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Old May 10, 2011, 01:40 PM
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Build Log
Small scale rc hovercraft

I started this project 2 months ago and i built this hovercraft from scratch. At first i wanted myself the famous Ikarus Dragstair but because its far too expensive i decided to make it myself, and a smaller version.

I started with 80mm ducted fan but it broked and then i had to make it with bigger fan.

So all the materials i used is actually old rubbish
I set the goal that my machine must run at least 30km/h (Ikarus goes 40km/h with brushed motors). Now when the hovercraft is almost ready it makes me happy because it came out just like i wanted - fast, good maneuverability, small and pretty good looking too
The skirt needs some upgrading, body finishing and then its READY. I designed the stickers to it so it will be almost like Ikarus Dragstair... only my version.

Hovercraft has flipped over 2 times in water- disaster (can see it on the video too).. all the electronics survived on both times but camera did not. I dont know how it affects the battery but it still works fine.

Technical information:
7,4V LiPo, 1800mAh
100A speed regulator, fwd, bckwd
35A speed regulator, fwd
2 brushed motors


I will try brushless version soon to get maximum speed from it.

And theres the video:
RC Hovercraft small scale Estonia (7 min 53 sec)


Build log video coming soon when its finished!!!
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Last edited by piito; May 10, 2011 at 01:54 PM.
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Old May 11, 2011, 03:25 PM
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Hi, it looks like you have the right general principles applied - keep it light, keep the cushion area maximised (don't go for funny V shapes), balance you weight distribution etc. The Dragstair is similarly poor on water, so don't use it as a comparison! It's definitely most at home on land, so only just can it be called amphibious. Your's however looks quite comfortable on the water! As a general principle it is worth waterproofing all electronics if you are going to operate extensively on water - balloons and condoms are excellent for this purpose!!
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Old May 11, 2011, 07:08 PM
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Quote:
Originally Posted by jpcwebb View Post
Hi, it looks like you have the right general principles applied - keep it light, keep the cushion area maximised (don't go for funny V shapes), balance you weight distribution etc. The Dragstair is similarly poor on water, so don't use it as a comparison! It's definitely most at home on land, so only just can it be called amphibious. Your's however looks quite comfortable on the water! As a general principle it is worth waterproofing all electronics if you are going to operate extensively on water - balloons and condoms are excellent for this purpose!!
Im trying to make it go faster on water than Ikarus Dragstair. But if i add brushless motor there will be risk that the machine may overturn even more easily.

Thanks for the advice- ill keep in mind to buy a dozen of condoms for it But 3-5 condoms will add too much wight to it..

Im using the aluminium screws tho!
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Old May 12, 2011, 02:46 AM
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Hehe, I think you'll only need a maximum of two! In terms of max speed, it helps to get the skirt sorted out - a properly designed and well fitted skirt can make all the difference. And because you've gone for a two fan design, the centre of gravity will be lower than a single fan approach so that will add to the stability.
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Old Jun 07, 2011, 05:17 PM
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Ok, im almost ready with my hovercraft project. Now its fully painted, added stickers and made some improvements with the skirt.

I managed to make it better and now it can run on water AND land (only on water before). Modifications added some extra grams to overall weight.. 100-150g to be exact. Now the machine needs a better battery and brushless motor. I have these already, just have install them.
At the moment it weighs about 650g.

I think im gonna re-build the thrust motor and make it more like a duct fan to get more power.
At the moment the back part is too heavy and the nose is pointing up while driving. Maybe i should use 2 smaller batterys instead of 1. One to back and one to front... dont know yet.

I named it as "Larisa 950" (russian girl name). Im not russian but because its so robust and easy technology its similar to russian vehicles because of its simplicity. My hovercraft is an army machine.

Im really pleased with this small machine. It still runs really fast and now it can easily go over all sort of water plants and algae. Real swamp beast! Will chase waterfowls with onboard cam







In few days im going to make a longer video!
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Old Jul 02, 2011, 01:15 PM
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Oh, and it wont flip over anymore - thats like the most important thing which i achived.
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Old Jul 07, 2011, 11:04 PM
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looks good , i wish i had build skillz i'm so impatient
nice work
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Old Jul 11, 2011, 07:37 PM
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Yea looks good man! I like the meat tray canopy!
Do you have any pics of the build, or more specifically how you made the skirt?
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Old Jul 13, 2011, 05:18 PM
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Originally Posted by Firehawk989 View Post
Yea looks good man! I like the meat tray canopy!
Do you have any pics of the build, or more specifically how you made the skirt?
Thank you.

And yes, i have quite lot pictures of the building process. Just have to make a video of it. At the moment im so damn busy and i dont have even free time to drive this thing. But i have filmed a good video material already!
Video will come soon!
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Old Aug 13, 2011, 08:25 PM
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5x5 prop

Any idea where could i buy a 5x5 or 5x4.5 pushing prop similar to this:


Its design is kind of unique and its pretty wide tho. The best i could find was APC 5x5 or Speed400 4.5x4.1 prop but i think its not that good as Ikarus original.

Im upgrading my hovercraft to brushless and already tryed it with 3S LiPo - it went crazy. 11,1V makes a big difference. It can lift more weight now.

Help help help!
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Old Aug 14, 2011, 04:39 AM
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APC-E props work very well with brushless motors though for very high revs you may be better with a lower pitch as it will draw less current. Graupner do a 6x4 four bladed pusher prop, which you could cut down.
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Old Aug 21, 2011, 03:31 PM
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Ok, i made a new test-run today with brushless setup and modified back part. And i succeeded! It runs about 30-40% faster than with the 380 brushed motor.

One problem occured.. it doesnt hold the nose straight but leans to left. It might be the skirt which isnt even from both sides.. i will find and solve this problem in few days.

Anyways, i had a fun time but at the end i crashed straight to the aquatic plants. It flipped over and i had to rescue it with the price of one wet feet. Then i went back to home really fast, dried up with hairdryer. All the electronics survived, luckyly. A brand new 3S battery got wet tho!!!

What happens with the brushless motor (outrunner) if it gets wet?? Ive noticed that brushed motors can handle the water pretty well.

I will make a long video soon if i have plenty of material!


Upgraded version includes:
11.1V LiPo, 1100mAh
30Amp speed regulator, fwd
35A speed regulator, fwd
1 brushed 180 motor
1 brushless 1800kv motor
Carbon fiber parts
4-bladed 6x3 prop (cut down to 5)
Overall weight is about 550g
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Last edited by piito; Aug 22, 2011 at 03:46 PM.
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Old Aug 21, 2011, 03:42 PM
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Motors, brushless or otherwise, are generally pretty robust when it comes to fresh water, the problem comes if you try to run on brackish or saltwater as it is conductive. Actually, even freshwater is slightly conductive, but the motor windings are insulated and it is only the connections which are usually exposed so they generally don't bother a bit of water though it is a good idea to dry them out thoroughly after a ducking. The thing you need to protect is the ESC as this is much more sensitive to getting wet. I tend to seal mine using electronic-safe silicone sealant (the normal household stuff is no good as it contains an acid which can eat away the metals in the circuit). Alternatively a hot glue gun will do a reasonable job of sealing ESCs.
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Old Aug 21, 2011, 04:34 PM
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Water

As Jason says the motor will be fine i speak from experince but your ESC will be a gonner unless you have sealed it
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Old Aug 22, 2011, 03:43 PM
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Quote:
Originally Posted by jpcwebb View Post
APC-E props work very well with brushless motors though for very high revs you may be better with a lower pitch as it will draw less current. Graupner do a 6x4 four bladed pusher prop, which you could cut down.


I ordered the Graupner 6x3 prop and got it today. Didnt find any 6x4 version ...

So i plugged it to the motor and hit the throttle- craft moved backwards. I unplugged the prop, flipped it and gave it another shot- craft still moved backwards. This new 4-bladed Graupner prop has the pitch opposite to Ikarus 2-bladed prop.
Before when i used the 2-bladed Ikarus prop i had set the wires like this (between the speed controller and brushless motor):
RED > RED
BLUE > BLUE
BLACK > BLACK


Now for the Graupner 4-bladed prop i set the wires like this:
RED > RED
BLUE > BLACK
BLACK > BLUE


.. and then the hovercraft moved forward. Its kind of embarrassing but i dont actually know does it make any difference for the brushless motor if i change the wires like this? What other options i have? Is the brushless motor ment to work only in one direction or can it work (rotate) in both directions by the same power and speed?
And now the machine shakes a bit when i stop it. You can see it from the video which i just did:
http://youtu.be/RavswUEFl_o

Tomorrow i can test it outdoors. Excited to see it on the water with the new 4-bladed prop

Heres the new look of the machine. As you can see, im using carbon fiber plates. The white part needs to be painted:
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