Question on channels and chain plates

[src]

Hey All,

Not sure if this belongs in furniture or rigging I am sure the admins will kindly move it if its in the wrong forum so here goes.

 

The instructions for my Enterprise call for a simple plank protruding out from the hull for the channels. This seems rather weak, I have seen a couple of pictures around showing a "shelf bracket" (Knee??) underneath for support. In Antscherl's Fully Framed Model he shows a bracket above for the Swan class. Are the channels simply there to direct the shrouds out and away from the hull or do they also come under stress? I guess what I am trying to ask is do I need additional support?

 

As far as the Chain Plates are concerned, the kit supplied me with stamped/photo etched parts to make chain plates. There are three holes in them to mount to the hull.  The instructions show the bottom hole used but no mention about the other two? Are the kit supplied parts and directions any where near correct for this class/period ship (1780's-1810)? 

 

Since this is classed as an "intermediate" kit - whatever that is - I suspect this is simply the manufacturers method of keeping the build simple.  I know I can have a respectable looking ship going with the kit parts, but I am trying to educate myself at the same time. Daffi has a great tutorial on chain plates here:

http://modelshipworld.com/index.php?/topic/487-chain-plates/

If its correct for my build I am considering going his rout but would like some input from others.

 

Kit supplied Chain Plate

 

Mocked up, What are the two extra holes for and should there be a Knee (correct term?) for support of the channel?

 

Manufacturers suggested assembly

 

Manufacturers suggested installation. Shouldnt the Chain Plates continue the angle of the shroud instead of 90 degrees to the channel?

 

 Thoughts? Suggestions?

Thanks for your time.

Sam

 

[twintrow]

Sam the channel should remain 90 degrees from the hull.  

And you are correct  the channel should be braced, but not with a knee from the bottom, from on top of the channel.

The purpose of the channel is to anchor the masts using the shrouds.  And since the tensioning of the shrouds would necessarily place a great deal of strain on the channel in an upward motion, the channel needs to be braced either with block supports as shown in the picture (picture from Pettersson's Rigging book), or with metal braces, from the top side.

And after nailing or pinning the chainplate in place at the bottom hole, insert nails or pins in the other two holes as well.

 

Also you will want to run the chainplates as an extension of the shroud following the same angle down from it's attachment to the mast.  I take a piece of line and before starting the shroud set up, pull the line down to the channel as the shroud will set, past the channel to show the angle of the chain plate.  Using the first hole to mark the angle. You can see the angle of the chainplates in the picture.

Hope that makes sense.

 

Tom

Edited June 8, 2013 by twintrow

[Ferit]

Hey All,

Thoughts? Suggestions?

Thanks for your time.

Sam

Suggestion from two articles...

[russ]

Sam:

Those chainplates are not appropriate for an early 19th century navy schooner. They would have had the metal strop on the deadeye, along with the U shaped links, and a backing link. What they have in your kit is really closer to what you would see on a late 19th or early 20th century working schooner. The holes in the plate are for fastening into the ship's hull.

 

If you look at the illustration that Tom posted, that is how your chainplates should appear. And yes, they should follow the angle of the shroud that they support. So, the chainplates are at different angles along the hull.

 

Russ

[src]

Awesome! Thanks everybody! If I am seeing this correctly the channels take the brunt of the load holding the masts in place. I am assuming then that the chainplates transfer a portion of the load to the hull? Looks like I need to get the masts at least mocked up before I can set the channels.

[russ]

The rake of the masts will tell you a lot about the postion of the channels. Most times the forward end of the channels will be at or slightly abaft the mast.

 

The channels will have slots cut into the outer edge into which the neck of the deadeye strops will fit. Then a separate cap will be fastened onto the outer edge of the channels to hold the strops and chainplates in place.

 

Russ

[src]

Alrighty-then, looks like channels wait for a bit.

Sam

[allanyed]

You have a lot of good information so far, but here is a bit more to further confuse the issue.  I believe the channels are not at ninety degrees to the hull, but rather they are horizontal.  If there is a lot of tumble home or other curvature of the hull where the channels anchor to the hull and it is ninety degrees to the hull at that point, they may point up or down, not lay horizontal.

Support brackets under the channel or knees were used on top.    Iron Tee brackets were often used if under the channels while  wooden knees were found mainly above. 

 

Allan

[trippwj]

Good point, Allan. Horizontal relative to sea surface since that is where the shroud alignment would exert the force. Supports below to counter force exerted by chain plates when no shrouds attached and above to counter flex of mast when underway. As in so many aspects of the builds, it is important to understand the purpose to in turn understand the design. Channels were not only about absorbing strain but also about increasing the width of the ship slightly for mast stability and keeping the shrouds and deadeyes away from the rails.

Edited June 11, 2013 by trippwj

[RiverRat]

Hmmmmm.....The channels on my Rattlesnake (ship-rigged) are given no support. Except for one model I've seen that has a small "ledge" underneath at least some channels, there are no supports shown on drawings such as by Hahn or Chapelle or any other model picture I've seen.

 

Brian

[twintrow]

Allen and Wayne.

90 Degrees from the hull would also be parallel to the water, assuming the hull was sitting level.

Brian, I just took a look at 4 different AOS ( I have 8) and all had some form of support to the channel.  I have one that shows only the chains as being the support.

It is your ship, build her the way that satisfied you.

I'm not positive given the recent events, but I'm not aware yet of thee being someone who checks our builds for details ;o)

Tom

[RiverRat]

 

Brian, I just took a look at 4 different AOS ( I have 8) and all had some form of support to the channel.  I have one that shows only the chains as being the support.

It is your ship, build her the way that satisfied you.

I'm not positive given the recent events, but I'm not aware yet of thee being someone who checks our builds for details ;o)

Tom

 

Tom,

 

I've absolutely NO idea what your last comments mean.

What are these "recent events" you mention?

How on earth COULD thou be aware if I check on "our builds for details". Who is this "our" you speak of?

 

I don't inhabit MSW 24/7 and read each and every post. Sorry, I have other life activities. PM your explanation if you want.

[allanyed]

Hi Tom,

Sorry to disagree, but the channels would not necessarily be parallel to the water if they are ninety degrees to the hull. It depends on where they meet with the hull.  The attached shows what I mean.  Now, I may be totally wrong on this  but I have not seen the channels angled on contemporary models or drawings.

Allan

[pompey2]

If you look at it from a forces point of view:

It the chain plates and shrouds were all perfectly adjusted and tensioned, then the channel would only be in compression.

In those circumstances supports would not be required.

Of course perfect alignment is never going to happen so there will be a bending element, up or down.

That would then need supports to counteract.

Also from an ideal perspective the chanel would be 90 degrees from the face it mounts to to maintain the 'compression' picture.

And again, if that is not so, supports would be needed.

Like most things on these types of ships, the balancing of forces, opposing tensioning etc is a really complex and interesting subject. A huge compliment to the designers of the day.

[twintrow]

Alan

I base my opinion on what I see in the AOS drawings.  For example. below are two scans of drawings showing the chainplates, the two drawings (on the left) are of the Constitution and the single from the Endeavour.  They show the channel at a 90 degree angle from the ship center.   And assuming the ship to be level in the water that would also be horizontal to the sea.

The tumblehome the two ships is slightly different, so my assumption is regardless of the tumble home they would be mounted at 90 degrees.

If I am incorrect in my assessment please let me know because, I mount them always this way.

thanks

Tom.

 

[src]

Wow, This turned into quit a discussion. I am getting an education, thank you. I see I need to be more concise in my questions. Perpendicular to the centerline of the ship is what I was envisioning which just happens to be at a slight angle to my hull. 

I was also interested in the tension/compression issue but dont have the engineering vocabulary to ask correctly. I saw the channels as a means to clear the cap rail but didnt see it as a way to widen the hull although that is exactly what is happening.

Thanks for the information

Sam

[allanyed]

Did a little more digging as I was starting to doubt my own comments. The attached drawing is from David Steel.  I have drawn in red lines that show the angle of the channel if it was 90 degrees to the hull.  The red line is 8 degrees higher than horizontal.  Also, what most models do not show is the gap between the hull and the channel.  I do not know if it applies earlier than about 1800 but is written in Steel's Naval Architecture as follows:

 

"They should fay to the sides only where the bolts come through, having an open space of about two inches in the rest of their length to admit a free current of air, and passage of wet and dirt, in order to prevent the sides from rotting."

 

Allan

[RiverRat]

"They should fay to the sides only where the bolts come through, having an open space of about two inches in the rest of their length to admit a free current of air, and passage of wet and dirt, in order to prevent the sides from rotting."

 

Interesting. Any mention of number/spacing/size of the bolts?

 

Brian

[allanyed]

Brian

There are scantlings for sure on the size and number of bolts.  I will take a look when I get home and have access to the Steel book.

Allan

[src]

Allen, thanks, I hadnt considered the water/dirt issue. I was going to mortice my channels into the hull since I have already stained and oiled her, gonna have to rethink my installation. Maybe Just smaller mortices although with mahogany thats interesting to say the least. I may change them to manzonia.

 

As far as support, my channels butt right up against the upper wale, I am thinking a support below might be more appropriate? I still have limited research material, the closest I have to my ship is the "Fully Framed Swan Class" series.

 

Thanks again everybody for the education.

Sam

[allanyed]

Brian and Sam

The number and size of bolts varied for size of ship and whether it is the fore, main, or mizzen channel as would be expected.  Samples follow:

 

                                                                              64 gun                       18 gun

Main Channel

Number of bolts                                                        9                                7

Bolt diameter                                                            1.25"                         7/8"

Iron T-Plates or supports in lieu of wood                    6                               4

 

Fore Channel

Number of bolts                                                           8                                6

Bolt diameter                                                              1.25"                         7/8"

Iron T-Plates or supports in lieu of wood                     5                              3

 

Mizzen Channel

Number of bolts                                                              6                                5

Bolt diameter                                                              1.125"                         7/8"

Iron T-Plates or supports in lieu of wood                        3                              2

 

I found no mention of spacing for the bolts or the T-plates.

 

Allan

[druxey]

From my observations on contemporary models, the channels are horizontal, not at right angles to the part of the hull to which they attach.

 

Bolt spacing would rationally fall between the slots for the chains, not under them. I've not actually seen a model showing the air spaces - yet!

Edited June 15, 2013 by druxey

[chris watton]

From my observations on contemporary models, the channels are horizontal, not at right angles to the part of the hull to which they attach.

 

Bolt spacing would rationally fall between the slots for the chains, not under them. I've not actually seen a model showing the air spaces - yet!

I have to concur.

[src]

I've not actually seen a model showing the air spaces - yet!

Me-thinks I am being challenged! 

Sam

[Rich_engr]

Wow- never heard of the "air space."

 

But, not to get too mathematical here (remembering my college work back in the day), the channel was designed to be static, not dynamic (fixed forces, as opposed to acceleration/movement involved).  I recall back to my Statics Engineering course, and there are only 2 formulas to remember:  

 

1.  The sum of the forces (in any direction) equals zero, and

2.  The sum of the moments (applied torques) also equals zero.  

 

If you draw a free-body diagram of the channel, showing the shrouds and chainplates (tension along themselves), the vector components of the forces cause the channel to be in compression.  Then, if you have a net tension in the +y-direction (ie, up the shrouds), in order to counter this you'd add a support strap below (to pull down and balance this force).  In a similar fashion, reverse this logic if the chainplates exhibit a net tension downwards by adding a wooden brace underneath the channel, or a tension rod above it).

 

This makes me wonder- when they were rigging the ships back then, did they have some device to measure the forces/tension in the shrouds (like a fish scale)?  Definitely gotta give the old shipwrights and riggers credit for knowing these problems and being able to solve them (without a calculator or an IPhone app)!    If they didn't know this, I doubt their ships would have made it across the ocean to the New World!

[src]

I have a ways to go before I get back to the channels since it appears I need to set the masts first. In the meantime I have noticed there seem to be a formula for everything shipbuilding. For instance I have seen mention of shroud diameter to be 1/x of the diameter of the mast. Based on the info Allan provided above I would assume that the Fore Mast on an 18 gun ship would have six shrouds; 7 bolts would leave 6 spaces between. But, what about shroud spacing? Is there a formula that says the space between shrouds is to be some fraction of the mast height or maybe of the diameter?

 

Looks like I need to buy a rigging book, suggestions?

 

Sam

[trippwj]

Sam -

 

I am not sure if there was a specific formula used to determine the number of shrouds or whether it was based on common practice.  A good place to do some digging would be Steel's 1794 The Elements and Practice of Rigging And Seamanship.

 

The table below (from page 102 of the book) shows the number of shrouds for the foremast on a ship of 24 guns as 7 pairs.

 

Now, for comparison, a 16 gun ship had 6 pairs as you can see in the table below from page 122

 

I will try and do some digging in Lees and some of the primary documents and see if there is any formula provided.  Also note that this relates to a specific timeframe (published in 1794, so common practice from about 1750 - publication) and nation (Great Britain).  Other times and nations may have had different practices they used.

 

http://www.hnsa.org/doc/steel/

[dafi]

Very interesting the information about the spacing. I already wondered by doing the "by the deep 17" why there are no drainage holes in the channels. 

 

I read the same thing about the fenders, those also should be spaced (source do not remember, thankful for hints) and also the sidesteps had holes which also helped to hold while climbing up

 

DAniel

[popeye2sea]

Src,

The only spacing guidance that I am aware of for shrouds is that the are spaced so that their associated chains do not pass in front of any gunports.

[src]

Thanks Henry, clearing the gunports makes sense. You probably just saved me from a redo. 

 

I didnt phrase my question correctly. When I look at a shroud I see a triangle formed by the outer two shrouds and the channel as the base. What I am curious about is should the base of that triangle, the channel, be a certain percentage of the mast height or multiple of the diameter? 

 

Wow I just checked Amazon, The Masting and Rigging of English Ships of War 1625-1860 is $228.00 US.      I have blown my building budget clear into September......   The Elements and Practice of Rigging And Seamanship. referenced above is available as an online reference and book copies are more in line with my budget at the moment. Looks like that will be my reference for the time being.

 

Sam