I have an older wood Eggharbor 37 want to use HDPE for worm shoe

Got hauled out by Travelift 2 weeks ago for bottom work and paint.

The keel base is 4" wide flat and long, extending front to rear but about 3/4 way of the length of boat
Hull is round chine lobster boat or downeast looking style and weighs 20,000 lbs

I am thinking of screwing in solid HDPE plank 1/2" thick, 4" width to use as a 'worm shoe' to attach to the white oak keel.
A person told me the boat will slide off the keel blocks when hauled claims to have seen several large boats fall off keel blocks with no HDPE worm shoes, so says expect a disaster.
Also claims a strong wind will push the hull off the keel blocks.

I don't think that will happen. The shore D hardness of HDPE is 68, wood shore D is 70, Compressive strength of HDPE is 750 PSI with 10% deformation at 1000 PSI. Some guy claims is so slippery it will slip all over the keel blocks.

Every worm shoe I put on this boat gets eaten with worms, so tired of doing wood which always fails, time effort money is wasted

So what do you think

 

Nobody else has replied, so I will offer my 2 cents worth.

Methinks why not have a bash at it - it can only be an improvement on a traditional timber worm shoe.

I don't see why she should want to slide off the keel blocks, unless you have a lot rake on the keel, and decide to chock her up with the waterline horizontal - but even so, it should then be possible to put some form of stopper on a keel block at the aft end of the keel to stop this from happening?

And provided that she is chocked level transversely, and has at least 3 supports on each side, I don't see why she would want to slide transversely on the keel blocks.

If you do fit an HDPE worm shoe, I would bed it in well on a suitable sealant, to make sure that the worms cannot get into the main keel through the joint.

 

From my limited experience with the more slippery plastics I wouldn't be too sure of the sealant actually sticking but if it does,its all good.What species of wood have you used for the worm shoe?I raise the point because on our coast,when they need to use wood on structures to resist either erosion or wear on the face of wharves,the wood of choice is greenheart as it is actually somewhat poisonous.The worms don't seem to like that.

 

The whole point of the worm shoe is to offer the worms something other than the boat itself, hence the term “worm shoe”.

Imagine your horror when you haul out after installing the new plastic shoe and the worms have decide the keel is the place to ‘chew’.

 

I plan to coat the wood keel bottom and sides with 5200. Then perhaps screw on a 'worm shoe' of some kind of plastic.
It could even be cutup strips of old FG boat hull.

Worms eat any exposed underwater wood, worm shoe and wood hulls,, they dont care as long as it is wood they will attack and eat it.

I would argue having a vulnerable wood worm shoe which worm will eat is a liability to the rest of the wood hull. The worms release millions of worm larvae and now they are all around your hull walking all over it looking for a place to feed. So you're growing millions of potential wood eaters right close to your boat.

Worm shoe is misunderstood, it does not stop worms from eating underwater wood, if the paint on wood is missing, they will find that spot.

 

Another idea is use strips from old cutup FG boat hull, screwed onto keel, I see a boat hull cutup close to me at the marina. Just the back 6 feet is left and it is pushed back in the weeds.

Another idea, is use heavy 1000 denier Nylon fabric, glued to keel bottom with 5200, and going up the keel sides. Advantage is no screws required, and seamless protection. In 5200 property sheet it has excellent adhesion to nylon and nylon is abrasion resistant and can stretch

 

IT has been oak and Cumaru hard wood. The worms fully ate both. Did not even need to unscrew it, just a chisel and hammer to break it off the keel.

Greenheart? have to read on it. We have Yukon Lumber in Norfolk, he said worms will eat IPE, I do think they sell Greenheart. I am in USA.

 

Just want to avoid wood, as it just another chore to replace a worm shoe which is long and boat is heavy, who wants to do it more than once?

 

This sounds good in theory - have you heard of anybody who has done it before?

Timber fishing boats here have traditionally been fitted with greenheart 'false keels' - they have more resistance to worms than most other woods, but they are still regarded as sacrificial, and the teredo worms will eventually chomp their way through these.
We used to have jetties all along the coast that were built with greenheart piles, and although it took a while, the worms eventually got the better of them as well.

Slight thread drift I know, but @sdowney717 could you also post some photos of your fine Egg Harbour please?

 

Sure enough, I did post some pics on the electrolysis thread of the bottom where I am doing some work now.

electrolysis in wood | Page 2 | Boat Design Net

But I will start my own thread later as I make more progress. I have completely wooded the hull.

About using heavy Nylon fabric, have not, but dont see why it cant work
The 5200 spec sheet lists nylon as something it stick well to.

 

What protects the wood from borers is the antifouling. If the worms ate your keel shoe it means the antifouling was compromised. This begins in the slings, they can rub the paint off at launch, you don't even need to touch bottom for it to happen.

The traditional solution for a keel shoe is either a teredo resistant wood (treated also woks if that's still allowed where you live) or metal sheating (copper, bronze, lead). HDPE is ok, if you're worried it's to slippery just sprinkle some sharp sand on the keel blocks before you lay the boat on them.
In any case, make sure the keel is properly antifouled before you screw anything to it.

 

interesting idea about the sand

Yes the slings will tear off the soft bottom paint, they stretch under the weight of the boat and rub hard like an abrasive on the wood. Really no way around it, simply then don't use wood or your breeding millions of worm larvae that do want to eat your boat everywhere they can, Like creating a concentrated worm factory on your boat, with you wherever you go.

Same issue happens with my wood splash rail, underwater at the round chine. This haul half was wormy on the starboard side, bad enough must be replaced, actually splash rail collapsed when hauled, Port side is ok

While not easy, redoing a splash rail is easier than a worm shoe

 

Another thing about bottom paint..mine has flaked off in places. This is because I tried to mechanically key and not chemically key. I was very careful and painted on a clean surface, but AF on tacky primer is best. Since you are into it this much; probably the old AF needs full removal.. but be careful to get new AF on tacky primer!

 

There are roughly two adhesives that work really well on HDPE, 3M™ Scotch-Weld™ Structural Plastic Adhesives DP8010/DP8010NS and 8005. You might find the $50 price tag on a 1.2 oz tube discouraging. Some epoxies might bond if you flame treat the surface first. Belzona had one, but the exact one escapes me. A terpolymer roof sealing goo that never really sets up hard might be better. Solar seal 900 comes to mind.

One problem with HDPE to be aware of is that it has a very high thermal coefficient of expansion, which is not generally a major issue on a keel underwater. When hauled in hot weather, the expansion could build a lot of stress. Almost all plastics have high thermal expansion and HDPE is just typical, not unusual in that respect. The recycled fiberglass would be much better in that respect.

 

Why not fibreglass the entire keel or use a thicker buildup on the bottom of the keel?