Boatshop Timber Rack

I had been awaiting a delivery of 10 sheets of 4mm genuine Bruynzeel Hectout Gaboon/Okume plywood. With the close down of Bruynzeel local distribution a couple of years ago, this has to be specially imported. After some research I found the only source for this was through Andrew Denman of Denman Marine in Tasmania. I had to wait about 3 months for Andrew to restock his supplies and my order arrived earlier than expected last week.  This made for a frantic construction of the A frame storage rack I had intended to build to fit this in my tiny boatshop (no space for the better horizontal stacking).  Anyway after a frantic day of construction and emptying out the boatshop I got it done and the ply unpacked and stacked - I'll finesse the clamping flat a bit further. Here's a pic 

The pic makes it look skew but believe me the rack is inline. I built in two shelves in the middle of the A frame which might be useful for stacking timber and various boat parts components. Also note 3 sets of wheels (two with brakes on)  to move it around the boat shop as necessary - gotta watch it doesn't get away from me with a slight gradient already in the boatshop and downhill driveway beyond. I'll be adding a mooring line to the back of the rack tethered to a cleat back there somewhere.  

Model - Plank Patterns & Stern Extension

Looking at a model from different directions gets you thinking whether your comfortable with the proportions of the boat. I already had a few thoughts yet to be settled re mast position and cabin size but the main thought on looking at the model is the stern looked chopped off too soon. Also the anticipated waterline being 3 inches higher gave part of the transom buried in the water. From my dinghy racing days I learned of the speed drop from dragging the back of the boat in the water. So I decided to extend the transom back 9 inches which should see its bottom just clear of the waterline and a bit of extra design length to fiddle with cabin shape and centreboard case positioning.  Here's the result of the change.

Now it's time to get the planking process underway.  The plan is to make cutting template patterns for the planks from thin light ply, then use these templates to cut one set of planking stock patterns (with generous trimming margin according to these templates), which will be then fitted and trimmed to perfect fit as the final version of patterns in stock thickness.  I am hoping these will be useful for the full size build (blown up 5 times) as templates for scarfing up stock for each plank pretty close to full size fit.

For the template patterns I am using 1mm Finish beech 'aircraft' plywood.  It's a bit expensive but I had some left over just enough to do do a full set of templates. It's light to handle and can be cut with a knife.

Here's some pics of the process of holding up the sheet to the model and progressively marking out and cutting the templates.  I hope to be able to remove most of the screws holding the ribands and glue these on and smooth the whole mould shape before I trim and dry fit final patterns from planking stock (this will be  2.7mm standard ply - 5 times this is a bit thicker than the 9mm ply I intend to use on the final boat but probably has more representative stiffness for the model than the thinner beech ply being used for templates).  Re the ribands I have been reminded  of the Tom Hill method which is to trim moulds by riband thickness and thus not have to rebate.  This gives more freedom to align them before fixing and no need to flatten moulds in between plank landings - I'll definitely be doing this on the final boat. 

 

Quite a stretch on available small clamps to be able to clamp the sheet and templates while they are fitted because of small gaps between ribands. Also had barely enough room to get my hand in under the jig to mark the sheet from underneath the ribands. By having most key points marked I was able to use a fairing batten to get the full template pretty close.

 It's good to mark each plank as you go for plank name, station positions and orientation.

 Leave trimming off both ends until the final planks are glued on the backbone - it's a bit of a disaster if you cut these off too short too early.  The forward overhang at the stem is referred to as "hoodends".  I got five plank templates out today - hopefully will finish the rest tomorrow.

Model - Ribands On

I decided to rebate the moulds to fit ribands to the markings for plank edges. I figure working on my own this will make fitting the planking easier on the full size boat. Whilst Iain Oughtred's book does not encourage this he is Ok with it if you fair the ribands right up to the stem.  Here's the moulds below rebated to take the ribands.

I made another shop-made tool to help hacking out slots in the molds to get the ribands to sit in line with the mould edge as they twist along the hull.  It's manual jig saw - cut the shape of the top of the blade into a flat piece of brass, then added two other flat peices either side, plus mahogony handles and through bolts and voila - a hand made hand jig saw - a jigamething.

And after a lot of fiddling and a few broken ribands we have something starting to look like a boat.

Model - Lining Off Lessons

The Mould coordinates came from my modelling process using DelftShip (CAD software covered in an earlier post). I started with Iain Oughtred's standard full scale mould plan drawings to get 3D coordinates for the Sheer line and outer edge of plank marks. These were then adjusted allowing for the "wedge insert" to expand the hull width and the raising of sheer line. Using Delfship I then faired lines and adjusted the initial station points to get something looking good for body and plan view lines. One further change I made was to pull out the tumblehome in the sheer at the transom. This was partly to provide a bit more width to play with the framing to support twin rudders and centered outboard.

So it was going to be interesting to see how all this translated to a real 3D view of the boat in the form of the moulds. Well it soon became pretty clear to me that the plank lands emerging from this modelling work were not going to give an even and pleasing view of planking. I think the mould shapes are pretty much OK but the positioning of the plank lands needs to be done from scratch. Of course in a full size build we would be sorting out the plank land markings on the moulds before we assemble them on the building jig. But I am not too worried about this, it's all part of lessons along the way. So I rig up a small ribbon tape measure to remark all the plank lands using Iain Oughtred's well thought out method in his Book Chapter 3 - Lining Off. He even has his percentages there for Fulmar which also helps. One good tip - for good visuals of plank lines offset the width of the gunnel before applying the percentages to the girth of each mould.  Here's a pic of the measuring off of new plank lands on the jig. 

In the pic below you can see how the marks have changed from the original markings. You might also note the stem looks pretty rough and I have a bit more to do on this with the help of fairing battens.

The next challenge will be to get the lands marked for the stem and I will need to fit all the battens (with small brass pins this time) to get this sorted. Before doing so I have tried a sheerline, plank 3 and garboard clamp-fitted, to see whether I like the plank lines developing from the new markings and I think so far they look pretty good.

I'm using 6mm square oak battens plus the wider one on the sheer which is sitka spruce. I won't be leaving the battens on for planking - to do so I would need to trim all the moulds (or rebate them) by the batten thickness for this to work.  I have another plan for how to mark out the plank patterns - more later on this.

Model - Building Jig and Mould setup

Here's a view of my Model building jig with moulds set up and lining off testing in process. (it's not a great background for the pic but you will get a better view in posts on the lining off process).

I cut the moulds out of uniform rectangular shaped 6mm marine ply - it was pretty cheap stuff from the hardware store but had a nice smooth facing which was great for drawing on. By using the uniform rectangular pieces I now have two sets of moulds - Male and Female. I will be using the Male Moulds for the sheer and lining off checking process.  The Female Moulds might be useful later (once I have final patterns for planking) to use trimmed edge versions of these to fill in the Female moulds (i.e like a stitch and glue process). This would give me a clean internal version of the hull to model the internals (some insurance against me stuffing up the Male mould version when I try to pull the moulds out of the planking). I read about the female mould approach to modelling in an article by Danny Greene in Wooden Boat Magazine last year.

Anyway here's a view of the building jig with moulds set up and stem, keelson and transom in place. The jig sits on a solid melomine faced piece of chipboard. I've got snap hook sling at each end so I can hang it up in the boatshed.  The stem and keelson have been a bit of a learning process - more on that later.  

Shop Made Tools and Jigs

The books on wooden boat building talk off shop made tools and jigs.  John Brooks book in particular has some good inspirations on this and it does add to the fun. I made what you might call a "shop made tool" to help cut more accurate molds for my model. It's not totally original (you will find similar in forums) but I've added a neat vacuum dust sucker and workbench holding base. It's a upside down mounted jig saw (I used a spare one I have which is an AEG PST 500X) which you might call DIY band saw - lets call it a bandicoot - good Aussie marsupial.

The jigsaw base is level with the 9mm ply platform and the saw is held in by an aluminium bar I made to fit the guide holder slot. The length of platform was set so that I can have a full go at the length of cuts needed for my 1/5th model moulds. Now I thought I should add a protective cover over the naked blade so I had some quad aluminium sections and plastic joining connectors to do this. But as an added bonus I decided since the quad and connectors were hollow, why don't I connect my shop vac to the end of the tubing and voila! -  no dust to obscure lining up the cutting blade and mould curves and no dust falling into the saw motor.  A further twist I added to the design is the narrow base (a piece of 90x45mm hardwood which I clamp in my bench vice which gives the platform juts at the right height for operation - so no extra machine stand required.  The pic below is not that great but hope you get the gist of it from the description.  Cutting the moulds was a breeze!

A jig I have made for holding battens to test planking shapes uses brass screw in L brackets you find in amongst picture hanging stuff at the hardware store. I screw them into small pine blocks which I can then clamp firmly onto the moulds with small spring clamps. The 6mm ply moulds are pretty thin to be renailing in battens to see what the planking positions and sheerline looks like. So clamping these little fellers on doesn't preclude making changes to positions (just what I ended of having to do as you will read in the next post). Some pic below.  

Model - Lofting

Most boat building books emphasize the importance of "lofting" - so named as that mystical art which the "loftmen" did upstairs in the "loft" above the boat yard. It is recommended to do full size lofting before starting the build. Whilts Defltship has been very useful, I decided to do proper lofting of the 1/5th model of Skye Maid.  I want my model building to get me in the rhythm of all boat building steps.

Pic Below: Using Sitka Spruce batten with nails and small spring clamps to check for a fair curve of plank edges, I'm using some realtively ceap 6mm hardwood faced marine ply from Bunnings - it has a very smooth facing and great for drawing accurate lines in pen and pencil.  I use biros from permanent markings.
 

 Pic Below: Finished adjusted profiles of planking - plan and profile view.  I only did the top section in profile view as this was the main area where I had to vary Iain Oughtred's mould marks given the changes made to beam and sheer line (covered in an earlier blog post).

   The lofting exercise sure brings home how accurate you need to be in transferring plan specs to a build.  Tom Hill says the eye can pick a 1/16th variation in a curve from a fair line.