seahouse wrote: This area takes all of the down force of the shrouds, but most of that is on the rear pivot bolt, IIRC.(?)
Not sure if it was mentioned before, but could the aft pivot bolt be bent?
Or the holes in the bracket could be elongated causing the mast to sit lower to the deck? another thing is the angle of the front lip could be bent inwards, try to bend it out towards forward a little
this would take the load of the deck.
I am too far away from my boat to go and check, but thi is something I will look for during my pre-spring launch inspection.
Aft pivot bolt straight - check
Bracket holes round - check
Front lip is gusseted and welded in place - no way to bend - check
Boat built after happy hour started - check
Hard to believe your not getting expert help from Mac people. According to one of our members(yukonbob) i think, the mac was designed using naval architects, and a team of engineers with certified,registared and stamped approved detailed exacting drawings suitable for courtroom evidence, I would of thought Roger and a team of engineers would have shown up on your doorstep to assist. Not really but I guess it doesn't hurt to fantasize your boat wasn't designed on yellow legal pad and napkins at the local Denny's.........LOL You did a decent job I wouldn't worry to much.It was probably done on initial rigging when the side stays were to long and let the mast tilt to far forward before being restrained, once side stays are set for length they will not let the mast lean forward far enough to cause penetration like that.
I think the design was fairly solid (would really like access to the details that would help me repair) - but also seems my boat was built:
A) a couple of hours into happy hour
B) by off season vegetable pickers
C) by employees of the Lighthouse for the Blind
I have found a variety of small things that I can overlook, but a mast breaking through the deck seems to be something a factory rep would be eager to help address. I have a engineering and manufacturing background and find this lack of product support very _______ odd.
Last edited by RobertB on Wed Apr 15, 2015 7:38 am, edited 1 time in total.
I have an 11 model and there is slight damage to the area. I was never that concerned with it since I know I can fix the area. One thing I did do was file off the sharp edge on the metal that directly touches the problem area. Ix
My boat does have damage to the gelcoat in the area as well, which I'd put down to my mast collision incident, but it may be a flaw in the boats design. It seems like a common problem for sure. There should be a metal receiving plate built into the mast foot at that point to distribute the load. You could have one welded across, but then you'd only be able to remove the daggerboard from below.
That is why I think the proper repair here is a deck doubler plate under the deck brackets with a cutout for the daggerboard (about 6 by 9 inches I think, 1/10 inch thick would be enough for stainless steel). This plate would need to be cut and drilled to match each boat, not sure how to make a universal part.
Laura at Tattoo stated the mast was not supported at the front of the mast step - but looking at it, this plate bolts to the mast base at the center only (not a rigid connection) and a downward force has to be spread between the pivot bolt and the forward foot. this forward foot needs a solid base.
The fact that the mast pivots changes everything. You can no longer just support the base by the rear pivot bolt without placing undue strain and friction on the pivot bearing.That might have been overlooked, which would explain Laura's answer.
Concur. There's no way that forces are not divided between the bolt and the forward foot. They don't have to be equal, but they're definitely present. And I concur that another SS plate below the mast foot cut out for the daggerboard is the correct fix, but I worry about corrosion between the plates where water will settle and be worked in by mast pumping action. I think it might be a lot simpler to just weld a small plate on the forward bracket for the foot to rest on.
How difficult will removing and re-bedding the mast-foot be?
Hard to tell, but another option is to weld (since we are welding) two short pins (say 3/8" dia by 1" long, with flats, for e.g.) protruding out the side of the mast bottom plate so that when the mast is pivoted forward they rest on the top edge of the angle irons mounted on the top of the deck (that are put there by the factory to take the force). That way all the force is downward over a large footprint onto the deck surface (through the already-in-place angle irons), and in an area already reinforced to take it. (?)
Now there would be no force on the area already demonstrated to have weakness.
raycarlson wrote:Hard to believe your not getting expert help from Mac people. According to one of our members(yukonbob) i think, the mac was designed using naval architects, and a team of engineers with certified,registared and stamped approved detailed exacting drawings suitable for courtroom evidence, I would of thought Roger and a team of engineers would have shown up on your doorstep to assist. Not really but I guess it doesn't hurt to fantasize your boat wasn't designed on yellow legal pad and napkins at the local Denny's.........LOL You did a decent job I wouldn't worry to much.It was probably done on initial rigging when the side stays were to long and let the mast tilt to far forward before being restrained, once side stays are set for length they will not let the mast lean forward far enough to cause penetration like that.
Rob's right, this isn't a design issue but a manufacturing issue. You can design and engineer the sh*t out of just about anything, but it comes down to QC and the people/person who buld it. Ix is also right that as well as you yourself point out that there are many variables regarding the cause of damage. Is it user error? the Manufacturer? the supllier (bad batch of resin/glass etc)? Lot of 'if's" here. Repair job looks solid, want some finished product pics too when you glass over it.
A few years ago (for repaingning FG decks) I had thrown the idea of injecting a slurry of resin and short strand glass using a large mouth plastic sirynge that would be able to fill voids even in tight spaces. I have noticed there are a ton of small bubbles in the gel coat and every year I notice another one or two, especially in the cockopit. Little voids that when pressed or hit crumble the gel and leave little black holes. Maybe going a little heavy on the second gel coat to save time? Maybe something similar at your mast base. There seems to be similar issues but not the faliure Rob's seeing?
Matt - agree that a metal base is needed but cannot add just under the forward foot - would need to space up the aft part of the bracket also where the pin is (unless it was inset into the deck, sort of like I have done with the small brass plate). Seahouse's idea of a pin (or plate) to rest on the top of the deck brackets is also a good workable solution - one that could actually be stocked as a replacement/upgrade part (anyone at BWY following this? - Product improvement opportunity).
Looks pretty easy to remove/replace the deck brackets - the 4 bolts are easily accessible. Also reasonable to make a new set of brackets with a connecting plate at the forward end - with the aft mount hole moved up to accommodate the thickness of the plate.
Drill a second hole similar to the rear bolt. With the shape of the foot it just might work / fit. A second option would be to remove the entire bracket and get a base plate / shim made up to fit under the entire bracket with solid plates wherever you needed them. You’d have to lengthen the rigging but should be within the chain plates and turnbuckles allotment.
yukonbob wrote:A second option would be to remove the entire bracket and get a base plate / shim made up to fit under the entire bracket with solid plates wherever you needed them. You’d have to lengthen the rigging but should be within the chain plates and turnbuckles allotment.
That's what I'd probably do, if moving the angles to center them on the slot isn't an option. A U-shaped piece that clears the slot, with holes for the bolts, is all that's needed.
It just seems odd that so much compressive force is placed (normally) on such a small patch of gel-coated FRP as exists under the corners of that bent tang.
