Extension sur l'embase Btravo

Bonjour

A nos membres qui touchent à la compétition,

Qui connait ce produit :

http://www.land-and-sea.com/marine/stern-jack/sternjack.htm

A+

salut,
il y a cette piece a vendre sur ebay.com
http://cgi.ebay.com/ebaymotors/Bravo-1-Mercruiser-Outdrive-Gaffrig-Livorsi-Offshore_W0QQcmdZViewItemQQcategoryZ50442QQihZ006QQitemZ160126732191QQrdZ1QQsspagenameZWDVW
je crois que c'est "l'ancetre" des extensions boxs que propose latham et mercruiser avec its.
christophe

C'est là que je l'ai vu

Et j'y ai trouvé le lien

A+

bajalux a écrit:

Qui connait ce produit :

L'idée était trés bon mais malheureusement ne fonctionne pas sur les tous les types de bateau. Nous avons montés plusieurs avec des résultats "moyen" . Personellement je trouve que ça fonctionne mieux avec les embases alpha qu'avec des Bravo

"The Land & Sea Stern Jack is designed for boats that require a substantial amount of trim to achieve top speed. It provides the effects of a standoff or setback box with an additional feature.
The Stern Jack mounts after the outdrive gimbal housing rather than before it, as is the case with a typical setback box. This geometry results in the prop being raised vertically higher in the water when trimming out than achievable with typical setback boxes at the same trim angle. Similarly, trimming in results in the prop being vertically deeper in the water at the same trim angle. For some boats and set-ups, this combination of setback and vertical height can improve top speed and handling.
Moving the prop farther back from the transom has several effects. It moves the weight of the outdrives farther aft which also moves the center of gravity of the boat aft. This can allow an unstepped hull to rise higher in the water as speed increases before the center of pressure moves behind the center of gravity and trim out is required to hold up the bow. This effect alone can result in an increase in top speed.
Since water rises off the transom of a boat, moving the prop aft puts it in smoother, deeper water. In addition to improving the thrust generated, the propeller can also be raised higher, changing the geometry of the thrust force relative to the vertical height of the boat's center of gravity.
This can have both positive and negative effects, depending on the boat and its set-up. Increasing the prop's vertical height relative to the boat's center of gravity reduces bow lift at neutral trim. This may have a negative effect on boat speed and handling if the boat needs more bow lift.
It can also make it possible for the thrust vector to pass through the boat's center of gravity at some negative trim angle. This can provide a lifting component of force without changing the boat's angle of attack. Raising the boat in the water reduces wetted area and therefore increases top speed. Many race boats, equipped with surface props, run at negative trim angles to achieve top speed.
It should be noted that moving a prop farther aft could alter the angle of the water impinging on its blades. This can affect thrust magnitude and drive trim geometry, either favorably or unfavorably. Propeller optimization may be necessary for best results.
Moving the propeller aft increases the leverage that the thrust force has in influencing the angle of attack with trim. It may be possible to effect bow or stern lift at smaller drive trim angles than required with the prop closer to the transom. In this case, more thrust is available in the forward direction to increase boat speed.
As well as providing setback, the Stern Jack also increases vertical prop travel with trim. This produces a combination of all the effects previously mentioned. With the prop deeper in the water, improved propeller bit along with thrust geometry relative to the boat's center of gravity can improve acceleration out of the hole."