Warp lines?

[Danielsan]

are warp lines necessary for planning boats? Boats in general?

greetz,

Daniel Peeters

[jehardiman]

Yes... All vessels should carry warp lines and the prudent seaman should know what they are for and how to use them. I perfer single braid dacron of circumfrence equal to the anchor rode and at least 2 of them, with a total length of at least 5 times the LOD or 200 feet which ever is greater.

But somehow I don't think that is what you are trying to get at....

Are we talking about some arbitrarily defined geomorphic mechanization that only exists in the mathmatics of some surface modeling computer program? In that case no, the shape of a "good" hull is infinitely variable depending upon the design criteria, hull material, construction method, and personal preference.

[Danielsan]

Yes, it concerns the hull
But it was more as a general question for a small (7.50m) planning cruser.
As for now I have a realy simplified design of a hull having a 22deg deadrise which is constant for 2/3 of LOA with some chine flats of about 30 cm on each side of the hull. I read there are some recomendations for jetdrives there's te reason of my question.

in my other thread there are some pics see also word doc.

PVC foam core thickness?

greetings,

Daniel Peeters

Are you referring to the shape of the boats hull bottom? Old woodies did have the most " warped bottom lines " to compensate for heavy, low horsepower and slow reving engines.

[Danielsan]

Indeed the bottom of the hull. What is the exact use of them, stability, faster planning,....

We do talk about the same things? I mean the litle corner shaped extensions that make the hull look like it is having some little stairs over the length off the hull, maybe they have an other name.

Click on page #2 of this thread. Scroll down to " designers of small wood power boats ". Then go to # 8. That is the boat I am building . IT HAS a severe case of " warped bottom lines designed into it ". Look at the rear 1/2 of the hull frames. Notice the flattening out towards the transom. Click on the pictures.

[Danielsan]

Yes, I would say it has a warped shape, but what I actually mean are the little 2 or 3cm dents that come out of the hull by way of speaking

The flatter bottom frames really drops the horsepower to get the boat on plane , empty or fully loaded. It does 45 mph with 220 hp and loaded with people. Bad side is at planing speeds and windy day you are constantly steering. not like a CONSTANT DEEP V trimmed out on full plane. The bottom of the bow can be as high as 2.5' out of the water at full speed all the time. I have made the hull a constant DEEP V of 24 degrees. Sides will flare out all the way back to the transom for a drier ride. No boat is ever perfect.

[Danielsan]

I am heading for home now, I hope i can do some progress on my design. After all I can add the warp lines after applying the foam layer. but it would be nice to have them on my design the right way before beginning the construction of the boat.

Greetz

I think you are asking about the small runners on the bottom? they are called at least 3 different names. --chine flats---planing chines---planing strakes. Each is a little different from the other. BUT they all are added to REDUCE the planing horsepower requirements.

[jehardiman]

Originally Posted by Danielsan

We do talk about the same things? I mean the little corner shaped extensions that make the hull look like it is having some little stairs over the length off the hull, maybe they have an other name.

Originally Posted by Richard Petersen

I think you are asking about the small runners on the bottom? they are called at least 3 different names. --chine flats---planing chines---planing strakes. Each is a little different from the other.

Richard is correct, there are different names and reasons for the strakes/chines added to the bottom of a hull. Some are added to V-hulls to increase the vertical lift force to decrease wetted surface. Some are added to a hull to control flow fields. Some are added to ventilate to reduce friction. Some are added to flat hulls to give directional stability. Not all planing hulls have them or need them (such as a radius bottom ski boat or a three-point hydroplane). Additionally, improperly designed/sized ones add, rather than reduce drag (not so much a problem in small, high-power boats, but significant in larger hulls).

Edit: I re-read and noticed the remark about a jet drive. Because the propulsion unit of an inboard mounted jet drive may not add directional stability to low deadrise hulls (i.e. it is behind the transom and not a "rudder" below the keel like and outdrive), it may be necessary to add some laterial area to the aft hull in the form of strakes to give directional stability at low speed. This is normally done by ROTE then adjusted during trials.

[Danielsan]

I once aigain mixed things up it was strakes I was looking for not warp lines???
I must have been drinking when looking at StarTrek. LOL.
As for now I have none of them, and don't know if I will put them without having the right calc.

greetz,

Daniel Peeters

I think your best help on your boat will come from all the jet boat manufacturers in Austrialia. Their jet boats are the best because so many of them race their boats in jetboat competition. then apply it to the cruisers. Ask each one for a catalogue with specs and features. You may copy any boat for your own use from their catalogues. Exact dimensions are not as critical as putting the strakes in the same places and same lengths. A few emails should do it for you.

[Raggi_Thor]

Strakes give extra stiffness to the hull, they work like longitudinal stringers.
They turn the spray down in high speeds.
Theortically they are supposed to give you a smaller wetted surface at high speeds, but at 24 degrees deadrise I don't know if the water will really let go...
At lower speeds they will increase restistance, not much, but...

[Danielsan]

I think when I know wich jet I will be using, I will ask for the necc. specs. for the strakes.
I know that Hamilton say were not to put them, thats a good start but do I need them and where, that surely is an other question.


Greetz,

Daniel Peeters