Mast repair

[doc2b4fun]

hello all, i am looking for some advice as to how best repair my problem.

I have a hunter 23.5 When i bought it a few years ago, the original owner had broke the original mast and replace it with a similar but not exactly the same size extrusion from dwyer mast. Due to the shape being slightly different a different hing plate assembly was needed so it will look different than stock.
He had used the original spreaders but put them on dwyer mounts which didnt hold them tight and i assume this is why the mast base became weak. this year while lowering the mast the base broke free from the mount and cause the "slot" like defects where the base mount was affixed to the extrusion. I have a new base to put into the extrusion base but am looking for advise on how best to handle the fact that there are now gaps where the screws pulled thru and stripped "slots" into the aluminum of the extrusion.

I have gotten several bits of advise but seek other opinions.

1) Heliarc weld the base plate to the mast as is. I was also advised against this by some who say that the welding of aluminum may further weaken it from the heat

2) cut the mast short by the approx 1 cm and see if i have enough play left to tighten the rigging and if not ad a spacer block under the base (between the base plate and the top of the hinge step of block aluminum)

wondering what advise or experience might be out there....

pictures are of the damage; the base plate; the hinge plate, and how they go together

 

[Chief RA]

Welding sounds best but realize that part of your mast heigth is about 1/2" on the bottom of your mast mount. The welder must add 1/2" of aluminum stock to the bottom of that mast as he welds it to the hinge plate or your mast will come out too short. That will cure your problem. Chief

 

[doc2b4fun]

thanks for the reply. i have gotten a new mast base piece. so the welder i spoke to was planning on welding the mast base to the extrusion base. the mast base attaches to the hinge step by drilling two ss screws thru the the bottom of the mast plate and thru the hinge step where two nuts hold it down....

i was just worried when i was advised that welding might weaken the aluminum of the base due to the heat....

thoughts?

Welding sounds best but realize that part of your mast heigth is about 1/2" on the bottom of your mast mount. The welder must add 1/2" of aluminum stock to the bottom of that mast as he welds it to the hinge plate or your mast will come out too short. That will cure your problem. Chief

 

[centerline]

hello all, i am looking for some advice as to how best repair my problem.

I have a hunter 23.5 When i bought it a few years ago, the original owner had broke the original mast and replace it with a similar but not exactly the same size extrusion from dwyer mast. Due to the shape being slightly different a different hing plate assembly was needed so it will look different than stock.
He had used the original spreaders but put them on dwyer mounts which didnt hold them tight and i assume this is why the mast base became weak. this year while lowering the mast the base broke free from the mount and cause the "slot" like defects where the base mount was affixed to the extrusion. I have a new base to put into the extrusion base but am looking for advise on how best to handle the fact that there are now gaps where the screws pulled thru and stripped "slots" into the aluminum of the extrusion.

I have gotten several bits of advise but seek other opinions.

1) Heliarc weld the base plate to the mast as is. I was also advised against this by some who say that the welding of aluminum may further weaken it from the heat

2) cut the mast short by the approx 1 cm and see if i have enough play left to tighten the rigging and if not ad a spacer block under the base (between the base plate and the top of the hinge step of block aluminum)

wondering what advise or experience might be out there....

pictures are of the damage; the base plate; the hinge plate, and how they go together

With the base plate insert you have shown, there is plenty of surface area to drill new holes in the mast and base plate... leave the existing torn out holes to their fate.

If you want the hide the battle scars, take a piece of 1"wide×1/8"thick aluminum strip and wrap around the mast to form a band.... place it over the torn holes and put the newly located base mounting screws thru it to hold it in place.... no one will ever know.

 

[doc2b4fun]

centerline..thanks. my worry was that if you look at the new base plate..there are cut outs in it. i wasnt sure how far away from "slot" defects in the extrusion i would have to go to have full strength. screws or rivets??

With the base plate insert you have shown, there is plenty of surface area to drill new holes in the mast and base plate... leave the existing torn out holes to their fate.

If you want the hide the battle scars, take a piece of 1"wide×1/8"thick aluminum strip and wrap around the mast to form a band.... place it over the torn holes and put the newly located base mounting screws thru it to hold it in place.... no one will ever know.

 

[Chief RA]

I was not aware that your base plate is aluminum as it does not look like it in the picture. A weld will definitely be stronger than those screws! Cheaper/easier to just go with Centerlines suggestion. With the new screw holes further out to fore and aft it will be stronger during its hinged rotation anyway. Chief

 

[doc2b4fun]

corry for confusion: mast extrusion is aluminum. the base plate (shown broken in the picture by itself but i have a new one seen in the last pic ) is some sort of composite; the hinge plate is stainless steel....

I was not aware that your base plate is aluminum as it does not look like it in the picture. A weld will definitely be stronger than those screws! Cheaper/easier to just go with Centerlines suggestion. With the new screw holes further out to fore and aft it will be stronger during its hinged rotation anyway. Chief

 

[Chief RA]

HOLD IT! Whole new ball game! Forget welding a SS plate to an aluminum mast. Now you REALLY better do what Centerline suggested! Chief

 

[doc2b4fun]

great thanks!. the base insert is some sort of composite not stainless. that base plate attaches by bolts to the ss hinge plate.

so screws it is...cheaper too!! or should i use rivets? any strength difference? i really dont need to access the inside of the extrusion and if did i could access thru the top of the mast

as a second off topic question. i have to drill a hole thru that hinge plate as the only one of the predrilled is properly located .... any advise on that? do i need a drill press or can my home drill do it and if so what type of bit..i have titanium bits but have dulled them to **** before drilling out ss rivets

thanks..this is my first boat!

HOLD IT! Whole new ball game! Forget welding a SS plate to an aluminum mast. Now you REALLY better do what Centerline suggested! Chief

 

[Rick Webb]

Confused

What does the spreader have to do with the damage done to the base while lowering the mast?

Did you have the mast raising bridles attached when you were lowering the mast?

As for your mast foot repair. I would use the same holes but put some fender washers on new screws and watch that the holes do not grow. All the screws do is to hold the base onto the mast when it is down. once the mast is raised they are superfluous.

The fender washers will hide the damage and provide enough grip to keep the foot attached. Check the holes frequently but I would bet you will be OK.

 

[doc2b4fun]

Re: Confused

thanks... mast raising bridles..yes. i think the fact that he used some unstable spreaders allowed the mast to move under sail when he had the boat in the years before i got it which weakened the base but i dont know. the base ripped out while lowering at the end of this year

 

[Chief RA]

Rick: Take a close look at that system. Using the old holes will not work! Notice that the mast is secured to that bottom SS pivot plate and as it is dropped it will try to pivot at the mast base too because the SS pivot is a couple inches away from the foot and will pry on it too as it lowers. The pivot point should be just under the back of the mast not 2" back. Thats provided the mast drops to the stern. Chief

 

[Chief RA]

Anytime you drill through hardstuff like SS just start with a small drill and work up. Chief

 

[Rick Webb]

Position of the Base on the Plate

Look at the original foot and base:

http://shop.hunterowners.com/fisco_img/52464.jpg

http://shop.hunterowners.com/fisco_img/52420.jpg

If the geometry is off at all it will add a great deal of pressure to the base and the bridle when lowering or raising the mast. I'd have to look but I am fairly certain that the pivot point for the mast is line with the part of the stanchions that the bridle attaches. My spreaders are a bit sloppy when the mast is lowered but are rigid when the shrouds put tension on them. If they are loose when the mast is up and tightening the shrouds does not help then you should certainly look at fixing that. I am assuming they are swept back just as the original ones were.

To mount the fool to the mast I mentioned using the same holes and fender washers. When original mast was made the foot was attached with pop rivets. I would go that way with fender washers. the aluminum casting of the foot can be a little tough to run a tap through. As for the stainless steel base I'd be inclined to take it to a machine shop and let them do it. They have the equipment to do it easily. You may spend as much as they would charge in drill bits not to mention the frustration. You could let them drill and tap the foot as well if you want to go with screws rather than pop rivets.

This is one that Crazy Dave would have a much more authoritative answer than anyone else is going to give you.

 

[Chief RA]

The problem is with what he has, not what used to be on it. The pin pivot WAS next to the mast base NOW it is 2" further back! Don't use the same ripped out holes due to that extra stress generated. Chief

 

[isaksp00]

I would use aluminum rivets to attach the extrusion to the cast base. In case you happen to twist the mast when raising or lowering again, which I also did once, the rivets may end up being the sacrificial part. That assumes the rivets are indeed strong enough to handle the stresses given that your hinge is further from the mast's center than the way Hunter designed the original.

Without knowing how the stainless plate attaches to the deck, or where, is it feasible to mount the casting closer to the rear of the plate, so the stresses are reduced? That is, get the center of the mast closer to the hinge point.

 

[doc2b4fun]

I was actually thinking about the same thing once that point was brought up. I suppose i can since i will have to reattach the base insert to the hinge plate anyway. Currently the aft edge of the base insert sits about 3/4 inch forward. But when i drill the new holes i could move it back. Will that effect the lenght of my shouds? Theres no backstay. Only a forestay. That being said i think the bottom half of the hinge plate is centered over the original center location so that may ultimately mean the mast is a bit aft of the designed location. Will that matter? I raise and lower the mast several time a season.

 

[Rick Webb]

I'll Look at Mine and Send a Picture

It maybe that you should look into moving the plate attached to the boat to get the geometry correct. The bridle and the mast should hinge on the same plane otherwise it is going to get real sloppy and fall off to one side and bend stuff or get real tight and snap stuff.

Crazy Dave may have already been through this once before and have some wisdom I would not make any significant moves to doing the repair until he gets back online.

 

[centerline]

centerline..thanks. my worry was that if you look at the new base plate..there are cut outs in it. i wasnt sure how far away from "slot" defects in the extrusion i would have to go to have full strength. screws or rivets??

you have to move away from the edge 1.5 times the diameter of the hole you will drill into it, to maintain full strength of the hole... you have plenty of room to go 2x the diameter of the hole and be that much safer...

but still, the mast holes will always be the weakest point.... if it is attached as it was before, and no problems arise again, it will last forever, because the compression is downward with a lot of force when its working... a lot of big boats with deck stepped masts dont have the screws attaching them to the base plate... they just set there with the rigging holding them in place

or.. you can weld it all up, fill the holes, make it as pretty as is it was new, just out of the box... and if, or when there is another problem, you will be either back to square one, or depending on how well it was welded, it may cause worse damage to something else. either way it will be just more expense.... in my metallurgical opinion, it will be just as good to fix it the inexpensive way with a band around it to hide the scar, and if it has no more issues, it will last the life of the boat....

 

[centerline]

Anytime you drill through hardstuff like SS just start with a small drill and work up. Chief

im sure there are different techniques for drilling, but ive drilled all thicknesses and types of stainless and i would recommend a good cutting oil, diluted to the proper viscosity with WATER... and turn the bit very slow, about 120 to 150 rpm... thats 2 revolutions per second.... so thats pretty slow.

cutting fluid is a water soluble oil. nothing else works because pure oil does not absorb heat well, and water does, so the water can absorb and carry the heat away.
if you get the cutting fluid mixed too thick, it wont carry the heat away... too thin and the lubrication goes down.

with this method, any HSS bit will cut it. cobalt may be a bit better, but mostly for when you are drilling many repetitive holes.... but for 30 or 40 holes, a regular bit will work.

i would drill only one time per hole using the size of bit that you need the hole to be.

the problem with drilling stainless is, it will "work harden" itself where the heat builds up (under the bit), so if you try to drill too fast it will create heat and then the hole will never ever be able to be drilled thru in that location.
heat is a mortal enemy to drill bits and stainless steel in combination.

turn the bit slow and steady with a constant stream of fluid to lubricate and cool, and you will find that drilling stainless is no different than drilling mild steel.