Trunnels a New Thread

[Dave Fleming]

Sorry Mr.S but, I must disagree with your trunnel views.

A 1/2 inch diameter trunnel would need at least a frame 3 times the trunnel diameter better 4 times.

That is a pretty heavy boat as I see it.

What works in a static piece of shop furniture probably does not experience the same forces as does a plank on a boat.

[ 11-12-2005, 09:24 PM: Message edited by: Dave Fleming ]

[Bob Smalser]

No argument from me, Dave.

But it might be worth a try on something I could afford to have fail.

I'm also interested in how the Japanese trunnels hold up over time, because those don't meet the standard trunnel rules and are also pretty shallow tapers compared to the holding power of my wedges, that can be driven hard across the grain.

[ 11-12-2005, 09:40 PM: Message edited by: Bob Smalser ]

[Aramas]

Since we're migrating from the other thread (I have no idea why), the Indonesian pinisi planking is edge fastened with trunnels, but it's also fastened to the frames and through the frames to the ceiling with trunnels. A lot of Asian cultures use trunnels in both boat and general construction, and have done for thousands of years. The Chinese were using trunnels when the Greeks were edge joining planks with mortices and tenons, and our ancestors were still using dugouts and hide boats and wearing blue paint. It's just possible that some Asian traditions are better than ours.

The whole idea of the other thread is that Asian trunnel traditions use lighter construction than their European counterparts, so arguing that trunnel construction is heavy becuause European trunnel construction is heavy is just cultural imperialism, or the 'Not Invented Here Syndrome'.

There is plenty of information available on European style trunnel construction, so there's really not a lot of point in discussing it, imo. However, there is very little information available on the Asian traditions - at least in English, and I'm not so insular or parochial as to assume that the methods of my ancestors are inherently superior to the methods of other people's ancestors.

So let's put the circular arguments aside, and hopefully someone with experience of lightweight trunnel construction in Asian boatbuilding traditions can enlighten us.

Here are some photos of 'primitive' Marshalese lashed construction, and I have no doubt that this lovely 'little' (52 feet) vessel, and even its 'vintage' predecessor in the black and white photo could sail past athe fastest America's Cup racers in the world like they were standing still. They are also some of the most elegant, beautifully engineered and constructed vessels I have ever seen.





Perhaps some of us are content to keep repeating the traditions of our own ancestors, but some of us can see farther than they could.

[ 11-12-2005, 10:27 PM: Message edited by: Aramas ]

[Rick Tyler]

Originally posted by Aramas:
I have no doubt that this lovely 'little' (52 feet) vessel, and even its 'vintage' predecessor in the black and white photo could sail past athe fastest America's Cup racers in the world like they were standing still.

I wouldn't race Conner's catamaran with one. [img]smile.gif[/img]

What's with the chip on the shoulder? All I've read in either of these threads is admiration for traditional methods. You are the only one talking smack.

[Dave Lesser]

Those Miller Dowels look interesting. Anyone have experience with them? I see that they have Black Locust dowels for $26.99 per hundred. That price compares favorably with Jamestown Distributors' 12 x 2 stainless steel wood screws at $25.24 per hundred or 12 x 2 silicon bronze at $34.56 per hundred.

[Dave Fleming]

"A" I cannot see a south seas vessel such as you have shown doing well in the North Atlantic in mid winter.

European sailing vessels had to endure weather conditions that those lovely lightly built South Sea vessels would not be able to endure much less survive.

THAT is the big difference.

Full respect from me in regard to the boat building traditions of other cultures be assured.

Imagine the Basques in the 13th and 14th century venturing across the Atlantic to fish for COD off the North American coast, setting up camps on the shores of Newfoundland and Nova Scotia to dry the fish and then sailing back to the Iberian Peninsula with hopefully full holds of fish to feed the people through the winter.

Bit different scenario in the South Seas no?

[Dave Fleming]

Re: Miller Dowels, I have used a bag full in recent months. Seem to work fine in interior joiner work but....you have to use their drill bits for the application. That means you are locked in to their system.

I for one, am not that comfortable with that idea.

Oh, I suppose I could find a tool maker who could grind me a bit to match the Miller profile but, I just don't like the idea in principal.
Jes' me I suppose, sigh.

[PeterSibley]

Posted on the other thread by Aramas
"One rule, regarding the dimensions of trunnels, which appears to work well, is; half the thickness of the hull planking plus 2-3 mm. At the same time, they should not be thinner than 25mm

I've been thinking about that rule,especially the 25mm/1" minimum.Does anyone have any figures handy for tensile and shear values for various hardwoods? I can't find my book. That figure looks way too high....perhaps its there to allow for age deterioration.

As a rough ballpark a 4mm square copper nail (8 gauge)should fail at around 500lb at 20,000psi tensile, (shear ?)...how would that compare with say,a 3/4" oak round....wish I had my figures for Aust.

[TimothyB]

I think these pictures say a lot as to the strength of Pinisi construction. I wouldn't be worried in them, and I wouldn't pay much attention to weather forecasts. The second photo is if a vessel being fitted out, hence her off trim. Also, it is a luxury charter vessel, so the high house.

I don't think either way is 'better'. The Pinisi are edge fastened because they have had access to good quality ironwood for a long time. Otherwise, they look remarkably similar to regular carvel.

Also, building the planking first and then bending in the frames is the same method that nordic clinker is built. The only difference is that in the North they don't have ironwood, so edge fastening is right out. Hence, clinker.

Honestly, saying which is better or stronger reminds me of 'my dad is better than your dad'.. boats evolve to suit existing conditions. The Pinisi took advantage of the stronger and more stable wood they had and used a lighter planking construction, edge fastened so they could use wider planks and have fewer seams, as well as the longitudinal and wracking strength boost you get from edge fastening, just as you get it in clinker with the rows of rivetted planks.

[ 11-13-2005, 09:15 AM: Message edited by: TimothyB ]

[PeterSibley]

TimothyB,there is an excellent article in Classic Boat,Feb '94 of your vessels being built on Kalimantan.As you say,edge trunneled and also to the frames.interestingly the trunnels( there a clear photo of a young bloke ( planing them to shape) are about 1" round for both uses...this is on planking about 2 1/2" thick.The vessels are BIG...100 to 150 feet long.There are 5 under costruction in one photo ! looks like something from Maine in 1890.

[Ian McColgin]

The rule for trunnel diameter I learned, about 1" per 100' LWL, works out to about the same as a diameter of somewhere near half the planking thickness.

I've no experience with trunnels in new construction, only repair, but I experienced no structural problems with half inch trunnels in 2" frames.

There would be problems if the frames worked as roofing frames work, taking a straight on bending load, but they don't. They are curved, often compound curved, with both racking and pressure strains shared through the skin. A 2" beam with a 1/2" hole is only as strong as a 1-1/2" beam. But a boat frame is a different application and the trunnel hole won't matter so much.

That said, I don't know where the practical limit is and I'd personally be loath to diminish the frame's continuous run by more that 1/3 or so. Certainly a 1" trunnel in a 2" frame would give me pause, but when would that even happen?

[Aramas]

Talking 'smack'?

[ 11-14-2005, 09:40 AM: Message edited by: Aramas ]

[Rick Tyler]

Originally posted by Aramas:
Talking 'smack'?

"smack n 1. offensive speech about another person. ('I hear you've been talking smack about me.')" -- definition from "The Online Slang Dictionary"

[PeterSibley]

General term for a small decked or half-decked vessel, sailing under various rigs and used principally for fishing::
http://www.reference.com/browse/wiki/Smack
[img]smile.gif[/img]

[ssor]

A couple of hundred years ago the British Admiralty launched a study concerning bronze fasteners versus traditional fasteners ( trunnels ). The problem that caused the Admirality to favor metal fasteners over the more traditional methods involved repairs. Replacing a plank with trunnels removed an unacceptable amount of wood from the structure (read frames) and the metal fastener was less damaging.

[Dave Lesser]

I inquired about prices for larger quantities at Miller Dowel, and got this reply by email:

David,

Here is a list of exterior prices for 1x 500 bags. These are list price. Actual price will be lower. Professional woodworker’s also receive an additional discount.

Mahogany – $257.
Purple Heart – $186
Teak – $637
White Oak – $200
Ipe – $285
Black Locust – $129

It would seem to me that these might be useful in glued construction, either double-diagonal or longitudinal, such as was done with Paul Gartside's "Surprise" in the following photo. At the least, you could eliminate the bungs. Any thoughts?

[Bob Cleek]

Can anybody tell me the advantage of a Miller dowel over a straight dowel epoxied in place? I know the Miller's are stepped and fit into a stepped drilled hole, but I don't see the benefit of that particularly. Am I missing something here?

[Ian McColgin]

My impression from looking at the Millers and using straight trennels is that the former really need to be epoxied in.

The Millers do not work like screws, where the head holds the plank down. Rather, the fat part goes down into the frame but then the thin part carries deeper, better anchoring the trennel. The plan is to provide lots of diameter where it's needed for shear strength- at the frame plank interface - and where it's not a problem - in the plank - but have a less intrusive bit deeper in the frame, thus providing holding power but not the weakening of a cylindrical trennel.

As I mentioned above, I don't consider that a trennel unacceptably weakens a frame in normal scantlings for boats say 10 tons or more, but there could be times when the Miller notion makes more sense.

If you've a good fit, neither epoxy nor wedges and blind wedges are needed for real trennels. I epoxy my trennels to provide lubrication driving them in and seal the endgrain of the plank and frame, not really to hold them in. A tight trennel's not going anywhere and a loose one will break at the glue line anyway.

G'luck

G'luck

[Bob Cleek]

Thank's Ian, that's kinda what I thought.

[PeterSibley]

Heres some data from our local Forestry Dept . on a local hardwood,tallowwood,e.microcorys .It's strong,reasonably easy to work but with a dense interwoven cross grain.It does not split easily......probably ideal for trunnels.
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Peter,

We don't have data for tensile strength however the shear data you requested for tallowwood is listed below:

Green- 1560 lb/sq.in. (radial); 1630 lb/sq.in. (tangential).

12% moisture content- 2200 lb/sq.in. (radial); 2420 lb/sq.in. (tangential).

These data were determined from a population of 20-25 samples.
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

At those figures a 1/2" diameter trunnel would withstand 430 lb of shear and a 3/4" diameter 970 lb. All you need now is an automatic lathe to turn them out by the thousand! [img]smile.gif[/img]

[Aramas]

Originally posted by PeterSibley:
All you need now is an automatic lathe to turn them out by the thousand! [img]smile.gif[/img]

Or in the Great Capitalist Tradition, just find a kid to exploit! It's even cheaper if you breed your own [img]smile.gif[/img]

[ 11-18-2005, 10:21 PM: Message edited by: Aramas ]

[StevenBauer]

You mean like this:





Steven

[Lucky Luke]

Steven
Aramas, Dave: I replied to some questions here regarding trunnels in the "Japanese trunnels" thread.

[ 11-19-2005, 01:42 AM: Message edited by: Lucky Luke ]

[Bob Cleek]

No need to turn treenails on a lathe. Just take a piece of iron pipe with an inside diameter matching the diameter of the dowel you want. Grind the edge sharp. Mount it in a sturdy vice. Cut billets the length you want and drive 'em through the pipe with a mallet. They will pop out the bottom of the pipe into a handy bucket below the vice, exactly to size.

[PeterSibley]

Don't try that with tallowwood Bob ,you'd need a new mallet pretty often

[Jay Greer]

I worked on contract built mine sweeps after the Korean War. They were Trunnel fastened and I turned them by the thousands out of "Black Locust". Black Locust is the traditional wood to use for trunnel
fastening. Aside from being nearly impervious to rot and expansion or contraction during changes in water content, Black Locust has another amazing property in that when cut across the end grain with an adze or even a Farrier's file, it will not splinter or fuzz!
JG

[Paul G.]

"A" I cannot see a south seas vessel such as you have shown doing well in the North Atlantic in mid winter.

European sailing vessels had to endure weather conditions that those lovely lightly built South Sea vessels would not be able to endure much less survive.

I beg to differ, cyclones are a regular occurrence in the tropics, of how about a few reinforced trades?

[Dave Fleming]

Jay, did the Navy Inspector make sure the trunnels were 'Square Fastened'?

[Dave Fleming]

Paul G., to compare a Cyclone to days or weeks of brutal weather in the North Atlantic in Winter is kinda a stretch.
I don't mean to trivialize any heavy weather be it Cyclone or Hurricane ( rode out 2 Hurricanes and it ain't fun McGee!).

There is a difference between a few hours or a day of Cyclonish weather compared to the long time line of a North Atlantic winter weather voyage.

[scepticus]

My impression of why those stepped dowels are supposed to be "better" is that you get a long length of dowel and only a short length of tight fit... easier insertion.