Rudder improvements and improving ground handling

Much of today's effort was spent wandering the isles of Home Depot, but Michael and I made some good progress. Unfortunately we forgot the gopro so no timelapse for today.

Our first challenge was to decrease the weight of the rudders. As such we started by removing most of the wood from the poplar boards. This cut the weight down significantly. My searches for local suppliers of shrink wrap came up empty so I'm going to have to order it online. So the rudders will need to be covered later.

Here are the rudders propped in place awaiting the shrink wrap

The weight of the rudders is probably 1/5th to 1/10th of the previous weight and I think they're still quite a bit stronger than needed.


From there we moved onto working on eliminating the rudder backlash. The pin at the rear is a 1/4" bolt, but the socket for mounting the steering cable is closer to 5/16". This provided quite a bit of slop. I found some nice spacer flanges that could expand the bolt from 1/4" to 3/8" but that was way too big. And drilling out the socket on the cable looked like it would significantly decrease it's strength. So we kept looking.

We found some plastic tubing with 1/4" ID and 3/8" OD in the plumbing isle. And after some experimentation with various ways to slim down the plastic tubing. We put a longer segment (1.25" ) of the tubing over a 1/4" bolt, then chucked it in the drill. And then ran it over a piece of sandpaper. At first the sandpaper was handheld, but for more effective pressure we put the sandpaper on a fixed block of wood. (The 1/4" bolt allowed us to apply a lot more lateral pressure as well to speed up the process)

The slimmed plastic tubing.

 After sanding it down we cut off the last 3/8" which we needed for the fitting. And the backlash in the steering was cut in half. Now I think we're approaching the limits of the steering cable itself.


The other problem that we tackled was starting to think about how to load the hovercraft into and out of the trailer. We spend a lot of time looking at wheels and how to mount them to the vehicle etc. However, after quite a few trips through the isles we realized that we were thinking too hard about this and that maybe there was a dolly we could just use. And after that I noticed the hand trucks near the back, and we realized it would be much easier to use them with the axles and wheels already assembled instead of engineering it all ourselves.

We picked up the sturdiest looking of the simple hand trucks, as well as some straps to secure it to the hovercraft and headed home.

The first challenge was to get it into my car.

The hand truck barely fitting in the back of the car

To get it in required a little bit of squeeze and all the seats and cargo netting/protection to be removed. 

Once home the first order of business was to remove the handle. The grinder with a cutoff blade made short work of it. Something like 20 seconds of grinding for each end. 

The handle removed. 

The handle removed view 2

Of course we spent a little bit longer grinding down the exposed results so there's no sharp edges.

Michael having fun with the grinder.

 With the handle removed we could simply slide the hand truck under the hovercraft, "the wrong way up".

The hand cart inserted under the hovercraft.

And we used some straps to hold the "top" of the hand truck centered and off the ground.

The strap holding the hand truck to the underside. 

In our testing we were able to move it around relatively easily with just the two of us lifting the front. In a pinch I think I could do it myself on flat ground. But at least two people will be necessary for getting it up the ramp.

Though I think that the cleats will be of great use for us when we get to that. With the fiberglass around the perimeter the cleats are much stronger.

There are a few improvements I'd like to make to the hand cart. The straps should probably pull forward a little. And I'd like to make them a fixed length and go to special screw eyes so that it remains centered and doesn't take much thought to attach.

I'd like to add a little bit of fixturing at the rear to both keep it centered and from sliding backwards. With the handle removed the truck slides under the craft nicely. However it also slides out from underneath well too. And I think that a little bit of a block near the base could also keep the "top" of the truck from pointing down as it rides on the skirt attachment more than the hull surface.

Fiberglass reinforcements

Michael and I got an early start and tested the rewired kill switch for the thrust engine. And we noticed that I'd not quite lined up the lift fan's duct with the baffle underneath. So we realligned that and verified that it filled the skirt better.

A little later Adrian and I first looked into methods for reducing the rudder's weight, mostly by hawging out the rudder wood. The 1" poplar is way stronger than we need. I'm hoping to keep the frame but cut out all the interior space and stretch a fabric/plastic across it to block the wind but be much lighter than the whole volume of wood.

But we decided to first take on reinforcing the perimeter of the body with fiberglass. We started by sanding down the surfaces and rounding things off slightly near the cleats.

Below you can see the timelapse of us adding the fiberglass.

With the reinforcements around the perimeter I expect the craft to be much stronger. Previously it was relying on the foam to transfer loads between the sheets of plywood. Now the foam can just be a spacer. The full box beam has not been completed as the bottom corners are not completed, but it's way stronger.

The bottom corners are going to be much harder to do as they're both inside the skirt and include the bottom edge. The epoxy will hold somewhat on the bottom, but it won't be as clean as if I flip the whole vehicle over to fix it. I'll probably defer it to later when I am ready to redo the skirt with the final material.

With Adrian applying the epoxy and me flushing it down with my fingers we went through a lot of gloves. It wouldn't have been too many, but we needed to break out the scissors for the handles, and cleats, as well as the corners. And I needed to break out and cut more strips at some point.

At the rear we removed the rudder hardware and applied the fiberglass to the surface. Once the epoxy has hardened we can remount the hardware. (It's the oarlock mounts.

The hovercraft with the epoxy setting around the perimeter.

And as a bonus. Adrian brought his new FLIR camera which plugs into his phone and took these pictures of the heater running. It's way hotter than 216 degrees but you can see that it's overloading the sensor. The blackspots on the top of the heater register as 4 degrees F according to the camera.

An IR view of the heater running. 

The temperature on the ceiling above the heater, even with the fan running. 

Duct, rudder, and kill switch tuning

Today I spend the day filling in various small projects.

I've been hoping to reinforce the corners with fiberglass. On Saturday I attemped to warm up the garage above the minimum 55 degrees necessary for the epoxy to cure. It was just below 55 degrees so I opened the garage door hoping the afternoon sun would warm things up. At which point it clouded over and that plan didn't go anywhere.

As such I did some research and looked around for some other techniques for heating the garage. There are quite a few options that Home Depot advertises however most of them are not available anywhere nearby. And even better is when you get to Home Depot, no one knows where they would be. They don't seem to carry the more classic horizontal tube like heaters anymore. And I found one high capacity one finally, in the "light cloud". The "light cloud" is the section of the store where they have all the sample lights??

After way too long at the store I got it home and fired it up. It's rated for up to 1350 square feet, so it warmed up the garage quite quickly.

The heater warming up the garage with the fan next to it to circulate the heat better. 

I took apart the thrust engine kill switch, but realized I needed some more connectors to connect the kill switch properly, so paused that.

The lift engine cowling had been rotating while I was testing so I pinned it from each side using just some wood screws. I would like to beef it up with 1/4-20 bolts in the future, but didn't want to disassemble the lift engine just to secure it. I'll try to remember to do that next time it's open.

The rudders are very heavy so I'm planning to take the wood and remove most of the interior material and then just cover the outside with cloth. I haven't decided if it should be plastic, skirt material or fiberglass. I'll leave the perimeter from the existing board to be the main structure, as well as a lattice of the original boards to take the main load.

One other bit of tuning for the rudders is to find a spacer washer to give it less backlash in the controls. They are passing over a 1/4-20 bolt as a pin, but the hole is at least 1/4" clearance giving I estimate a 16th of an inch of backlash, which is a lot for a 2" throw overall.

Here's my first timelapse.

I had to take a break and get some more supplies.

Coming back several hours later, everything was cold again. In the 15-30 minutes I ran the heater I got the ceiling up to 70 degrees, while the hovercraft body got to close to 60 degrees. The floor remained approximately 53 degrees. I was hoping that the heat would remain longer and I would not need to keep heating while the epoxy cures.

While at the store I also found some end caps for the throttle leavers to make them a little bit safer.

End caps for the throttles

And I finished up by getting the thrust kill switch wired up. Though I didn't test it due to it being late at night.

Here's the timelapse of part two.