A bunch of frames

Building of pathfinder "Astrid" has finally got underway again. Here's an update on the progress on frames and stem "girder". All such parts have been fitted with the pine doublers for seats, decks and fixing to the boat's floor. This weekend I will glue the outer stem lamination (out of 5mm sipo mahogany lamells) that has been dry fitted to help take the shape.

Frame 6A and transom are the next two that need finishing. The objective is to have all of the frames done before the summer break and then build the strongback in september. I should have some time off in november/december where I hope to plank the whole hull.....

Excuses?? well I have a few!

.... here's another typical post saying "it's been a while since my last post ....blabla.... excuse1 .... excuse2.... etc"

Well in my case the past months have been quite busy with work and family commitments; in addition to that every spare minute of time was devoted to preparing the final two exams for my music degree at the local music conservatory.
With that finally out of the way I spent some time readying my current boat "Janas" for the upcoming sailing season and what better season opener than participating in the Venice lagoon raid for a week among like minded people??

I had a new main and jib cut by Morgan sails  and Janas required a new boom to accommodate the larger mainsail. Ian did a great job and the new sails have performed really well and have been much admired during the raid. Thank you Ian, I will contact you again when I get to the point of ordering the sails for the Pathfinder! I also had to build a new tille (the old one snapped in Sardinia last summer) and give a major overhaul to the home-made inboard engine.

The VeLa raid is a great opportunity to go sailing and explore the Venice lagoon. This year 60 boats took part and more then 150 people shared their passion in a 5 day marathon around the beautiful scenery of the lagoon.
I had a great time meeting people from all over Europe (Italy, France, UK, Holland, Germany, Austria, Romania), some I had met already some became new dear friends. I hope to take part to the next edition (june 2016) sailing my new Pathfinder!

Janas fared well during the 100 mile - plus - long raid and despite being the smallest boat in size taking part, we were not always the last ones to cross the finish line.
Single handing over 5 days on a small boat, handling the shallows, the busy water space, the currents and the lack of sleep made it all in all a very intense week.... definitely something to look forward again to for 2016!

Not a five minute job....

The centercase is finally assembled and glued up.... this is a complex bit of kit and it takes quite some time to get it together.
First I found myself struggling to source the 40x70 hardwood logs... I ended up finding out that a neighbour living a few houses from mine runs a fine supply business for all sort of construction and joinery wood. He cut my logs from some nice sipo  mahogany he had in stock.

The inside of the case is epoxy primed then glassed before a further coat of epoxy is applied. These areas will be exposed to water and potential surface scratching as the board is lifted and lowered.
I also spent quite a bit of time figuring out my lifting mechanism (see previous post). In addition to that, before you can safely go on and seal the box you have to have the centerboard itself made to make sure it fits and swings correctly as intended.

All in all quite a bit of work, but I am pleased with the result.
You can see the slots routed in the forward log that will house my pulley based lifting mechanism. I "scavenged" the 35mm pulleys from some Barton blocks I purchased on eBay.

To support the centerboard pivot I opted for some brass oarlock sockets that are permanently epoxied to the box' sides. They are made to take a 14mm stainless steel pin; I will use two brass plugs with o-rings at each end to seal out the water.

The centerboard is now built as well (see previous posts). Today I drilled a 35mm hole where the pin goes and subsequently filled it with thickened epoxy using a high density additive. I will drill the 14.5mm or 15mm whole for the pin at a later stage.

Next is moving further aft preparing frames 5, 6 6a and the transom.... not too much to do there, just pull out the CNC precut frames and add the doublers (seat supports, etc.) as detailed in the drawings.

P.S. : ... back to the centrercase: there is a slight error in the dimensions qoted in the drawings for the seat and deck supports to be glued each side of the box. I figured out the right ones using the corresponding heights in frames 3, 4, and 5

Centerboard lifting mechanism

I decided to go a different route for the centerboard lifting mechanism. Basically it took us so long to finally have a small sailing boat with a potential fore "sunbathing platform" for my wife and I didn't want to spoil the dream by having taught ropes going across it.
In the original arrangement a 2 or 3 part block system is used to draw lines from the centerboard lifting point to the mast base.

In my version I will rather have pulley wheels fitted to the centerboard lifting point, to inside the forward log of the centerboard case assembly and on the deck at the base of the case itself.

Here's a sketch of the principle idea. The system of ropes is basically doubled up yielding a 4:1 purchase on the lifting effort. The lift line can be fed directly to the cockpit are or to a jammer on the side of the centerboard case.... no ropes fed to the mast step!

Here is how the implementation of the design look in a prototype set up. You can see the pulley wheels in slots routed in the case fore log. Also it should be quite clear how the system will eventually work.
For the moment it seems to be behaving extremely well and I am very pleased!!

Centerboard shaping

As I mentioned in my previous post I was a little worried about how to shape correctly the centerboard stock.
Scouting a bit the boatbuilding forums I came across a very clever idea proposed by Ross Langford and appearing on duckworks magazine pages:
another approach to shaping foils

Great idea I thought right away, and I decided to follow its principle. Ross provides the complete solution including an excel sheet to design the router gig he proposes for the purpose.
For the fun of it I decided to apply the method but to redo the calculation, using 2D cartesian equations rather than trigonometry. I therefore wrote a MATLAB script that computes the foils NACA profile, its offset for the router cutter and finally outputs an AutoCAD script for printing purposes.
I am happy to provide the scripts to anyone interested ... they worked out pretty well!

Here's the model for my pathfinder's centerboard NACA profiler:

which is then used to build the router support:
 

And here we go, with the gig cut and assembled the router comes into (loud) play. The idea as that the router slides over the guide it cuts away the unwanted material from the centerboard stock, to obtained the required NACA profile.

The process is into two phases and mall portions of the centerboard are left unshaped to allow to turn the board around and shape its other face.   

Its great to see the NACA profile appear through the sawdust and the noise of the router.

I have no idea how I could have achieved a precise and constant profile throughout the board otherwise!

The centerboard and its case

I am working on preparing and building the frames moving aft ... next step is the centerboard and its case.
The case doublers, seat and deck supports are now glued and before I can build up the case it is wise to build and give the right shape to the centerboard.
The board is glued from strips or lamells of both hard and softwood. Hardwood (mahogany) is mostly for the leading edge and the pivot area, while softwood (pine) is used elsewhere. While I was at it I also included a couple of hardwood strips in the middle of the lamination to ensure stiffness.

Once glued together, one realises how heavy and thick the stock is!
The profile of the board is so important as it affects the sailing performance of the boat. Not easy therefore to embark on this shaping task given what's at stake.
John Welsford (aka the boat designers) provides a template for the board cross shape. It goes from a 10mm radius circle at the leading edge, to maximum thickness (60mm) at 175mm and then tapers to 5mm thickness at the trailing edge.

First go at some real boatbuilding...

This weekend  our Pathfinder build got into its actual operational phase. Enough fiddling with CAD software, printing templates on paper for checking, assembling scaled models, ... etc...
Hand over the epoxy and lets start putting together the parts we got just before the summer from the CNC cutting shop.
I decided to prepare each component of the boat frames from bow to transom. First on the list was therefore the stem profile, followed by frame 1, frame 2 etc..
At this stage I am glueing doublers and floor supports.

I could not resist and had a go at dry assembly the fore section of the boat. The notches I included in the cutting templates allow to place the frames precisley on the stem profile.
In these pictures is the progress over just a weekend. In the background hanging on the garage wall is the floor planks and their puzzle joints .