Hovercraft Project

Haven't posted since the contest ended. Just got too busy with other stuff.

Had a lot of activity trying to finish off the build. I've completed enough that I'll wait till spring for the little stuff.

The recent activity was to finish the steering and trim and the steering control. Then went from the temporay wiring to the final wiring. The choke is on the left with the ignition and voltmeter on the right. The switches are for the strobe light (required by the Coast Guard), the running lights and headlight (that aren't installed yet).

I also have a tach, but haven't installed that yet.

Attachment 4066

Lacking any inspiration on a graphic design - I went with the military look.
Attachment 4065

I want to move on to some woodworking projects that have been on the back burner. I also just got some sheet steel that I want to use the plasma torch on to build decorative security shutters.

Are you entering the new contest ?

Looks like your making good progess with your project, can't wait for update how it handles and how fast it goes. Keep us up to date.:O

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Originally Posted by zoama585

Are you entering the new contest ?

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Unfortunately, no. I work at a start-up and have a big delivery coming up. So I'll be focused on work for a while.

I will still be on as I work on my metal work projects though. I really like the forums and the folks on them.

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Originally Posted by 67cudafb

Looks like your making good progess with your project, can't wait for update how it handles and how fast it goes. Keep us up to date.:O

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Will do - but I'm pretty much done until spring. I just need the boat registration (already submitted) and the trailer completed to try it out (lots of little stuff I want to do, but it's flyable now).

It was a totally consuming project for a little over a year, and I need a break now.

Nice project! I worked for a guy that had one of them, we used it to get to his island vacation home when the lake was half frozen. Single prop design, it ducted some air down for lift. I can vouch for the speed over ice. The thing would just keep accelerating, we'd point it to a wide open spot and try to keep it going straight till we got there, let the power off and the thing would lose the lift, grind along the ice till it stopped and then we'd make a turn. Very scary. There was no 'gentle turning' on ice, you'd get it almost turned, and it would spin around quick, (a few times) the fan did not want to point into the wind. Your two prop design will probably be nicer to steer, if you can keep some lift going while cutting some thrust.
Going 60 mph sideways over open holes and ice made me wonder how much I needed that job. It should be lots of fun on a nice hot summer day tho. Good luck, enjoy..

Wow that has come a long long way since I was last able to see it. I read through the posts pretty quick and didnt see if you have been able to start it up and have it at least hover yet? I would love to see a video when you get it finished or running.

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Originally Posted by Jake98

Nice project! I worked for a guy that had one of them, we used it to get to his island vacation home when the lake was half frozen. Single prop design, it ducted some air down for lift. I can vouch for the speed over ice. The thing would just keep accelerating, we'd point it to a wide open spot and try to keep it going straight till we got there, let the power off and the thing would lose the lift, grind along the ice till it stopped and then we'd make a turn. Very scary. There was no 'gentle turning' on ice, you'd get it almost turned, and it would spin around quick, (a few times) the fan did not want to point into the wind. Your two prop design will probably be nicer to steer, if you can keep some lift going while cutting some thrust.
Going 60 mph sideways over open holes and ice made me wonder how much I needed that job. It should be lots of fun on a nice hot summer day tho. Good luck, enjoy..

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Amazing that when we were young and dumb the thought of getting hurt or killed never crossed our mind, older and wiser we look back and shake our head and go what the hell was I thinking but sure was fun lol. You have done nice job on the build be safe.

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Originally Posted by 67cudafb

Amazing that when we were young and dumb the thought of getting hurt or killed never crossed our mind

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You're not kidding...

wow !!! cool project!

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Originally Posted by 67cudafb

Amazing that when we were young and dumb the thought of getting hurt or killed never crossed our mind, older and wiser we look back and shake our head and go what the hell was I thinking but sure was fun lol. You have done nice job on the build be safe.

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Originally Posted by Jake98

You're not kidding...

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Maybe it's not that it never crossed our minds... just sort of a reckless abandon. When you're a kid, life still doesn't mean a whole lot to you yet, because it's not full, and it hasn't been that long? I know it crossed my mind a lot... "oh, this idea could kill me." and then it would soon be followed by "meh... oh well."

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Originally Posted by Spike

Maybe it's not that it never crossed our minds... just sort of a reckless abandon. When you're a kid, life still doesn't mean a whole lot to you yet, because it's not full, and it hasn't been that long? I know it crossed my mind a lot... "oh, this idea could kill me." and then it would soon be followed by "meh... oh well."

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When I was young I thought I was 10' tall and bullet proof and come to find I am 5'9" and old crippled man but it was sure fun while it lasted lol.:)

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Originally Posted by EmptyNester

Jason,

But, the biggest cost has been using the hovercraft as an excuse for tools.

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I do the same. Oh darn! I must buy this welder*, if not for this welder*, I would never complete this project properly!

On a more technical note, do you need to use a special epoxy that does not melt the foam. I know some epoxies and glues can be pretty aggressive against plastics and foams and such.

by the way, it looks like a great project, and I'll be following your progress

Can`t wait to see this thing in action!

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Originally Posted by d.fisher

On a more technical note, do you need to use a special epoxy that does not melt the foam. I know some epoxies and glues can be pretty aggressive against plastics and foams and such.

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You can't use polyethylene based epoxy, it will melt the foam. I made a mistake and tried to use bondo fiberglass repair to fill a couple small holes. All it did was make a couple very bigs holes.

I used a "standard" epoxy resin.

I haven't been on the forums since before Christmas. Life has a way of interfering with fun :)

I did get to work on the craft over the fall and winter. By Christmas it was ready for a test flight, but I had no way to get it anywhere. Plus, it was just too cold. But anyone who visited got to ride it while it hovered in the garage.

I've been working on the trailer. I started with an HF 4x8 tilt trailer and have been modifying it. I welded a lot of the joints for peace of mind (and I like to practice my welding). I had to extend the tongue to fit the craft. I'm now building a wooden deck on it.

To load it, the best concept was using a truck crane. So, last weekend I fabricated a hitch mount for it. The picture below shows how I expect it all to come together.

Attachment 5755

Tonight it was warm enough and I got home early enough that I tested the loading system. I was pleased with how it worked. I may need to make some minor tuning adjustments, but the concept seems sound. Once the hovercraft is in the air, I'll just slide the trailer underneath by hand.

Attachment 5753

After I put it down, I slapped the prop and it and tried powered flight for the first time. I only had about 10 feet of space, so it was a very short test. It worked! I had steering control and forward motion. But, when I cut back on the throttle - the belt for the prop jumpted the pulley. This has been a problem that I thought I had fixed, but I guess not.

So, I think I can finish the trailer in a weekend. Then, if I work out the drive belt issue - I'll be ready for a real test flight.

Excellent, I hope you can post some video!

Thanks for the info. on the resin. I haven't experimented much with it, but it's good to know, the only time I ever tried to bond foam together resulted in disaster.

Once again, really nice work! Can't wait to see some video of the craft in action. I'm sure it's been asked in the past, but how much does the craft weigh?

d.

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Originally Posted by d.fisher

I'm sure it's been asked in the past, but how much does the craft weigh?

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The specs say 500 lbs. But, I think that may be on the heavy side.

The primary components are:
engine - 100 lbs.

hull:
- 7 sheets of 2" extruded styrofoam insulation (got mine at Lowes)
- 7 sheets of 1/4" marine grade plywood
- 1/2 sheet 1" extruded foam (on top of the front)
- 2 part marine foam (fills around the lift fan)

(3) 1"x4"x16" for cockpit stringers and skirt attach strip
(1) 4' x 8' x 1/4" for seats
(1) 4' x 8' x 1/2" extruded foam for rudders and trim wing

Epoxy and fiberglass

Drive train components:
- rear drive pulley with bushings
- rear idlers pulleys (2) for 90 degree bend to prop
- front idler pulleys (2) for slight bend to lift fan
- lift fan drive pulley with bushings

Skirt material (this was much heavier than I would have though - I would guess aroudn 30 pounds).

I spent a while in the spring trying to finish everything up for a test flight.

My work is right by the river and everybody I work with was anxious to see it (all engineers). With software guys doing mechanical things - there's always the possiblity for an entertaining failure. And, I didn't disappoint:)

I parked in the lot and figured I would just fly it to the ramp. It was down a slight hill, but I didn't think that would be an issue.

The first thing was that the limestone dust in the parking area got sucked into the thrust prop and took the paint right off the leading edge of the prop.

I started heading toward the ramp and the craft started sliding sideways down the hill. To stop I did a 180 and gunned the engine. It jumped the curb going backward and stopped right before dropping off a three foot drop onto rocks on the bank. (It was almost like a cartoon. As I started to step off the craft and it began to tip backwards until I jumped back on.) After a bunch of friends help lift it off the curb, I continued on to the ramp.

Had one more incident where I tried to stop and almost hit a rock pile going backwards. (And scared the crap out of a guy fishing on the other side. I felt bad, but the cell phone video somebody got was funny. Turns out, I would have never hit anyone because they were on the other side of a large pile of rocks.)

Once I got it on the water - everything seemed to work reasonably well. I didn't go too fast because I didn't want to risk any catastrophic failure and my throttle cable needed adjusted and I could only get about half throttle.

Other than ripping a number of very large holes in the skirt and scaring the crap out of myself a couple times - I figured it was a success. (Flight 2 was also good, the most recent - flight 3 wasn't so successful).

Video of the first flight is below:
http://www.youtube.com/watch?v=cun0DngT6gI

Pretty cool. One very nice project and fabrication.
I'd drive it!

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Originally Posted by EmptyNester

Other than ripping a number of very large holes in the skirt and scaring the crap out of myself a couple times - I figured it was a success. (Flight 2 was also good, the most recent - flight 3 wasn't so successful).

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There was one over here... I never got a good look at it but the skirt had some kind of flaps on it. I guess it make it more durable. Hard to describe it... Kind of like large fish scales, but heavy rubber.

Question... Does it float if the engine dies while in the water??? Hate to lose something that nice... BTW great work. Looks really well made.

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Originally Posted by Brian Ski

There was one over here... I never got a good look at it but the skirt had some kind of flaps on it. I guess it make it more durable. Hard to describe it... Kind of like large fish scales, but heavy rubber.

Question... Does it float if the engine dies while in the water??? Hate to lose something that nice... BTW great work. Looks really well made.

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What you probably saw was a "finger skirt". It has a lot of individual air compartments that vent. They give a smoother ride, but are much higher maintenance. What I have is called a "bag skirt" since it is really like a sealed bag with air blown in the top.

The hull is made of two layers of 2" foam board insulation (for houses). They say that it will fload even if you cut it in half. I have had it floating on the water. The problem I had after that is my skirt drain holes aren't quite right and I never drained the water, so couldn't go over about 2 mph.

Does it have a muffler or just a straight exhaust ?

Zoama - I'm glad you asked :)

It does have a muffler. Originally, the engine was mounted per the plans with the muffler facing forward. However, my muffler goes lower than the engine mount. Because of that - I had to increase the forward up angle of the engine so the belt didn't hit the muffler. As a result of the up angle, I had issues with the rear/drive belt coming off.

My last mod was to rotate the engine 90 degrees and remove the added up-angle on the engine. One of the problems with the current mount is that the output of the tailpipe is only 8" from the base of the lift duct. In the last test (probably only 15 or 20 minutes of running), the heat of the exhaust gas cracked the fiberglass on the duct.

I need to figure out how to divert the exhaust. The problems I have are two-fold:
- finding the right diameter and type of pipe to use
- getting a bend in it with a radius that will fit the space I have (both how to get the bend done, and how to get it to fit)

The exhaust ID is around 1 1/4" and the OD is around 1 3/8".

Attachment 7449Attachment 7450

Any suggestions would be appreciated.

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Originally Posted by EmptyNester

Zoama - I'm glad you asked :)

It does have a muffler. Originally, the engine was mounted per the plans with the muffler facing forward. However, my muffler goes lower than the engine mount. Because of that - I had to increase the forward up angle of the engine so the belt didn't hit the muffler. As a result of the up angle, I had issues with the rear/drive belt coming off.

My last mod was to rotate the engine 90 degrees and remove the added up-angle on the engine. One of the problems with the current mount is that the output of the tailpipe is only 8" from the base of the lift duct. In the last test (probably only 15 or 20 minutes of running), the heat of the exhaust gas cracked the fiberglass on the duct.

I need to figure out how to divert the exhaust. The problems I have are two-fold:
- finding the right diameter and type of pipe to use
- getting a bend in it with a radius that will fit the space I have (both how to get the bend done, and how to get it to fit)

The exhaust ID is around 1 1/4" and the OD is around 1 3/8".

Attachment 7449Attachment 7450

Any suggestions would be appreciated.

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Mandrel bends... cut and use what you need http://www.ebay.com/itm/Exhaust-U-Be...d34c94&vxp=mtr and header wrap http://www.ebay.com/sch/i.html?_trks...+wrap&_sacat=0

Oh.... excellent, thank you!

I had been trying to figure out what do to do for a while and hadn't come up with anything good. This is perfect.

For the mandrel, I assume that the 1 1/4" is the OD. Is that right?

I'll order that today!

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Originally Posted by EmptyNester

I assume that the 1 1/4" is the OD. Is that right?

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Tubing is measured by OD.

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Originally Posted by EmptyNester

Oh.... excellent, thank you!

I had been trying to figure out what do to do for a while and hadn't come up with anything good. This is perfect.

For the mandrel, I assume that the 1 1/4" is the OD. Is that right?

I'll order that today!

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Links are just for reference. Always shop for the best deal for you.

Another possibility is to bend a piece of PVC pipe to the right shape and length with a heat gun.
Take it to a muffler shop and have them replicate it, all in one piece.

rivets

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Originally Posted by EmptyNester

Attachment 7450

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How about just using a piece of sheet metal as a deflector? A few simple cuts and bends should make something appropriate. Tack it to the back of the muffler so that it scatters/deflects the exhaust into the air stream.

I had thought about sheet metal, but one of the things I've heard is that diverting the muffler from in front of the prop will decrease the noise. (Apparently, the prop magnifies the exhaust noise.) I had thought a pipe would do that better, I just hadn't figure out what to use and how to get the tight bend.

I had gone to a local muffler shop, but they didn't have anything that small (I think 1 3/4" was the minimum they had.)

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Originally Posted by EmptyNester

I had thought about sheet metal, but one of the things I've heard is that diverting the muffler from in front of the prop will decrease the noise. (Apparently, the prop magnifies the exhaust noise.) I had thought a pipe would do that better, I just hadn't figure out what to use and how to get the tight bend.

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Never thought about amplifying the noise, I guess it would bounce off the prop every time it passes and would get scattered or concentrated in various ways.

A pipe would look more professional too, it is just the frugal bastard inside of me trying to save you a buck. ;)

I wonder if somebody who does motorcycle mufflers could do something for you.

I took Zoama's advice and ordered a mandrel. I had talked to a local muffler shop, but I'd rather do it myself. It probably won't look as good - but it's another learning experience.

I'm just waiting for the mandrel to arrive. When I do it, I'll post do a project post thread for it.

I really need to get back to the craft to do repairs and adjustments, I've just been focusing on my CNC table build. But, the table is progressing well - so I will probably make time to work on it soon.