Memory Foam for Bows

[nero]

Does anyone have suggestions for what type of flexible foam is workable for bows? What I am looking for is a material that can be shaped, coated, and then stuck to the front bulkhead. This will form the bows of my catamaran. The width is about 300 mm at the widest. Depth is about 380mm. Height is 1600 mm.

Why flexible? Damage control. Might not piss off a whale as much if I were to bump into him ... and slide up on his back. (bad images in my mind)

Closed cell would probably be the best. Maybe a guess at the density?

Thanks in advance.

[kach22i]

Because water does not compress, but the foam does; once under speed the bow may deform or deflect from the pressure. If done in a thin water cutting blade like shape it could just fold over and act as a parachute at the bow (esp. while turning). A bulbous bow of foam might work because of it's shape, this has been mentioned in a tread before, do a search.

All that said I would think that foam filled fender technology could be adapted.

Example:
http://www.qingdaoyongtai.com/en/cp/cpxx.asp?id2=12
http://www.qingdaoyongtai.com/en/admins/photo/2007851955868261.jpg
The ter-resistant skin is formed using high tensile reinforced polyethylene polyurea elastomer (SUPA). Transition layer are also be used to enhance the adhesiveness between every kinds material...............................In the event of rupture of the outer skin, the closed cell property of the Baltec memory flexible foam seals off water ingress. The outer shin can be repaired quickly and economically.

[rwatson]

On the subject, but at a slightly different angle, dolphins are supposed to benefit hydrodynamically because their skin distorts slightly to water pressure. The math behind this is beyond me, but I wonder if flexible skin could enhance a boats performance too ?

[kach22i]

On the subject, but at a slightly different angle, dolphins are supposed to benefit hydrodynamically because their skin distorts slightly to water pressure. The math behind this is beyond me, but I wonder if flexible skin could enhance a boats performance too ?

Even dolphins have hard noses, but the body ripples as you mentioned. There is a good thread on this, but the information is burried pretty deep.

Link:
http://www.boatdesign.net/forums/showthread.php?t=9630

Best to use the search function for this topic.

I should mention that I've thought about the foam bow before in the context of hovercraft and RIB's. When a wave hits either one of these there is a "heave" dynamic who's acceleration leads to sea or motion sickness.

Please post what you find on this, as I am very interested in this topic.

[brian eiland]

Does anyone have suggestions for what type of flexible foam is workable for bows? What I am looking for is a material that can be shaped, coated, and then stuck to the front bulkhead. This will form the bows of my catamaran.
I've often thought of this myself for both damage control, repairability, as well as the possibility of interchangable bow designs on the same vessel.

I never did a formal research into the exact material as it seems there were new ones coming out every month or so. I had thought that some of the 'car bumper' materials might be considered?

I don't think the material can be very 'flexible' due to the high loads it will see. But at least, it would be sacrificial to expensive repairs and water ingress impacts.

[Willallison]

What about styrofoam?

http://www.dow.com/styrofoam/index.htm

It doesn't have the mechanical properties of 'rigid' foams like corecell, but it has a low density, is closed cell and with appropriate laminate protection could possibly work....

[nero]

Extruded polysteren, which is the blue, pink, green stuff would work to make a rigid, sacraficial bow. Rob Denney used it in some of his proas. This was also my choice at the outstart of this project. What I would like to advance is a nose bumper that would not be damaged from bumps and small collisions. ... thus not having to repair the dents all the time.

Being only 5 to 8 inches at the waterline with 3 inches of width. I do not see load forces that will have enough torsion to fold over (more like rip off) the lower sections. This area will need to be fairly high density foam.

So far I have found a few manufactures but have yet to contact them for their suggestions. Will post results when I can do so in a coherent manner. One of the australian sites has a hand mixable foam. Which would illiminate the problem of how to smoothly shape a flexible foam. Do not think flexible foams can be sanded.

Thanks for all the ideas.

[kach22i]

Crazy idea..............there are water beds with multicells. Why not a multicell bow in which the cells fill with water to help maintain it's shape but upon sharp collision pressure activated baffles open up allowinf deformation.

Could also be done with air, but even more problematic.

I once saw in the mid 1970's bus bumpers filled with air, water, styrofoam peanut beads and popcorn. This may of lead to the stiff foam backed automotive bumpers we see today.

Interesting product, somewhat related:
http://www.upyourboat.com/pages/model_hydroport.htm
http://www.upyourboat.com/images/HP-03lg.jpg

[kach22i]

Found this..................

Stern PVC
http://www.scrumble.com.au/if-i-had-a-boat-i-should-have-gone-sailing/
http://www.scrumble.com.au/images/20050626FittingExternalStemPVCconduit03.jpg
http://www.scrumble.com.au/images/20050626FittingExternalStemPVCconduit04.jpg

Bow PVC tubing:
http://www.scrumble.com.au/creating-the-fine-bow/
http://www.scrumble.com.au/images/20050702FittingPortBowStemPVCConduit24.jpg
http://www.scrumble.com.au/images/20050702FittingPortBowStemPVCConduit37.jpg

Why not just glue a pool noodle or rubber handrail from an escalator to the bow keel?

Bigger, better.............

Goodrich
http://www.epp.goodrich.com/prodapps/rubber.shtml
http://www.epp.goodrich.com/images/rubber/bow_dome.jpg
Wire Reinforced Sonar Domes – Our bow domes and keel domes have been used by navy surface ships around the world for anti-submarine warfare (ASW).

Goodrich
http://www.epp.goodrich.com/prodapps/rubber.shtml
http://www.epp.goodrich.com/images/rubber/sdrcw_dome.jpg
We have been providing high performance rubber products and bonded rubber components to the US Navy and foreign navies for decades. Products include acoustic sonar windows, acoustic baffles and reflectors for use with transducer assemblies.

[achipmunk]

oh, nice to see that pics, thanks

[yipster]

second that

[westlawn5554X]

Interesting material usage... am kinda akin to rubber... do enjoy this subject.

[captainjsw]

Hi Nero,

I am building a similar foam bow for my catamaran, the designer and engineer recommended any 80 desity foam - I am using Diabs Divinycell H80. 25mm thick to minimise the laminations - you might be able to get thicker but thats all my supplier could get in a hurry. The dimensions of my bow is similar to yours - maximum depth 400mm Height 1800mm maximum width about 270mm (I think)

Regards John

[kapnD]

I have some soaker hoses in my hedges that are made of a porous foam. They emit a surprisingly even dribble of water over the length of the hose.
What if the entire hull were covered with a similar material that emitted air bubbles? I know it would take energy to produce the compressed air, but the tradeoff would be reduced hull friction, while the hull would be protected by the layer of foam. It might even act as a shock absorber to reduce pounding at speed.
In reality, though, if you run into a whale, a little foam on the bow is not going to matter much one way or another! Your best defense against this is to make lots of noise so the whale can locate you, as they will usually avoid you if they can, and post a lookout on the bow.

[nero]

Thanks to all for the ideas.

The PVC pipe with foam inside would work well for bumping into docks. But it would do little in a major impact. It is a cool idea.

I will have to make a portion of the 40 cm bow section in corecell. This would help absorb the impact, but it would be damaged in any impact.

Rubber is too heavy.

What I have found so far is that elastomeric foam is available in many flavors. There are several manufactures and distributors. Their websites state that most of the products can be shaped and sanded with high-speed wood working tools. Routers, bandsaws, table saws, sanders, as well as hot wire techniques were all listed. This is is a wonderful surprise!

These places seem like good leads.
http://www.zotefoams.com/pages/EN/products.asp
http://www.flextechfoam.com/materials.html
http://www.foamdesign.com/materials.htm
http://www.armacell.com/www/armacell/armacell.nsf/
ansHTMLSeitenLookUp/USA-TF_Frame?OpenDocument

I have to get samples ordered. As well as illustrations that explain what I am trying to do.

Regards

[kach22i]

Does salt water like to eat the spongy foams?

Salt water is so rough on everything else, I'd just assume.

[nero]

Finally, making the time to work on build plans. The below pict is how I intend to build the nose crash blocks. The center is a stack of extruded polysteren. This is the 100 psi (cheapest) pink or blue insulation foam that is found at the local building supply. On the outside of this is 12 mm of CoreCell (SANS foam). The forms below it are to heat form the CoreCell. While the CoreCell skin is still in the forms, the main block will be fitted and bonded into it.

The layer block below the dwl is of CoreCell.

The blue and yellow sweeps are the area I intend to use memory foam.

Minicell is the memory foam product intended. Claims to be impervious to rot, mildew, mold. It comes in 4 inch thick slabs. Can't test samples since I am currently in France.