Hovercraft - 4 years of tinkering it's working again

[kach22i]

UPDATE: June 02, 2008

The key to working upside down I found is to get your resin into a paste-like state. You do this by adding fillers. Use the graphite additives for a slippery hull bottom and the recommended filler for body. It also helps if you duct tape one end of the cloth so you can have a good starting point which does not move around on you. Also the duct tape allows you to pull on the fiberglass cloth so there is no stretching or slack.

Much of the cloth texture is left exposed using this method, even if laying it on thick. I used one thin layer of paste-like resin followed later by a thinner finish coat to really gloss it up and seal it good.

http://s184.photobucket.com/albums/x295/kach22i/
Duct tape both ends and each side so that the fabric is stretched flush.


After curing, cut away with a mat knife unresined or unused cloth and any lose parts which you can pull off with a little tug.


Cut away openings so that a second lap layer can be done.


I used 2 inch wide cloth at the edges and pressed in with more resin mud. Reinforce high wear or high stress areas too. Then the whole thing gets painted with resin to soak in and protect intersections of differing materials.


Just another picture angle, this area received more colored resin in the air lift supply holes to seal the open cell foam. Open cell foam is bad, some of the expanding foam in a can is almost as bad when it comes to absorbing water.

[kach22i]

Once I figured out a simple way to make operable controls I had to give it a try. Single cable operating the top elevator, five little pulleys and a bungee cord. I had it all working fine with the operator end tied down until I could get to making a hand lever. Then while playing around with it and giving it some shock and load tests a sudden SNAP!

The over the pivot end of the acrylic leading edge broke off. I cut off the other side to match and fastened everything in a fixed position.

I glued in the air brakes at the front, the operable cable, travel agents and springs will have to wait until the skirt is installed.

I'm done with operable controls (for now), I need to study up on this topic big time. I really seem to suck at it, but have to admit it was a material failure - my choice of material though - hey it was free.

http://s184.photobucket.com/albums/x295/kach22i/

[kach22i]

FYI:
The other half of the wavy splitter (another part of the experiment - to cut down on sound).

http://s184.photobucket.com/albums/x295/kach22i/

[azasadny]

George,

Excellent work! A true Armenian genius at work!!!

[kach22i]

Originally Posted by azasadny

George,

Excellent work! A true Armenian genius at work!!!

I do shoddy work, but I am willing to do it two or three times until it's working right.

This project is about exploring concepts in a rough or sketch mode. It's not about having a nice finished project.

I'll know it's done when it's in a million pieces and even I can't put it back together.

[kmhemi]

glad to see you finally found the results you were looking for. I like the way you redid the hull and used the bag skirt. I lost interest in mine. its on Ebay right now.

[kach22i]

Originally Posted by kmhemi

I lost interest in mine.

I think they are more fun to tinker with than to fly around on (sometimes).

[kach22i]

UPDATE: 07/17/2008

First Gen, Transparent skirt:
http://www.hoverclubofamerica.org/forum/in...p?showtopic=412

Second Gen, Heavy Yellow Skirt:
http://www.hoverclubofamerica.org/forum/in...p?showtopic=962

Third Gen, Gray Balloon Fabric Skirt:
http://www.hoverclubofamerica.org/forum/in...p;hl=gray+skirt

Fourth Gen, Black Thermal Polyurethane Skirt:

Video Link-1:
http://www.youtube.com/watch?v=zs_H4uOQP0o

Video Link-2
http://www.youtube.com/watch?v=Fh99M1YpsA8

I would like to do an article for the HoverNews about how I ironed my skirt together. So I'll make this thread more about the design as it is, what it took to get this far and what the next skirt modification might be.

Pass:
1. The heat welded (ironed) skirt held, no seams opened up or popped.

2. Fan duct lining held up and helped lower the sound levels.

3. Tail cone held up and helped with thrust and sound levels.

4. The wavy edge diverter/splitter worked fine, I think it also helped lower sound levels by breaking up nodes.

5. The skirt material shows no signs of wear or abrasion.

6. The landing skids did not fall off, neither did the vinyl crush tubes at the bow.

7. The pointed nose bow skirt worked out.

8. No plow in, plow plan did not come off.

9. Was able to get back on cushion after trying to turn to tightly, good thrust.


Fail:
1. The sewn zipper holding the bow drape, about 12" of stitching near the contact line came out when I accidentally went backwards (half off cushion) in a tight turn.

2. The double bag stern skirt when inflated pushed the tail up and the nose down. When weeps were cut to equalize the pressure the bottom loop of the stern skirt failed to inflate and was dragged along for the ride.

3. About 1/4 of the side skirt length located just aft of the center of lift and center of gravity were dragging in the water. I need to adjust the skirt for a small irregularity in the hull which pushes the skirt out or down.

4. Contact cement will not hold the vinyl teeth to the bow for more than one use, must mechanical secure, no regular one step glues will bond to Polyurethane.

5. Repairs to Polyurethane skirt are not resolved to a point I like. Patches are sewn on, heat welded patches are difficult because the material is not coated on both sides.



In General:
1. I want to try my hand at a full flow but not a conventional combination skirt. I'm inspired by the old air cushion landing systems, and leave it at that.

2. I hope to resolve the weird pressure issue in the side skirts and get more lift air flow. This change follows my intent to explore a skirt system for a craft four times the Scat's size. See item #1 above.

3. I want to regain loss lift area by extending the bow into a point, another two feet. This change in center of lift will allow me to remove tail weights (steel bars).

4. I want to get a real tune-up and "going over" of the engine to find power lost by age and hours of use.

[kach22i]

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.

[kach22i]

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