Weighing of the marauder Désiré
Presented in the AS Marauder's bible in Chapter 26, here are the explanations in pictures, transmitted by the AS Marauder, of a simple and effective method to weigh a transportable boat and know its displacement.
Désiré, an example of the famous dinghy, is installed on its trailer in the initial position. A scale is installed under the jockey wheel to measure the load (R) on it. The distance L between the axle and the jockey wheel is measured.
After taking the measurement, the boat is backed up on its trailer to the equilibrium position, corresponding to the moment when the load on the jockey wheel is cancelled. At this moment, the center of gravity is located above the main axle. We then measure the distance d by which the boat has been moved.
Considering the balance of the moments, a simple rule of proportionality allows to find the value P of the displacement or weight of the boat.
P= C x (L/d)
In the case of Désiré which has been completely emptied, the load on the jockey wheel is 61 kg. The displacement to reach the balance is 60.5 cm. The distance between the wheels of the trailer and its jockey wheel is 305 cm.
The calculation of Desire's weight is therefore : 61 x (305/60.5) = 307 kg .
Corrections to be made
Antoine Boutron, who developed the method, announces a margin of error related to the measurements of 2.60%. For Désiré, this represents +/- 8 kg .
The marauder CI (Construction Individuelle) by François Vivier is a remake of the original boat designed by Jean Jacques Herbulot.
The weight for the measurement (without armament or sail) must be 300 kg. "Désiré" weighs 308 kg, in the configuration in which it was weighed, which can be explained by some comfort modifications, with an anchor locker, a companionway cover, portholes and cockpit benches.
We can then calculate the light weight, which is the weight of the boat ready to sail. We must therefore add :
- sails (mainsail, jib and spinnaker) + 12,0
- mast, boom and standing rigging + 16.0
- helm and rudder + 6,0
- mainsail hoist, downhaul, sheets, hawsers + 2,0
- bucket, fender, fire extinguisher, gaff + 2,0
A total of 38 kg
The light weight of the marauder CI "Désiré" is therefore 307 + 38 = 345 kg
François Vivier announces a tonnage of 300 kg and a light weight of 325 kg
Again, the addition of equipment explains the difference.
To obtain the real displacement, it is advisable to add all the equipment of comfort or for example here an outboard motor of 15 kg, life jackets, a tool kit, a gasoline reserve...
The final weight of Désiré on the trailer, ready to travel, reaches 380 kg . This is still reasonable for safe road travel and very easy launching on gentle ramps with 30 cm of water at the end of the trailer.
Valuable information for towing your boat
In the case of Désiré, the weight of the trailer is estimated at 230 kg. This makes a total weight of 610 kg. The careful driver will be able to check his total weight in charge (PTAC). In our case, the Peugeot Expert van admits 2650 kg of maximum load. The weight of the whole convoy is 610 +2650 = 3260 kg The vehicle can be driven with a simple B driver's license because it weighs less than 3500 kg.
