This is a company promotional, so it must be approached with some skepticism, but if the results are anywhere close to those claimed it looks like it is worth considering.
This is the results of a study of the effects of adding a “hull vane” to the stern of the Netherlands 108 meter (354 foot) Holland Class OPVs.
Since the operational profile for these ships is likely to similar to those of large Coast Guard cutter, this may be worth a look.
- They claim a 12.5% reduction in fuel consumption,
- A 4% reduction in heave,
- A 7%% reduction in pitch, and
- A 13% reduction in vertical acceleration at the flight deck.
Ooh a trim trab………..
Their sales team are reaching a bit with this aren’t they? It is hardly new is it?
The Hollands already have a trim tab. This is a bit more radical. Does remind me of putting a wing on your car. But now no race cars go out without aerodynamic augmentation.
True. Modern electronics make the “management” of these mechanics easier I suppose. But complicated hull attachments never quite take off do they?
A lot of the advantages of these mechanism can be offset by just building bigger ships.
Here are some comments that were passed to me second hand by e-mail,
There was a paper presented on the application and benefits of hull vanes at FAST 2015 but I had also seen other information on them before.
I would also imagine that the benefits might be quickly eroded as these appendages accumulate marine growth.
Not with modern anti-fouling, surely?
As for that e-mail well all I can say is they say potato………. 🙂
And this sums up the problem………
“Hull vanes and their benefit are real..but very tricky to design and apply because of our still limited abilities to accurately predict the flow field below and aft a bluff transom vessel.”
See my earlier comment on that one. I could also add the answer to the problem of a bluff transom problem is not, um, to use a bluff transom! See the design of Queen Mary 2………
We are in short fat frigate territory I think the supposed advantages of the new are easily addressed with cheap steel bent into an appropriate shape. And savings in fuel are more easily found with better engines and better paint on the hull.
I don’t post over at Think Defence any more, but it would be nice to hear what regular commentator on that site “Not A Boffin” has to say about it all.
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Hi Chuck, and others,
First a disclaimer: I am from the Hull Vane sales team and I have presented the paper at the FAST conference. You can download a copy of this paper on our website (www.hullvane.com) from the news section. That will clarify a lot.
Then to answer some of the comments here (and the email quoted, which is not from our team as far as I know):
1. The Hull Vane is very different from a trim tab, because it’s a hydrofoil. Actually the design is not so much speed-dependent, but hull-shape dependent. When it works, it works on quite a wide speed range, as long as the speed is high enough (Froude number in general above 0.2). On the Holland-Class, we achieve a positive result over the entire speed range (from 5 knots to 22 knots), but that’s in part because the Hull Vane allowed (and actually required) a reduction of the depth of the trim wedge which is currently installed.
2. The Hull Vane is a new and patented fuel saving device. Of course hydrofoils have been used before, but never on displacement vessels with the purpose of generating forward thrust and reducing the wavemaking resistance.
3. The angle of attack is more a function of the buttock angle of the bottom plating than it is of the speed. That’s why having an adjustable Hull Vane (we looked at it) gives you a very marginal performance increase, while adding a lot of complexity (hydraulics, control mechanism, maintenance, etc.). The fixed Hull Vane works really well and is not more complex than bilge keels or a bulbous bow. The design is indeed complex and requires both know-how and accurate CFD simulations, taking into account both frictional and pressure drag. From our 12+ years of experience, we know how to get it right, but we also know that it’s very easy to get it wrong. There are ship types where we can’t achieve a positive result, but on patrol vessels and naval vessels, we have consistently achieved very good results.
4. Just like the rudders, and propellers, you indeed want to avoid marine growth, which has a more detrimental effect on appendages than on the main hull. There are solutions to this (coatings), and furthermore the Hull Vane is easily accessible for cleaning without drydocking. On the vessels sailing with the Hull Vane, marine growth has not been an issue.
5. Regarding our “limited abilities to accurately predict the flow field below and aft of a bluff transom vessel”, I completely disagree on that. Our parent company Van Oossanen Naval Architects has used CFD (Fine/Marine) for many years with excellent results, confirmed both by model tests and sea trial results. This includes the results we have obtained for the Hull Vane performance. For stuff like the Hull Vane, where viscous effects (and the thickness of the boundary layer) are important, we believe CFD to be more accurate than model tests.
6. The Hull Vane is not limited to “short fat frigate territory”. We have achieved good results also on the DTMB 5415, a slender destroyer hull shape released for research purposes. The performance is better however on the fuller-bodied and wider-transomed hull shapes like the typical US Coast Guard cutters, which we would very much like to do some work on.
To sum it up briefly, the Hull Vane is very comparable with the bulbous bow, although it looks totally different. If the bulbous bow hadn’t been applied as widely as it is, people would also find it hard to believe that it can reduce the resistance. The bulbous bow also requires careful design to work well and has a speed range in which it works well. One of the main advantages of the Hull Vane is that it also improves the seakeeping (reduced pitching, heaving, yawing and rolling). There’s a video on our website explaining the working principles very clearly. If you have any questions, don’t hesitate to contact me.
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