Which alloy of aluminium does Fortress use for its anchors

[DJE]

If it's 6061 then you really need to know the degree of heat-treatment. From memory 6061-T6 is about twice the strength of the same alloy without heat treatment.

 

[Neeves]

If it's 6061 then you really need to know the degree of heat-treatment. From memory 6061-T6 is about twice the strength of the same alloy without heat treatment.

You are the first to mention it. Tensile strength of 6061 T6 around 300MPa (compared to a mild steel to AISI 1020 of 420 MPa). The Bendy shanks, that Vyv refers, to were meant to be 800 MPa (the original spec).

Whilst they own the dies for extruding the actual work is subcontracted. I assume the extruder conducts the tempering. I recall they do not use 5083 as the alloy as 6061, is better for extrusion.

T6 seems the choice for an anchor.

Jonathan

 

[noelex]

It all seems a bit contradictory;. I wish you would offer clarity what point you are trying to make. and get the colours of Fortress correct (a pub quiz may depend on the accuracy of the information you provide )

Jonathan

Sarabande is correct in noting that Fortress have used colour coding to denote changes in the design over the years. This means when ordering replacement parts (say due to a bent shank) the correct part can be sent.

As has been posted, the most recent anchors are coloured red, earlier anchors were mostly blue or black with the latter being the oldest, but otherwise colours have been used.

It is also true to say that Fortress have made some significant changes over the years, hence the need for this colour coding. The alterations include making the shank thicker (for greater strength) and adding the "mud palms". It has also been mentioned that the very early models did not have an adjustable fluke angle. Personally, I have never seen a Fortress anchor without this feature, but if buying one secondhand it is worth checking that the fluke angle can be altered.

Note this colour coding is only applied to the Fortress logo. Fortress also very briefly marketed different coloured anchors. The whole shank and fluke was available in various colours. The design of these was the most modern "red" version, but the Fortress logo was highlighted in white on these brightly coloured anchors.

 

[Neeves]

Sarabande is correct in noting that Fortress have used colour coding to denote changes in the design over the years. This means when ordering replacement parts (say due to a bent shank) the correct part can be sent.

As has been posted, the most recent anchors are coloured red, earlier anchors were mostly blue or black with the latter being the oldest, but otherwise colours have been used.

It is also true to say that Fortress have made some significant changes over the years, hence the need for this colour coding. The alterations include making the shank thicker (for greater strength) and adding the "mud palms". It has also been mentioned that the very early models did not have an adjustable fluke angle. Personally, I have never seen a Fortress anchor without this feature, but if buying one secondhand it is worth checking that the fluke angle can be altered.

Note this colour coding is only applied to the Fortress logo. Fortress also very briefly marketed different coloured anchors. The whole shank and fluke was available in various colours. The design of these was the most modern "red" version, but the Fortress logo was highlighted in white on these brightly coloured anchors.

So since the late 80s the Fortress has enjoyed significant changes.

A thicker shank so that it does not bend (to reduce the frequency of claims for bent shanks) and the attachment of mud palms. Big deal.

The comment on 'design and development' I originally made was in answer to an earlier post suggesting design and development would have been on going over the last 5 years. I suggested dreams were free - and have yet to learn of any changes in the period - earlier it was acknowledged that mud palms were added - and the thicker shank is hardly rocket science.

What it shows is the design was about right from the outset - and there was little room for improvement (basically 2 changes in the almost 4 decades since its release). I've never seen the Lewmar clone - it will be interesting to know if they learnt. What is strange about the Lewmar development of their fortress clone is that it must have been a significant investment to machine the dies for the extrusions - and since then there has been no promotion and certainly not a mention on forum (the same goes for Epsilon).

Shanks should not bend, especially after the bendy shank saga. To sell an anchor now with all the knowledge we have all learnt is ignorance and crass stupidity. To ship out anchors with inadequate shanks, knowing that new, stronger, shanks are already being shipped, is morally indefensible.

Jonathan

 

[gaylord694]

In fact this information is available. Rocna, Mantus, Delta, Bugel have all released materials information for their products. Most of it can be found in my book Metals in Boats

I totally disagree with the suggestion that there is no place for this information on the forum. Anyone who remembers the 'bent shank Rocna' saga will be aware that internet pressure caused the truth to come out and ultimately led to the takeover of the company by CMP and a complete rethink of the materials.

Similarly, the original shanks on Mantus anchors were shown to be insufficiently strong thanks to forum discussion. Mantus upgraded the material to their credit before any incidents occurred.

When I was looking at sorting a rocna for the boat I phoned them and they were most helpful in the makeup of there anchor, ie what metals and materials......Why on earth would they not after all they want to sell as many as possible

 

[Neeves]

When I was looking at sorting a rocna for the boat I phoned them and they were most helpful in the makeup of there anchor, ie what metals and materials......Why on earth would they not after all they want to sell as many as possible

If you were keen you can test the metal easily, Vyv has a ball bearing test you can use. You simply need a linen glass, ballbearing, about 10mm diameter is easy to handle, and a big bench vice. I assume its somewhere in his website. Though you would need to be really keen as you need to remove a small patch of the galvanising. Its a comparative test, hardness is related to tensile strength, and I have collected samples of steels, primarily bolts, of different tensile strengths to allow comparison. I have assumed you could test aluminium the same way.

Jonathan

 

[vyv_cox]

If you were keen you can test the metal easily, Vyv has a ball bearing test you can use. You simply need a linen glass, ballbearing, about 10mm diameter is easy to handle, and a big bench vice. I assume its somewhere in his website. Though you would need to be really keen as you need to remove a small patch of the galvanising. Its a comparative test, hardness is related to tensile strength, and I have collected samples of steels, primarily bolts, of different tensile strengths to allow comparison. I have assumed you could test aluminium the same way.

Jonathan

The method works well for high hardness steels because the heat treatment of the stronger bolts is accurately controlled. I suspect that there might be a range of hardnesses in, say, a 4.5 or 5.8 bolt that might not give accurate values for softer test metals.

 

[noelex]

The usual problem when examining an aluminium component on a boat is to determine if a proper marine grade aluminium has been used (in simple terms, one of the six series or preferably one of the five series, such as 5083), or if the manufacturer has made compromises.

Unfortunately, many of the non marine general purpose grade of aluminium with inferior corrosion resistance have a very similar hardness. There are exceptions. Some of the non marine aluminium grades are significantly harder, but for most products you are unlikely to determine if a marine grade aluminium has been used with a simple hardness test.

 

[Neeves]

The usual problem when examining an aluminium component on a boat is to determine if a proper marine grade aluminium has been used (in simple terms, one of the six series or preferably one of the five series, such as 5083), or if the manufacturer has made compromises.

Unfortunately, many of the non marine general purpose grade of aluminium with inferior corrosion resistance have a very similar hardness. There are exceptions. Some of the non marine aluminium grades are significantly harder, but for most products you are unlikely to determine if a marine grade aluminium has been used with a simple hardness test.

But if the indentation you make in the aluminium alloy is the same size indent under identical compression in an aluminium or steel of known hardness then you have a very good idea of the tensile strength of the metal in question (as hardness is largely proportional to tensile strength). I believe Fortress use the 6 series as it is better, easier, to extrude than the 5 series. Interestingly, as previously mentioned, LFRs are commonly made from the 7 series (and anodised) - which is reputed to have poor corrosion resistance, un-anodised, in sea water.

Jonathan