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May 15, 2015, 07:14 AM
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New single engine skirtless hovercraft


Here is a video and some info on my latest project.

This is a scale model of what I'm planning to build using a single 400watt out runner and 4000mah 3 cell lipo.
It measures 800mm x 500mm and the maximum hover height is about 60 mm, weight is approx. 2kg.
Its not as fast as my Stingray design but easier to control and more stable, which is what i want for a full scale one man craft.
The controls allow it to hover stationary using all the power for lift, or divide it evenly to control speed and hover height.
Its taken a lot of experimentation to get it working properly, and keep it to scale.

New Hovercraft Design (0 min 44 sec)
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May 15, 2015, 09:45 AM
Boaters are nice people.
That's awsome!

I've never seen/owned a skirtless hovercraft and would like to learn more about your design.
Will there be plans, or a kit available in the near future?

Regards, Jan.
May 15, 2015, 11:19 AM
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Nice! That's really cool!
May 15, 2015, 08:28 PM
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Here are some sketches i did a while ago based on the Stingray design. Its pretty easy to get a model to work using these basic plans if you keep the proportions about the same. For good hover height keep it as light as possible and use depron foam or thin balsa sheet. Also bigger models seem to work best. The new design in the video is a bit more complicated so if you're keen to build something without a skirt have a go with this first. There's also some skirt design info if you need it. Pete
May 16, 2015, 01:21 PM
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Thanks for posting those, on your peripheral cross section are there any critical angles or dimensions you've found? I see how you do the tape, like a tiny wall skirt that doesn't extend below the hull.

What's your deck spacing and how does it relate to the perimeter gap? Do you try to match the perimeter's plenum area to the prop duct area(or a percentage of it)?

And how about the thrust duct? Are you taking bleed air right off the main plenum? Is it a flap like a control surface or do you use some sort of shutter/slide/butterfly?

Also, do you any countertorque ducting inside your hulls? I'm considering making my hull spacers act as a set of stator vanes (as well as a correction vane arrangement below the prop). If done right i could see it countering torque, but more importantly, increasing efficiency by correcting a lot of the vortex flow under the prop and through the hull.

What i think is that the vanes can be oriented in a curved polar array that provides some countertorque to the motor. As well, and an even bigger deal would be that cleaning up the airflow may really boost performance, lowering power requirements. Look at the way stator vanes are used in jet turbine applications, especially centrifugal flow units, each turbine stage has a corrector that greatly increases efficiency of then ext stage by feeding flow into i at the proper aoa for maximum efficiency. I want to feed the hull exits good air using the same principles. I wish i had some readiboard left, i'd build one right now and just find out the answers, hehe!

Your craft fly beautifully. How much power are you thinking he full scale is going to take? Have any idea yet?
Last edited by Rusty Mustard; May 16, 2015 at 01:33 PM.
May 16, 2015, 03:48 PM
Boaters are nice people.
Hi Pete,

Thanks for the info!
The last three thumbnails are really small though, making them bigger only makes them pixelated, not readable.
Would you be so kind to subsitute them with high resolution images?

Regards, Jan.
May 16, 2015, 09:01 PM
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Quote:
Originally Posted by Rusty Mustard
Thanks for posting those, on your peripheral cross section are there any critical angles or dimensions you've found? I see how you do the tape, like a tiny wall skirt that doesn't extend below the hull.

What's your deck spacing and how does it relate to the perimeter gap? Do you try to match the perimeter's plenum area to the prop duct area(or a percentage of it)?

And how about the thrust duct? Are you taking bleed air right off the main plenum? Is it a flap like a control surface or do you use some sort of shutter/slide/butterfly?

Also, do you any countertorque ducting inside your hulls? I'm considering making my hull spacers act as a set of stator vanes (as well as a correction vane arrangement below the prop). If done right i could see it countering torque, but more importantly, increasing efficiency by correcting a lot of the vortex flow under the prop and through the hull.

What i think is that the vanes can be oriented in a curved polar array that provides some countertorque to the motor. As well, and an even bigger deal would be that cleaning up the airflow may really boost performance, lowering power requirements. Look at the way stator vanes are used in jet turbine applications, especially centrifugal flow units, each turbine stage has a corrector that greatly increases efficiency of then ext stage by feeding flow into i at the proper aoa for maximum efficiency. I want to feed the hull exits good air using the same principles. I wish i had some readiboard left, i'd build one right now and just find out the answers, hehe!

Your craft fly beautifully. How much power are you thinking he full scale is going to take? Have any idea yet?

Theres a lot of variables with this type of model, depending on the design the cross section area etc need to be set according to the airflow requirements i.e. power stability method, integrated or separate lift and thrust. The drawings above are based on my other model but they can be a good starting point for any experiments.
The main difference between these designs and skirted models is they need to be much lighter to work properly and that makes them unstable at higher speeds, so a lot of thought has to go into stability and control.
My Stingray design needs a tail similar to a WIG to stop it flipping at high speed, but once adjusted properly its speed is only limited by the amount of thrust you have available. I have tried weight shifting and gyro controlled stabilisers but found the T tail worked best. All my testing is done over salt water so i don't like things going wrong
The vortex flow inside is definitely an issue so vanes are a good idea. You can actually make the craft rotate the same direction as the prop. Dual counter rotating props are effective but add weight and complexity. -You may be better off using the second motor and prop for thrust and control instead.
Just have a go at something simple to start with and then try to refine it.

Im hoping to use about 50 hp for the full scale craft, but it will only be a one person design, unlike similar powered skirted craft which carry 3-4 people. Performance should be much better though.
May 16, 2015, 09:07 PM
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Quote:
Originally Posted by pompebled
Hi Pete,

Thanks for the info!
The last three thumbnails are really small though, making them bigger only makes them pixelated, not readable.
Would you be so kind to subsitute them with high resolution images?

Regards, Jan.
Sorry about that hope these are ok. They were just some rough notes i made but the info is pretty handy.
May 17, 2015, 12:19 AM
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Quote:
Originally Posted by windnsea
Theres a lot of variables with this type of model, depending on the design the cross section area etc need to be set according to the airflow requirements i.e. power stability method, integrated or separate lift and thrust. The drawings above are based on my other model but they can be a good starting point for any experiments.
The main difference between these designs and skirted models is they need to be much lighter to work properly and that makes them unstable at higher speeds, so a lot of thought has to go into stability and control.
My Stingray design needs a tail similar to a WIG to stop it flipping at high speed, but once adjusted properly its speed is only limited by the amount of thrust you have available. I have tried weight shifting and gyro controlled stabilisers but found the T tail worked best. All my testing is done over salt water so i don't like things going wrong
The vortex flow inside is definitely an issue so vanes are a good idea. You can actually make the craft rotate the same direction as the prop. Dual counter rotating props are effective but add weight and complexity. -You may be better off using the second motor and prop for thrust and control instead.
Just have a go at something simple to start with and then try to refine it.

Im hoping to use about 50 hp for the full scale craft, but it will only be a one person design, unlike similar powered skirted craft which carry 3-4 people. Performance should be much better though.
Building light is no problem, most hovercraft seem like overbuilt hovertanks, flying coffee tables, i never understood it. On my craft i've been using various wings and stabilizers to get downforce applied to the front of the craft. I've found that a wing with negative incidence high and aft provides the best forward downforce. I saw your stingray and noticed the incidence and such on the T-tail in your vids as well

I've also been playing with WIG craft as well, i've got an EDF bixel i've been working on that i want to go seriously fast with. Right now it will fly but i just haven't had the space to run it up and trim it out. I broke out of GE last time testing in the park, and out of room i had to just fly it out like a parkjet and land. Ended up about 50' high and circling to approach with a WIG, hehe!

But yeah, i understand the stability needs, i want to try and crack 100mph with an ekranoplan on the dry lake. Maybe with multiple edf's or some mean pylon racing power systems, or even possibly some pulsejets.

As soon as i get some more foam i'll try out a skirtless single with some of these ideas and see where it leads.

Thanks for posting!
May 17, 2015, 03:54 AM
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Be interesting to see your WIG craft in action. Will you use some sort of sensor for altitude control or will the craft just stay in ground effect without any trim adjustment. i.e. at 100mph its going to be difficult to see how high it is, or see it at all - my craft was disappearing fast at 60 km/h and very hard to judge what was happening at a distance, so very difficult to know what elevator trim is needed to control height etc?
May 17, 2015, 10:00 AM
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For the fast one i'm planning on using CC3D for attitude control, possibly with some optical/radar/sonar altimeter that will try to keep it in the sweet spot, and piloting via FPV on a 22 mile diameter dry lake.
May 17, 2015, 08:26 PM
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That sounds technical but going by your previous models I'm sure it will work.
Looking forward to some FPV video
May 18, 2015, 04:15 AM
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Loving your skirtless exploits Pete. Apart from stability issues, how does it perform in terms of steering/ drift? I imagine fine control is a lot harder than with a skirted craft.
May 18, 2015, 07:07 AM
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Originally Posted by jpcwebb
Loving your skirtless exploits Pete. Apart from stability issues, how does it perform in terms of steering/ drift? I imagine fine control is a lot harder than with a skirted craft.
Glad you find them so entertaining Its a couple of years now since i managed to get something working properly, and that was after a couple of years experimenting, so I'm looking forward to see what other people can achieve with their ideas. - Haven't been able to find any video of a similar model but maybe theres a top secret project out there somewhere ?
Control is pretty good with this model, much easier to complete a smooth turn than my other design. Surprisingly it is pretty similar to a skirted model, and quite good on choppy water up to hover height.
May 18, 2015, 06:46 PM
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So i tried this, but i think i cheated, i made the tape a bit long ant it pretty much became a small wall skirt. Is a 1" skirt like that cheating?

Skirtless hovercraft testing (1 min 28 sec)



That's on 2s, and in quite a bit of wind so it wasn't easy to fly one handed and try to video.

It also works without any tape at all , but with the tape it's got great ground clearance!


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