|
Hovercraft - 4 years of tinkering it's working again
The original finger skirt was taken off four years ago to repair the hull and duct, which were damaged. The damage was caused by losing a bottom aluminum rail to a rock in a river, this caused a gap between the two hull halves which came undone in a dramatic way about a year later and almost left me stranded.
I never liked the constant spray in my face of the original skirt; the sorry obstacle clearance and the inherent instability which made it a poor cruiser yet gave it fair maneuverability and banking ability. I sought to change and improve what I thought I could, even tried to make it quieter in the process. The point of the continuing experiment is to learn as much as possible using the school of hard knocks method or perhaps an artistic rather than conventional engineering method. The excitement and possibility of doing something which has not been done before defies practicality and logic yet is the sprit of many inventions and innovations. Graduating from the theories found reading and the play of models, I sought to “scale up” my experience and knowledge base within a reasonable budget and investment of time. In retrospect I could of built a hovercraft from plans with the same amount of effort and time, but I don’t think I would of gotten out of it what this furrowed path has brought. Concept: Hovercraft operates in water the majority of the time, make the skirt more like a boat hull and see what happens. One of the rescue workers said of my Sunday morning river run; we had to do a double take, it looked like a Zodiac at first. 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 This thread is the Third Generation, and it may not be the last - we will just have to wait and see. http://i184.photobucket.com/albums/x...LIFT-FRONT.jpg http://i184.photobucket.com/albums/x...0-INTERIOR.jpg http://i184.photobucket.com/albums/x...BOW-CONSTR.jpg http://i184.photobucket.com/albums/x...ERN-CONSTR.jpg http://i184.photobucket.com/albums/x...7-HELPER-2.jpg http://i184.photobucket.com/albums/x.../G6-HELPER.jpg http://i184.photobucket.com/albums/x295/kach22i/G5.jpg http://i184.photobucket.com/albums/x295/kach22i/G4.jpg It's a work in progress, I'll try to back-track as much as possible. The stern skirt which kind of looks like a diaper with temporary straps got torn up on some rocks before it could be adjusted for air pressure and final connection to the two side skirts. There is some serious re-engineering going on in my head about this right now. The gray skirt is ballon material, a large bag filled (almost 90 feet x 4 feet) weighed in at about 10 pounds, I used 7 pounds. The old yellow skirt weighed in at 60.5 lbs....................a weight savings of over 50 lbs!!!!!!! I also redid the stern counter weights by removing the dumbells, and placing steel bars on the twin tail farther from the center of lift and center of mass/gravity. This was another weight savings, I'd like to take all the weights off by just having a larger engine one day. The hot air balloon material is not very abrasion resistant, I may be going to a conventional material or combination material skirt in the fall. Big thanks to my wife Kim who did all the sewing. |
This sketch may help you understand the inner workings.
http://www.hoverclubofamerica.org/forum/in...si&img=1145 http://www.hoverclubofamerica.org/fo...1_6_110131.jpg Video of first flight on grass, later flight on wet grass in the morning were much faster and encouraged me to go out on to the water several times. Flight 10a (grass): http://www.youtube.com/watch?v=Mt-EhS40788 Flight 10b (going out in water): http://www.youtube.com/watch?v=xs_58qICi0c Flight 10c (coming back in to shore): http://www.youtube.com/watch?v=ywfD2-c_4lw The pressure in the skirts was much higher than the capture air bubble under the craft. When I tried to turn the stiff skirt burried its self into the water slowing the craft down enough to take it off cushion. With no reserve thrust I could not power out of this situation and had to make it to shore flying across the sandbar and getting back on cushion. Water operation on straight high speed runs was encourging, but not being able to slow down (no brakes) really was scary as the water level was low and many sharp rocks were everywhere. I tried to balance the air pressure, there are two (2 inch PVC pipes) feeding the stern skirt, and only one 3 inch hole feeding air from the duct to each port and starboard spnoson/pontoon skirt. I can either bleed air out of the bags like an Aerocruiser or attempt a combination bad/finger skirt of some sort. I could also just have very tiny holes feeding the bag skirts which will give me more lift. I closed off six other air holes each side, when they were all open the bags were ready to burst and over the grass performance was not as good. |
Someone recently posted a picture of their mock UH paper skirt fitting. Thank you to who ever that was, it inspired me to work in paper at model and full scale and saved me from repeating mistakes.
http://i184.photobucket.com/albums/x295/kach22i/S1.jpg http://i184.photobucket.com/albums/x295/kach22i/S2.jpg http://i184.photobucket.com/albums/x295/kach22i/S4.jpg Squaring out the stern was done for several reasons. 1. Make the skirt fit 2. So it floats more level 3. Is similar to a large "dream hovercraft" I have on paper and in 3-foot foam model form Getting the square end up the boat ramp and on to the trailer was not fun. I also suspect it shortened the stern skirts life with this geometry. http://i184.photobucket.com/albums/x295/kach22i/T2.jpg http://i184.photobucket.com/albums/x295/kach22i/T2B.jpg The "DARTS" went full for the final mock-ups, early model shown. http://i184.photobucket.com/albums/x295/kach22i/T2G.jpg http://i184.photobucket.com/albums/x295/kach22i/T2H.jpg Like a fish with the meat cleaned off leaving only the head, sad to see the Flying Tiger Teeth go bye bye. http://i184.photobucket.com/albums/x295/kach22i/T2I.jpg |
Getting the hull to fit the skirt was worth it, should of done this the first time.
http://i184.photobucket.com/albums/x295/kach22i/T2J.jpg I call this the "paper canoe", I love it when a plan comes together. :) http://i184.photobucket.com/albums/x295/kach22i/T2K.jpg http://i184.photobucket.com/albums/x295/kach22i/T2L.jpg The tail was a little rough going at first, it's symmetrical with the front. http://i184.photobucket.com/albums/x...ch22i/T2-1.jpg http://i184.photobucket.com/albums/x295/kach22i/T2N.jpg http://i184.photobucket.com/albums/x295/kach22i/T2O.jpg The paper bow fit perfectly, I forgot to click a picture of it's final fitting. I did the darts on the outside with a stapler to save time. http://i184.photobucket.com/albums/x295/kach22i/T2P.jpg You can see in this picture why the tail had to be suspended from a hard hull. The Russians with the Mars hovercraft have a stacked skirt, the top one is Zodiac-like and foam filled. I don't know if it's rigid stiff foam or soft like a matress. I'm guessing it's stiff as I know of no soft foam which will not act like an open celled sponge and absorb water. http://i184.photobucket.com/albums/x...i/GUN-LAKE.jpg Original (factory) configuration with tigershark teeth: http://i184.photobucket.com/albums/x...over-Mark2.jpg |
UPDATE: 07/02/07
I've been meaning to do some work on the old Porsche and the old house, but the hovercraft is still fresh in my mind so I started to take it apart for repairs and updates. To do list: 1. Replace stern skirt and modify the rear bottom hull lip so it does not chop it in half again. Thinking round tube covered in rubber all across the edge. 2. Repair bow skirt and add outer fabric wear material. I have several complex and cool ideas for this, but I have to make it simple so my wife doing the sewing will still say yes to helping out. 3. The side skirts have no wear at all. All the damage to the skirt was done by contact with the hull. There are a couple of holes made by sticks and sharp river rocks; changes in materials should take care of this. 4. I'm sealing up air leaks to get more lift (closing off weeps and duct joint leaks) and balancing out the air pressure between the captured air bubble under the craft and the bag skirts. This should give me more or better lift under conditions such as banking/turning and stopping. 5. Finish up duct lining and feather the edges for more thrust and revise the splitter so there is enough thrust to get over hump speed on water. Link to pictures: http://s184.photobucket.com/albums/x295/kach22i/ |
George,
Excellent work!!! |
Quote:
My brief moment of glory, mixed in with a future idea at work............how I see it playing out.:D http://i184.photobucket.com/albums/x...Sketch-Yea.jpg |
Just before the recent heat wave I added some structure to keep the stern from deflecting so much when tilting it up off a steep boat ramp.
Now it's looking architectural, complete with a truss!:D All the oil caning is from the settling it's already done. I just did not have time before the national hovercraft rally to get all the detail down right. http://i184.photobucket.com/albums/x...HOV-TRUSS1.jpg http://i184.photobucket.com/albums/x...HOV-TRUSS2.jpg As for the cable hand lever brakes for the foreward puff-ports, I found something called a "Travel Agent" which doubles the cable travel. This is something I need to finish the bow braking system. The amount of air and the braking or bow steering power will be slight, but it's a exercise in working with controls for me. Another first time experience, so it's going to be a little rough.;) http://www.performancebike.com/shop/profile.cfm?SKU=2647&subcategory_ID=5221 http://www.performancebike.com/produ...88-SIL-TOP.jpg http://sheldonbrown.com/harris/cable-hardware-brake.html http://www.sheldonbrown.com/harris/i...ent-br0300.jpg An old guy reparing bikes at the "Student Bike Shop" said expect about one inch of travel. When I asked him about "Travel Agents" he said they are not in his catalog and he has never heard of them. He runs a budget operation and said I could get a pair of cable activated lever brakes with cables for around $30.00 which is less than I've seen on-line from the specialty shops. I need to get a strong spring (about 2" high compressed to 3/4") to keep the air dryer vent closed, that's next. I'm thinking a rubber or dense foam gasket may help keep the air seal. |
Hovercraft are cool. :cool:
|
Nice to see someone's wheels turning, I'm ok at maintaining but my creativity quotient is pretty low. A HC came through the shop a few years ago, a buddy of mine bought it but I never saw it run before he sold it. Rocks can not be your friend.
Jim |
An update on the splitter 07/30/2007:
Imagine standing at he the back of the hovercraft and looking at the back of the fan. Visualize a line down the middle (up and down) separating the fan right and left. The airflow thrust on the right side of the fan is swirling downward when running. The airflow thrust on the left side is swirling upward. I've cut up the original splitter and angled it to match the angle of the blades (1/4" gap) and the directional flow of thrust air. The middle part (the hub) and the transition between the three pieces is something I could use some suggestions on. The middle part is actually just below the hub height to help prevent escaping air; the paddle effect of the fan maintains air pressure. I'll be fiberglassing the whole thing together and gluing it on to the blue foam. I'm thinking that the middle part of the splitter will look a little like a bow-tie or a propeller without a hub. I'm not sure if anyone has done something exactly like this before, I'm just tying in bits and pieces of other peoples work plus a few ideas of my own. If you have seen something like this before, please post an image or list a name so that I can reseach it. I might have to look at Neoteric again for a start. Think of this splitter as a kind of a STATOR. http://i184.photobucket.com/albums/x...SPLITTER-5.jpg http://i184.photobucket.com/albums/x...SPLITTER-6.jpg http://i184.photobucket.com/albums/x...SPLITTER-1.jpg http://i184.photobucket.com/albums/x...SPLITTER-2.jpg http://i184.photobucket.com/albums/x...SPLITTER-3.jpg http://i184.photobucket.com/albums/x...SPLITTER-4.jpg |
UPDATE: 07/30/2007
http://i184.photobucket.com/albums/x295/kach22i/C1.jpg It's been very difficult to get the cone shape without a lathe, and without putting a layer of fiberglass to the flat part first (that I could find something to secure to) it's been tough going. If you can learn from my mistakes, bless you. I'm just waiting for the weak as caulk adhesive to dry. Had the thing working for a couple of minutes, but the glue not exposed to the outside was not curing inside of the plastic dish. I know this does not look safe, but it's got to be safer than using the hovercraft engine/fan/hub as a lathe. VIDEO: http://s184.photobucket.com/albums/x295/ka...nt=e3139e36.flv http://i184.photobucket.com/albums/x...22i/CONE-3.jpg http://i184.photobucket.com/albums/x...22i/CONE-2.jpg http://i184.photobucket.com/albums/x...22i/CONE-1.jpg |
Beyond cool.
I'd love to see the look on peoples' faces when I drove it up out of the water onto the beach, chased a few bikini-clad nubiles around and then drove back into the water, thwarting any pursuit. Oh, the possibilities. . . |
Quote:
|
Ouch - if he got that close not good. . . One thing to joke about (hopefully you know I wasn't serious and just kidding around), another for someone to actually do that. Not good at all. I imagine those things don't exactly stop on a dime and someone could get pretty badly hurt if they ever got hit by one.
It would be kind of fun to drive from land to sea and back again though - very neat in that regard. That'd I'd seriously do - without endangering anyone of course. |
Quote:
|
UPDATE: 09/04/07
I wrote down what I'm doing to the craft, ten things at once - yikes. At two weeks an item that comes to 20 weeks of work. I'm happy when I'm busy, so I guess I'm happy. SKIDS: I have to add a 45 degree wood pieces to each of the the sides of the skid pads, and add fiberglass all the way around. http://i184.photobucket.com/albums/x...22i/SKID-1.jpg Leading and trailing edges are beveled/canted 45 degrees. BOW PLANE: Everyone says that the Scat and Scat II have plow-in problems and most of that is because it has no plow plane, where a UH or Sevtec (approx. 10 degrees) have plow planes. I marked off the bow with some duct tape for a cutting line (approx. 15 degrees). Pulled out my reciprocating and cut away the offending edge. I then took a bread knife and cut a 1/2" recess in the foam for a MDO plywood insert. I took out my jigsaw and cut a half circle piece which was then glued flush. The entire area will be fiberglassed next week (I hope). http://i184.photobucket.com/albums/x...h22i/BOW-1.jpg http://i184.photobucket.com/albums/x...h22i/BOW-2.jpg http://i184.photobucket.com/albums/x...h22i/BOW-3.jpg If you were to do this for a stock fingered skirt, I imagine some additional modification to the bow skirts or at least their loop ties and lengthen the plastic zip ties. On my craft there will be no connection to the hull as the front drape is attached to each side skirt. I found the connection points on my previous set-up was a souce of wear and stress as ithe connect got trapped under the bow hull. |
UPDATE: may 19, 2008
It will feel like summer here all week, no rain. I might get something done. http://s184.photobucket.com/albums/x295/kach22i/ http://i184.photobucket.com/albums/x...22i/HOV101.jpg http://i184.photobucket.com/albums/x...22i/HOV102.jpg http://i184.photobucket.com/albums/x...22i/HOV103.jpg http://i184.photobucket.com/albums/x...22i/HOV104.jpg http://i184.photobucket.com/albums/x...22i/HOV105.jpg http://i184.photobucket.com/albums/x...22i/HOV106.jpg |
UPDATE: June, 02. 2008
Cone in place. Finish quality is pretty shoddy, but even at idle it's effects are very noticeable. Full throttle absolutely rocks.:) http://s184.photobucket.com/albums/x295/kach22i/ http://i184.photobucket.com/albums/x...22i/DUCT-1.jpg Thin layer of light weight fiberglass cloth. Finish coat of West Systems resin with low friction graphite (black) 423 & 406 (filler). I never finished the cone and duct with (410) feather filler before applying the finish black coat, which is why it looks so funky. I'm on a deadline now, and have to start a new skirt ASAP. |
| All times are GMT -8. The time now is 04:43 AM. |
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2025, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2025 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website