Attaching engine to stringers

[S. Weaver]

Treated is generally frowned on in the wooden boat community. A few folks have claimed positive results in limited applications. Concern has generally centered around what you brought up, Mike - the adherence of paint or other finishes.

[DetroiTug]

Per penetrating the epoxy barrier, I would use WEST's or System Three's info on mounting fasteners. It matters. There's a way to do it that protects the wood and facilitates ease of removing the fastener later.

With respect to mounting machinery on wooden stringers, tapped holes with machine thread studs or bolts are stronger than lags in tensile and sheer. This seems heretical at first blush, but there has been extensive testing in the wooden boat building community that favors the strength of machine threads over traditional "wood" threads in wood.

I'm a tough sell on that notion. In aluminum and plastics, it's frowned upon in the automotive tooling industry to not use hardened helicoils in areas of high stress. The reason being that the coil greatly increases the diameter and thread face area for the intended fastener. At the very least use coarse threads. Then in very soft materials like rubber and UHMW, other types of inserts are used with very coarse wood screw like threads on the exterior. I think what's being confused by those doing the tests is that a #10 machine screw is a much better fastener than a #10 wood screw. Wood screws are typically just cold rolled and not heat treated, machine screws are typically grade 5 (heat treated alloy)and up. Yes they are much stronger and threaded in to piece of wood while everything is new will give the impression that they are a better candidate. Unfortunately, wood is not static and continually moves. Swelling and contracting around the bolts with heat and humidity would lead to a loose bolt in the hole - and very little thread face to fall back on. Also, fasteners need to be serviceable, shallow not-very-well defined threads in material of little integrity for threading would make reinstallation of a fastener simply guess work. If the wood screws aren't strong enough, increase size or quantity for a long term solution.

-Ron

[S. Weaver]

I stand by the engineering, and empirical results in heavy service.

[farmerden]

Mike the difference in the treated wood.The one with all the perforations and slits is pressure treated -Much better product! The other one is just dipped-if the wood was wet or "green" when dipped the penetration would not be that great.Also Douglas Fir and cedar do not make good candidates for treating because of the resins already present so they use so-called junk wood -which rots quickly if they receive poor penetration. The treated fence posts I pound in on the farm rot from the center out but with no "old Growth" cedar available any more,it's our only reasonable option!
This forum is sorta like the "Learning Channel" isn't it Den

[Lopez Mike]

I think my life has been more like Comedy Central than the Learning Channel only I'm the straight man!!! I keep finding new mistakes to make.
Mike

[Mike Rometer]

One could say this goes against the 'grain'.

Do I take it we're talking properly tapped holes in the wood here, i.e. drilled a suitable undersize etc., not just the bolts screwed in 'self taper' style? It's a new on on me that's for sure.

[Johnlanark]

West advocate drilling oversize holes in the wood and setting your hold-down studs in epoxy. But this would not be advisable where the studs may become hot, such as for a boiler, as it may melt the epoxy.

For my boiler, I plan to use cross dowel nuts. If you have ever built an Ikea bed you will know the idea. The bearers are set fore and aft. Half inch holes will be drilled through them near the bottom, across the boat. 3/8" clearing vertical holes will be drilled down from the top to meet them. Pieces of half inch bar will be cut to the width of the bearers and threaded radially 3/8 in the centre. They will be fed into the cross holes to take 3/8 hold down studs. Hope that makes sense. Any thoughts on this? John

[Lopez Mike]

Those Cross Dowel things are great IF you put anti seize on the threads where the rod screws into the dowel. I have had to take too many things apart after poorly thought out installations (mine included). Much blue air and taking everyone's name in vain.

The beauty of them is that you can make your own to suit.

We may be over thinking this a bit though. My sailboat motor mounts were put in on a beer soaked 1971 Friday afternoon in Costa Mesa at Islander Yachts by minimum wage guys from Michoacan with ordinary galvanized lag bolts. I've had then out twice and put them right back in the same holes and cranked them down with no give. Been through some blows where I was scairt to go into the cockpit and they are still there!

Mike

[S. Weaver]

Rometer - I read that one is supposed to use the next smaller size tap.

John - that's good perspective on the thermal effect to the epoxy anulus, the cornerstone of the WEST methodology.

Lopez - thanks for the perspective. A lag in a hardwood stringer protected from moisture is a fearsome thing!