Monday, 7 April 2014

Board Building Project - HD Creeper 48 - Stage 3 - Shaping the Deck

I am not one to rip into full length cuts using a plane, I prefer to mark out the rails and hotwire them. I like to create the hotwire guide lines from the CAD model and these allow you to remove the bulk of the deck roll and rail while maintaining a smooth flowing shape.  The faceted faces on the rail are then fine tuned with a sanding block with 80, then blended/rounded using 80 and then 120 grit. 

If you try to shape only sections of the rail to the finished profile you will end up in all sorts of trouble and it will show on the finished board - there will be really bumpy highlights and reflections.  I like to create construction geometry around the rail profile at various intervals along the length of the board.  Then I create some tangent lines at key angles and extend these to what would be the outline of the EPS block.  The position where the tangent line meets the block is marked and all the matching tangent - surface intersections are joined along the length of the board using the outline and rocker templates as giant french curves.  Using these curves also helps the volume flow nicely as you are using the same curves with which the outline was cut. You also need to mark the wide point clearly to allow the rail tuck to be shaped correctly.















So I went to shape the lower rails(below the wide-point) and found I had made a error on the tuck calculation - I allowed for the 3mm shell on the outline but not on the pre-cut 6mm Dcell on the Hull. I ripped off 3mm from the wide-point with the router, squared them up, re-marked the wide-point and re-blended the rails.  The Dcell hull was trimmed with my tuck template using a snap-off knife.   



Next was the deck concave which was originally going to be 3mm, I changed it to 6mm.   The mast track area steps down an even 2mm from the hot-wired deck.







Next up is smoothing the rough sand and fitting the deck sandwich.

Friday, 21 February 2014

Board Building Project - HD Creeper 48 - Stage 2 - Bottom Sandwich

Well I am a few steps ahead of this post so I thought I had catch up otherwise I will never find the time...

Well our recent heatwave has stretched the timeline a little, 40 degrees in the shed over the weekend and the high risk of blackouts meant bagging the bottom was too risky. Last night we had gale force winds and blackouts in adjacent suburbs so I thought I would do what Forest Gumps mate did on the shrimpin boat and try my luck with taunting the weather gods otherwise the board will never get finished. With the howling wind it was pretty hard to find bag leaks and my first run with the new vacuum system highlighted a few issues:
  •  I need a much bigger vacuum reservoir for the bigger bags which always seem to have a few leaks. I like FormulaNova's idea in the Seabreeze vacuum system thread of the pipes down the shed wall... 
  •  I won’t try sealing the vacuum tube in a mastic "zip" in the bag opening again! Get it sealed and it opens 15 minutes later. 
  • I need to cut the bloody corner off of my rocker stick so I can feed the bag on more easily. 
  • I need to tape the FULL length of the rocker stick to the Dcell. 
The power was on when I woke up and the digital alarm clock wasn't blinking so I was relieved. I went out to the shed to find only -4kPa on the gauge but the bag had good clamping force, looks like the base went on well. The stupid mastic wad worked itself free from around the suction tube so I think I will go back to the old through bag fitting. I will also try out some clip lock seal on the ends of the bag as I use really heavy 200um LDPE for durability. The mastic/tacky tape used was purchased in 2007 and may have lost some of its sealing and leak filling properties as the folded tape in the corner folds of the bag were creating slight leaks at the end of the tape and not staying sealed.

I tried placing the rail and outline templates on the deck to equalise the forces on the foam, looks like it worked pretty well combined with the low clamping force of -25kPa with 5kPa hysteresis kicking it up to 30. I still have the stringer 9mm proud on the deck so the templates butted up nicely to the side rather than overlapping and pushing on the stringer. If the templates were to overlap they might fight against the clamping pressure of the rocker stick holding the hull d/cell onto the underside of the stringer.

 I made some changes to the tail by adding some winglets behind the front foot, widening the tail under the back foot and then adding some bigger wingers behind the back foot for a pinnier tail.

Last night I finished hotwiring the plan, and marked out the rails for shaping. I ended up squaring off the nose to match the tail and I have always liked them anyway... 











Tuesday, 11 February 2014

Lake George Glass (Video)

Following on from my Lake George Speed Run video is this vid of a light wind session with a few glassy patches.  The wind was probably 13-18 at most!

Wednesday, 5 February 2014

A Lake George Speed Run (Video)

Here is a short clip of the "normal" speed run at Lake George(near Beachport in South Australia).  The launch is on the northern side of cocky's point with the upwind leg heading WSW.  Winds on the day were only into the low 30's and I ended up with a PB 10s average of 43.89 GPSTC

Thursday, 30 January 2014

DIY - Handheld Hotwire Cutter

I thought I would share my experiences sourcing parts for the new Handheld Hotwire Cutter I have just completed.  Previously I used wire from a TV coil hooked up to various car battery chargers that had a factory set current output.  These worked occasionally but you never had much control of the wire temperature. 

Hotwire Foam Cutter
After scouring the pages of ebay I came across a neat little hot wire power supply from Australia. There were 2 options for maximum wire length(when used with the recommended nichrome wire) of 1m and 1.5m and the unit ended up costing around $100.  I went for the 1m version as I will only be cutting the short side of full EPS blocks and I didn't want wires burning out when cutting thinner material.

Hotwire Power Supply
The unit weighs next to nothing and is quite compact so I mounted it to the hotwire bow for ease of adjustment. You can get optional wire with the banana connectors on request.

Hotwire Termination
Mounting of the wire is achieved by looping it around a bolt in between 2 washers, a wingnut is then tightened to clamp the wire between the washers.  The end of the wire hangs out for easy connection to the power supply.

Hotwire Bow Spring Tensioner
The wire lengthens when heated so one end of the bow pivots on a socket head cap screw.  An old trampoline spring maintains the required spring tension.  Folded 50x3 aluminium flat bar is folded to form the opposite fixed connection as well as the hinge seen above.  Scraps of 45x35(?) pine were used for the arms but these might be upgraded to CF roll wrap tube when I have more time.

Freshly cut EPS without sanding...
This is the first board(HD Creeper 48) cut with the hotwire and the above foam is straight off the wire with no sanding whatsoever.

Tuesday, 28 January 2014

Board Building Project - HD Creeper 48 - Stage 1

Well I am up to my elbows in foam again and I must say I have really missed it.  The last board I built was in 2007 and this time round I have done things properly and have not cut corners.  First up was a dedicated vacuum system followed by a new hot-wire bow with dedicated power supply(not just a battery charger putting out whatever current it factory set). I am also cutting full size 3mm MDF hot-wire templates, I used to use thick cardboard which could get burnt if the hot-wire got snagged.

So far I have:
Designed the board and printed full size templates on my A0(roll) printer.
Cut full size templates for center rocker, side rocker(to form the vee), plan and tuck templates.
Cut each side of the board with its panel vee.
Laminated the halves together with a 3mm PVC stringer to preserve the intended rocker line.

Here are the progress pics: