DF95 September Update
At the start of the DF95 sailing time, Hurricane Dorian was a category 5 storm with 180 mph wind speed, heading west at 5 mph and 120 miles east of Palm Beach Gardens. The Hurricane Center promised us it would slow down, turn North and never hit us. The storm did slow down and turn North a few days later and we never got the full impact.
The hurricane did however provide wind speeds of 10 - 15 mph from the North. Five boats sailed with four different winners in the first four races. By the start of the last race, I measured wind speed on the lake at 15 mph. The dragons, all on A rigs, were flying downwind in that race. Eight races were run and Jon Luscomb took the day.
We had a new member Charlie Sumner join us for racing with # 790. Welcome Charlie!
We had wind from the SW with many different wind speeds depending on the race and position on the lake. Six boats sailed six races with four different winners. Chris Wright took the day with three wins followed closely by George Balaschak.
The wind was up. It was a beautiful sunny day. The wind shifted to the NW during the Soling races and weeds floated out of the canal on to the race course and stopped the Solings in their tracks. We had to suspend racing for the rest of the day.
Strong gusty NE winds were the order of the day. Usually when the autumnal equinox arrives at the end of September, the winds tend to pick up and this year has been no exception. We had five boats sail and ran five races with three different winners. Jon Luscomb took the day with three wins.
NE winds were again the order of the day but not as severe as the previous week. Four boats ran six races with three different winners. Jon Luscomb won the day with four wins.
During September, the city mandated that we reduce the number of buoys and make our buoys uniform in type and color. During October, all the buoys will be lobster trap buoys painted yellow and numbered. We will then have twelve buoys down from fifteen.
The Region 7 DF95 Championship Regatta (in St. Augustine) had to be cancelled due to the hurricane (Dorian) and was rescheduled for September 28 - 29.
Dragon Sailing North America ( DSNA ) is currently producing video tutorials related to the Dragon classes and will list them on their YouTube channel:
Topics to be covered will be boat and rig assembly, radio setup, tuning guides, race tactics and more. None of those videos are on the channel yet. Check this site every so often for new additions. There is, however, an excellent 22 minute video “Intro to Racing Rules of Sailing” hosted by Patrick Rynne of the Miami RC Sailing Squadron which uses race videos, drones eye videos and animation to explain the rules.
In a two sail system, jib and main, how much lift is provided by each sail? Is it:
A) The jib more than the main
B) The main more than the jib
C) Both sails contribute equally
D) I don’t care as long as they keep me ahead of Jon Luscomb
While D might be a popular answer, the correct answer is A : the jib ( foresail ) provides more lift than the main. According to the book “ The Physics of Sailing Explained” by Bryon D. Anderson:
….there is a net larger displacement of the air perpendicular to the general direction of flow for the two sail case when compared to a single sail….the two sails create, in effect, a larger wing around which the air must move, The total path around the outside is also longer, and the differential in air speeds on the leeward and windward sides is greater with two sails, which helps to create even more lift.
For some time, this effect was believed to be due to something referred to as the “slot effect” with the gap between the two sails supposedly funneling more air at a higher speed along the outer surface of the mainsail, thus causing the mainsail to produce more lift. Since then, however, measurements of the actual lift along both sails have shown that this is not really the case. Rather it is the fact that the combination essentially produces a single larger airfoil that creates a greater total lift. Note that it is normally true that it will be the foresail, not the main, that produces the greater part of total lift.
“The Physics of Sailing Explained” is available on Amazon as a new paperback for less than $ 20.
11/16/2022 10:06:31 am
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