bunks on boat trailers
 

Why do boat trailers stop the keel bunks several feet from the end of the trailer, and only use bunks out near the strakes and chines to support the boat's transom?

btw, I stole this picture from another thread a while ago. This beautiful trailer is not mine, but another OSOers.

On that trailer the transom will be at the end of the rear bunks. The exta space and bar across the rear of the trailer is protection for the drives. The bar acts as a bumper in case of collision and swings clear when time to launch.

Trailer
 

The particular trailer in the picture is a beauty. If you look carefully at the rear bar with the Myco emblem, it is designed to be removed or swing out. The transom of the boat actually will sit at the rear of double bunks. The drives are protected by the additional removeable, swingable cross beam(bar) at the rear of the trailer.

Once the beam is in place it is like a rear bumper!

Most cat trailers are built in this fashion as well.

Thanks guys for your answers, but I'm not asking about the drive protector!!! The only picture I had of an empty trailer happened to be this one with a drive protector. Sorry about using a picture of a trailer that was confusing.

Look at the last cross member prior to the drive protector, and you'll see the bunks are at the outer edges of the boat.

Now look up three cross members, and you'll see bunks closer to the keel of the boat. That's what I'm asking about.

Express Cat, noticed you've got Pure Adrenalin and a Cig logo. Are you the new owner of a mint 35 cig of that name?

Good question.
I found a pic in the OSO Classifieds of an Apache belonging to Peter Pavkovich.
In the pic you can see where the rear bunks contact on this hull. Only thing I can say is that the contact area must be where the greatest strength is in the hull. Possibly due to where the stringers and engine beds are? Same for the contact points further forward?

Mr. Pavkovich, I hope you don't mind if I use one of your pics as an example.

Now that's a boat garage!!!

I wish I had one the size of an "aircraft hanger" too. :D

Directly above the chines are the stringers... stronger part of the hull... less chance of distorting the hull while it sits for a long time on the trailer.. That is why the bunks are put in those positions. I've seen boat trailers that didn't have good bunks.. and the hull sagged over the rollers along the bottom... ruined the hull... ( it was a junk hull anyway.)

So trailer mfg's don't put keel bunks at the transom to insure the outer bunks support the trailer at the stringers? That makes sense, but in the picture above Myco added a second bunk just inside of the outer bunk that lines up near the stringer, and the inner bunk would support the boat where there is no stringer or support at all. Whereas there is usually a stringer along the keel in the engine compartment, but not in front of the engine compartment due to the fuel tank. In addition, half the weight of the engines is supported by the keel stringer in the engine compartment, which is not supported by the trailer. I'm no naval architect, but this is not making sense to me.