All the bits are back.
Well the early hours of yesterday morning were the darkest yet. Laying in bed wide awake with thoughts that you would always push aside now seemingly standing around the bed looking back at you. I looked forward to the morning light.
When it came we all jumped in the RIB and headed across to 'speed-spot' to pick up the wing. It had blown real hard the previous afternoon and the wing had been sand-blasted... but it was OK... or as good as we had left it.
We removed the flaps. They were broken in a few places and all the hinges were stripped, but they were easily repairable. The one we took home yesterday was the worst. I turned the wing over and looked at the underside. A piece of the strut was still attached. When Hiskia saw one of the pictures of the strut from yesterday he commented 'Look, it's made the number 4'. It had.
I am amazed at how little damage there is to the main section of the wing, especially when you see what it did to the hard carbon beam. The white, moulded leading edge component is a bit scratched and cracked in places but nothing compared to the first, lesser crash.
We loaded it all onto the front of the RIB and scraped back across the lagoon on a low-tide. Once back at the container we stripped the wing covering for a closer inspection. There was some delamination on the 'Fibre-fusion' ribs... but that was about it. the Compo-Tech spar had survived yet again.
The wing in general had survived.
The beam seems to have suffered the worst. It is split and broken everywhere. Lengthwise, chord-wise, internally and on the ends. The entire leading edge is split as is a large section of the back. That is going to be the biggest job. Just like last time we will cut away all the trash and approach each repair individually. It can be repaired. It has to be as it is really the only option.
The bigger issue of course is why is it doing this? The word that keeps coming up is 'Fundamental'.
Something is fundamentally wrong with either the boat or our approach.
One of the problems is simply getting data off the boat. Already my 'seat-of-the-pants' assessment of what happened is probably changing. Things happen in rapid succession and understanding the order of events is vital.
Whatever that order is, the result is undeniable. A huge round-up towards certain destruction that the driver struggles to prevent let alone correct.
Yep, something is fundamentally wrong.
I've said it before and I will say it again. The boat simply must have no tendency to go that way AT ALL.
Why can't we make it have the same tendency in the other direction? Why does sheeting on the wing make the problem worse? It defies my logic. Maybe it was the air rudder and the fact that we had it set at an angle that was good to a point but then it stalled and became a drag force. We are looking through all options. I don't think that the boat needs a major re-design. Having a free swinging beam is a known theory but it also adds a whole new level of complication. You have to fully understand this boat before you can put that forward as an option. we are still trying.
The last few days have been a real kick in the guts. It feels like we just copped our second 'strike'.
But that's cool.
It's not going to end like this.
Our support cast of sponsors and friends has already begun to swing into action and we are not alone out here.
I will pull on the white-suit and start 'operating' today. Meanwhile the discussion will remain open as to how we will resolve this boats suicidal tendencies.
We have a month until our visas run-out.
We have a month to try and sort this out.
We will give it our best shot.
Cheers, Paul.
Paul Larsen
Mobile: + 44 (0) 794 684 1929
E-mail: paularsen1@aol.com
www.sailrocket.com
Mobile: + 44 (0) 794 684 1929
E-mail: paularsen1@aol.com
www.sailrocket.com
posted by Paul at 10:39 am
5 Comments:
My deepest respect for your perseverence. That takes some character !
The free swinging rigging is as for balance, control etc is concerned the best, my design has it and it does work. But to make it work you need a design that is far different from Sailrocket and that inevitably does have more parasitic drag. And for a boat that's going for the ultimate world record it is not a good idea.
(Although I think it can be done but that takes a boat even different (and bigger) from the one you and I are working on.)
I also do not understand why sheeting in makes you go windward. Maybe like you say there was an other factor involved, like the rudder.
But I do understand why the wing slams in the beam when you do.
And I do understand why 20 knots of wind doesn't make you go 50. And I have some real concern about the front foil loosing contact while the beam is so far in front. As you will go faster this risc is going to be greater and it can result in a real dangerous flipover.
Just consider these comparisons:
Just the fact that Sailrocket is bigger is an advantage. the same sail to weight ratio in extacly the same boat but say two times bigger makes you go faster of course. But Sailrocket is in a lot of other aspects not in the advantage:
Tillman weighs some 80 kg and uses a 9 meter (and doesn't get lifted !) in 30-40 knots of wind (or even more ?)
Sailrocket weighs some 280 kg total and uses 18 meter of sail in 20-30 knots.
Sailrocket has an inclined foil and excentricly placed weight.
Tillman has no foil that creates a downward force and is perfectly balanced and has a much smaller and more efficient (adapting) planing surface.
Parasitic drag is hard to compare, but I have no reason to think Sailrocket is in the advantage there.
What wind to speed ratio's have you got untill now ? Approx 1:1 íf I'm not mistaken. How do you think this will improve with the plans you have for Sailrocket ? You have no planing hump to pass and the wind/speed ratio mostly doesn't get any better with more wind, especially when you don't have a capsizing momentum to decrease like normal boats when reefing.
So I'm afraid I must say I think sailrocket needs at least as much wind as Tillman. And is Sailrocket ready for that, I think not.
It's really not to just critisise.
My heart and soul goes in the concept for 14 years now and it is really how I see things and it is just to help the concept go to it's full potential.
Good luck with the repair.
Johan
The severe and sudden rounding up issues indicate the craft is not naturally balanced. Once the hull under the wing lifts clear, then the forward force of wing will make the craft turn. The beam is very long and the wing is perched right at the end. This is a massive lever that has to be resisted by the rudder.
When the wing hull is in touch with the water, the drag helps prevent the rounding up.
You should consider putting a rudder on the wing hull. A small rudder here with the leverage of the beam may resist the rounding up better.
There may be other issues like the planing surfaces or the underwater foil suddenly hydraulically failing and acting as a brake causing massive drag on the main hull. The craft will then just pivot round on the main hull
The Macquarie boat has its wing much closer to the planing surfaces. The wing will provide a bearing off force but as the craft heels the planing hulls will want to round up to balance the craft. I suspect the Macquarie boat is pretty well balanced hence its rudders are tiny. This is also why it can hit around three times wind speed.
These are only my layman views !
Hope you get things repaired and the chance for a few more attempts.
Steve
It's a very hard boat to understand and both the previous comments have good and bad points. For starters, we operate in a wind to speed ratio of around 2.5 to 1. When we did 38.3 knots we only measured a mean wind speed of around 17.4! Windsurfers and kiteboards have very little righting moment in comparison and are forced to run away from the apparent build up whilst we run right into it.
On another note, although the drive source is out on a 30' arm, the line of drive is in fact in allignment with the foil. It is a sail... not an outboard. When we are going fast the boat is configured so that if the beam became string, the wing would stay where it is.
There is a problem with the boat and it is fundamental. the base concept is sound and almost indesputable. We have had it checked by the best. If there is something basically wrong then I am not going to spend another minute wasting my time. What we do need to work out is how to make it all work in a controllable manner.
We will.
keep the tips coming. we read them all and consider them on there merits.
Cheers, Paul.
This is Steven again. Thanks for the reply. Maybe I'm missing something here. If the line of drive from the wing is in line with the foil, it will be in line with the hull, ie. a bit like having a tow with the tow rope attached to the nose of the hull. But the wing is 30' out on one side. The drive may be parallel to the hull/foil but its not in line.
I still believe the drive from the wing is turning the hull. At lower speeds, say 20 knots hull speed you will have some 40 knots of apparent over the wing. At 40 knots hull speed, the apparent jumps to 60 knots. The drive forces more than double. At the same time the hull drag doubles or probably a lot more, especially with the rudder (water or air) on full lock). If the wing float clears the water, the boat will just round up. Has it ever beared off the wind without using the rudder ?
At lower speeds the wing float is planing and the drag from this on 30' arm coupled with the rudder action helps balance the boat.
Adding an extra underwater foil to the hull will help the hull to track better but it will add more drag. I still think the boat will round up at a certain speed.
Of course, all my lay views and I hope I'm proved wrong
When you sailed 38 knots, over what distance was it ? And what was the average speed over 500 meter when the wind was 18 knots ?
But it's good to hear speed/wind is more then I thought.
But the fact that kiteboarders go downwind doesn't make the speedprediction any less valid.
It does give another picture on when a kiter or sailrocket will get lifted when no inclined foil is involved. But sailrocket is heavier compared to sail area and if the boat is well balanced a skipping foil is no problem. You could even make it curved but vertical. Neutral as long as it is in the water but creating a downforce once partly out.
But Sailrocket as it is now is very dangerous when the foil skips, and it has already. It's better to have a boat where it doesn't matter when this occurs because you never can be sure.
And isn't it a goord idea to prevent the wing from slamin into the beam when a round up occurs. Of the stearing you are not sure yet but it seems to me you can be sure that if a roudup iccurs the wing will come down again.
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