Deadrise

[Sea-Dog]

Hi

Two more words - Hull Length

The longer a displacement boat, the faster it can go. The naval architects amongst us can explain why

Whichway

Its the "Suck Factor" isn't it?

[Wahoo]

Its the "Suck Factor" isn't it?

thats right Sea dog
thats why more boats should be made with a stepped hull

Daz

[wessel]

280 000 shp!! OK, time to go back to my corner and keep quiet.

Wessel

[BM]

Stepped hulls have come and gone. John Haines tried it in the very late 80's early 90's. They aren't around anymore so that tells you it doesn't work.

Cheers

[whichway]

Hi

Getting a bit off the topic of deadrise, but I think for displacement boats, long waterline length is faster (something to do with bow and stern waves if I recall), but for planing boats the shorter the better, to reduce the skin friction drag because planing hulls don't have bow and stern waves.

Better quit now, I am really starting to get into areas that I do not understand

Whichway

[Greg P]

Stepped hulls have come and gone. John Haines tried it in the very late 80's early 90's. They aren't around anymore so that tells you it doesn't work.

Cheers

Don't believe you are correct unless you are talking about something different. In fact I think Haines is doing them on a new signature model (can't remember the model but around 5-6m). Lots of US manufacturers use them especially on big CC. Laminar flow interrupters are still used and being developed.


Whether they work or not I don't know - how do you know they dont?

[BM]

Sorry Greg,

I was referring to the stepped hulls at the stern (designed to run the engine higher for more speed and lower gearcase drag).

The stepped hulls being referred to here are indeed in production in may US boats. The concept of course is to break the surface tension earlier and allow the boat to plane at less speed.

In fact there is one being built here in Vic by a friend of mine (boat builder). It's being built into a small 5.3mtr hull. It will be interesting to see how it performs, although without a standard but identical hull to do a true comparison its really only going to amount to a "wow factor" modification rather than a performance modification backed up by scientific testing. Shame, as it would be great to test them side by side.

Cheers

[Wahoo]

Sorry Greg,

I was referring to the stepped hulls at the stern (designed to run the engine higher for more speed and lower gearcase drag).

The stepped hulls being referred to here are indeed in production in may US boats. The concept of course is to break the surface tension earlier and allow the boat to plane at less speed.



Cheers

there is a few reasons for a stepped hull, i also know of a alloy boatbuilder that might be doing one also

Daz

[kingtin]

Hi

The larger boats can handle higher deadrises. When they are at rest, because they weigh more they are less inclined to rock as the crew moves around, because the weight of the crew is less significant compared to the weight of the hull.

Whichway

(Wow I Just went Silver!)

Congratulations on going silver

Mate, I have a whittley sea legend 650 with A 23d deadrise. At rest, she's absolutely crap. Wouldn't recommend her to anyone. Even with 4 bodies on board she rolls in the slightest swell and if you can stay on your feet on the marlin board, I'll give you a medal.

Took me a fair time to find the best in her when motoring but yes, she does handle it well...........better than anything I've had before, but she's also worse than anything I've had before when we're actually fishing.

The sum total is that my crew always complained about the ride in my quintrex challenger. They were more concerned with ride than rest, so I put the emphasis on riding qualities as opposed to "fishing at rest" qualities. I sometimes wonder if I made the right choice now that the kids are throwing up all the time

kev

Top Tip:

Bus drivers. Increase the number of people who believe you when you cite traffic as an excuse for your late arrival by not stopping halfway through a route to exchange a racist joke with a passing colleague.

[tunaticer]

Sorry Greg,


In fact there is one being built here in Vic by a friend of mine (boat builder). It's being built into a small 5.3mtr hull. It will be interesting to see how it performs, although without a standard but identical hull to do a true comparison its really only going to amount to a "wow factor" modification rather than a performance modification backed up by scientific testing. Shame, as it would be great to test them side by side.

Cheers

Hi BM,

I would really like to see some pics and evaluations of this stepped design once your friend has it running around. Would be a very interesting thread to read i think.

Jack.

[BM]

Tuna,

I will be working back at the marina this week and he is located essentially on the marina, so I will pop in a take a couple of pics. He did have a model there a few weeks back that its based on so Ill see if I can photograph that.

Like I said, it would be nice to accurately assess the stepped hull and a conventional hull to really see if the design benefits to a measurable amount.

Cheers

[whichway]

Hi

Interesting about the Whittley. Most of the other fg manufacturers in the 6-6.2m class are running 20 or 21 deadrises. Around the 5-5.5m the deadrises are generally below 20 (17 or 18 I think from memory).

It would seem that 23 is too much for 6.5m I think the 680 Haines still is at 21 deadrise. The 23 degree Fishers use ballast tubes - wonder why nobody does this in fglass.

With regard to stepped hulls, I don't know if there are floatation issues hanging 4 strokes off the back of a boat with a stepped hull. Most manufacturers have gone to extended transoms, which is the opposite of a stepped hull. Not to say it can't be done, and you've really got to admire a manufacturer who is prepared to be innovative.

Whichway