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

 

River Dart - Totnes to Dartmouth trip

Tied up at the pontoon where we enjoy our coffee and sandwiches

The boating party

Approaching Dartmouth the yachts get bigger and new marinas appear

Dittisham where we spot Rocket the Dimbleby Yacht of the popular T/V adventure series

Keeping strictly to the 6 knot speed limit

The upper reaches approaching Totnes and the quiet Honda outboard helps keep our intrusion minimal on the peaceful scenary.

Woody Runabout - Sea Trial

 With two well built crew this little craft performs beyond expectations with it's 20 hp Honda outboard (4 stroke).

The youtube video here was taken in Labrador Bay, South Devon where there are a several cruise liners anchored with zero passengers and nowhere to go.

The sea state was only slightly choppy and with a gentle ground swell. The wind was light and the run shows us about two miles offshore, between The Ness and The Oar Stone. Just around the headland is Torbay, Torquay and Brixham.

Woody Runabout Pase 23 & Launch Time

"Hurry slowly" has to be the mantra towards achieving the result wanted at this late stage and the varnishing of oil based over epoxy resin. Application onto a surface of epoxy that still shed an amine bloom after three days of rubbing down and washing. The result was a coat that wrinkled and failed to dry properly. Like toffee, it was scraped off and sanded with wet and dry, then allowed to dry for several more days before another coat of varnish was applied and ft to sufficiently dry for work to continue as normal.  The interesting thing was the fact that the bow section of deck was not so severely affected, due to the fact that it had sun dried beneath the garage skylights.
Even at this late stage I am finding items that require attention. The heavy duty battery wiring had to be soldered for more durable connections, The floor needed a further coat of yacht enamel to obliterate some messy touching up and scuffs. The rubber grommets for the remotes had to be secured with sikaflex adhesive (rubbery and very sticky to apply). The "tennis racquet" seats secured more rigidly with cable ties onto the bench seat support.
The trailer is made ready with side rails - additional support alongside the rollers, and adjusted to conform more closely to the hull shape.

The motor  is checked over and the wiring is good to go. The fair weather weekend gives the moment for launching. I am awake at 4am and like a kid at Christmas about to creep downstairs to see what Santa has left !

The old car battery chose to give up the ghost, so an early morning trip to Mole Valley Farmers store gets me a new one (as backup). By 10.30am William and me are afloat on the Teign Estuary with grins from ear to ear. Not too much throttle, gently with the steering and heading west upstream into the warm westerly breeze.
At Coombe Cellars we turned to head back under the Shaldon Bridge and return to the harbour. Busy with summer traffic. We head out through the mouth of the estuary on the ebb tide at a rate of knots. The choppy bar is crossed without hesitation and the Bass are jumping by the Ness and we head on into Labrador bay.

Impressed by the quiet exhaust note and the ample power available at half throttle. The running in period is strictly adhered to, though the temptation to push forward is ever present. Briefly we opened up the throttle a little and she gradually rises up onto the plane. Into the turns the ride is quite flat, hardly any bank as the deep spray rails do what they are supposed to do - of keeping the craft on rails.

The buoyancy / stability is excellent, as I lean out over the gunnel there is only minimal roll. My worries over the degree of rocker I had used were quite unfounded, since there is no tendency to porpoise when the rise up onto the plane remains perfectly level. Apologies for not having images to show just yet. Too much excitement to bother with the camera, but they will follow shortly now this brief shakedown is done with.

Altogether I can say I am tickled pink with my design.

Ready for the road

Ready for the water

Ready to go !

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 21

Tired of waiting for my local wood supplier to dig out some Sycamore I chose to look further afield. Within easy reach (45 miles up the A303) I discovered Yandles wood merchants (Link) tool shop and craft centre. Not only was their self selection department open, the variety of woods is amazing and the prices significantly lower than I have been used to paying in Exeter.

I came away having spent more cash than I needed to complete the boat. Some too good to overlook that will come in handy for later projects. The Sycamore plank freshly cut from the tree is complete with waney edges. The creamy white texture is easily worked and will soon take on a golden honey colour, once varnished and exposed to the light.

The gunnels are in place, plugged with dowels into the holes that were the ones made by screwing temporary fixings, while the epoxy glue set. The epoxy was thickened to make it adhere better to the vertical surfaces. Also attended to is the motor well edges that have the lovely white contrasting wood enhance the appearance of this design.  A cosmetic indulgence to spend so much time at this stage.
The  35 fixing dowels/plugs whittled down individually and laborious but satisfying.

Now using Abranet, an open abrasive fabric that does not clog like sandpaper does.  I do recommend  it to any woodworker. Also recommended is diamond abrasive sharpening stones that put a keen edge on steel with the minimum of effort.

On the to do list :....  fit windscreen and cleats (after the deck is varnished) . Box in the batteries and switch gear. Run control cables through rear bulkhead. Fit seal to base of motor well.  Fabricate and fit front seat backrests. Fit support rails to road trailer. 

Grey tinted screen dry fitted to be supported each side by an additional pair of knees

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 stage 14

 Pressing on with the topside. The deck layout can be seen in the rough stages of fitting the carlins and deck beams. The cut out transom with very little freeboard, but relieved by the fitting of an inner transom and outboard well in between the two.
I have settled for the idea of having a false floor of 5mm ply;  easier to bale out and may even be self baling if the waterline is not too high.

The inner transom will be faced with ply infil tp provide a flotation chamber and motor well

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.