Learning CAD for boat design

From little acorns big trees grow. As a relative newcomer to the CAD scene, I began with a particular boat in mind. An upgrade project to follow on from the wooden runabout I already made during the first pandemic lock down. The idea had already formed by December 2019 and stemmed from a couple of pencil sketches and a small solid scale model. 

Now I need to elaborate on an upgrade with cleaner lines and a more speedy little boat that may also be build in my small garage.

Sketches may be drawn to very precise scale, formed into solid components and rendered to provide a quite realistic impression.  Also useful is the facility to view in-depth from a variety of perspectives

Not difficult to find drawing programmes for the laptop,  which vary in complexity from the simplistic to the baffling and complex. At the upper end of the scale some are available to the student or sole user-hobbyist for free, and I opted for Fusion360. It has an educational version ideal for the sketching of a small boat. The program incorporates guidance for the beginner which is useful and I found Youtube videos very helpful as well -  a few by boat builders, others by professional designers

Spray rails and a 17deg deadrise enable early planing

Sophia 11 :     Note the forward canted windscreen

 

Woody Runabout Phase 22

Now confident of getting waterborne in early August.

Linking the control lines through the rear bulkhead, attaching the windscreen and cleats, then a couple more coats of varnishing to do. 

Having set myself many little design features and cosmetic titivation's on this classic style small boat project,  the road to completion has taken many more hours than originally anticipated. The windscreen has four brackets that each required  individual fashioning and fitting with associated under-deck strengthening points for their attachment. The screen is detachable for the eventual maintenance of the hull, when she will have to be turned over.

The seat backs are laminated out of Ash and tennis racket shape,  strung ready for fixing to the bench seat. So the finished result will be quite unique.  A flight of fancy, where the design has evolved en-route.

The decks are surfaced in clear Epoxy Resin ready for topping off and finishing with  Epiphanes varnish. A real buzz reward to enjoy after the 800 hour project begun in January.

The road trailer will require some adjustment, together with the addition of support rails alongside the roller supports.

Almost ready for the water

Two or three more coats of varnish but no more than five

Waterline beam width should give ample stability

The seats are ultra lightweight but quite strong

Woody Runabout phase 16

One of several mistakes made during construction (yet to be rectified) was the inadvertent use of a waxy sanding sealer on the side panels. The adhesion is poor and I shall probably have to re varnish. The lesson: ALWAYS READ THE LABEL. I  discovered the error when using gaffa tape to hold a few slivers of wood where the frames meet the gunnels. On removal of the tape a patch of bare wood was revealed minus the varnish!   I intend leaving the job until autumn.  The wax base will need to be removed with a solvent and vigorous sanding.

The floor  is laid and incorporates sealed flotation chambers between the frames, now being painted before completion of the decking, fore-deck and transom decking.  The outboard unavailable till June because of the Covid-19 epidemic, as is the interruption to wood supplies which threatens to slow up progress.

In advance of decking, there have been fixing points for cleats added, and also fixing points for screw down straps that will secure the fuel tank and battery. Remote controls for the outboard run either side down the gunnels, and I am pondering the idea of inserting some PvC pipework to contain it, so as to make insertion and removal simpler to do. Putting such ideas down helps in the decision making and yes, I think I need ponder no more, just do it!

Unexpected problems always arise in scratch built projects such as this, and solving them becomes part of the enjoyment of brain teasing, burning of the midnight oil. One of them is how best to arrange the seating. Two seats, three or four, and should the rear one(s) face forward, sideways or rearwards, The best solution I am presently considering is to have the rear pair of seats facing inwards, facing each other so that weight would then be into the centre and away from the stern. So far, only one of the seat backs has been fabricated, in the form of an an ellipsoid hoop that I intend to make fold forwards. Laced with supportive Dyneema paracord. Sounds like one of granddad's lash up bodges, or it might just be some artistic licence and definitely unique. 

Woody Runabout Phase 12

15th April and well under way with veneering the side panels with Mahogany - more like paper hanging than woodworking - done with the help of a razor plane and scalpel,  glueing on the ply with Instant impact adhesive. No second chances to adjust fit.
I shall be sealing with Luberon Sanding Sealer prior to applying varnish. Turning right side up will hopefully take place towards the end of this month (April).

Veneered starboard side panel

Port side veneer almost completed

Silky smooth finish ready to be sanding sealed

Transom now cut down for outboard with fifteen inch depth

Varnishing should take about ten days before turning right side up

WoodyRunabout Phase 11

3rd April sees me preparing the underside for painting an Ivory colour and ready to veneer the side panels with Mahogany, prior to laying on Epiphanes varnish.
The gunnels are fitted ,but will require additional layers once the woodshop re-opens.
The gunnels are glued and pegged with bamboo pins, avoiding screws in all but high stress areas, such as the prow and transom. I shall use screws for fixing the thwarts and dashboard because these need to be removable. 

Transom marked for the  cutout in way of the outboard motor.

Bottom panels prepared with Pre-Coat white base

Gunnels glued and pegged in position

Spray rails and keel ready for the plastic keel bands

Woody Phase 10 & design process !

Nearing the stage of turning right side up but potentially delaying due to limited access to woodshop and certain other materials during pandemic lockdown. ..

The skinning of the bottom and side panels is now virtually complete. I have to glue on the transom outer ply facing and will be ready to begin surface finishing and painting the underside. The side panels may be clad in Mahogany veneer but still undecided upon which glue and method of application to use. 

Almost ready to turn right side up

Transom ready for the outer skin of 5mm ply.

Sketch shows side tank flotation chambers but this feature will be omitted in favour of a false floor cockpit which should be self draining

Lightweight seating to be steam bent, laced frames, mounted  on cussion pads.

Doodle sketches

1/8th scale model shows outboard moter well, in front of the transom.

Underside shows chine, but the mould stations have been erased at this point.

Cockpit space open to variation but intention is to add two thwarts for mounting the seats onto. False floor not shown here.

Shaping up the Cold Moulded hull

Phew !  At last I begin to see something worth the effort. Its wooden and coming together. Staples have been removed and a light sanding given, the shape is slowly emerging of some sort of craft. The outside gunnel strip added,  previously steam bent and spliced together out of two lengths of Oak and now glued in place. It will add stiffness as the hull is turned over - right side up.
As  I  begin to lay lay down the ply strips on the port side the benefit of re-reading the John Leather book on the subject of cold moulding becomes more apparant.
Much better to cut the ply strips in batches and prepare a dozen or more together then fit them in a session so that constant switching of tools is reduced.
The weight upon the mobile jig is becoming more noticable as one of the caster wheels has shed its rubber tyre and had to be helped by a lash up support alongside and formed with the use of a skateboard.

The coloured mould strips are simply adorned with insulating tape to prevent glue attaching the ply to the mould and making it difficult to lift off the hull. I shall need help at that stage.

Alternate strips of  3mm ply being laid - the first of three layers on the port side

How to build a Dinghy in Cold Moulded Ply.

From the lines of this classic dinghy I have modified myself a rowing and pottering boat for general purpose use capable of being powered by a small outboard (The best outboard for the world and known as the Seagull Plus).
A 1/8th scale half mould was made and sectioned off so that I could make the eight full scale moulds that need to be mounted on a mobile horse in the confined garage space available.
As of the 8th of February I am at the stage of mounting the moulds onto the horse/jig. In order to ensure all is correctly alligned I shall be using spirit level, set square, sight lines and making many adjustments until I am satisfied that the dinghy will be fair in shape from all angles.
14th March and the mould is being built up. The stem, hog, keel and transom are joined together and in place.
17th March and the slats are being added to the mould.
Once the entire mould is covered and faired smooth and rounded, the surface will be sheathed in 1.5mm marine ply laid diagonally in strips two inches wide. Each strip will be stapled in place temporarily and the second and third layers added (glued in place) withdrawing the staples  in the immediate underlayer as the work progresses.
28th March and almost ready to begin laying the ply. Took delivery of ply but the wrong thickness, so the idea of  using 1.5mm changed to using 3mm ply in three layers instead of the intended four layers of 1.5mm ... Fortunately my supplier had a special offer and resultant cost is substantially less.
5th April and I am laying on the 2" wide strips of ply. Because the edges don't lay parallel (due to the compound curvature hull shape) a gap is left to be later filled by a second tranch of alternate strips. Each of these will need to be spiled to fit using a marking gauge.  

11th April and one side covered with the first of three layers of ply. So 1/6th of the way along a road which is probably going to take a month before the hull may be released from the mould.

Half model at 1/8th scale

Scaled up paper patterns from which the full-size moulds are taken

The moulds mounted on a mobile horse/jig

Level and trued up

Ribbands follow the mould shape

Viewed from inside

Transom keel and stem glued together with cascamite resin. The pine slats are to be planed fair to remove as many high spots as possible

Mould (plug) ready for the ply strips but require polythene film interlayer to prevent layup sticking to the slats

The first layer of 2" 3mm ply strips  laid with a gap between - just the bow remains with three to go.

The mobile jig is supported on six castor wheels

Shaping up slowly - Hopefully I shall speed up once the routine is mastered

The 14mm staples just about hold the ply down, but go deep into the layer beneath and can break on removal. I may well find that lifting off from the plug will be tricky. The solution may require remove of the plug in sections from below.  I will try using shorter staples later today.