Boat Trailer Design

[Gudenuph]

I got to thinking. Now my head hurts! Seriously though, why support the boat on a trailer with the keel when the boat is in its element, the keel is suspended from the hull? I've seen "oil canning" of a flat bottom, fin keel glass boat when the total weight is on the keel. That can't be good! The keel trough for my O'Day 25 sure gets in the way of maintenance. A number of removable bunker pads (removed one-at-a-time for bottom painting) should do the trick. Removable horizontal restraint for the keel might be installed for a long tow. Then if the axles could be spread enough to permit removing the centerboard I'd be a happy mechanic.
Am I overlooking something that can't be worked around? Sure would like to hear your comments.
Thanks much, Geohan

 

[caguy]

Geohan, when the boat is in the water it is supported by hydrostatic pressure evenly throughout the hull. when on the trailer is supported by the bunks bar other devices on just the hull, it will cause concentrated pressures leading to oil canning or damage the hull. It is my understanding that 60 percent should be on the keel, and the rest on other supports

 

[Gudenuph]

Thanks for the reply. My thinking was to use many support pads to spread the load to a much greater extent than just standard bunk boards. Perhaps, even cross section profiles judiciously spaced along the waterline length.

Geohan

 

[FourPoints]

Even if your trailer was a full cradle, you would still need to support the keel. The keel to hull joint is not designed to hold the dynamic weight of the keel when the trailer hits a pothole while going 65mph.

 

[Benjmin]

Trailer porn....

 

[Gudenuph]

Benjmin
Thanks for the pics. Is there an air gap under the keel of your boat or are my old eyes playing tricks again?

 

[Gudenuph]

FourPoints

Very good point about vertical accelerations during road travel. While the trailer suspension would reduce them to some degree, it would have to be evaluated. Perhaps an accelerometer reading along with the ballast weight would give a force estimate which along with some assumptions of cross sectional areas could result in a useful comparison with known strengths of materials. Whew!! Are you still with me?

I've dropped into some fairly deep troughs with no damage and taken some pretty good groundings with only localized damage but can't compare them to your conditions.

Thanks for your thoughts, Geohan

 

[Benjmin]

Benjmin
Thanks for the pics. Is there an air gap under the keel of your boat or are my old eyes playing tricks again?

As you can see in those pictures my boat is still in the travel lift slings. They were in the process of screwing the pads u?p or down? During that picture.

Here is after it was pulled to the place that painted it.

 

[ralphbell]

Thanks for the pics of the V-guides to center the keel. This is my worst problem when loading the boat, I have to try to guess where the center of the trailer is to guide the keel onto the flat keel support bunk which usually takes several tries. I will modify my trailer this year to incorporate your simple solution. I may make them to easily bolt on or take off so I can apply antifouling paint to the keel more easily.