After a year of sailing and testing we decided to make some changes to our “V6 ACC” design.
Here’s some shots from yesterday, a stern scoop has been added taking the loa out to a full 2m.
Other changers were to move the rig & keel back to make better use of the length.
We’ll be “scooping” the 4 boats we have built and changing the tooling for future hulls.
The plan is to have 2 boats out in the next week or so for some match racing & video shoots.
very nice boats,where did you take your plans?Go on whit your nice work.Gilles B.
I designed the boat using Delftship, the hull is made using a 2 part female mold.
Basically the concept started with a V5 AC boat but with less overhang and a more fair overall hull shape.
you got what I sent you about hull decorations ?
Looking great John & love that main
Looks fantastic - another advantage with the additional length (if as you say you’re playing around with fin position) is to possibly increase draft & ballast and then move the rig aft slightly and also increase the height - hence enlarge the sail area. Just thinking out loud …
With the additional 20cm from the sugar scoop have you noticed any increase in hull speed now she has the extended waterline?
Hi John, very nice looking boat. gotta love your sails they look fantastic ! like Row curious to see what the extra 20cm brought in terms of speed ?
Hard to say regarding the effect on speed. We aren’t planning on doing any testing between V1 & V2
My gut feeling is the boat is a little quicker since the scoop is in the water and helping move the stern wave aft.
Regarding Sail Area & Draft/Ballast we have no plans to change them. This will be the final configuration of the boat and our One Design spec.
The mast is pretty tall at 2.37m. We don’t want to end up needing a shorting rig for heavy air, as it stands now we are using A,B&C sails to cover the range with one rig.
In addition we are trying to keep the boats to a size that will fit in a small car.
Draft is 740mm with, ballast is 9.5 kilos.
There’s no doubt that in certain ranges we could gain more speed by playing with the sail area, draft & ballast but we want the boat to be a solid performer in all ranges and have simple One Design Specs.
curious to see what the extra 20cm brought in terms of speed ?
Performance of this boat really challenges the traditional expectations for displacement hulls. About a month ago we were sailing the 1.8m hull one last time before the scoop conversion. I grabbed my handheld GPS, reset the trip meter and max. speed field and taped it on the deck for a few minutes of sailing. Wind was about 10 kt average, up and down a bit. Max. speed we saw was 4.9 kt. From memory this was no where near the fastest we have seen this design go. I suspect that the formula does not work well as the length/beam ratios get very high; in this case ours is about 8:1 based on a waterline beam of about 9". Point is that it will be hard to quantify how much the added 6" in length will change things. Either way this boat really covers a lot of distance in a hurry. But with the quality of today’s r/c gear and the visibility of the 2.4m tall rig we’re comfortable sailing at pretty long distances when not using the chase boat.
It’s been a lot of work and fun!
Nice boat !
According to the formula with average wind and no waves :
Speed (in m/s) = 1.25 x square root of LWL
For 2 meter long LWL : Speed = 1.25 x 2^1/2 = 1.76m/s or 6.3km/h or 3.43 knots
To go up to 4.9kt, the boat shall enter into the planning regime with strong wind or speed > 2.5m/s
PS: see this site http://www.psychosnail.com/boatspeedcalculator.aspx
We have verified speed of roughly 5 kt. both in a chase boat and with the GPS attached to the model. This has been in fairly flat water and wind speeds of under 15 kt. I think the behavior of this hull is more “semi displacement” in nature. Much more like a multihull with one hull in the water. Using the calculator you reference above, but using the “semi displacement” calculation, speeds of 2.5 x √2 = 6.4 kt. should be possible. This is much more in line with our observations. We’ll do a bit more testing but I suspect that many long slender hulls will exhibit similar behavior. Thanks for your interest.
Those numbers sound in the ball park based in the GPS telemetry data I get from my boat.
Being without a comparable sail boat in the area… I have a system that relays speed & heading in real time to help push development and improve performance.
Upwind I am sailing at 5-7kph and on a reach/run I can regularly be above 12kph. Max speed has been 16kph dead downwind.
So in nautical terms up to 3.7 knts upwind/ 6.5 knts reaching/ run & max 8 knts.
Taking this into account and the much longer LWL your going to be a good margin over those figures.
Great day of 2 boat testing 10-17 knots of wind. This was the first time for us getting 2 of these boats out head to head, and it was a sight!
Sails were “B” size.
Great action shots - just to clarify, have they both had the additional 20 cm added to the stern?
Yes they both do. When we decided to add the “scoop” we made an additional mold to make 4 pieces for the existing hulls. We will be changing the hull tooling over the winter to incorporate the change into the basic hull. Here’s a link to our photobucket site with many more pictures including some of construction. Thanks for your interest.
Here’s a shot from behind showing the scoops better:
Did a little tuning session yesterday, working on the setups between A & B sail sizes.
I picked up from your album this picture :
Have you got any rudder stall effect with low/medium winds ?