Try this in the constructor.
Ship::Ship()
: sf::Sprite()
{
texture.loadFromFile("10B.png");
this->setTexture(texture);
this->scale(sf::Vector2f(0.25f, 0.25f));
this->setPosition(100.0f, 100.0f);
this->setOrigin( this->getLocalBounds().width / 2, this->getLocalBounds().height / 2 );
// Definimos la velocidad
this->speed.x = 300.0f;
this->speed.y = 300.0f;
}