Bow plate looks "scary"

[Delancey]

Originally Posted by boatpoker

We are going to have to disagree .... I have done it.

Hey no worries, I like being wrong as it means I usually learn something new. Like I said if they can produce a finished part like that using ceramic shell investment including wax work for $120 then I have a lot of work for them! I would certainly appreciate it if you passed along their name please and I am sure they would likewise be happy to have the work.

If they do sand casting, as is much more common, you would certainly know it. Sand casting has a much lower resolution than ceramic shell which everyone who has seen a cast bronze valve or through hull will recognize as the coarse pebbled texture and part lines visible where the fiinished piece has not received any secondary machining. Ceramic shell can precisely cast parts to very high tolerances and can eliminate the need for this machining and a lot of finishing work as well.

One thought that occurred to me is that the OP could fill in the inside of his chocks with wax or Bondo and then cut out the negative space post sand casting with whatever saws and die grinders required. This will be extra work but because of the pebbled texture he will have a lot of grinding and polishing anyway if he wants to achieve the smooth finished appearance of the original.

Boatpoker like I said, let me know your foundery's name. Most appreciated. Cheers

[boatpoker]

Originally Posted by Delancey

Hey no worries, I like being wrong as it means I usually learn something new. Like I said if they can produce a finished part like that using ceramic shell investment including wax work for $120 then I have a lot of work for them! I would certainly appreciate it if you passed along their name please and I am sure they would likewise be happy to have the work.

If they do sand casting, as is much more common, you would certainly know it. Sand casting has a much lower resolution than ceramic shell which everyone who has seen a cast bronze valve or through hull will recognize as the coarse pebbled texture and part lines visible where the fiinished piece has not received any secondary machining. Ceramic shell can precisely cast parts to very high tolerances and can eliminate the need for this machining and a lot of finishing work as well.

One thought that occurred to me is that the OP could fill in the inside of his chocks with wax or Bondo and then cut out the negative space post sand casting with whatever saws and die grinders required. This will be extra work but because of the pebbled texture he will have a lot of grinding and polishing anyway if he wants to achieve the smooth finished appearance of the original.

Boatpoker like I said, let me know your foundery's name. Most appreciated. Cheers

Sorry, I must have read your post too fast ... I have been talking about sand casting all along. The Foundry I use Is Skara Metal Foundry. Jimmy Skara and his wife do a lot of favours for boat people. It is not really their market but they like odd challenges and our world seems full of them.

[Delancey]

Darn it! You had me all excited. Like they say if it sounds too good to be true it probably is.

I would surprised if anybody would do the wax work and ceramic investment on a one off like this for less than $500, not including the actual burnout and casting or any of the work that follows. Once you have the silicone mold made multiple wax copies come relatively cheap but still need to be invested which means adding the sprue and risers followed by days of dipping and drying the investment.

Sand casting is very common. Ceramic investment not very. Anybody who does it would advertise it specifically because there is a big difference between the two. Art bronze founderies are the place to look for folks who want this kind of specialty one-off work done and it usually ain't cheap.

That said, if the OP wants to fill in the undercuts on the chocks as described he could maybe get his local guy to sand cast for a number a lot closer to what you are talking about, he is just going to have to do A LOT of work cutting, grinding, and finishing the piece if he wants it to look pretty. Of course he has to get the original part off the boat which could be a project in and of itself. So does he have the tools and skills? What is his time worth to him?

Maybe drilling two holes and tightening nuts on a U-bolt is the way to go? Personally I'd rather be sailing than grinding.

When making a pattern for a sand casting the pattern itself must be releasable from the two halves of the flask which means it must have draft and no undercuts. For reference see below-
https://en.m.wikipedia.org/wiki/Draft_(engineering)

[Boatyarddog]

Looks to be Aluminum, pull it off and have it heli arc, welded, watch that you don't exceed the tang size on the rigging connector for the clevis pin.
Not that big a deal.


Sent from SV Cloud Duster

[Delancey]

Originally Posted by Boatyarddog

Looks to be Aluminum, pull it off and have it heli arc, welded, watch that you don't exceed the tang size on the rigging connector for the clevis pin.
Not that big a deal.


Sent from SV Cloud Duster

I've cast aluminum and I've welded extruded aluminum shapes, plate, and sheet but I've never welded cast aluminum to extruded aluminum shapes, plate, or sheet.

Other than having seen examples and knowing it can be done and that you can also have problems with parts turning black when anodized it's not something I have experience with and is a bit of a mystery to me.

What alloy would you recommend to replace the broken portion of the eye and what alloy filler rod would you recommend using?

Since the alloys used for casting are different from those used for extruded shapes, plate, or sheet does it matter that you don't know what the original is made from?

Since I assume if you are going to go through the trouble of pulling the piece and welding it that you would have it anodized to protect it, how do you know it won't turn black if you don't know what alloy it is?

Obviously this part gets stressed since it has already broken once, is the heat affected zone on this part somehow something not to be concerned with?

[brianlara 3]

CAST aluminium for a stemhead fitting was, in my opinion, a poor choice in the first place, much cheaper in mass production.
Who here would round a Cape with it when new?
Welded by A Guru wont make it stronger.
Imho...silicon bronzie or s/s fabrication.
People... this is a forestay attachment. The origional was a poor mans choice at best......unless oc course 10kn sailing is only ever anticipated.

[bsurvey]

its casted aluminum, cant be fixed. have one custom made out of 316 stainless

[Delancey]

Originally Posted by brianlara 3

CAST aluminium for a stemhead fitting was, in my opinion, a poor choice in the first place, much cheaper in mass production.
Who here would round a Cape with it when new?
Welded by A Guru wont make it stronger.
Imho...silicon bronzie or s/s fabrication.
People... this is a forestay attachment. The origional was a poor mans choice at best......unless oc course 10kn sailing is only ever anticipated.

I tend to agree. I believe most aluminum winches use castings for the drums but they are largely in compression.

My boat has a cast aluminum stem fitting which is broken, presumably when the PO crashed into a dock or something. The broken portion measures 1/4" thick by about 6" long and it was a clean break. None of the rigging attachments are made to the cast aluminum. Really it's just a bow roller with chocks. The forestay attaches to a chain plate and the tack to a through-bolted U-bolt.

When I was doing aluminum casting we used to pour the leftovers into a steel ingot mold. After it cooled we would come back and break it into smaller pieces where the ingot mild had indentations.

The sections of the ingot mold that had the indentations measured 3" x 4" and you could break them with a single swing of a sledge hammer. Surprisingly easily.

I would be very wary of anyone recommending a welded repair to this piece unless they had actual personal experience welding structural cast aluminum parts. I don't and somehow I suspect anyone who has recommended this doesn't either.

[AKA-None]

You can't properly weld cast aluminum. Period, you can putz with it al you want but it just doesn't work. No strength no penetration, don't even bother.

And yes I was a welder in a former life, not best of the best but pretty darn good and I have never seen any cast al that worked and I've worked with some of the best. Anyone seen al foil welded, I have.


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[brianlara 3]

Delancy, spot on. Cast aluminium has the tensile strength, pound for pound as butter.
Forged aluminium, we make Formula 1 pistons out of that stuff!!
Either silicon bronze or ss fabrication.
But if it was on my boat today I know I can repair it with what I already have on board...1/4" plate usind 1/8 dia rod for the gusset...all 45% silver brazed, flux coatet rods using HI CAL Propane.
Simple job.
Strong, cheap for the OP.

[brianlara 3]

AKA, when I was a younger boy I was welding wheel arches for tourist coaches with 20 dual wheels equals a very big wheel arch.
20 gauge, oxy-acetylene, butt welds....truck loads of massive holes...funny looking back. And a hole that big can't be repaired....if anyone knows this stuff YOU do.
Thought you'd like that yarn.

[jimbunyard]

Scary indeed.

What looks most worrying to me is what appears to be a crack on the port side that runs from just to the right of the rear mounting screw forward to the port fairlead. If that is really a crack, then the fitting has to be repaired or replaced. If not, unless you need all four holes, you could just grind the broken off piece smooth and no one would know the difference.

As far as welding, more than likely it can be done, but you need someone who knows what they're doing.

I don't see how you can avoid removing the fitting. It can't be welded in place, and anyway you really need to know the actual condition of it before you can trust it. If that is a crack on the port side, I'd be seriously looking at getting someone to fabricate something simpler out of 316 SS.

[Celestialsailor]

From a Machinist... This is another junkie aluminum fitting from the good people at Morgan. If you want to do it correctly, take the other one off and eith have another casted (preferably bronze) or better aluminum or take it to a sheet metal fabrication shop (not a machine shop) and hav eat least a 3/16" 316 Stainless one fabricated. From the looks of it the forward shroad attachment point is gone.

[Celestialsailor]

Originally Posted by boatpoker

Take it off, patch up the broken part with Bondo, look up "foundry" in yellow pages, have one cast in Silcon Bronze using the old one as the pattern for about $8 per lb. then take the casting to a machine shop and have it drilled. Total cost should be about $120 if you find the right small foundry.

+1

[slowpoker]

alanbranch; Being a Morgan, it's cast aluminum and looks as if it has a crack on the port side already.
Make it a simple and stronger fix. No new casting, no welding onto the aluminum, do not even have to remove the aluminum piece at all.
Just get a stainless bar, say 3/8" thick x 1 1/4" wide and maybe up to 12" long. Drill a hole for the forestay on one end and two other holes on the other end, about 3" apart for two bolts to go through the hull at the bow with some washers or backing, inside the pointy end of the boat like Seasick said. round off the jagged part that is broken on the aluminum.
For the Jib, or if you are going to put on a separate roller furling drum, attach it to the deck itself, (aft of the aluminum stem piece), by drilling for a heavy 'U' bolt with two washers and nuts under the deck with a strong backing piece there, caulked up well.
Cheap, neat and strong.