Paul sent me this about a bloke who made an engine well using a plastic pipe
Brave to use PVC pipe! It would work ok but the risk of fracture is present and care would be needed to get a good bond. If it does fracture then the boat goes down very fast. I think GRP pipe would be better for a good nights sleep. Or wrap the PVC in GRP, then bond in place.
You could get a section of those thick plastic pipes they use for water mains or gas mains.
Now what a novel idea, a sewer pipe in the cockpit. Wonder why those naval engineers who designed the boats to be safe never thought of this – just plain stupid that is why. We all want boats to be as sea worthy as possible, then some idiot thinks they know better. If an outboard is ok in the stern, why not put it on the bow for a front drive, use rope, pulleys, and other so you can get the thing to pull the boat where you want to go. Now why didn’t the engineers think of that?
Schedule 40 pvc pipe is rated for up to 810 psi.
should be strong enough for this application
just read the duckworks blog
stated ‘heavy wall’ pipe
probably schedule 80 (1230 psi rating) although it is usually grey or green in color.
I was looking at a Bristol Alberg-designed Corinthian that had a fully-immersed motor well that was offset to clear the long keel and rudder. But what was interesting was that when you didn’t need the well there was a FG plug that inserted from the top closing off the opening flush with the hull, and reducing any turbulence created by the well’s opening being beneath the water line. Most of them fit tightly-enough that it prevented any water from entering the cockpit via the open well. Plus you could then use the plug as a small cockpit locker.
The larger Alberg-designed Bristols of the period had the outboard well in the stern-overhang’s lazarette with the motor opening above the waterline, and the compartment was free-flooding and self-venting.
If fiberglass pipe is available, I think I’d truss the bond to the hull’s FG more than using PVC. It’s also not as “brittle” as PVC schedule-40.
If it was me, I’d use the pipe as a former and then wrap it inside and outside in a thick layer epoxy and glassfibre so the tube essentially becomes part of the hull of the boat. A layer as thick as the layup of the hull anyway.
I wouldn’t just rely on joining the pipe to the hull and deck mouldings at the ends of the pipe.
Most plastics will not bond directly with resin polyester or epoxy, The joint will be very weak a bit like using a wrong glue. Best to fabricate a tube of material designed for the purpose, or wood.
Mark’s got it. My profession is pipe. HDPE would resolve the brittle problem but relying on a chemical bond to seal HDPE or PVC is iffy at best. Making it part of the boat with fiberglass is the way to go and really not much more complicated. Other than that, a brilliant solution.
drill holes in it to allow the grp to bond through it?
still not sure what boat will appear
might be lucky enough to get one with a good engine –
How about just wrap GRP on the outside? You could then step the pipe for easier fitting – flange on the top of the hull inner surface, and another flange on the top surface of the cockpit floor – making the hole in the cockpit floor bigger so the pipe can be dropped in from the top. Top flange could include the outboard bracket.
The more that can be made on the workbench and the less in-situ inside the hull the better – both for the quality of the job and your sanity.
A tube that is strong enough for this job must presumably have a reasonably thick wall. I wouldn’t drill through it but I would seriously rough-up the surface, perhaps abrading it with a saw blade in order to groove the surface in many directions etc. Don’t leave any shine on the surface. Use a good quality epoxy resin. Glass the whole of the outside of the tube with minimum of three layers of glass cloth no lighter than 200gm/sq.m. and the mechanical bond between the tube and the glass should be very strong.Having said that, my concerns with this plastic tube method is how you manufacture and attach the “transom piece” that the engine will clamp to and the long-term effects of vibration on the structure and bonding.Sorry if this casts doubt etc.
no worries about more doubts – I can invent plenty of my own so others welcomed and added to the pile. I still think I am favouring the plywood version.
I think its a brilliant idea, far better than the wood idea. and like Dylan says if it had a row of hole around the bonding edges for the resin to grip through it has to be a better hold than surface grip alone? certainly food for thoughtJulian
Very good idea-the bonding/wrapping needs a little thought as mentioned,but I reckon it’d do a good job.The outboard well on my Coromandel is a nightmare of poor design-very hard to get the engine in or out on land,let alone at sea to access the prop. (honda 5 hp) if I get the chance I shall re-design it with a pipe.
Why not just build-up a new fiberglass shaft using the PVC as a mandrel-mold, and remove the PVC pipe once the FG has set-up? Then glass it into the boat? that way you could form a few reinforcing-flanges for the hull and the cockpit floor.
Roger should be able to give you the appropriate fiberglass lay-up specs.
Tho’ I still have misgivings about have a HUGE hole in the floor of the cockpit, and the amount of floor-space that will be compromised by the engine. In a short chop or a following-sea, I’d worry about seawater surging up the glory-hole, and nothing that falls on the cockpit floor will be safe from falling through the well.
Here in the States many boats have line-cutters fitted to the prop-shaft between the gland and the prop that shear right-through fishing-pot lines and poly-ropes..
Hi Dylan,Keep making the video’s – they’re great.
You may know all the below factors already but thought I’d combine them with the above ;
1) Normal polyester resin used in GRP boats doesn’t stick to fully cured fibreglass that well – it makes a mechanical bond not a chemical one, but is cheap.
2) Epoxy resin sticks very strongly but is more expensive.
3) The normal cheap chopped strand mat most commonly used for fibre glassing alterations is held together with a substance (no idea what it is) that is soluble in polyester resin but is NOT soluble in epoxy resin – so should not be used with epoxy. When using epoxy for layup you have to use the more expensive woven rovings that are held together by the weaving and don’t use a chemical to hold it together.
Taking these three facts together with the posts above it would seem to make sense to use whatever is easiest, cheapest and to hand to make a former in exactly the right shape (ie pipe or ply) with appropriate flanges, reinforcement for a place to hang the outboard, etc. then build up layers to the required thickness of chopped strand mat with polyester resin whilst outside the boat, then glue the resulting structure in place with epoxy suitably thickened (to fill the small voids and so the ‘glue’ doesn’t run away when gluing upside down), then build up layers of epoxy and woven rovings to cover the joins to make really strong..If you can catch the polyester resin before its fully cured then the bond to the epoxy will be stronger.Also when layering epoxy slap the next layer on as soon as poss. before the first layer goes off completely hard because it normally produces a ‘bloom’ on the surface when curing which has to be washed off which wastes a load of time.
And as you know its all temperature critical so shouldn’t be attempted in anything less than 8 degrees C minimum – which really means the summer time not winter, which is when you want to be sailing, or indoors in a workshop (which sounds expensive – except for the part when building up on the male mould which can be done in your garage).
4) Also note that you need to measure the quantities of hardner and resin accurately with epoxy, because unlike with the polyester resin which is a catalyst so is less quantity sensitive, the hardener with expoxy resin reacts with the resin and is consumed in the hardening process, which is why most people use either the separate pumps on top of the containers that give measured quantities of resin and harder each or, as I now realise, use electronic scales to accurately weigh the pot before filling and after filling.
The point made above about having a large hole in the bottom of the boat is thought provoking – but could be overcome by fitting a plywood bulkhead (wouldn’t necessarily have to be that thick or expensive marine ply just waterproof glue) across the entire hull width just forward of the hole, which if glassed in would stop the boat sinking if disaster did strike.
Well I’ve put my oar in, I hope there was something useful in there.
Or you could abandon the holy project and go for something like this: http://www.ebay.co.uk/itm/28ft-Yacht-for-sale-or-exchange-/321828010173?hash=item4aee71b8bd
Full canvas cockpit cover, sleeps 7 and has a lifting keel. Kills many birds with one stone, although not a bilge keeler but wouldn’t be too nasty if you sat on the sand. Or modify it with stub keels.. Reinforcing the hull to take bilge keels and drilling small holes for the keel bolts may be a better option than drilling a gert big hole in the bottom…
joking apart, have you considered a fin keeled yacht for your west coast exploits. There are tons around as we don’t dry out much and the waters deep.
Seriously there are not many places on the west a 4-5 foot draft cant get into. You could look at this while your up there:
heaven forefend – a boat that falls over when the tide goes out – what are they thinking?
just move a few inches closer to the deep bit and you’ll be ok. I know you’re an east coast sailor but you have KTL for that. I have read MG and i get all that. But doing the west is not the same… that’s all and it looked a nice solution to your interim problem not your long term one.
Did you have a twin keeled Snotty for goodness sake!
would have been ok to use as a mould but otherwise thats total crapola.
I really don’t understand all this making holes in boats. There are hundreds of variations all ready out there, most designed by marine designers and I would feel a lot safer in any of them. There are allsorts of considerations that the amateur hasn’t got a clue about. sorry
I have been working with PVC pipe, fittings and valves for many years and have seen them used in a variety of weird and wonderful applications, but I have never seen them used in an engine well! Not really sure how this will fair but I can say PVC is certainly one very durable material, so it will be able to take some cold/warm temperatures and a few knocks! You can see some other PVC pipe and fittings applications on this page here, including some more conventional PVC boating and marine applications: https://www.eeziflo-fittings.com/applications
sadly, or maybe joyfully, this project has not yet happened – I was offered a boat with a very good inboard – tearing it out to prove a point would have been bonkers – it is still unfinished business though