. The blades need to be razor sharp...and they are dangerous to bystanders trying to help. Don't even think about running it in areas where there are other people within 100 yards. The longer the base of the "T" the better to keep the boat upright going over bumps and ice fishing holes. Curved runner leading edges help run over rough ice. I'm not trying to discourage you, just giving you a reality check.

The idea worked a lot better in the summer with wheels on pavement. Stopping was still a problem, but steering was a lot better. I used rubber airplane wheels. Actually if I was to do it again I'd use electric power, reversing the motor would be the best brake available.


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Old 09-20-2011, 12:23 AM
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Default RE: Prop powered iceboat



RPM, I plan on using metal runners with a smooth curve in the front. I want to use reciprocating saw blades as brakes (much like the toe spikes on the front of ice skates). I want to situate them right in front of the engine, preferably under the fuel tank. A servo would run the lever that would press them down into the ice. I'm hoping to make it strong enough to lift the entire rear end off the ice about a quarter inch. That should stop it. I also plan on using the wing off the back of an RC buggy to gain downforce on the front (steering) runner. That should facilitate some grab for steering.

I was thinking about fashioning some pontoons for the summertime instead of wheels. I might have to look into wheels, as well.

Old 09-20-2011, 02:04 PM
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Default RE: Prop powered iceboat

You have to better understand the physics of how brakes work. They work by changing kinetic energy (the forward motion of the boat) into heat energy. Generating heat requires friction, and saw blades will not be very efficient at doing that. You simply don't have the weight-to-point ratio that an ice skater has to push the "saw blades" into the ice with a high point loading. Snowmobile brakes work better at slowing the sled if the track is not locked up because they generate heat better than cleats on ice do.

And think about it, lifting the rear of the boat off the ice means losing all control - a real problem at 60 mph! A parachute would work better at high speed. Regardless of how you plan to slow the iceboat, you will have to be very careful how and where you run it. I'm just sayin'.



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Old 09-21-2011, 01:00 PM
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Default RE: Prop powered iceboat

@RPM
First and foremost:I do not plan on running this around people. I'm not stupid or impulsive and I understand that I'm an amateur with an experimental vehicle.
Initial "brake" idea:
Here's a pic of what I was thinking of using:
Look at items L and M. I expected that a two inch segment of this on either side of the "fuselage" would provide sufficient point loading to facilitate a usable amount of friction. However, you brought up heat which got me to thinking that slowing in such a manner would bring ice chips up just above the freezing point. When those chips come into contact with the sub-freezing point blades, they'll refreeze and stick, most likely clogging the teeth. I think I'll try one nail on each side instead.
On the matter of loss of control: If I lift the rear of the vehicle with something that is causing excessive friction, any attempted deviation from a straight course will cause one of the rear runners to come into contact with the surface, and should regain any control that was lost. I only want to be able to lift the center 1/4". It will have a span of 2' in the rear. Not extremely worried about loss of control.
A parachute is a possibility, but only as a failsafe if I lose contact with the vehicle. The "brakes" are just another measure of control. I just want a system in place to slow it down quicker than the friction of the sharpened runners.

EDIT: I just re-read this post and think I should add that I'm not trying to be disrespectful. I'm just trying to clarify my thought process.
Old 09-27-2011, 01:27 PM
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Default RE: Prop powered iceboat

Well thought out...Curious how this will work - I like the lack of friction ultimate speed concept.
Old 09-29-2011, 07:55 AM
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Default RE: Prop powered iceboat


EDIT: I just re-read this post and think I should add that I'm not trying to be disrespectful. I'm just trying to clarify my thought process.
I did not read it as being disrespectful at all. I just tried to impart my experience with similar craft. Good luck and keep us posted!



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Old 10-06-2011, 12:07 PM
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Default RE: Prop powered iceboat

cool little idea
from what I understand you are having a single ruder up front...
I would make this the back and steer form the back as well just keep same as you have just other end is front
you could also use puller props this why and the craft would be much more stable there would also be les force on the steering skate
the brake idea is good but only use one at the back 2 will make the craft lost control when braking. one side will not catch the same as the other making the craft spinout
Old 10-15-2011, 04:35 PM
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Default RE: Prop powered iceboat

I love iceboats . I have included pictures from my files on iceboats . Theone with the modelT engine shows how early this was going on . The Mechanics Illustrated article shows my favorite . The blue police boat is the same as the ones used in the movie Bear Island . There are some great action shots on the snow , ice and open water in that movie .The last shot is a mock-up of what I want to do with a Quadra 35 and a wake board from Canadian Tire . I want it mostly for snow . It has great sponsons already carved out and a round hull in between . .Good luck with your project . Bye from Friendly Manitoba .... D.J.
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Old 10-17-2011, 05:52 PM
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Default RE: Prop powered iceboat

I think you will be better off with an AIR brake. Just use a plank of the top of the hull to raise with a servo to create alot of drag and downforce.

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