Hovercraft Project

[MoparCar]

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

[Brian Ski]

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).

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.

[EmptyNester]

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.

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.

[zoama]

Does it have a muffler or just a straight exhaust ?

[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".



Any suggestions would be appreciated.

[zoama]

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".



Any suggestions would be appreciated.

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

[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!

[Rambozo]

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

Tubing is measured by OD.

[zoama]

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!

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

[Rivets]

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

[redbeard]

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.

[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.

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.)

[redbeard]

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.

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.

[EmptyNester]

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.