Thursday, February 15, 2018

NEW HALBERG RASSY 57 VERSUS AMEL 55


A design comparison since while the Amel has been on the water already for some years, the Halberg Rassy 57 is being built. Even so, looking at the design data, much can be said regarding the similarities and differences between the two boats, if we know how to interpret them.

Looking at the new Halberg-Rassy we can say that they changed for good, leaving definitively old outdated designs and proposing contemporary state of the art designs for bluewater sailing.

The first ones to be congratulated for this are the boat designer and the director of the company, both sons of the ones that preceded them and that are the main responsible for this change on Halberg Rassy character, once very conservative sailboats, now modern ones.

And of course, the clients deserve congratulations too because if they had stuck to the outdated designs it would be impossible for Halberg-Rassy to have maintained this direction that started with the 372, already 8 years ago.

Some brands, like Amel, embraced contemporary design without maintaining the good things those old designs had, namely a very good seaworthiness with great safety stability and a great AVS but that was not the case with Halberg Rassy. In what regards that the differences between the Amel 55 and the new Halberg Rassy 57 are simply huge.

Both boats have similar bulbed keels, the Halberg Rassy has more draft as standard, 2.43 to 2.20m (and more draft potentiates ballast) having the Rassy 35% B/D and the Amel 55 27% B/D. If we chose to have a Rassy with only 2.20m draft (like the Amel 55) then the B/D would be considerably higher than 35% to compensate the RM.

In what regards B/D there is a huge difference that  is proportional to the difference on reserve stability, AVS and inverted stability between the two boats.

But we know that such difference, even if very important to boat seaworthiness, does not translate necessarily in a big advantage in what regards sailing. Today, with beamy hulls, only on stronger conditions that extra B/D would make a difference and the excess of weight, due to more ballast, can have a negative effect on light wind or downwind performance.

And in fact the HR 57 (a bigger boat too) is heavier, 28T to 21.8 but that difference in weight is proportionally much less than the difference between the ballast of the two boats (9.9T to 5.9T). Besides ballast and ballast CG the other big factors for stability are beam, hull shape and weight.

Being the HR heavier, having much more ballast, with a lower ballast CG, having a hull shape that increases hull form stability and being considerably beamier (5.11 to 4.14m) the overall stability of the Halberg Rassy is much bigger. If we add that to the much better reserve stability, bigger AVS, smaller inverted stability and ability to sail better on strong conditions we will have a more seaworthy boat and a much better bluewater boat.

Regarding speed on light conditions does the much bigger ballast and superior displacement mean that the lighter and narrower Amel 55 will be faster on those conditions? Beam, on light wind conditions, has some negative consequences even if not as much as weight and in what regards both counts the Amel has less so it would only need a bit less SA/D to match the Halberg Rassy performance, assuming a similar D/L.

But if the differences regarding SA/D are not very big (HR has 20.1, Amel has 19.8) the differences regarding D/L are very considerable, being the HR a lighter boat (165.6 to 185.5) if we consider as we should the LWL.

Since the entries on the HR don’t seem less finer than the ones on the Amel (even if the boat is beamier) I would say that the performance in light wind with the standard sails should be very similar  but using a code 0 the HR would be faster, since it can carry much more sail area (much more stability). 

In fact these boats compared with their older sisters sail remarkably well in light wind. The HR announces 8.75 knots in a 90 degree true wind angle with 10 knots true wind and that is a good sail performance. On medium and strong conditions the Halberg Rassy will be faster or much faster and also easier to sail fast downwind on autopilot due to more beam and transom’s shape.

Both  are good looking boats with different sail layouts and different interiors both with a very good build quality, with several interior layout options. Lots of storage with space for everything, from the washing machine to the AC and generator. The tankage is good, all the systems are designed for push button sailing making these boats easy to sail for a duo crew or even solo and both have a big engine that will give them a motor-sailor capacity.

If the sailing program is coastal sailing with offshore passages, transats or circumnavigations on low latitudes and on the right season choosing between one or the other is a question of taste. But if someone wishes to have a boat that if things go wrong can have an outstanding behavior and performance, if the program includes sailing on high latitudes or out of the season, the obvious choice is the Halberg Rassy 57.

The funny thing here is that the Amel is the one that has the fame of being a great bluewater boat (due to past models) while in fact, if we look at the contemporary models, it is the Halberg Rassy that is by far a better boat in what concerns bluewater sailing on adverse conditions.

5 comments:

  1. Why not mention the twin spade rudders of the HR vs the skeged rudder of the Amel?

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    1. I did not refer the difference in rudders because it is secondary in what regards the difference between the two boats in what regards seaworthiness and sail performance in bad weather.

      In what regards rudder design and performance the twin rudders of the HR57 are several steeps ahead of the Amel 55 rudder. Amel has recognized this since on their last design, the Amel 50 they use already twin rudders similar to the ones on the HR.

      I assume you are new to the blog since I had already made a post about rudder design were all this is explained:

      http://interestingsailboats.blogspot.pt/2014/11/what-rudder-is-best-for-cruising-skeg.html

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  2. Considered as a bluewater boat the HR57 is kind of disappointing if you compare the stability curve of the older HR55 to the HR57 the AVS is quite poor and approx. 10 degrees lower compared to the HR55. Also the important righting force at 90 degrees (touch down) develops the same force than at 18 degrees only! The same figure for the HR55 lies clearly above 30 degrees.

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  3. You should be kidding, if you call the 120º AVS of the HR57 poor what would you call to the Amel 55 AVS that should be between 110 and 115º degrees?LOL

    Bigger boats don't need an AVS as big as smaller ones since the chances of a capsize are smaller and that is taken into account on what is demanded by the RCD in what regards AVS. An AVS of 120 º is a good one for a boat of this size and weight.

    I don't know if the stability curves are comparable since they have modified the way they are calculated for the RCD. On the time of the certification of the 55 only one curve was needed while on the 57 two curves are demanded.

    But I do know that the stability curve on the 57 is wrong: the curve with the boat on full load has to have a bigger RM (as it is the case) but a smaller AVS and on this case it has a bigger AVS and that is obviously impossible.

    Anyway looking at the data from the two boats I don't believe on that difference on the AVS. Probably they are very close and certainly the 57 has a lot more RM at 25º, a bigger Max RM while the RM at 90º should be very similar as well the inverted stability proportion.

    Meaning that the 57 is as good as the 55 in what regards seaworthiness and it is a faster and more powerful boat.

    If you have doubts ask HR and I am quite sure they will tell you the same I am saying even if they should be a bit embarrassed with that mistake on the stability curve. LOL

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  4. Thx Paulo. Your detailed answer is much appreciated!

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