Originally Posted by Paul L
Back to the B&R rig issues, for a decently performing cruising boat there will be many cases where DDW is not the best performance.
I guess we can agree to disagree.
I just haven't ever seen evidence other than "we do better" for not sailing DDW if speed to destination
is prime objective. Yes, it feels faster, but at the expense of too much extra distance.
Now for hard evidence using math:
Using trigonometry (law of cosines) you can calculate the following by sketching triangles of angles:
DDW speed angle up from DDW sailed break even speed at angle
6 10 degrees 6.1
6 20 6.4
6 30 7
6 40 7.8
6 50 9.3
assuming DDW speed wing on wing is 6 knots-
if you head up by 10 degrees, you need 6.1 knots to break even
if you head up by 20 degrees, you need 6.4 knots
if you head up by 30 degrees, you need 7 knots
if you head up by 40 degrees, you need 7.8 knots
if you head up by 50 degrees, you need 9.3 knots
The first 2 angles (10-20 degrees) are really not possible without poled or asymmetric
like spinnakers or code zeroes. The genoa
will just be blanketed and unless it's a tiny jib
and a huge main, the loss of sail area will preclude speed gains.
In many boats, heading up 30 degrees from DDW is the minimum needed to fill the genoa meaningfully, and up to 40 degrees is needed to derive significant speed gains. I am not sure many cruising boats will gain that much more speed sailing an angle.
This is not counting current
which may add to difference.
Subjective proof is also in my observations and racing
in 2 local fleets in and near Annapolis
, where folks know what they are doing in non-spinnaker classes
boat races downwind wing on wing with poled out genoa on a DDW course, rather than sailing jibing angles. Occasionally someone will try to sail out on a deep reach and they always lose out. Again I believe this is because of lost effective sail area of genoa blanketed behind main. You just have to head up too much to get the genoa pulling, vs wing on wing where both sails are full.
The only boats I have ever seen race
with downwind jibing angles, are spinnaker boats.
Of course, choices when cruising come down to comfort. For some boats, DDW will be more comfortable to avoid quartering waves and corkscrew motion. For others, especially in high wind condition, the risk of jibing or stuffing into a wave sailing DDW makes sailing a deep reach preferable.
I just don't think you can get there faster sailing angles unless you have an unconventional rig (huge mainsail tiny jib) or a specialized downwind sail.