I've got an idea from way out in left field that I'd like some feedback on to know if it is a stupid idea or if it's worth doing.
Would laying in a layer or two of kevlar in the bow section of the boat have any benefit to mitigating damage from hitting partially submerged objects or a dock?
I've removed my fwd water tank and am thinking of reinforcement before I rebuild that area into a deeper chain locker and easily-cleaned new water tank under the v berth.
I know that the transom and after section of the hull above the water line are only about 1/4" - 3/8" thick, but not sure what's up forward.
Thanks
Any additional material would help in mitigating damage. Perhaps the question is whether or not the effort is worth the investment of time and money and only you can answer that question.
Seeing as you have removed the forward water tank and are planning to remake the chain locker, you might want to redirect your efforts into designing a collision bulkhead to minimize any water migration to the rest of the boat in the event of a bow penetration. You may never stop the impact damage but you might save the vessel with secondary precautions.
A larger known area of concern is the bilge bottom in regards to a hard grounding. Reinforcing that area may be more beneficial if you are concerned with unintentional water in flow.
Dale
Good point about the collision bulkheads, Dale,
I plan on installing two, one is the division between the new anchor locker and new,smaller water tank, the other one is the after end of the water tank.
First one will be about 24" aft of the fwd end of the vberth (a bit fwd of where the water tank baffle was) and the second will be where the after end of the fwd water tank was. Both will rise up to the underside of the verth platform.
I am also going to seal off the bottoms of the two lockers in the after end of the v berth, including up the after end of those up to the underside of the vberth platform.
I was just not sure if adding a few layers of kevlar to the interior surfaces of the hull will lessen damage cause by things trying to poke through hull any more than a few layers of biax cloth.
Hello,
I have worked on composites professionally on small UAV's for a while and wanted to add my 0.02$
Kevlar on the inside won't do much, and anything poking through has already done serious damage and will likely delaminate the 1 or 2 layers of kevlar from the glass. Kevlar on the outside of the hull will decrease friction and possibly mitigate damage, but you'd need at least 2 layers of thick stuff to delay damage due to boat-type impacts offshore. For dock-type impacts it would do wonders! Kevlar is strong and slick, and hitting a dock you inevitably slide up it. The kevlar will take the sliding much better than glass, but you'll still need new paint.
If I were doing the same I would want my anchor locker to not drain mud down the bilge. I always wash my chain and rode but sometimes muddy water gets down there. A previous boat had the locker drain to the sea. It wouldn't work too well on our boat, but perhaps there could be a third option like a dedicated sump with separate bilge pump...
Cheers
Mike Sytsma
S/V Tardis, Pearson 367 Cutter #26
I removed my forward water tank and moved the bottom portion of the chain locker bulkhead aft to allow the chain to fall further down. I made the lower bulkhead watertight and added a bronze strainer with a 1 1/2" hose that runs back to the sump. All the water that comes into the chain locker then runs back to the sump and is pumped overboard by the bilge pump.
Here's my $.02
I agree with swiftbis, and have played with Kevlar, both 29 and 49. in the aerospace world. The Kevlar fiber absorbs water, so is best used where it will either not get wet, or where the swelling doesn't stress a resin it's bonded too. It's a bigger issue if you combine it with large temperature swings. Some resins get along ok with Kevlar, and some don't. Kevlar laminates can also be hard to drill cleanly if you need to. You get a fuzzy hole ID unless you use special drill bits. It's also hard to work into tight corners and hard to cut.
If you feel you want to add strength, I would go with biaxial glass and mix up the orientations and taper it out. Epoxy absorbs more energy than polyester resin usually. I do like the bulkhead idea, that would provide a big crush zone if you hit something solid. Just remember if it needs to work, it has to be tied in well so it doesn't seperate at the tabs as the hull flexes in an impact.
I have also heard of inflatable emergency collision bags that essentially fill large areas using a co2 cylinder in the prevent if a collision. Don't know anything about them though or if they would work in Pearson.
I am curious as to why you think it's necessary. Has this happen a lot out there? I see the issue with the hollow aft end of the bilge, that would seem to be a higher priority to me to reinforce.
The Pearson 365 hull to me seems to be indestructible and capable of hitting submerged rocks and not sinking as-is. (recall there's a video out there somewhere) Mine had a large bulls eye in the hull from hitting a submerged rock that we found during the initial haul-out. These cracks were located on the port side alongside the leading edge of the keel. This makes sense as the force on the hull will increase to the breaking point as the inclined plane of the bow attempts to lift the much heavier keel out of the water. Chances are good the damage from sliding up on a rock will occur aft of any bulkhead you might want to reinforce in the bow area.
I've seen a sailboat run straight into a dock. The bow ran straight up out of the water and then slide back down. No damage. Wasn't my boat. Pete
Della and Dave,
I don't know of problems with submerged objects around here, except for logs washed out the rivers (Pascagoula, Mobile, Pensacola area), but while I had the forepeak torn up, I though I might strengthen things up a bit and include a watertight bulkhead. Best I can do is up the the bottom of the v berth.
Swiftibis and DD, thanks for the info on the kevlar and biaxial for reinforcement.
I haven't yet built the chain locker yet, but was successful in stripping off the layers of unknown paint to. PO had painted all hull surfaces he/they could reach with some kind of white paint that doesn't stick well in some. It's mostly gone now, thanks for home-brew of drano and water. Couldn't find any other source of lye and didn't want to use shore-side strippers with methylene chloride.
Lou, I might follow your steps with the locker drain and run it all the way to the deep bilge. I was thinking of a bilge pump in the chain locker, but that'd prolly just get plugged with weed and mud (and corroded).
I've always wondered about after part of the keel. When the boat was out for work this winter, I clearly saw the hollow part because of contrasting condensation and on my boat (367, #42), the hollow is the after 24" of keel. It's just really hard to reach down there to clean and glass.
So, thanks for the don't-use-kevlar-on-inside-of-hull-it's-a-waste-of-time advice. I'll move on to other ideas that are more practical.
Thanks again for all the advice.
Quote from: PeteW on July 12, 2015, 04:37:47 PMI've seen a sailboat run straight into a dock. The bow ran straight up out of the water and then slide back down. No damage. Wasn't my boat.
What marina was it at? I ask for no particular reason :)
some where on the Internet was a film where they did crash test with a Dehler 8). Under full sail it ran on a floating boat dock, a tree trunk (it split in halve), and the ran it even to the basalt shore line (which resulted a crew member found its way to the cabin floor due to the sudden stop with as result minor scratches to the hull and some dents at the bow but no water leaking (fantastic plastik ;D) ok a collision with a big seagoing vessel you will probably lose ::) but a reinforced bow section will not help I am afraid.
Thanks Dutchie,
I found the video, nice.
https://www.youtube.com/watch?v=y_CKmWwB_Tg