Maiden Voyage

Today was the maiden voyage!

Here's the launch!


Here's an album from the day if you want more pictures and videos than are here in the post below.

Adding drain holes

After testing the new skirts on land, in preparation for taking the vehicle out for testing on the water I worked with Victor to add some drain holes at the back to allow any water in the bag to be released.

We sketched out an area, cut some slits and then covered it with a flap of rubber with a rear facing opening to avoid snats.

The holes cut with markings for positioning the covering flaps.

The covering flap with vinyl cement applied.

The port pair of drain holes covered up

The starboard drain holes covered

The center drain holes covered.

The center drain holes needed some extra wax paper as the first application of vinyl cement had the cover with the glued side facing the wrong way, so it would scoop water instead of drain water. 8-)

Testing the New Skirts

With some help from Victor we were able to get out and test the new skirts in the driveway.

Here's coming out of the garage.



I took it for a quick spin down the driveway.




Then Victor took a try.

And finally we slid it back into the garage.

New skirts inflated

I successfully tested the new skirts today.

The corners aren't pretty but they hold air and I think they'll scuff the ground and likely wear down. But if I keep an eye on them, I suspect that they'll wear nicely to show where they need to be trimmed back and a few sequences of patches the skirt will evolve to be a more natural shape.

Front left corner

Backleft

Back right

Front right

Here's what it looks like. (Warning: lots of noise.)

Skirt corners glued

With some extra hands from Jenny I was able to get the remaining 3 corners glued shut. It's not super pretty, but I think it will hold air. And I'll plan to adjust it after inflation tests. I think it may even be worth trying to glue it while under pressure for then it will at least be holding shape, and with letting the glue get tacky before hand it sticks pretty well in one shot.

Port aft

Forward Port

Starboard Aft

More Skirts

With some help from Michael today I made good progress on the rest of the skirts.

We started cutting out out sections for the front and rear of the vehicle. They're slightly deeper so go across the half way point so we couldn't put them side by side.

Practice skirt over new material for front and back.

Attaching the skirts makes it look a lot more like a real hovercraft.

Outer edges of skirts attached

We moved on to attaching the inner edge of the skirt in the front.

Inside of first skirt attached.

Punching the holes on the underside is a pain. So we switched the order and lined up and punched the holes first on top, before moving to the underside.

All the holes punched and validated

While working on it the screws would pop off easily as we were working on it so I switched to using zip ties for guidance.

Using zip ties for guidance.

Cable ties down the port side skirt.

The small spacing between the batton straps and the rub rails made the prepunching even more important since visibility is limited. And being under-hung it's hard to hold everything in place simultaneously.

There's also important aspects to how to overlap the skirt parts. By switching the overlap we were able to make it so it will slide better over the ground without getting hooked.

After with lip facing backwards 

Before with lip facing forward

We trimmed some of the corners off to make the joint more rounded, but it's definitely going to be pretty ugly at the corners. But hopefully it will float high enough so that it will not matter too much. I know it's not going to deal with plow in well anyway. We glued it in a moderately curved manner. The heavier skirt material is harder to bend and secure in the billowed shape.

Here's the first results. It looks like it will hold the air. We'll have to see how it looks once it's inflated.

First corner glued

Later in the afternoon I had a little bit more time so I attached the aft and port skirt inside edges. And now it's starting to take shape. Just some more gluing to do.

Looking underneath with the skirts mostly attached.

New skirts started

Today with the great help from Victor I've started recreating the hovercraft skirts using the vinyl material that came with the skirt replacing the cheap plastic practice ones.

There was a little bit of sanding left over but the bottom of the craft looks good. And it's good to see the craft back flat in the garage.

Back horizontal, but on blocks for work

Laying out the old skirts on top of the new material we've cut oversided elements. After attaching them we'll cut them down. The skirt material cuts in half nicely to form the size of the skirt for each side.

Side skirt laid on top of the new uncut materaial

The new skirt material compared to the test skirt templates.

The attachment battons worked out well. Though we had to find a way to make holes in the right places. But it turns out there's a good tool in inventory for that, a hole punch ;-)

The very specialized tooling.

And even better the standoff distance needed from the edge was approximately the same as the depth of the hole punch so you just had to line up the lateral alignment.

The first side took alittle while to put on, and we put the batten on the wrong side up at first. But the 2nd one went quickly. And we stretched it out the full length first, then slide it up to punch the holds and put in the intermediate holes for the batten screws.

First side attached.

And we briefly tested the vinyl cement that looks like it will be fine to just cement the joints without stitching. And it nicely sets in a few minutes so gluing the corners shouldn't be too much of a challenge.

Here's the final view with skirt material dangling from both sides.

FInishing bottom reinforcement

Thanks to some help from Jenny today we've more or less finished sealing up the bottom of the hovercraft.

There's two small joints that I'd like to fiberglass over. However, my epoxy level reached a critically low level such that the pump for the resin started sucking air. So I had to use my estimate for the right ratio to mix the epoxy.

We started off the day by sanding down a the previous epoxy work. And we got the hovercraft balanced back on it's other side. With the skirt attachment point it's actually semi-balanced not quite on it's side. So I tied it in place to the rafters.

The hovercraft propped on it's starboard side.Ready for work.

We cut a few more strips. I switched back to using scissors from the razor blade. It cuts with less pulling stress, and allows me to follow the weave better. This leaves the edges much more square with less dangling fibers.

Marking the fiberglass with a pen prior to cutting for better weave cutting.

We finished up the side with the last of the epoxy. Here's the full timelapse.


One oddity when flipping the vehicle was that I had a little bit of oil leak from the front engine on the port side. But on the starboard side fuel started coming out of the primer pump. And there was a bit of a leak from the thrust engine but turning off the fuel cutoff helped that a lot. ;-)

And here's the results as it's drying. I found just enough epoxy to seal up the small side joint too.

The glued edges, still curing.

Fiberglass reinforcing the bottom

With great help from Jenny and Jennifer L we made a lot of progress today!

It was super hot today which both made things uncomfortable as well as challenging with the epoxy.

We started off sanding down the corners and surfaces we planned to glue. While preparing the fiberglass strips.

The challenges started early when the resin didn't look right when I pumped it and it came out much whiter than it should with particles from 1/4" downward. And the pump didn't refil correctly. After some investigation it appears that the resin has sat too long in the pump and has partially reacted somehow.

White precipitate in the resin pump. Unfortunately the focus in this picture is on the wrong part.

I pumped it a bunch and tried to clear as much as possible and we got back to relatively clear fluid flow. But new pumps are in order. And we're almost through with this batch of epoxy so that's not too bad.

As I noted in the last post there was quite a bit of gap in the front edge. So we started by trying out the silica thickener that I got to fill the gap. Since this was less critical I used the large pool of leftovers and tried to mix the hardener in in the right ratio and put the thickened epoxy into the gap.

Using the thickener in the epoxy

It seemed to work quite well.

After inserting that, we applied the glass down the outside, and then clamped the surface down. Hopefully with the epoxy squeezing everywhere it will come back apart ... ;-)

The clamped front end.

We moved onto doing the lower part of the lift duct. And ended up clamping it too for a small section of lifted plywood.

Duct post epoxy/fiber pre clamp

Duct clamp top size

Duct clamp bottom side

The clamps being attachable/detachable was quite convenient for sneaking the rod through the fan housing.

We continued from the front edge to the starboard side, and the rear. However we stopped doing the port side since it's fighting gravity and figured we'd wait until this hardened and do that side separately.

The end result was 3 sides done. And with a little extra time we also did the center joint between the plywood.

Edges done from the rear

Edges done from the front

And I had a little extra epoxy so I used the thickener again and filled in under the skid boards that I'd identified as having broken away previously.

Starboard skid board aft end

Port skid board aft end

Here's a timelapse. Unfortunately it's pretty long, but missing a good portion of the epoxy application due to poor batter management/tending.... Once the epoxy is flowing there's not much extra time for anything like thinking about the camera.

Cleaning up bottom

I finally bit the bullet and decided to take the skirt off and fix up the bottom of the hovercraft.

I'll also use this time to change the skirts from the plastic drop cloth to the proper rubber surfaces. I still have some experimentation but I found that the plastic had failed in several places already.

Tears in the front port interior corner. These were clearly from rubbing back on the skid bars.

Tears in the front starboard interior corner.

A little bit of the wear and tear can be seen on the skirts here. With roughing going on down the sides.

Here's a full timelapse of removing the skirt.

I also made some interesting discoveries inside the bag. With non-trivial amounts of dirt of non-trivial size. I guess the smaller stuff blew out at some point.

There was also a surprising amount of dirt inside the skirt

After removing the skirt my next step is to clean up and seal the bottom of the hull. The top of the hull has been fiberglass reinfored at the joints but not the bottom yet. This is both putting the full load on the foam, as well as providing surfaces for water intrusion.

So with a bunch of help from Jenny I've tipped the hovercraft up on it's side. Here's a video it was a good anount of effort. 

Here's the final result

Here it is resting on the fan housing, it makes a nice roll bar...

And the bottom you can see the blemishes clearly in the streaking sunlight.

 There's a bunch of work to do down here. For example the corners especially the front and rear need some reinforcing.


And one of the skid boards, is only attached in the front half.

I can fit my whole finger behind the skid board.

However the skid boards appear to be doing their job well. There was no noticable damage to the skirt attachments and there was clearly some wear and tear on the skid boards themselves.

An example of the wear on the skid boards up close.

Here's some closeups of the joints that need reinforcement. Clearly glue on foam w/o vacuum application doesn't really work too well. I'll make up for it with some good fiber/epoxy corners.

The bottom edge of the bow.

Bubbling along the bottom of the boat.

The dolly mechanism does appear to have left some wear and tear on the transom.

Damage to the bottom edge of the transom?

A second view of the transom damage