Hovercraft - Experimental Skirt Project

Tail Cone: not connected to spinning fan hub.




Stern Skirt inflation test on the trailer, June 26, 2008 just before going to the National Hovercraft Rally in Ohio.

Video link-3:
http://www.youtube.com/watch?v=RJo1l6sudzI

Stern skirt (bag and double bag modification) pictures:

Single bag:


Outer bag prior to it being ironed on to the first.


Partial installation showing feed holes between the chambers.


It's on there, all dog eared without any air going through it.

 

Boat-like bow drape shape- before final trimming.


Rear view:


Side view:


Bow point:


At the USA "National Hoverally" in Ohio a few weeks ago I forgot to wear ear plugs when I took it on the lawn and out on the water. My ears were not ringing a usual, in fact I think I'm in a "cruiser craft" noise zone now.

I have no measurements, but my seat of the pants and by ear opinion is that the closing up of duct clearances, adding a cone and doing the wavy splitter have all made a large difference (together).

Here is the big part; my wife said the craft is quieter, and sounds more powerful/throatier, sounds lower in frequency (more car-like) and not as disturbing or offensive.


Link-4: to HCGB on sound levels
http://hovercraft.org.uk/FUDforum2/index.p...ee9ac#msg_11426

 

i was wondering if there was anyone i could talk to about a skirt me and some friends are bulding a hovercraft we wanted to do a finger skirt but we have no idea how to do it we cant find any books or anything on it is there anyone that would point me in a direction where to look for this or help explain it to me thank you

 

There are some pdf's which you may be able to download from here:
http://www.hovercraft.org.uk/

You can also post as a guest here:
http://www.hoverclubofamerica.org/

Most home-builts use bag skirts, not finger/segment skirts. There are many reasons for this, like it's easier.

Home-builts using fingers many times copy or slightly modify the design of a factory built craft which has been around a long time.

You may be asked to post diagrams or drawings of your craft/model/craft under construction because there are so many variables.

You may just want to do a Google "image" search with the words "hovercraft skirt" for starters.

I can start a thread for you at the Hoverclub of America forum site, just PM me here.

 

That would be awsome if you could do that for us we do have a few pics of the craft so far as well as the desighns at this following link if they need the specifications for it if it is easier we can do a bag skirt we were just thinking that a finger skirt would be better any information that can help us with this is greatly appreciated

http://www.midwestjeepthing.com/For...rcraft&forum_title=Projects&replies=5&M=0&S=1

 

Okay, you have your own thread now. Go there and introduce yourself posting as a "Guest", I think you can type in a temporary user name. You have to sign up as a member of the club to post as a member, so you can do things like post topics.

Link:
http://www.hoverclubofamerica.org/forum/index.php?showtopic=1881

You are not the first group to try an out of the box and do your own thing - design.

The other guys did get to scoot around a bit (on land) and had a lot of fun. However their goal and blazing a new path of hovercraft technology and racing faded a little with every setback, but they gave it a darn good effort.

Their threads (UCF):
One:
http://www.hoverclubofamerica.org/forum/index.php?showtopic=1421
Two:
http://www.hoverclubofamerica.org/forum/index.php?showtopic=1407&hl=
Three:
http://www.hoverclubofamerica.org/forum/index.php?showtopic=1128&hl=

 

Thank you very much for the help we were thinking we were heavy but didnt realize how critically over weight we really are with it i was unable to post on the other fourm but when i get a few free minutes imna become a member there any idea what a craft should weigh fully loaded that is 6 ft by 12 ft also i noticed someone mencioned somthing about tube and a wire mesh for the thrust fan housing what sort of tubing can we use for that also we have a 6.5 hp engine for lift and a 28 HP engine for thrust we were planning on fully loaded weight of around 600-800 IBS is that going way over or what is a more realistic number of what we will need

which plans should we buy that would be most like our craft just to get general ideas for this thing were can we find thoose plans

also our plans were completly drawn up in english class i am a Sr in Highschool got bored during class one day and drew up thoose blueprints normally i do small scale RC airplanes and helis never messed with hovercrafts beforei work at a hobby shop so i do have a few ideas about some of this but on i much smaller scale but i wanted somthing all my friends could get in on this time so this is what we ended up with i did take a few things from the 12' scat but its 90% my desighns i appreciate all of the help with this any information

 

This bites, looks like it's only the Classified section in which you can post as a "Guest".
http://www.hoverclubofamerica.org/forum/index.php?showforum=24

I'll cut and paste your questions.

Did you put this on a scale yet?

I bet the hull "as-is" weighs 600lbs, add engines, fans, resin/paint, floatation, skirt and operator and you might go over 1,000 lbs. Still 1,000 lbs at the size you have is better than 500lbs at half the size.

 

I really do appreciate all of your help on this i am going to goin the HCA once i get home from school tonight and do a little more research before we continue working on it are there any good books that you would recomend or any other means of good research

we have our lift fan ordered through hoverhawk.com however we are now looking for skirt material and a thrust fan any recomendations for who to go through for getting these

if we do the fan gaurd (tubes and wire mesh) instead of the fan housing (inclosed prop with a slight slop to increase thrust) what all we we be losing i am very confidant that we can make a fan housing with the correct slopes etc to help our thrust and not hinder it as many of our dads are enginers and can help us with this but is it worth the weight in our case or should we just not bother with it and put up tubes and a wire mesh

 

There are so many, here are a few.

http://www.slipstreamhover.com/

http://www.amphibiousmarine.com/catalog/

www.hovercraft.com
(see Parts & Materials)

From the HCA site:
3. Parts & Materials Suppliers & Distributors
http://www.hoverclubofamerica.org/Links/index.html

The skirt on my craft is very experimental, I ironed it together.


Heat Sealable Nylon Fabrics
http://www.rockywoods.com/

I think you will have enough problems, stick with something tried and true.

The HCA sells books, also check out that UK site I posted they have a lot of free stuff you can download.

 

First posted in the HCA forum:
http://www.hoverclubofamerica.org/forum/index.php?showtopic=1881

[/QUOTE]

 

A proper duct is a lot of work. A few people who are starting out don't bother with it. At best, it gives you static thrust (acceleration) increase of about 10% at low speed, and that drops off as you go faster. The point of diminishing returns happens at around 60 mph on most hovercraft ducts.

The duct wall needs to be an airfoil shape, more or less. The inside surface is a cylinder from about 1/3 the length (from front) to the trailing edge, and then an airfoil with a large radius so that the inside of the duct is the "top" of the wing. The prop tip to duct gap for a thrust setup should be 1/4 inch or less. Some time back a friend of mine made his 54" duct (prop diameter 54") and it weighed about 12 pounds finished and ready to attach to the craft. I never weighed mine. As well, the duct should be able to withstand a 100 lbs force in any direction without interfering with the prop. Meaning you throw you shoulder into it fairly hard.

If you get plans from Universal Hovercraft, they show you how to make an acceptable duct. Like I said though, it is a lot of work.

I would not use a fan for the thrust. Go with a 2-bladed prop. They are more efficient, quieter and all around better.

Edit:
Most commercially built hovercrafts have bad ducts. The duct in those cases is essentially a guard and a cosmetic feature, and does no good at all as far as thrust improvements. The duct you guys have shown is not even slightly workable. Consider that ducts are expected to prevent prop breakage (or at least contain the pieces) even if the craft flips over on land at high speed.

The crafts which omit the duct lose a little bit of acceleration off the line, but they can use a larger diameter prop and make up for it somewhat. I know several people who just don't bother. It's much easier to make a safe craft with a tubing guard than it is to make an effective duct. If you decide to build from plans, then consider making the duct. In that case, you will almost certainly come up with a machine which works well, and in that case it will be worth the extra effort.

 

We weighed our craft and it came in at 312 pounds thats the hull lift engine duct and all we then went back and were able to shave off 48 Pounds so now were down to 264 when we redo our duct we will be able to shave off even more is this a realistic weight to think that we can make it work we still have to get a thrust engine rudders gas tank and all of that im just wondering if we have a good start or if we still need to do more to it

 

That's still pretty heavy, I'm not sure at this stage of the build how much though.

I think my bare UH-18sp hull came out something close to that, and it's overweight for that size. I never actually weighed it at that point though.

We need to define what exactly you are trying to accomplish here. Are you just trying to make it hover in the parking lot, or do you want a functional hovercraft that you can use for years, driving on water and such? The most useful advice can only be given after you decide that.

 

Basically we want a craft that we can mess with for the summer than we are donating it to our school for the next year of kids to take it over when we first started it out original goal was to hit 45 MPH in a transition from land to water now we are starting to realize how hard that is going to be but yet our goal stands strong we will continue to do whatever we need to and if we cant reach this goal we hope that we can pass it down to some kids who will