Paul Gartside 18' Racing Gaff Cutter • Cabinversion designed by Dominik Gschwind


Week 3/4 - Backbonebevels / Lining off / Stripplanking

Week 3 was all about fitting the backbonestructure on the moldes to be ready to start planking.
In the aft end of the boat we had to chisel a curved rabbet from the keel up the bilge along the deadwood all the way to the new drilled hole for the ruddershaft.

As visible on the photo to the right we use the technique of chiseling pockets which allows to see the marked lines from the lofting until the end and makes sure the very much changing angles of the later to be glued on plankingstrips will be as accurate as possible.

Along the hog and inner stem we only had to bevel the edges instead of working with a rabbet.
To get the most of the material off relatively effective we used a drawknive an then planed the fine adjusted bevel with the blockplane and the flat spokeshave.

Finally we glued the transom on the sternpost and from that moment on the whole backbone was ready to receive the planking.

There is a very important step before starting with the stripplanking which is called "lining off". It means that you take fibreglassbattens or ideally plankingstrips and lay them along the whole length over the moldes and check if the shape of them is fair all over and in every position on the moldes.
To be honest we realized actually when lining off that there where some inaccuracies on som moldes. So the only way was to unscrew all the moldes.... take them back each separately on the loftingboards and check where the problem comes from.

We found out that the bodylines where all very accurate but the moldes centrelines haven't been exact enough. Well, after setting up all the adjusted moldes back on the basebox we got very nice lines all over... good learning experience to be honest!

So... another milestone > start with stripplanking!
Because of Glóey's pronounced curves it was really important to find a good position to start glueing the first cedarstrips on. The deal is that the strips should sit as relaxed as possible along the whole length. At that moment we still can't say if we will manage to plank the whole hull with parallel strips or if we have to make a cut at a certain position and then go on planking in a slightly different angle.

On the photo beside you can see that we started somewhere in the middle with the strips setup more or less along a diagonalline.

The cedarstrips are glued with the cove-side up on each other and on to the transom and innerstem (further up on to the hog) with a tixotropic PU-adhesive (gel).
That stuff sets in about 10 min. and allows a quite a effective planking workflow.

To avoid the strips beeing glued on the moldes we taped the edges with the brown releasetape. So the strips will only temporarely be fixed with screws and washers to the edges of the moldes.

As can be seen on the following pictures the strips are also clamped together along the unsupported parts from molde to molde with either tape or mostly with staples and hardboardpieces. As a non-gap-filling glue PU needs to be applied with clampingpressure!

The cedarstrips have very different colors. We tried to alter between light and dark to get a nice pattern for the later to be bright varnished inside of the hull.

Another interesting detail are the scarfs which had to be done to extend the strips to the needed length. As visible on the photo they appear every second strip,... actually on every strip but we alter the position like one at the bow ... one at the aft ... and so on. They are cut with a 1:6 ratio referring to Lloyds standards.

Stripplanking is a relatively fast method to build a hull but there are high stresses and tensions in the glued strips and therefore it is absolutely important to stabilize them by either sheating with fibre glass and epoxy or by coldmolding 2 layers of veneer over the strips. We have decided to choose the sheating technique on both sides with biaxial cloth. But this will be subject of one of my next posts.
We ended week 4 with about halv the hull planked as shown on the last photo and with a beer in the Royal Standard of course.


Week 2 - Backbone / Hullstrips

The second week started with the machining work for the hullmaterial.
As mentioned earlier the hull will be stripplanked with western red cedar. The thickness will be 5/8 " (16mm) and then both inside and outside sheated with fibreglass cloth and epoxy. So the cedar is actually the core of a composite sandwich construction.
This method is a relatively modern one which allows a very fast built in a light and very stiff construction. Beside those advantages stripplanking also is a method of quite economic use of ressources meaning that the wastematerial is much less compared to traditional wooden hulls with massive planks.
We machined the heavy pieces of stockmaterial all the way down to strips of 1" x 5/8 " (25 x 16mm) and then routed bead and cove ends on them. As visible on the lower picture in the photo the strips then fit in to each other as males and females. The dimensions of strips in stripplanking will ideally be chosen depending on size and shape of the boat. Glóey is a very "curvy" lady specially along the bilge in the aft and we decided therefor to use a relatively narrow stripstructure.
The western red cedar emittes a very nice smell which reminds one being in a north american forest. But nevertheless the dust when machining is toxic and a dustmask should be used.
The strips will now be stored on the floor inside the mainworkshop until starting planking next week so that they can go on drying until reaching a perfect moisturecontent.

Parallel to the machining we started glueing heavy pieces of sapeele mahogany used as deadwood in the aft end of the keel.
The same for the innerkeel called the hog.
This one also already got a slot for the later coming centreboard.
Because of the length of over 4 m the hog had to be build of featherscarf extended boards.
It takes quite some time to shape all elements mainly with different types of planes and the use of chalk to fit them really tight without voids together.

These used timbers are all hardwoods and it's absolutely essential to hone the cutters of every used tool to the max.

After fitting the deadwood, hog, sternpost and apron we glued all together and finally got the backbonestructure as one long piece.