Tuesday 13 August 2019

Conduits And Limber Holes

Now that bulkhead 7 was complete it was time to make sure the conduits and limber holes in the floors and bulkheads were clear. They were all blocked with fibreglass cloth and epoxy resin when the hull bottom was 'glassed out.

The holes for the conduits are in the starboard side of the floors to run cables for the electrics, if  I decide to fit any.

And the limber holes are in the bottom of all the floors and bulkheads 2 and 7, to allow water to drain between compartments for drying out the bilge.

I cut away the 'glass cloth in the conduits with a craft knife, but all the limber holes were solidly blocked with cloth and resin. 

Something powerful but delicate, and capable of getting into small cavities on the hull bottom was required.

So I used a Dremel 4300 corded rotating multi tool, borrowed from my son.

Like the Japanese saw in the previous post, it was a revelation in terms of effectiveness and efficiency. I wish I had discovered it earlier. It would have been useful in shaping the smaller fillets.

Fitted with a flexible drive extension and a 9.5 mm diameter conical grinding bit it made short work of the blockages, and produced a smooth and clean surface in the limber holes. I ran it at 2000 RPM, which is plenty and allows easier control of the bit.

This is the grinding bit.

Here is the Dremel being used to clean out the limber hole in the bottom of bulkhead 2.

The flexible drive and the slim chuck holder make it easy to work in very tight spaces.

And here it is being used to clean out the limber holes in bulkhead 7, which were solidly blocked. It took no time at all.

The conduits were easily cleaned out with a roll of sand paper.

I had been concerned that this might be a difficult task, but thanks to the Dremel it was easy - and good fun. Thanks Nick!

Bulkhead 7

While waiting for the second coat of resin to cure on the bottom panels inside the hull, I removed the cut-out sections of bulkhead 7. They are there to provide strength and stiffness to the bulkhead while the hull is being constructed. Without them the flimsy partition would inevitably get damaged.

I acquired a Japanese saw some weeks ago with this activity in mind. I had always wanted one, having seen a lot of builders use them. Mine came with two blades - rip and cross cut. This is it with the cross cut blade fitted, ready to cut the tabs in the bulkhead.

 Here is bulkhead 7 before I cut out the removable sections.

I removed the port side first, as here.

The saw cuts on the pull stroke, which takes a few minutes to get used to but is extremely effective. It is also incredibly sharp, as I discovered to my cost within seconds of cutting the first tab when the saw jumped and hit my carelessly placed hand and drew blood ...

And here is the starboard side removed.

Finally I tidied up the tabs and rough epoxy, sanding all smooth, as here.

And that was bulkhead 7 all done!

I was very impressed with the Japanese saw. I used it to cut halving joints on another small project, and it produces clean, smooth, accurate cuts which need minimal paring with a chisel to finish the joint. I won't be using my tenon saw any more!

Wednesday 7 August 2019

Yet More Work On The Centre Board

While I was applying more clear epoxy to the hull interior, I did the same to the centre board.

First I started to sand the fibreglass strip which I had applied over the leading edge of the board. To my dismay the resin had not cured and the 'glass strip had not bonded to the first layer of 'glass underneath. I have no idea why - the strip was applied weeks before and it had plenty of time to cure in a warm workshop.

Anyway, I simply scraped it all off with the Bahco scraper. It came off easily, in soft sticky white strips. Very strange.

I then sanded the board on both sides to a smooth, matt finish and gave it a third and final coat of clear epoxy. Here it is, cured and shiny.

I decided that the additional strip of 'glass was in any case unnecessary since I had gone to the trouble of adding epoxy armour to the leading and trailing edges.

The next job is to sand the board to its final finish, which I will do when I am sanding the hull interior. Again.

Second Coat Of Epoxy On The Bottom Of The Hull

With the hull's interior bottom and chines sanded ready for the next coat of clear epoxy, I got out the resin kit and started work with a 4" roller.

First I applied some 'band aid' fibreglass patches where I thought the bottom needed a bit more reinforcement.

The biggest was the overlap on the aft port side of bulkhead 2, where I had made a mess of the original and had previously ground off the rough 'glass ready for a patch. There were three or four other very small patches which may not have been important, but now I knew that the whole hull was fully covered inside with fibreglass cloth.

Here you can see the overlap onto bulkhead 2, and a patch where there was a small gap at the top of floor 3.

Then I cut and fitted some heavy duty 9 ounce 4" fibreglass tape to the inside of the stem and the chines in the bow compartment, wetting them out and applying a second coat of epoxy at the same time. As here.

After that I worked my way from the stern to the bow to apply a second coat to the transom and each bay until complete.

Here is bay 9.

And here is bay 8.

And finally by way of an example is bay 2.

Contrary to the opinion of some others I find that I am able to apply a thin, even coat with a roller. The cured surface is in any case sanded to a flat finish before the next coat. I will use a plastic squeegee to apply the third and final coat, to make sure it is super thin and even, ready for a paint finish.

Sanding Inside The Hull

I have read many times that building PocketShip is 90% sanding, and sometimes it really does feel like that.

So before I started the rather large task of sanding the first coat of epoxy on the recently applied fibreglass in the bottom of the hull, I had a serious think about how to do it efficiently.

There a quite a few tight places in the hull which are difficult to get to, such as around the floors.

I suspected that the Festool Rotex 90 would be too big and clumsy to do the job. It seemed to me that a small, cordless detail sander would be very useful.

Research, however, failed to find anything suitable. The detail sanders were all aimed at the occasional DIY user. They all had the same size pad as the 90; none of them had effective dust capture; and the grits for all of them were expensive and not easy to source in bulk.

So I abandoned that idea and went ahead with the Festool. It worked just fine!

The geared rotary sanding mode was ideal for aggressively feathering the edges of the fibreglass and roughing the surface, and the delta attachment was ideal for getting into awkward corners and doing the faces of the floors, bulkheads and the centre board case.

Here is the sander.

As mentioned in a previous post there are nine bays in the bottom of the hull, each with a port and a starboard panel. Each would receive two more coats of clear epoxy, sanded after each coat. It would be really easy to forget the status of each panel, so I drew up a spreadsheet when I 'glassed out the hull, to keep track. Like this.

This proved invaluable. There are still two more coats to apply and sand at this stage.

As an example of what they looked like afterwards here is bay 9, feather edged and sanded to a matt finish ready for the next coat.

And here is bay 8, starboard panel.

Note that there is now no unsightly raised edge on the fibreglass. It will look great when finished!

It took a total of 19 hours to sand all of the bottom interior and chines.

Summer Recess | Workshop Improvements

I had a long break from boat building over the recent six or seven weeks, during which I did the sort of things that people normally do in the summer. 

You know. Spending time with friends and family. Going on vacation. Sorting out things around the house and garden. Nothing whatever to do with boats.

I did make a few improvements to the working environment though, on return from holiday.

Some time previously I finally got fed up with using the dust extractor as a vacuum cleaner, which meant disconnecting the sander and fitting a nozzle to clean up the mess, and then refitting the sander. It wastes a lot of time and it's not really what the dust extractor is for anyway. The next big job is to sand the fibreglass in the interior of the hull, in preparation for a second coat of clear epoxy, and anything that could make that less onerous would be very welcome.

So I 'borrowed' an apparently unemployed vacuum cleaner from the house. Here it is, looking quite pleased with itself.

It was immediately useful and looks like a permanent fixture.

Sanding the interior also entails a lot of leaning over into the boat to reach the bottom panels, which often means standing on a stool or a work step. Early in the build I had the step slide away from underneath me a few times, slipping across the floor and dumping me into the boat, so I used a non-slip barrier mat to keep it safely in place.

So now I obtained several more mats and placed them around the boat, so it's easier to move around without dragging a mat along with the step. Here they are.

The workshop was clean, tidy, and ready for the next big job. More sanding. Can't wait.