|Posted: April 25 2008 at 15:15 | IP Logged
Currenlty I have a 1980 Carver 266 Santa Cruz. I tow with a Magic Tilt tandem axle trailer. Many boats, many trailers, many years.
Use the "standard" bunks that came with the trailer, usually sufficient. The bunk positions should be located such that the boat will rest on the first chines up from the keel. That's where the keel transitions to a ~3" horizontal "flat spot". Why? This is where there is hull reinforcement. Strong point. If they rest on the curved part of the hull there is no reinforcement. Also, your bunks are not beveled to match the curve of the hull. Thus, causing a sharp "point" load along the length of the hull at bunk contact point.
The CG or Center of Gravity of the boat should be positioned directly between the two axles, or the center axle if you trailer has three axles. A boat yard sling lift can find this for you using just a single sling. They only need to lift the boat a few inches to find the CG, or longitudinal (fore/aft) balance point of the boat. Rember full fuel tanks, boat toys, etc. will affect this. So maybe half tanks, and just the stuff you usually carry onboard.
Mark the CG on the hull for future reference. Why? Because you're not done yet.
Now you will probably need to adjust your tongue weight. This is done by moving the axles either fore or aft on the trailer frame. NOT willy nilly shifting the boat on the bunks. Remember you just paid to find the CG. It always remains centered betweent the axles. The boat and axles need to move fore/aft as a unit.
This is always the proper way to set up a boat/trailer combo. NEVER let anyone tell you it isn't. Boat salesmen are a very poor source for technical information. Show this to any Mechanical Engineer and I'm sure he will agree.
Ignorance is an educational deficiency. Stupidity is self taught.