humber 5.5m assult cruising speeds

[Jimboat]

seafreak - your chine walking might be cureable - your situation sounds pretty typical for a performance hull. You may also wish to check out my article on "Chine Walking")

Chine walking can arise with most high performance hulls. As the hull accelerates, lift increases and the wetted running surfaces that are required to support the hull are reduced (more Speed = more Lift = less Surface). As the speed increases throughout the velocity range, the hull often gets to a point where the lifting surfaces become very much reduced and the hull is now “balancing” on a small area of the hull. When that surface becomes sufficiently small, it becomes very tricky to “balance” the hull on its vee or pad. The result is a rocking of the hull from side-to-side, from port-chine to starboard-chine, back and forth. This rocking can tend to get a little more extreme with each motion, and so the “balancing” must then be provided by additional driver (steering/throttle/trim) input in order to maintain the hull in a balanced state.

If left unchecked, the boat will rock from side to side with increasing drama. This is because the boat is now “inherently unstable” – meaning that if left alone, the “imbalance” of the hull is more likely to get worse on it’s own, not better (the worse it gets, the worse it gets). If it gets out of hand, you can get into real trouble!

Setup of your hull and driver “seat-time” are the best solutions to the problem. Usually an alteration to the hull, or hull setup and/or modification to your driving methods (read seat-time) will improve the problem. There are definately some things you can do to minimize the problem.

[seafreak]

thanks for info

[Jimboat]

Jonathan - got your PM. I have sent to you copies of the 2 articles (chinewalking and porpoising). Hope this helps.

If you are interested in any other articles, check out on my website at: aeromarineresearch.com

/Jim

[Jimboat]

Jonathan - thanks for your email. i'm pleased that you found the articles helpful. The advice of your manufacturer seems to be in the right direction. the setup of each boat is always a little different.

As you read in the articles, there is always great advantage to be gained by making changes to your boat's setup. Try these approaches first...
1. Motor height
2. Check & adjust steering
3. Use solid mounts
4. Clean Hull Lines
5. Weight balance of hull
6. Propeller selection

And be sure to allow for sufficient "Seat time" so that you're comfortable with "driving through" the hump zone safely - that's always the most important factor with performance boats - be safe!

[chewy]

Whats seat time?

Had a quick search but couldn't find out?

[seafreak]

for seat time, read experience

[Downhilldai]

You could buy yourself a 5.5m Destroyer hull and transfer all your current rigging (engine, console, trailer, etc) over to that.
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then chuck the Insult hull in the skip. I've got a skip, if you need one

[Ian Sharlot]

You would get 40 knt out of a 5.5 Destroyer with your opti 115 and have a much better ride with a lot more room in the boat for more seating

[Downhilldai]

Now where could he get one of them from?

[BruceB]

Originally Posted by Downhilldai

then chuck the Insult hull in the skip. I've got a skip, if you need one

I second that, want to know where a skip is to put it in?
I am not biased at all, just had one for a few years and couldn't wait till I could afford to get rid of it and get a decent hull...........

[Pablo]

I really have difficulty believing that the Assault BruceB had is the same as the one I have. My 5.3m Assault is from 1999 so probably the same as SeaFreaks. In rough (upto 2m seas) I have a much more comfortable ride than a Narwhal 5.8m RIB for example. I've just put a 90hp Mercury 2-stroke on the back (max hp on my transom) and I got 42 kts out of it with a 19" Yamaha prop at 6500 revs. It was like the boat was on rails. Admittedly i'd tried a 21" Mercury prop and it chine walked at 39.5 kts. Later i'm off to get a 21" Yamaha prop in the hope that it'll be better.

Bruce, how was yours setup ? Humbers prefer lots of weight up front apparently, I know mine does.

Believe it or not but the Assault has the deepest V of all the Humbers at 30° at the transom. I don't doubt that Destroyers and Ocean Pros are better but there are alot worse than Assaults on the market.

For those who suggest he changes prop because he gets too many revs don't forget that its 5-UP ! On his own I'd bet it would be a different story.

Conclusion, I'd provide you with a skip. I'd even happily come and pick it up with a trailer if you wanna get rid of it

[seafreak]

what is better about a yamaha prop?

[Nos4r2]

If it's a standard ally prop,the merc prop will probably be better. Yam ally props have thicker blades and a thicker leading edge than merc props which appear to be forged..

They also lose big chunks when they hit things rather than bending.

[seafreak]

so my assault might not be the worst rib in the world?

[Ian Sharlot]

Humber ribs are good solid boats, so, no you definitely have not got the worst boat in the world. The Assult is a good solid hull that will look after you well but the other models offer a wider beam and deeper v giving more stability and a softer ride. A lot of poeple would prefer to spend a little more and get one of the other hulls.

[Downhilldai]

Originally Posted by Pablo

...Believe it or not but the Assault has the deepest V of all the Humbers at 30° at the transom.

Not

[BruceB]

I had as much weight at the front of mine as it would bear as well as the console as far forward as I could fit it. Are you sure Pablo that you have an Assault? The earlier version in Humbers model range of this type was the Attaque and this have been developed into the Ocean Pro. This is a proper deep V and the Attaque was a absolutely smashing hull for its size. I have no idea why they replaced it as apart from the way the floor was made up it was immeasurably superior to the Assault.
Humbers are solid boats and yes there are probably worse Hulls out there than an Assault but I think you will have a hard time finding one.
Assaults are built for a specific market. They are narrow and light enough to be towed on an unbraked trailer, fit in a standard garage and be towed by a medium sized family car.
They are not a performance boat by any means and they are certainly not deep V.
Its a long story how I ended up with mine but I spent the whole time I had it saving up to sell it and replace it with something decent.
The ride in any sort of chop is very wet and extremely hard. I found a 5.3m with a 60 on it bad enough, can't even imagine what twice the power will be like hitting waves
Here is a side view of an Assault where the lack of hull depth is very apparent. Now imagine hitting waves with this at speed with such a flat surface and consider your knees and what a knee replacement on the NHS will be like..........
Now if you still believe the Assault hull is a deep V after seeing this pic then I know some Nigerians who need a contact in the UK and you can make some easy money with them

[Pablo]

Do you really hope to be credible with a photo like that ? With light coming from the top and a dark hull we don't stand a chance of seeing a thing.

Yes the Assault does have a 30° deadrise at the transom. Ask Humber. There is no planing platform. Obviously there are other factors that come into play and its not me whos going to start comparing one to a Destroyer, i've never even been on one. Everybody whos tried both say that Destroyers are better.

I once wrote a post here
http://rib.net/forum/showthread.php?t=23009

Saying that Assaults are light weight and made to be towed behind a familly car is laughable too. They weigh 30kg less than the Attaque you recommended earlier. I'm sure thats going to make the difference between a Landie and a Ford Fiesta.

If you want we can each take photos of our Willies, so long as we don't put a tape measure in the photo we should be able to compare all night

[BruceB]

It perfectly obvious where the hull is in the pic to me? Its an old pic so I can't really go and take another.
The Assault is aimed at the market I said, go and ask Humber or look on their website-
"The Assault is easy to launch, can be towed by the average family car and fits in most garages. All this comes at a very affordable price. "
The Attaque was also aimed at the same market but was a considerably better hull.
The more you say the more I think you have an Attaque as the assault does have a flat planing platform, it is actually listed as a selling point (have no idea why!) and mine had it and I can even post a pic if you don't believe me? Compare weights to most similiar sized hulls to see what I mean by lightweight, even Humbers hulls.
I have not claimed here at any point that a Destroyer is perfect but I have driven Attaques, Destroyers and Assaults for some considerable "seat time" and even owned two of the three types. The only one I would not recommend is the Assault as it is a poorly designed,(construction is up to the usual Humber standard, rough but perfectly strong),and poorly thought out Hull.
I would not recommend one to anyone as there are far better hulls out there of the same size (infact IMO just about everything out there the same size is better )
If you read my posts in relation to your earlier posts above I am saying exactly the same things as here.
To recap
The assault is not a deep V hull by any stretch of the imagination and gives a very wet uncomfortable ride. These are facts which as far as I am concerned are unarguable.
The Assault is a poor hull and badly designed mainly for family use. These are opinions but
pretty valid ones I reckon based on experience with the type and the above facts.
Even when I had one I cannot at any point remember trying to argue it was a good hull........
Pablo, do me a favour and post a pic of you transom and the bow section of your hull, Assaults and Attaques look different and a pic will confirm what type you have..............

[Pablo]

Originally Posted by seafreak

what is better about a yamaha prop?

Not better, different shape. With the 19" Yamaha prop my boat felt like it was on rails. With the 21" Mercury prop it was very unstable. I'm hoping that with a 21" Yamaha prop it'll feel stable again but wont over rev.