Mini Zonda build

[hughb]

Here's a WIP of my Mini Zonda. It's approximately 680mm long.

The empty hull weighed about 720g. Light, but also flimsy.

20210328_150013_resized.jpg

First step I reinforced the tips and join at the front of the tunnel with an epoxy/chopped CF mix.

20210329_183058_resized.jpg

I did a CF inlay to the entire boat (beside under the deck). Firstly long strips to cover the seams, then an overall inlay. To get into the forward areas required some smaller pieces, I couldn't do it in one piece. I was afraid of the hull warping so left some heavy weights on the hull on a flat surface while the epoxy dried.

20210330_152127_resized.jpg

Once this was done I noticed some air pockets in the inlay, where the horizontal section of the tunnel meets the inside vertical section of the sponson. I had to cut out these pockets with a knife, sand the areas smooth, then do a further inlay. This time I used a technique with sand to press the CF into the surface. To do this, straight after laying in the inlay, lay some peel ply cloth into the boat, followed by some paper towel to soak up the excess resin, then lots of sand on top. The weight of the sand forces the CF to conform to the shape, and the peel ply creates a barrier so the sand and paper towel won't stick to the resin. Once the resin is dry the sand can be emptied out and the peel ply pulled out with minimal force. It leaves a nice dry surface that is not resin rich. It is kind of the opposite of vacuum bagging but with a similar result.

20210404_180126_resized.jpg

I put a small amount of 2 part expanding foam into the bow area. I also made a longitudinal bulkhead to support the deck and stop flexing from 2mm CF.

20210610_091441_resized.jpg

[hughb]

In the stern area I made two small longitudinal bulkheads to support the stern deck. I also had a plan to further reinforce the stern which first required me to bend up some brass tubing to act as a cooling pipe which goes from the starboard side of the transom through to the inside of the hull. A small bracket secures the front of this pipe. Then 2 part expanding foam was carefully poured into the stern areas to the left and right of the longitudinal bulkheads. This made this area very solid. It was too small of an area to try and do a CF inlay in. Once the foam dried it was cut flat and a small piece of CF added over neaten the area. Between the bulkheads I glued in another transom piece to reinforce where the rudder/strut will mount. I left about 1cm gap between the actual transom and this reinforcing piece. When this piece was glued in, I then drilled a hole in the transom and filled the void with epoxy to really strengthen up this area.

20210610_091417_resized.jpg 20210610_091424_resized.jpg 20210610_091348_resized.jpg

The outer bit of the transom was not flat so I glued in a piece of G10 material where the strut will mount, and filled the gap around it with a epoxy/microballon mix.

20210610_091452_resized.jpg

[hughb]

The ride pads of the boat were not flat, they actually had anhedral to them. I was tossing up whether to bother modifying them, but in the end decided I like building boats even more than running them, so set about to fix it. Firstly I glued some 2mm balsa wood to the ride pads, then sanded these flat and true, also I ensured there was no back/forward rock to the boat when checking on a flat surface.

20210527_152031_resized.jpg

Next I glued some 0.2mm CF over the balsa, then filled the gaps with epoxy/microballoons filler. Once dry I sanded the excess filler and now have ride pads that are flat and true with sharp 90 degree corners. Also I covered the "pockets" in the stern by cutting out thick pieces of balsa to fill most of pocket, then cutting out 0.5mm G10 and gluing it all in. I then added a fillet of epoxy/microballoons around the edge to ensure it was sealed off and no water would leak into the pockets. I good way to add a nice even fillet is using the epoxy in a 10ml syringe with a drawing up needle on the end. A drawing up needle is like a hypodermic needle but has a larger diameter and no sharp point. It is designed for drawing up medications from a vial into the syringe.

20210610_091257_resized.jpg 20210610_091246_resized.jpg 20210610_091310_resized.jpg

The boat now is in the region of 1200g, so a fair bit heavier from what we started from, but feels incredibly strong now.

[srislash]

Looks good Hugh. I had to go thru all that ride pad issue with my FC Fantasm for the exact same reason. Wish I would have thought to do a cf skin over the balsa tho.

[hughb]

Thanks Shawn. I took inspiration from your builds as well as many others on this forum.