Cat Dink - a coronavirus isolation project

As detailed elsewhere, this is a coronavirus isolation project. It is a 8' by 3'10" catamaran style dinghy where the rower and passengers sit on a middle bridge seat with their feet in the "wells" provided by the catamaran hulls. 

Mark demonstrating the Lil Nip's capabilities

The designer is Mark Gumprecht, the dinghy is the Li'l Nip and the plans are available from Duckworks. (The plans are now free)

I didn't take photos of the ply and marking out. But once the marking cutting and trimming was done we end up with shaped panels looking much like these.

Frames and panels (one pair of two) for the Cat Dink

 Next it was a commandeering and re purposing of some packing case material used for rough shelving into a strongback for the moulds. A centreline was drawn and the frame spacing marked and cleats fixed (for the frames to mount on).

The strongback with frames 1,2 and 3 - the extra frames resting in front are the "mistakes*

The plans provide the spacing's for the frames from the bow, with all frames bar Number 2 staying with the hull as part of the structure (forming water tight cells). Frame 2 is removed after the hull is glued to be reused for the second hull.

That done the side panels for one hull were "stitched"with zip ties at the bow and assembled around the frames/moulds, and glued with epoxy resin.

A certain amount of mucking about was involved in this and initially I made this much too hard for myself....but with the addition of some suitably insulated (packing tape) cross pieces (upper cleats?) the hull panels were positioned, aligned and glued to the frames. (but Not 2!!!)

*The sharp eyed will notice a spare pair of No1 frames in the background. I decided some access ports into the bow flotation chambers would be useful. I carefully positioned them in the centre of the finished frame height ....but forgot the seat cut-aways - this little error was a nuisance - not because of the extra work but because I had selected the best of an ordinary bunch of ply panels ...and they had been really nice. Also this compromised other ply choices as we shall see later. another lesson learned.

The above camera angle makes it look like the bow isn't quite true - the trick is to fix the parts into the correct position before gluing! (which I did - whew!).

The next step was to mark out the hull bottom.  And yes the panel has been flipped just before taking it outside for cutting (near the line). 

I had made an error with the transom height which meant I had to stitch it on after the bow and frames 1 and 3 had set up. As the frames and hulls were cut and shaped as a set this error had to be catered for in both hulls - it really wasn't a problem. As long as I ended up with a pair of hulls all was well and so it has proved to be. 

The pictures below show the frames for Hull 1 yet to be trimmed in the left and tidied up on the right. 
On the right the transom for Hull 2 is stitched and glued with the bottom for Hull 2 rough cut and waiting its turn to be glued. 
With autumn temperatures I employed a heater and had to wait 24hrs between steps. This isn't that hard to deal with as I could keep working on the other hull.

My practice has been to glue the rough cut panels down and then plane and sand down to "fit". This makes for a more professional look (professional in this case is open to interpretation). Maybe "better" is the right word :-)

The plans recommend glassing the bottom and running the glass 2 inches up the sides (down in this case). Before I did this I thought I would "dress" the bows with a strip of solid wood for protection, sealing and appearance. 

This worked out quite nicely I thought - as with many aspects of the build it is builders choice ( or in some cases for me - recovery from error ).

Around this time I reminded myself of the value of tape and plastic sheeting to prevent unsightly epoxy runs , reduce cleanup and sanding work. It is an extra few minutes work which pays the effort back "in spades". I realise its been some time since my last stitch and glue project and I have forgotten some basic tricks. This is a slap up project - but a bit of discipline and pace is worthwhile.

I didn't take a photo of the hull cutaways. These are cut from the two hulls to allow the fitting of the bridge "beams"which along with the seat will join the two hulls. The plans remind the builder to make sure that they have a left and right hull - I made the right decision but could imagine that a distraction at the wrong time could create havoc.

I set the hulls up on sawhorses and checked both horses and hulls for level. Pretty right first time. and a with a little judicious trimming  we were ready to join. The pic below shows a bit of scrap timber and the spirit level placed to visualise the next step.

First the bridge beams needed to be made up. This is where the earlier frame errors started to bite as the remaining ply was not so attractive. Still epoxy resin makes most timbers look better. I also sourced some of the solid timber from a stack in the back of the shed. Not the best choice for grain (cranky) as it turned out. I was trying to avoid heading back to the hardware store as the trip involved crossing the state border and my vehicle is registered in a third state - all legit enough but I was trying to avoid unnecessary travel and the foreign plates draw attention. No evidence of enforcement as it turns out.

Nevertheless I wished I had sourced better wood as soon as I tried to shape and trim the beams.

Once the beams were done it was time to join the hulls. The beams seem flimsy at first but the combination of ply and top and bottom stringers of solid wood create one sided "I beams and the back of the beam to frame is a really large glued area. 

In addition, the seat sits on two horizontal stringers which are glued to the inside of the seat cutaway providing further strength longitudinally and latterly as well as increasing the glued surface.

The seat is a little tricky and the designer reminds the builder to leave a plys' thickness below the beams.(room for the seat ply).
I slipped some scrap ply in place (having wrapped it in gladwrap first). The gladwrap stops the scrap from being a permanent fixture.

Once marked the seat is  rough trimmed and returned for gluing (with the help of random weights).

The next stage was to prepare and dry"fit the decks". This tale skips the jiggerypokery involved with the forward bridge fitting which while not as tricky as I had thought, escaped the photography.
I did compromise myself with the deck, as changes to travel restrictions had given me a new time-frame to return to head south. 
That was a problem as each glue step takes at least 24hrs at the moment with autumn temperatures requiring the support of a heater to make sure the glue sets up. 

I skipped a step and did both the bow decks and bridge deck at the same time. Further, that ply mistake meant that I had odd sizes and instead of extending the bridge deck across both hulls I had to give each section its own cover. (smaller pieces). It would have been better to have taken an extra day and glued the middle deck in first which would have allowed it to brace the outer two bow decks.
Doing them all at once required fiddly fitting and meant that with the slope of the sheer and the initial slipperiness of the glue that clamping was also tricky. Lessons learned again!!( a pre midnight check involved extra clamps being applied).

Side trim was added to strengthen the gunnels and aid in transport south where the dinghy could be finished and used!

As it turned out there was no rain through NSW, Vic and down through Tasmania to the home shed but I thought that at least an initial coat of resin would help with rain or general humidity. Squeegee application of the resin is very efficient compared to the brush, so I was able to lay out a good thin sealing coat over the ply before loading onto the van. 

During this initial build I have been able to fit in dog walks, house reno and general maintenance in as well. So much for an escape from the virus shutdown. It has nevertheless been a satisfying level of progress and even though the final product won't be furniture grade, it will be practical working boat standard. 

Progress has been supervised at all times by Rocco:
He may feel the cold but remains vigilant in providing  supervision and moral support.

Note Rocco's efficient use of the non boat side of the heater

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Following a trip down the Hume Highway and an overnight ferry trip, bio-security checks and another 4 hour drive we are home. With no room in the big shed the CatDink has been unceremoniously housed in the woodshed and the sanding begun.

The current build has taken about three weeks and has never been more than half a days work at each step. 

I plan to add some more trim and sand ,sand, sand. There's not a lot that can be said about sanding but at least some progress is being made. A long extension cord, orbital sander, a little spokeshaving and planing and back to the sanding. 

Progress of a kind....