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  #1  
Old 12-24-2011, 07:52 PM
kapnD kapnD is offline
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bow flare

I am a big fan of long/narrow powerboats, and have enjoyed all the discussion of same here on this forum, but am wondering why most of the designs of such have straight sides in the bow area.
In my (ocean) experience, this causes lots of water to be thrown into the air, and then, of course, it pours back over the boat and its occupants.
The famous photos of the Dashews effort show incredible amounts of water being slopped across the decks, and as a result, the waterproof window budget is astounding! Any activity underway outside the snug cabin will result in a soaking.
Wouldn't some graceful bow flare as is used on the Carolina sportfishing boats as well as most of the far eastern fishing fleets be appropriate here? Even the infamously ugly "tongue depressor" bows of the west coast Radon and Davis boats are very effective at keeping the boat dry when under way.
The increasing buoyancy of a flared bow as it is immersed is also a plus, and though it could be argued that it will increase pitching, I would personally prefer the boat to stay on top of the water rather than diving through every wave!
Any thoughts appreciated, as I am currently penciling in bow flare on boats like Passagemaker Lite, and think it looks pretty darn good.
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  #2  
Old 12-25-2011, 01:04 PM
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gonzo gonzo is offline
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Flare is more difficult to build, particularly for amateurs. Also, few designers are able to draw a hull with a lot of flare that looks good from all perspectives. Most look fine in profile or plan view and horrible from other angles.
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  #3  
Old 12-25-2011, 02:04 PM
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If you are using sheet material it can only be twisted so much to form flair, and if you do twist it the stem becomes raked. A raked stem means shorter waterline for given overall length, or longer overall length for a given waterline. Overall length has become a big deal due to the cost of marina moorage.

Two other reasons are styling and interior volume. Slab sides forward are modern and "edgy" because Wally (among others) used them and established a recognizable feature. Interior volume will sell the boat, popularly the master double is stuffed way forward into the bow, bulge the topsides out and make that bed huge.........

Forward windows on any boat need to be waterproof, thickness is adjusted with pane size, height above waterline, distance from the stem, and forward speed.....

You can see some flair in the forward sections of this strip-planked PL46+ under construction........any more than this distorts the sections close to the stem if the stem is vertical. You get a weird bulge down low, just above the spray shelf......And the spray shelf does work at moderate speed.....

bow flare-pl46plusconstruction.jpg
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Old 12-25-2011, 04:12 PM
michael pierzga michael pierzga is offline
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Quote:
Originally Posted by kapnD View Post
I am a big fan of long/narrow powerboats, and have enjoyed all the discussion of same here on this forum, but am wondering why most of the designs of such have straight sides in the bow area.
In my (ocean) experience, this causes lots of water to be thrown into the air, and then, of course, it pours back over the boat and its occupants.
The famous photos of the Dashews effort show incredible amounts of water being slopped across the decks, and as a result, the waterproof window budget is astounding! Any activity underway outside the snug cabin will result in a soaking.
Wouldn't some graceful bow flare as is used on the Carolina sportfishing boats as well as most of the far eastern fishing fleets be appropriate here? Even the infamously ugly "tongue depressor" bows of the west coast Radon and Davis boats are very effective at keeping the boat dry when under way.
The increasing buoyancy of a flared bow as it is immersed is also a plus, and though it could be argued that it will increase pitching, I would personally prefer the boat to stay on top of the water rather than diving through every wave!
Any thoughts appreciated, as I am currently penciling in bow flare on boats like Passagemaker Lite, and think it looks pretty darn good.
Your observation is correct. The modern, highly styled , plumb stem, slab sided yachts are wet.
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bow flare-vandutch40_gc3-1024x768.jpg  
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  #5  
Old 12-25-2011, 04:17 PM
Boston Boston is offline
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Quote:
Originally Posted by Tad View Post
If you are using sheet material it can only be twisted so much to form flair, and if you do twist it the stem becomes raked. A raked stem means shorter waterline for given overall length, or longer overall length for a given waterline. Overall length has become a big deal due to the cost of marina moorage.

Two other reasons are styling and interior volume. Slab sides forward are modern and "edgy" because Wally (among others) used them and established a recognizable feature. Interior volume will sell the boat, popularly the master double is stuffed way forward into the bow, bulge the topsides out and make that bed huge.........

Forward windows on any boat need to be waterproof, thickness is adjusted with pane size, height above waterline, distance from the stem, and forward speed.....

You can see some flair in the forward sections of this strip-planked PL46+ under construction........any more than this distorts the sections close to the stem if the stem is vertical. You get a weird bulge down low, just above the spray shelf......And the spray shelf does work at moderate speed.....

Attachment 65346
nice looking work Tad
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  #6  
Old 12-27-2011, 04:57 AM
FMS FMS is offline
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I always prefer some flare at the bow.
I like to keep my glasses dry at the helm over the "modern look".
Some flare helps the lines, at least to my eye, too.

Yes, very nice looking Tad.
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  #7  
Old 12-27-2011, 06:31 AM
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yipster yipster is offline
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Long narrow boats aim at a low pc / froudenr hence a long waterline with fwd stem
by going polyhull instead of sheet material a concave even carolina style topside is possible on f.e. a straight up stem, will ride and look different tho
want to share and upload what you pencilled KapnD?
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  #8  
Old 12-28-2011, 01:15 AM
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Easy Rider Easy Rider is offline
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THe Dashew boats I suspect are intended to be a bit of a wave piercing hull as a boat that light would experience some terrible G forces if any amount of flare was employed. Plus the designer was a sail boat person and obviously had sail boat in his head when designed his passage makers as it's obviously a modified sail boat and I do'nt think getting wet was of any concern at all.

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  #9  
Old 12-28-2011, 09:17 AM
timothy22 timothy22 is offline
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Bob Perry is on record as saying that the slab sided bow is faster (more easily driven) because it takes less energy to slide through a wave than to lift over it. Also a noted sailboat designer. Like many other features of succesful race boats, the narrow slab sided bow has been adopted into cruising boats where a dry (er) bow may be preferred by a particular owner.
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  #10  
Old 12-28-2011, 10:50 AM
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viking north viking north is offline
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Why not make it an afterbuild add on. Experiment with a flared shaped a foam piece that attaches at and below the deck edge running from the bow back. Play with it until it blends in and looks pleasing to the overall hull lines. More or less a rubbing strake idea. It doesn't take much flared area to deflect large amounts of water. Once you have developed the shape simply glass it over and thru bolt it in place or develop a mold --semi mass produce and sell as an aftermarket item for that particular craft. Do the Harley Dance sell the entire bike as aftermarket add ons

P.S. the photo below while not designed as a spray deflector will do so to a great extent. A similar set up but cross sectionally shaped properly, will go a long way in deflecting the heavy spray.(enlarge to better view)

A yacht is not defined by the vessel but by the care and love of her owner--
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bow flare-100_2406-3-.jpg  

Last edited by viking north : 12-28-2011 at 12:02 PM. Reason: add photo and description
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  #11  
Old 12-28-2011, 11:08 AM
michael pierzga michael pierzga is offline
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The axe bow workboats use addition spray deflectors running parallel. to waterline
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  #12  
Old 12-29-2011, 07:28 AM
HJS HJS is offline
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Quote:
Originally Posted by gonzo View Post
Flare is more difficult to build, particularly for amateurs. Also, few designers are able to draw a hull with a lot of flare that looks good from all perspectives. Most look fine in profile or plan view and horrible from other angles.
It is NOT difficult to create a boat with flare and with developable surfaces.
You just have to put the curvature in another direction than what may seem obvious.

js
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bow flare-ecodream-w-flare.jpg  
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  #13  
Old 01-03-2012, 10:11 AM
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Perm Stress Perm Stress is offline
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Quote:
Originally Posted by HJS View Post
It is NOT difficult to create a boat with flare and with developable surfaces.
You just have to put the curvature in another direction than what may seem obvious.

js
It is not allways so easy to make mathematically developable surface to develop in the real world .
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  #14  
Old 01-03-2012, 11:01 AM
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viking north viking north is offline
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I seem to recall some of those old Popular Mechanics/Science plans did have flared bow sections. If designed and presented as a home build it would certainly be more difficult to build for the general building public. They would be more in line with factory production where the cut tolerances and hand skills were available. It's possibly a case where, if the designs are made available for home build the designers would have to put up with too many complaints of the underskilled and over a period of time thru word of mouth the design would be unfairley labeled as too difficult or a poor design. Damed if you do and damed if you don't situation.--
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  #15  
Old 01-03-2012, 01:24 PM
DCockey DCockey is offline
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Two questions which I know the answers to:
- Do developable surfaces have straight frames?
- Do straight frames always result in developable surfaces?
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