Monday, 20 June 2011

Build - Bonnet cont.

Day 3 -
This morning I sanded back the left half of the bonnet. With a flexible kitchen knife it is easy to cut through the foam. So I worked the shape down until it was roughly where I wanted it then with a light sand it was pretty easy to shape. There are a few gaps and larger air bubbles in the foam so I will need to find some putty or filler on my next trip to Bunnings to smooth out the shape. This evening I had nothing to do so I succumbed once again to art store prices and bought 3 sheets of 5x100x915mm balsa for 24$. 

With one of these sheet I completed the remainder of the bonnet and fixed the right skeleton to the left foamed section. I then used the same tape method as before and then used the remainder of the second foam canister to fill what I could of the right half. I also cubed up some of the off-cuts of foam from earlier today so that I could try and get as much filled as I could. Unfortunately it came up a bit short so I will leave this until I have to foam the rest of the top. After setting the bonnet aside to dry I printed out the remaining sections I would need and  traced out some of them onto one of the sheets of balsa before cutting it all out.
So far with this project I'm impressed with how light and sturdy the whole structure will be. It still amazes me that balsa wood is so easy to cut with a Stanley knife yet when teamed with the foam it is extremely strong. I am still undecided how I am going to get the bonnet to seal to the rear section and also around the tubing. I am thinking about using a tongue and groove set up for attaching the 2 sections and then having bolts running down through to the foam base.

Almost Complete.

Sunday, 19 June 2011

Build - Bonnet

At the end of the first day of building
I had the initial structure of the left part
of the bonnet all pinned in place.
Day 1 -
I printed out some of the parts I would require this morning then forgot about the project for most of the day. After a trip all over Sydney I finally found one lone piece of 6.5mm balsa wood in bunnings, it had been trod on and was a little scrappy but it would do as with the small selection I had I could begin the project. I came home and began to cut out some pieces. After a shopping trip for dinner I purchased 2 pieces of 5x100x915mm balsa for $8 each from a craft store, it was very expensive but it would allow me to continue as I had almost run out already. 

Day 2 -
 Bottom of the L-Bonnet after taping.
I began the day by finishing off the balsa structure of the left half of the bonnet. I initially just pinned it together before looking for more balsa wood in bunnings. They still hadn't got stock in so I just purchased some masking tape and sand paper. I also searched for some tubing to join the 2 sections together. There   was only 50mm PVC pipe so I decided that I don't have any tools to melt and bend it so I needed some flexible tube. They only had 40mm diameter clear vinyl tubing so this would have to suffice, it was a bit expensive at $16 for a 900mm piece.
Top of the L-Bonnet after taping.
When I got home I decided to super glue the skeleton together before taping up the top in preparation of spraying foam. I had a 340ml can of foam but didn't see the fine print saying that the 3x expansion occurs over time. So I sprayed it all in to a few of the compartments before running out. I then decided to make a quick trip to buy another 340ml can for $8 and whilst there noticed the expansion over time clearly printed on the larger cans. After racing home to salvage it I scooped as much as I could into the other compartments and topped off the remainder with the new can before setting it to dry.
I hoped to begin shaping the foam this evening but after cutting into the foam the centre is still gooey so it will have to wait until the morning.

<  After first can of foam.

 After foam expanding and drying. >

< After removing the masking tape.

Using masking tape to cover the top worked extremely well, as you can see from the 3rd picture above the foam comes out pretty close to the final product.

As always, tips and tricks for the blog or project are always welcome. 



With university exams looming I decide I need a project to take on.
Many years ago I began toying with remote controlled hovercraft, initially a rubbish bin lid with a vacuum motor and decided that now I'm in uni I need to make something that reflects this.
I began by messing around on catia to get a model of what I wanted and after about a week I had a shape resembling what my initial idea.
My knowledge of Catia initially was limited but along the way I discovered various new techniques for creating what I wanted. This meant that after working for a while on one model I restarted to redefine what I wanted and get the modeling process to go more smoothly.
After getting the 3d model I used the drafting component to get sections to print and then translate into balsa wood.

Below is the design that I had come up with.

Underside of Catia Design

Exploded view showing all the individual components. 

Here is an excellent resource for building your own Hovercraft.
Its full of information on how to build a hovercraft capable of holding a person.