Axe Bow concept

[jmercer]

hey,

I'm new here, so I don't know if this has been a common topic, but from a quick scan I couldn't find much.

I've become very interested, as of late, in the Axe Bow concept. Does anyone know where I can get more information?

I've ready the notes from the 19th HISWA Symposium and from what i can find on design studio sites, but is there nothing more in-depth? Anything helps.

Cheers

Originally Posted by jmercer

hey,
I'm new here, so I don't know if this has been a common topic, but from a quick scan I couldn't find much.
I've become very interested, as of late, in the Axe Bow concept. Does anyone know where I can get more information?
I've ready the notes from the 19th HISWA Symposium and from what i can find on design studio sites, but is there nothing more in-depth? Anything helps.
Cheers

as far as I know only the "Damen" group in Holland is working with ax bows to some extend. But I assume you did know that already!?

http://www.damen.nl/PRODUCTS/DAMEN_F....aspx?mId=8628

Regards
Richard

[decoguy]

I guess this is what you have already read, but it is interesting reading:

http://hiswasymposium.com/pdf/2006/J.%20Gelling.pdf

[gideon]

we will be using the axe bow concept on our new eco powercat 495 to minimise energy consumption. up to 8 knots very low drag , above that speed the drag raises exponentially
gideon

[gonzo]

That bow looks like the one in the old bay boats in Virginia and North Carolina.

[gideon]

You are right , old warships around the 1920 also used this bow concept is was and is very efficient, just a bit different from a wave piercer but comfortable , low in both wave and parasitic drag. ( up to 8/9 knots for a 49 ft cat )
gideon

[gonzo]

Also, the hulls are rather narrow

[Gone Ballistic]

My company have recently built a patrol catamaran for the Port of London Authority in the UK. It has limited the axebow concept to just the underwater profile, leaving a raked bow above the waterline for asthetic reasons. As it is operating in the river and slamming is not an issue we also did without the droop bow used on offshore versions to stop the stem emmerging and therefor stop slamming.

The boat was very successful and we hope to start building more of them for the PLA very soon. More details are here: http://www.alnmaritec.co.uk/download...20Guardian.pdf if you're intersted.

[gonzo]

I've seen it pass by. It leaves very little wake

[hoytedow]

Damen products very sharp looking. Why did the look go out of style and then come back? Seaworthiness or appearence?

[gonzo]

It only works on narrow beam hulls. The trend is for fat hulls that have large interiors and carry a lot of people.

[jmercer]

That is the symposium reference i was referring to yes. Since i last posted i have been in contact with J.L. Gelling who sent me along some information, but basically the same as in the PDF from the symposium. The concept is very intriguing and i will continue to dig further. If i can uncover more i will keep you guys posted.

cheers

[Boston]

I was wondering if anyone can answer this one concerning the axe bow concept

whats the entrance angle that brings a boat into the realm of being defined as axe bow

Im working up a design and have drawn a version that I would think could be called an axe bow configuration

I reduced the entrance angle from about 18° to about 11° by adding a few feet to the bow and I might be able to get it lower still but will need to check a few things before I can say that with certainty

would an entrance angle of 11° be still to blunt to be considered an axe bow

I recently read an article on this that someone presented earlier in the conversation and it was really convincing about the efficiency of the concept but did not define the limitations in shape as clearly as it could have

anyone know the particulars of this configuration

thanks
B

[Mat-C]

Why not simply make the boat longer?
What does the Axe Bow offer that a more conventional shape does not?
I've also wondered why that sharp, deep forefoot isn't prone to broaching...

[Boston]

you should read up on this and then return with some amended questions

they tested for broaching and they tested for a different bow configuration ( wave piercing ) and found the axe bow to be superior

basically they elongated the boat I think one by 25% and another model by 50% and measured the effective changes to vertical motion and to forward resistance

I just would love to see the lines plan of there optimal model

the article does say that a 43~44 m yacht should roughly translate into a 50m axe bow configuration
or roughly a 13% increase in length

I went from a design of 47' and added 5' or an increase of about 10%

I suppose its no big deal to add an extra foot and get it just right but still I'd love to know what there parameters are for a hull qualifying to be regarded as and axe bow