Conducted by Ken Kershaw,
RYA Technical Manager, at
Present � Pat Blake (MROA
Chairman), Graham Williamson (MROA Rules Committee Chairman), Guy Winder
(Builder), Dan Alsop (MROA Main Committee), Linton Jenkins (Builder).
|
|
|
Wt of Corr. |
LCG |
|
Normal corrector distribution |
Correctors at ends |
No Correctors ( |
1/4 Correctors at Transom |
|
|
3539 Wood |
98.5 kg |
nil |
1.95 m |
T1 T2 Inertia VCG |
3.20 3.58 120.26 -628mm |
3.18 3.59 117.19 -645mm |
|
|
|
|
3571 Wood |
98 kg |
2.8 kg |
1.95 m |
T1 T2 Inertia VCG |
3.132 3.46 117.88 -677mm |
3.130 117.39 -684mm |
|
|
|
|
3612 FRP |
99.4 kg |
25 kg |
1.88 m |
T1 T2 Inertia VCG |
2.834 3.063 89.34 -687mm |
2.844 3.054 91.77 -711mm |
|
|
|
|
3609 FRP |
98.7 kg |
11.2 kg |
1.90 m |
T1 T2 Inertia VCG |
2.92 3.21 95.16 -661 |
2.92 3.21 95.30 -659 |
3.34 3.75 137.72 -661 |
3.05 3.38 95.15 |
99.89 -655 |
|
T1 |
Average time for 5 swing
cycles from hull suspension point 1 � approx 960 above hull shell floor |
|
T2 |
Average time for 5 swing
cycles from hull suspension point 2 � (T1 � 200mm) |
|
LCG |
Lateral Centre of Gravity
measured form transom to suspension point |
|
VCG |
Vertical Centre of
Gravity � measured below suspension point |
|
Inertia |
Expressed in kg-m2. |
The swing tests were
conducted under the supervision of the RYA Technical Department.
Boats � Two wooden boats from different builders,
and two FRP boats were swung.� The boats
had sheets, boom and spin poles, rudders and other loose items removed.� Standing rigging (Lowers and puller cascades,
Shroud cascades), kicking strap tackles, and centreboards remained.� All the boats were dry.
Location � the tests were conducted in an industrial unit of
approximately 4000sqft.� Doors were
closed.
Rig � The rig was an aluminium
A frame provided by the RYA.� The boats
were hung from their gunwhales by proprietary
brackets that allowed�
two sets of readings for each boat, the height of suspension was
changed by 200mm for each set of readings (T1 & T2).� The swing duration was measured by a photo
light cell linked to a computer.
Executing the test� each boat in turn was weighed, and suspended on
the rig.� The LCG was measured, and the
LCG and weight programmed into the computer.�
5 swing cycles (up and down = 1 cycle) were timed by the computer,
starting with the bow of the boat depressed 100mm.� Two sets of results for each boat were timed.
Once each boat had been
swung, one was re-suspended without its correctors fitted.� A variety of additional tests were carried
out to gain an indication of the effect of re-distributing the weight along the
hull.
Calculating the results � the computer programme,
developed by the Wolfson Institute and made available
to the RYA, calculated average swing time, Vertical Centre of Gravity, and
Inertia.�
Evaluating the results � Still in hand!!
Graham Williamson