Hull re-design

On the advice on some very experienced hovercraft designers, I have modified the hull design to maintain the full width for 7 feet of the length. This will increase payload capacity and increase the craft's lateral stability.

This does complicate the fabrication of the hull somewhat, as now the sides and their plow planes must be made in 2 cuts, and the walls must also be fabricated in 2 pieces. I am becoming concerned about the amount of 1" foam the design will need for the walls, bow panel, and top of the bow. If necessary, the top of the bow could be fabricated from 1/4" foam, since it is not structural.

I have also decided I'm going to need 2 more gallons of epoxy ($200), and most likely another roll of 10 oz. fiberglass ($7.xx / yd.). Many of the components could be fabricated with a lighter weight glass, (probably around 6Oz.), but purchasing a roll of 6 oz. in addition to a roll of 10 oz. would eat up a large portion of my already cramped budget. This weekend (easter weekend) I will visit home, so I will have the opportunity to ascertain exactly how much fiberglass and skirt material I have left over.

Anyway, renders of the re-design, courtesy of SolidWorks as usual (click for full resolution).

Side view:




Top view:




Underside view:




Isometric view:



Happily, modifying the hull allows me to take a much more conventional approach to constructing the lift duct. This will decrease construction time and angst quite a bit.

There is still a lot of design work to be done, even though it looks pretty finished. For instance, I'm going to need to install a tow hook in the bow in the event that the craft ever needs to be towed. This will require routing a hole in the forward section of the hull, epoxying in a large block of wood, and cutting another hole in the bow panel to allow the hook to pass through, then sealing the entire thing up. Little details like this are almost not worth the trouble to put on the plans, because all the fitting is done to other components, so any dimensions you give in SolidWorks are useless. The main thing is not forgetting to put the tow hook in.

As a second example, the back of the craft will not be left open: there will be small panels on either side of the prop cage that prevent water from entering the cockpit (for lack of a better word) when off cushion. In the bottom corners of those panels will need to be some drain holes that allow any water that enters the cockpit to drain out. After the panels are glassed in place, I will need to take a drill to them, and then seal the holes with epoxy.

As a third example, on my last craft I had issues with sand and other debris being carried by water into corners near the prop's plane of rotation. The debris would then get sucked into the prop, tearing up the tip tape. To prevent the same from happening on this craft, I'm going to make two low "dams" to direct any water and debris around the prop cage and engine mount area. But you won't find these on the renders, because they're a minor detail.

As a fourth example, (by now it should be obvious that I'm cataloging these here so I don't forget them), I have not designed the lift engine mounts that must be embedded in the lift duct. To be perfectly blunt, I have not given much thought to how these should be fabricated.

So as I said, a lot of little details remain to be planned out. Almost all of them can be dealt with "on the fly" as I construct the craft, but the challenge is to design to a high enough level of detail so that build time is minimized.