Those of you who have followed my Alioth development will know that I have been plagued by weather helm and had I known what I know now would have been 9 months ahead on development. I was reluctant to move the fin before the worlds being worried about splitting the top of the fin which I did when I finally moved the top of the fin back 7mm. rebuiliding the top was not a problem.
The fin leading edge at the top in the boat was 508 from the front of the bow bumper with the fin rake just over 1 degree. The symptom was that I struggled to bear away around windward marks or execute a 360 effectively struggling to get the boat to bear away. Upwind the boat, if left alone, tended to head up slowly into wind thus losing speed so any loss of concentration would see the boat slow.
My solution was to move the top of the fin back 7mm and keep the base of the fin in the same place so I maintained the fore and aft balance of weight. This would put the leading edge exactly vertical to the water line. It required considerable modification to the top of the fin but it all ended well.
The first test was at Datchet in mid to top end A rig conditions. Imaging my surprise when the boat steered upwind in a straight time with no rudder interventions and when I tried bearing off, it was easy as was performing a 360 turn. I am sure if I had plumped for an Alioth fin from Juan Egea I would not have had the issues but not being a designer, I had to learn the hard way. In inital racing the boat proved to be reasonably quick and finally I am happy with the configuration, the only remaining question being, which is faster, the Alioth fin, the Robot fin or the Craig Smith. I am not going to find that one out and will stick with the Smith fin.
To be brutally honest the boat still heads up ever so slightly but I am happy with that. Its been a long learning curve but the lessons from a year of experimenting have been so valuable even though it cost me valuable ranking points.
So is are the final configuration and measurements on my Alioth Design boat.
Hull: 2 piece Polymax PLA with 2 coats clearcoat printed and assembled by 3D Printed RC Yachts (Paul Barton)
Sails: Sailboat RC
Fin: Craig Smith, Bulb Robot
Bow to leading edge of fin at hull 515mm
Fin rake 90 degrees to waterline
CG of bulb 5mm forward of leading edge of fin
When set up in calm weather, bow is 25mm out of water and the stern is just out of the water. As soon as the boat moves maximum waterline length is achieved
Rudder: J Gill Small version
Rigs A rig prebend 16mm to 800mm from top. B rig 400,, 8mm. C straight
Mast rake A Rig 1035 B rig 1040 C rig as raked as possible
Mast step to boom band 135mm.
Rest of mast measurements as per BG Britpop setup on BG sails and Design web site. BG site is the best source on rig tuning.
Winch RedAnt stinger
Drum 40mm which provides complete control on sail setting
Battery LIFE 1000MA which is good for about 10 races. Whenvoltage start to drop to 6.4, change the battery or winch operates intermittently.
Futaba T6K transmitter with mix setup so I can achieve high mode by cranking sheet toggle to the left when sheeted fully in.
Any questions, you know how to contact me.
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