Tube height

[seawolfribs]

i think your both drunk and does really matter im drunk

[jwalker]

Perhaps I shouldn't have asked.

[Louise]

Originally Posted by Louise

please explain to me the advantage of having tubes in the water in a following sea? (Cos I'm just a girlie! )

You haven't answered my question Jeff.

[jwalker]

I think it's about the third from last sentence. The one where I used if instead of is. Did Richard miss that one?

[Louise]

Originally Posted by jwalker

Given that wave characteristics are essentially 'now you see them, now you don't', having the stability of the tubes in the wallowing sea if a definite plus.

A following sea isn't necessarily a wallowing sea though!

I still don't understand how having tubes dragging in the water behind you as you keep 5 knots or so ahead of the waves is going to help?

[Richard B]

Originally Posted by jwalker

Please, someone else, is what I've written unintelligible?

Well your latest edit has improved things slightly now that you've changed the figures, but parts of it are still jackanory! Here's the ORIGINAL text before you edited it... (I've highlighted in bold red the bit you changed )

Originally Posted by jwalker

I do that with my tubes in the water, it works fine. However, that technique is mostly only valid in a head sea. For the boats I've had experience of, the effect only really begins to happen at 30ish mph but it becomes reasonably effective at about 35mph+. Given that a reasonable sea is going to have waves advancing toward you at about 15-20mph then the combination of boat speed plus wave speed is in the region of 50+mph for the boat to start cresting the waves neatly. If you are in a following sea, then it would seam reasonable to assume that the boat speed is going to have to be in the region of 65+mph to achieve the same effect. However, because of the wave shape, it does tend to help by ramping the boat up the slope for the jump to the next wave so there is the benefit this gives. The upshot of all my blethers is, that you need a seriously fast boat to use that technique into anything but a head sea and even then the boat must be capable of a good turn of speed. And, if yo! u don't have very fast boat, in a following sea a comfortable speed to travel is just a couple of mph faster than the wave speed. This eliminates slamming and the boat doesn't attempt to dive into the face of the wave infront. Given that wave characteristics are essentially 'now you see them, now you don't', having the stability of the tubes in the wallowing sea if a definate plus. And, as I previously said, they're a plus in a beam sea too.

Tell me again why I don't want my rib tubes in the water...

Now let's have a look at what you were waffling, sorry blethering, about...

...it becomes reasonably effective at about 35mph+. Given that a reasonable sea is going to have waves advancing toward you at about 15-20mph then the combination of boat speed plus wave speed is in the region of 50+mph for the boat to start cresting the waves neatly.

You're over-estimating wave speeds, from my experience, although it's likely that we've encountered different ranges of sea states. I've found that anything over 35kts becomes effective in a head sea, with 40kts (50mph) giving an exhilarating, smooth ride. Confused seas without any particular wave direction can be approached with this technique too. Think about why it works so well - you're presenting the least possible hull surface to the water so you dont hit much of it. Unless you have very low tubes, in which case you're beating the waves into submission with a couple of flabby sausages!

If you are in a following sea, then it would seam reasonable to assume that the boat speed is going to have to be in the region of 65+mph to achieve the same effect.

Now you're getting carried away Jeff! In a following sea, your speed "through the water" (or at least relative to the waves) will be lower. Did you mean speed over the ground, or through the water? Speed through the water makes sense. You will only need a craft capable of 15mph faster than the waves to make comfortable progress. If you do 65+mph then you're heading for a big stuff!

you need a seriously fast boat to use that technique into anything but a head sea and even then the boat must be capable of a good turn of speed. And, if you don't have very fast boat, in a following sea a comfortable speed to travel is just a couple of mph faster than the wave speed.

At last you're making sense! I wouldn't advocate the technique in a following sea of any great height, I didn't suggest so, you've just chosen to follow that line of argument.

You still haven't qualified why you need your tubes in the water in a following sea. And you won't, because you can't, because it's complete pish.

I'm off to open a cold one, maybe two, then I may be able to understand you!

[jwalker]

Originally Posted by Louise

A following sea isn't necessarily a wallowing sea though!

Given the content of the previous two sentences in the paragraph and your boating experience, I expected you to understand and know that a boat will wallow in the trough as the wave formation subsides due to it's cyclic nature.

I still don't understand how having tubes dragging in the water behind you as you keep 5 knots or so ahead of the waves is going to help?

It's not just that they drag behind but that they also drag out to the side. This gives lateral stability to the boat and support to the stern while it is in a difficult situation. I appreciate that Scorps have very little tube to the stern so you may not have experience of the benefit.

Now your arithmetic is failing. I thought I said a couple of mph.

It would be worth swatting up what the water particles are doing inside a wave and how this effects the formation of the wave and it's motion through the water.

[jwalker]

Jeez, I thought you were clever. Boat at 35 + wave coming toward you at 15 = 50 over the waves

Boat at 35 - following wave at 15 gives speed over the waves of 20. We were talking about travelling over the wave crests, weren't we?

I did originally say 65 rather than 50 and that's why I did a smillie at your comment.

Oh yeh, I agree, approximately, with your speeds. I thought that is what I said. (My tubes in contact with the water obviously help my boat to travel over the waves more easily. )

[Louise]

Originally Posted by jwalker

I expected you to understand and know that a boat will wallow in the trough as the wave formation subsides due to it's cyclic nature

I don't recall 'wallowing' in any following sea I've been in - we've always cut through straight and true. The only 'wallowing' we do is when the boat is at rest.

It's not just that they drag behind but that they also drag out to the side. This gives lateral stability to the boat and support to the stern while it is in a difficult situation.

Only 'difficult' if you haven't got on the throttle quickly enough, surely?

I appreciate that Scorps have very little tube to the stern so you may not have experience of the benefit.

I've been in a boat that did and I didn't like the ride as much as in our boat.

Now your arithmetic is failing. I thought I said a couple of mph.

OK so we're arguing about 3.75mph!

It would be worth swatting up what the water particles are doing inside a wave and how this effects the formation of the wave and it's motion through the water.

Better still - explain it here please so we can all learn and discuss how it applies to the debate.

[jwalker]

Nah, it's getting silly and I can't be arsed. I'm off to concentrate on Goldie Hawn on the telly. Night, night.

[Richard B]

Lot of this about from you tonight, Jeff....

[jwalker]

I think you've lost. Bye.

[Richard B]

Originally Posted by jwalker

I think you've lost. Bye.

[Jonny Fuller]

It seems to me that Richard said in his original post summat like: "if your tube is in the water at speed, you will have very poor high speed handling"
Which is pretty true.

The Argument, sorry, discussion, seems to have been swung around to another angle.

I agree, if at low speed, having ya stableizers on might help with roll stability, but once you're travelling quickly (original statement), a combination of the dynamics of the hull design (a good one that is) and a good driver, who anticipates and corrects for the roll brought on by a beam, or 3/4 sea is fine.

Dragging ya fenders about at speed aint good, they're too bouncy.

A good, if rather extreme example is how easily some of the race ribs with bigger toobs have barrel rolled in a straight line, bouncing from toob to toob.

like this:

http://www.jfvideo.co.uk/gallery/Gen...ett_roll_small

or this:

[jwalker]

Yes, I watched the vid of that roll and it certainly went over very easily. Do you reckon it was just the bounce from the tubes?

[Rogue Wave]

I thought the twin Yanmar model with twin Jets represented good value. Any Chance of a trial when I get back from the Norf C. Also whats the smallest of your bots you could put a diesel jet combination on?

[Jonny Fuller]

Originally Posted by jwalker

Yes, I watched the vid of that roll and it certainly went over very easily. Do you reckon it was just the bounce from the tubes?

No, they're running close to 100mph, crossing a diagonal wake, a dangerous manoeuvre in any boat, but the tubes certainly seem to add to the 'pendulum effect', rather than damp it out.


Many of the 'pure race' type ribs have relatively small diameter tubes, these Buzzi 36's had quite large ones, and I know of 3 instances of them rolling in this way (whilst running straight, rather than 'in a turn', the latter is understandably more common)'

The later generation of that boat from Buzzi is 'tubeless'.

[Hightower]

You BIG boys are fine with your 200hp+/40 knotts+ RIBs but give a thought to us smaller guys.

In a head sea, it's all about how much punishment us humans can take before we back off.

In anything but the slightest following sea I have to back right off and as JW said, cruise at 5knotts faster than the wave. I've tried to go flat out as everyone suggests and it seems to work over some waves and not over others, I had a nasty stuff and ended up with a wheel shaped bruise on my chest. I just won't do it anymore, too dangerous! This test was carried out when I had my Yam 80 on the back, with the extra weight of the Merc and a deck locker on the stern the following wave handling has improved tremendously, but I'm yet to sample the type of sea's I conducted my tests in.

As for the tubes in water......I think the boat would sink if my tubes where deflated. When I replaced my outboard I noticed no difference in water level at the transom, suggesting the amount of bouyancy the tubes give.

As for Tube bounce, hadn't thought of that one Richard. Might be why Kohaku gets out of shape at 40knotts so easily, but I can always trim in to get rid of this but must have reached the maximum design speed for my hull. Perhaps Daniel could give me an indication of his top speed in his BWM with a 130 on the back.

[paul tilley]

the latest generation of buzzis may be hard boats but i think drew langdon regularly beats the hard boats in his buzzi RIB and is leading his class .

[paul tilley]

should have posted last comment on boatmad really !!