I would like to apologize for any hurt feelings regarding my comments however I get frustrated physics are ignored. I happen to be a mechanical engineer with years of experience repairing both fiberglass and aluminum boats. When I take the time to give advice to someone with potentially damaging setup and someone else comes along and infers that I don?t know what I?m talking about, I fear the OP is getting bad advice that may damage his boat. Other than Smoke, no one questioned why his set up is tearing up rollers which in the end turned out to be the problem.
Most trailers have 5 rollers on the centerline or less, each has a contact area with the hull of 5-10 square inches or less. Assuming your rollers are perfectly adjusted you are talking about 25-50 square inches supporting the entire boat. An all roller trailer uses hinges to evenly distribute the load, keel rollers affixed to the cross members don?t do this. Also consider that even if are your keel rollers are perfectly adjusted and evenly loaded, the cross members are going to be flexing for every bump in the road at different rates which will create uneven loading. Assuming a pair trailer bunks are only 3? long 2x4?s (extremely small and unlikely configuration), you are looking at over 250 square inches of support, properly positioned these will support the stringers and engine mounts of an i/o or evenly distribute support for an aluminum boat that may have lateral ribs instead as well as the transom with the engine load.
The whaler guidance referenced showed a trailer with 12 keel rollers, which is pretty uncommon. In my area all of the new whalers use float on trailers anyway. Finally a boat will load just fine up a trailer with properly configured bunks because the trailer is at an angle on the ramp while the boat is level on the water, the bow will be in contact with rollers keeping it straight and rolling smoothly till the bunks take up the weight in the last couple of feet or when the trailer is pulled up the ramp.
For what it?s worth, I vote for the clear polyurethane rollers. Rubber containing black carbon can cause corrosion to bare aluminum if salt is present and the polyurethane rollers do not leave ugly marks.
I appreciate the lively discussion and hope wish you all some happy days on the water.
Most trailers have 5 rollers on the centerline or less, each has a contact area with the hull of 5-10 square inches or less. Assuming your rollers are perfectly adjusted you are talking about 25-50 square inches supporting the entire boat. An all roller trailer uses hinges to evenly distribute the load, keel rollers affixed to the cross members don?t do this. Also consider that even if are your keel rollers are perfectly adjusted and evenly loaded, the cross members are going to be flexing for every bump in the road at different rates which will create uneven loading. Assuming a pair trailer bunks are only 3? long 2x4?s (extremely small and unlikely configuration), you are looking at over 250 square inches of support, properly positioned these will support the stringers and engine mounts of an i/o or evenly distribute support for an aluminum boat that may have lateral ribs instead as well as the transom with the engine load.
The whaler guidance referenced showed a trailer with 12 keel rollers, which is pretty uncommon. In my area all of the new whalers use float on trailers anyway. Finally a boat will load just fine up a trailer with properly configured bunks because the trailer is at an angle on the ramp while the boat is level on the water, the bow will be in contact with rollers keeping it straight and rolling smoothly till the bunks take up the weight in the last couple of feet or when the trailer is pulled up the ramp.
For what it?s worth, I vote for the clear polyurethane rollers. Rubber containing black carbon can cause corrosion to bare aluminum if salt is present and the polyurethane rollers do not leave ugly marks.
I appreciate the lively discussion and hope wish you all some happy days on the water.