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RobertB wrote:Your straight bunks will yield only one point of contact with the hull on each side. They would work for a pontoon boat but I cannot see how you are going to support and hold in place a rounded hull. If you are not goint to use the rollers, then I suggest you copy the cradle arrangement of the stock trailer.

BTW, I talked with Mike I at Macgregor yesterday about hull thickness. He stated that these boats (at least my ) have a hull thickness below the stripe of around 1/2 inch of solid fiberglass. This keeps the hull from developing flat spots when they sit on hard spots on the trailers.

I understand...thanks for being helpful and explaining....

What I mean by straight is this...

On the mac factory trailer the bunks are flat with 3 points of contact to the trailer...they are made of pressure treated 2x6 they are facing straight up, and have a slight bend in the middle...I realize the boat is not "Flat" I can re-create that "bend" with the bunks flat on the new trailer by adjusting the front supports up...

because my bunks are mounted on the old roller platforms my question is should I have them lay flat, or let the boat "settle" in the "V and make the adjustments then? Right now the bunks will form a "V" cradle...I can adjust the front and rear up and down to create the "bend" that I need....but I wonder if the boards are somewhat "sideways" will it be better, or harder to create that "cup shape" I'll need.....

I have seen both styles of trailer in powerboats...both flat bunks, V bunks, and also bunks that swivel side to side some...

Thanks

Dave

The boat trailers I've had with long longitudinal bunks only had support at two places per bunk, presumably so the force of the hull against the bunk would flex it into the hull shape, thereby spreading the load to some degree along the length. The two bunk support points were, without doubt, hard points though, so I would imagine they weren't randomly placed by the manufacturer.

If it were me, I'd do my best to duplicate the OEM trailer bunk arrangement. I did a drawing for my trailer bunk arrangement for future reference, or in case anyone here needed it, but I don't have one for any other models.

If someone wanted to take a few measurements with a long piece of mason twine and a tape measure, I'd be happy to gin up a CAD drawing of it.

Here's a pic of an Aquarius 7.0 I used to own, though you can't see the bunks very well (short vertical white channel iron at the end of the trailer supporting the aft end of one of them), and a Balboa 26 on a trailer (note the really long but flexed bunks, both inner and outer). My A7.0 had two rollers under the keel (maybe three - it was long ago), and presumably so did that B26. Both were made by Coastal Recreation, by the way (long since out of business), and both are on OEM steel trailers.

RobertB wrote:Your straight bunks will yield only one point of contact with the hull on each side. They would work for a pontoon boat but I cannot see how you are going to support and hold in place a rounded hull. If you are not goint to use the rollers, then I suggest you copy the cradle arrangement of the stock trailer.

BTW, I talked with Mike I at Macgregor yesterday about hull thickness. He stated that these boats (at least my ) have a hull thickness below the stripe of around 1/2 inch of solid fiberglass. This keeps the hull from developing flat spots when they sit on hard spots on the trailers.

I appreciate the advice..... I know the bunks looked flat in the pics, but considering the amount of space between the mounts to the trailer there was room for flex...

I was pretty sure, and correct, that the bunks would flex into position... We went to the lake Sunday (a friend towing the empty trailer) and tried to get her switched...ended up becoming a downpour halfway through...we eyeballed it and decided was good enough to not fall off or break something. I got home and realized the boat was "listing" pretty badly to port, but was stable.

Today I went back to the lake and spent two hours adjusting everything and this is where I am at




Towing back from the lake all the sway is gone, easily made 60mph for a short bit in a 55mph zone, then went back to being cautious as I have no keel support yet. Ramp was only 10 miles away so I risked it by strapping keel up with a ratchet to keep the road bounce off the cable... If it fell it would have swung 7 inches down and hit the keel support bar (with the handles) so I would've been ok i think.... I need to build a cradle for the keel and attach to the bar with handles

I need to take a piece of stock steel (signpost) and weld it across the middle of the trailer, and attach supports where the middle of the bend is in my 2x6 bunks, that should do the trick...will hold and support and also keep the bend when boat is not on the trailer (which it will be most times)...


I was going to weld the middle supports to the Keel support bar, but I think I realized why it has the handles...you can crank up the keel, undo the pressure with those two blue levers and remove the entire keel support bar without pulling boat off the trailer...this allows the keel to swing almost (not quite) all the way down for service....someone correct me if I am wrong...I think I scored on this part with this $400 trailer.

Here's another pic of the whole thing



Look like I missed anything? It tows like a dream...Working on the Keel V-bracket now (actually stealing it from the old mac trailer)

Look too high?
Think I need a roller on the bow way up front? It's sitting right dead center on the bunks, and no "bounce" out of the V-block at the winch...

Cheers!

Anyone in NC want an OEM Mac 23 trailer

Great work, you did good .

Those boats are so cool looking. I think the prettiest that Roger ever designed/built,

Sum

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Thanks a lot Sumner, coming from you that means a lot!

I wish I had your skills/resources/shop/ruth to work on mine, but I am learning as I go

Any ideas as to why the keel support bar has those handles?

keel doesn't drop far enough to really be a benifit, so I was debating welding the middle bunk brackets to it anyway

not tonight though...3 hours at the lake adjusting the buks was enough for today !

Dave

A good number to SWAG would be the total area of th trailer bunks and figure out the approximate amount of force per unit area on the bunks...I recall doing this for another thread and getting a number like 600 pounds per square foot, or about 4 pounds per square inch...

This is roughly the same pressure I apply to deck of my Mac standing on one foot thanks to my lard butt.....

Not sure what the support bars are you are talking about.

Sum

The Keel Support...On each side of the trialer, right between the tires there are two Blue Handles...

look at the pic of the bunks before I covered them and you can see them peeking out.. .

When Pushed down you can move the keel support either forward or back, lower it a few inches, or I guess remove it....

I am assuming that is what they are

Sumner wrote:
Those boats are so cool looking. I think the prettiest that Roger ever designed/built.

Without question. If and when I move on from my , that model is on my short list, along with the 26S. I've just got a 'thing' for a sweeping shear, and for a clipper bow, especially with bow sprit (and trailboards ) That is, if I don't go back to keel boats, but I'm really liking the advantages of a trailer boat lately.

The 23 doesn't have a clipper bow, but everything else about it is salty, and the sweeping shear is just as sexy as it gets in a boat.