HBMS Amphion 1798 by Matrim - 32 Gun 18pdr Frigate

[mtaylor]

Joss,

 

I'm looking forward to seeing the rework from the knowledge gained.   We're all learning from you and the others doing CAD work.

[prodas]

I liked it, I congratulate you for the initiative

[Matrim]

Thanks guys - at the very least I should be able to do a better job of logging those adjustments I am making to the original process.

 

Joss

[Matrim]

K, well time to cover the first stage of the reset. I was primarily unhappy for 2 reasons. 1 was almost unimportant and that was I did not think I had taken enough care in my first trace of the plan - nothing important note I had copied every important line but in the process I left lines of lesser importance (decoration mouldings, rigging supports) at either a very limited way or not included at all. As an example here we have my original trace

 

 

and here the new trace

 

 

Hopefully you can see that more care has been placed on some of the less obvious things. The upper plan does contain some extra work on details (these will be added to the new later)

 

The second and more important reason was that when I first started I was concentrating heavily on the lines and not the other resultant drawings that I would need at the end. I vaguely recollect figuring that when I needed them I would just take the relevant info from the other plans. But when I got to needing them I found myself wanting all the  data on my master plan so I could take it straight off. Basically I had increased in my cad confidence such that I was distinctly unhappy taking anything off the plans at all. This was the main reason to restart.

 

So I have now re-taken the lines (and used a better colour differnetiation structure now that I know what a lot of the lines are)

 

 

My next stage is to transfer the inside works and framing plans onto the same plan (using different layers of course). There may be differences between the plans but I will address them when I come to them. That way once I re-do the lines everything I need will be on one plan.

 

So confident in my plan I had the inner works and framing plan scanned and attempted to map that to the existing outline and instantly hit a problem. Basically the inner works were of a drastically different size to the traced plan. I almost broke into a cold sweat here thinking that either the trace is wrong (and perhaps the original plan) or the inner works is wrong. Either way it was bad. I then spent some time resolving the issue. First up I went back to the paper plans and measured the length of breadth and the height of the rear perpendicular to its highest point and did the same for the (0) station line. I then converted this to scale inches ( *48 / 25.4) to get the correct size. I then repeated this for the inner works plan and the framing plan.Fortunately they all matched bar an odd tenth of an inch or so.

 

This meant my plans were correct but one of the pc images was not. Armed with this method it was a simple enough task to measure the same heights on my traced plan. It was great news in that they matched.This meant the trace was good but the internal works had got warped somewhat in its transfer.

 

After playing with the measurements I eventually re-scaled the inner works over both axis and it matches closely. There is still an  issue at the bow by a foot.but as the inner works is primarily there for the decks and keel/stern I am less worried about the mismatch here.

 

So here is the overall shot of the inner works plan. You can see the perpendiculars and for some reason the rigging showing from the underlying plan

 

 

and here is the remaining problem area. As can be seen it is a distinct drop at the bow but not by much

 

 

This warp does appear evident on the paper plan so i suspect this is more an age thing than a further problem with the scanning process.

 

So next up is matching the inner works then repeating with the framing plan. After that I may re-use my original body plan trace.

 

Joss

 

 

[Garward]

Hi, Joss! You make magnificent work, I very much like your thorough approach!

[druxey]

There are almost always problems with the old plans because of either dimensional instability of the paper, or distortion in reproduction of the originals. Direct tracing will not correct this. In particular, different plans of the same ship will not match for this reason. This may be the issue that you have discovered.

[Matrim]

Cheers Druxey, in the meantime I took a line from the forward perpendicular and compared the plan measurement to the traced measurement and they both came out at 325 inches (and this matched across all three plans and the class plan which I also have) so I am confident this issue was primarily in the scan conversion and the trace is correctly sized..

 

Joss

[Matrim]

Brief post on scan placement. I find the easiest approach is as follows. Firstly ensure that the existing 'trace' is at 1:1 scale. The easiest way to do this is to use one of the provided 'figures' on the plans - lower deck length of breadth. This is easily seen on the plans as both Aft and Fore perpendiculars (vertical dotted lines) start from either end of this line. Work out the current distance between the two lines then divide one (I can never remember which) by the required figure (in my case 144ft so 1728 inches) to get the scale factor. This is then applied to one of the ratios in turbo cad (note whether you have keep aspect ratio on or off - if off then be aware that you are only adjusting one axis and will need to repeat for the vertical).

 

Length of breadth once correctly sized to 1:1

 

 

Once the trace is sized correctly we can attempt to match the next scan to the existing image. Firstly I would recommend cropping the image and possibly saving with a lower quality ratio. Most scanners contain far too much info and using the image 'as is' can contain extra junk that will slow your pc down. In my case I have turbo cad 20 64 bit so I have plenty of memory to play with. if you have less or an old pc then things will slow down if you do not do this first.

 

Anyway insert the image. Once done our first job is to straighten it. I find it easiest trusting the keel or rabbet lines. I straighten by starting a line at a point on the keel near the stern and ensuring this line is horizontal (press shift) plus dragging it past the end of the image at the bow side. Next starting from the same point (press v) I draw a different coloured line which follows the middle of the line I am using. Usually i start the line and just scroll to a point near the bow and place the line there then lengthen it past the image with the first.

 

 

Now we can drop a horizontal constructor and measure the angle (dont do the distance)

 

 

this then can be applied to the rotate to straighten the plan.

 

 

Note if your keel line is not straight then you may need a different line.

 

Once this is done validate the plan 'stability' by putting a line or a vertical constructor over the two perpendiculars. This will give you a good impression of whether the plan is square of warps slightly at either end

 

 

This plan is good at the bow and slightly off at the stern

 

Our next job is to place the image over the trace. Ensure the trace perpendiculars exist well beyond the trace and you can use one of those to get the image 'close'

 

Once placed re-place a new horizontal constructor on the image keel line and then measure the distance between this and the actual perpendicular

 

 

This can then be added/subtracted from the relevant axis (if using the keel it is the y if adjusting horizontally then you would be hitting the x) In any adjustment case look at the image when the adjustment occurs as it is easy to adjust the opposite way - this is usually blindingly obvious.

 

Once done on both axis I tend to validate the results by placing a horizontal line against an object which is clear on both plans and making sure when the image is made invisible that the line covers the same part on the trace. 

 

You can also measure certain heights on plan and compare them to the actual plans to ensure you have no problems with  any size adjustments.

 

Finally you can start tracing the new image. One thing to remember is that the plan is unlikely to match exactly and you have to make decisions as to which plan is the master. For example I am treating my sheer plan as my primary plan but for the gunports the frame plan should take precedence as the gunports would be placed according to the edges of the frames so as long as the framing plan gunports are similarly placed to the sheer plan then there would be little difficulty. The other thing I do is to use the force vertical (shift again) and right angle tool to draw most of the frame lines. Most of the time these match quite well (for the square frames only!) and it allows me to validate both the framing plan and sheer plan at the same time.

 

For example here is a shot of the rough trace of the framing plan over two central gunports

 

 

If I strip the image and include the sheer gunports you can see that though they are not exact they are very close. Also that the frames end points hits the dotted line of the sheer plan which is as expected as the barrier (probably not the correct term) moves up to that point and thus you would expect the frames to as well.

 

 

That'll do for now and I will go back to spending a week or so tracing over my next plan.

 

Joss

 

 

[Matrim]

Frame are in. Match up nicely (give or take a real life inch) with the gunports from the sheer, which is nice...

 

 

So as I contemplate my un-roofed extension filling up with torrential rain I can start on getting the body and sheer done and dusted next.

 

Joss.

 

 

[druxey]

This is looking good, Joss!

[Matrim]

Cheers Druxey, while I have the time I might as well utilise it to do the best I can

 

Joss.

[AnobiumPunctatum]

Joss,

 

your drawings are looking really good.

[mtaylor]

Nice work, Joss.  Looking forward to the next installment.

[Matrim]

Time for another un-thrilling update! I have just completed drawing in the new waterlines and as an expression of my greater confidence have drawn them at 3ft below the wale and 1.5 ft above (in the original plans I went for 2 ft and 1 ft respectively which just added extra work and did not allow the auto curve CAD functions to work as cleanly as they could).

 

Rather than go into exhaustive detail Wayne's tutorial covers this nicely. I did have to make a couple of leaps of faith though. Which I shall detail here just in case they are invalid leaps.

 

First up when working above the wale towards the rear of the ship you will notice that most plan sets suddenly stop 'bending' the lines to the keel and start sticking straight out as so - 

 

 

Below the wale the waterline should start at the rabbet line. Above the keel this does not exist. Instead I used the handy stern line (here in blue) 

 

 

coupled with one of the rear dotted plan lines from the sheet as my 'start' point above though  I am not entirely certain what this relates to - I don't think (what do I know) that this will affect anything later on as other superstructure builds up this.

 

Whatever else you do don't forget and treat this like a station line though as that will really damage your hull shape..

 

 

The other area is in the placement of the cap rail. annoyingly enough is not the highest rail on the ship but (at the rear) the following (in the light brown colour)

 

 

The superstructure above this is not part of the standard framing as can be seen if I switch on my underlying frames trace.

 

 

In the center of the ship I am using the bottom dotted line. Mainly because again that is where my frame plan frames complete.

 

 

At the bow I was confronted with more of a conundrum. Here the frames clearly end at the upper rail but when transposing horizontal constructions across the lines completed at the following (note the little horizontal green lines which indicate this point)

 

 

The lines above this suddenly shoot vertical so looking at my plans I drew a construction from the top of the timberheads where they crossed a station line and then threw a couple of horizontal construction lines off. This appears to match the vertical limit of the body plan lines on the body plan. My problem is that the timberheads (if I remember correctly) were an extension of the frames. So my problem is should I use that line as the cap rail on the sheer or the cap rail as it exists for the majority of the frames. - The timberheads are after all intermittent and do not occur on every frame..

 

 

 

Anyone this stage is fast so if anyone has any criticism of the approach then please say before I get back on to it. Thanks for reading..

 

 

Joss

 

 

 

 

[Wintergreen]

Thanks for your discussion Josh!
My own drafting and building has come to a grinding halt so it is a pleasure to follow you along.

 

I cant really get in to talk about your details and findings, just thinking "hm.. yup, ah, yeah that's right" and so

[Matrim]

Thanks for the comment, I find the cad work relaxing (at least when I believe I am working correctly that is)

 

Joss

[WackoWolf]

Joss.

 

   Your cad work is excellent. I have been following this from the beginning. Keep the pictures coming.

[Matrim]

Just a quick update. The plan is redone and faired and I am ready to start (back) on the primary drawings again. Keeping the original plan lines on a hidden layer proved useful in checking the validity of my completed plan as below. Here the new station lines are in blue and the original station lines in black

 

 

Last time through I started on separate completion plans for each section (i.e frames, keel etc etc) this time I am getting the basics correct on the primary plan and then simplifying to work on each new plan. Here is my working copy of the keel master plan. All I have done so far is copy the information from the main plan and started stripping down the info to what I want to show on the plan. No doubt there will be some adjustments I notice that will need to be mimicked back on the main plan but I should be in a better state to undertake this.

 

 

Hopefully I will get the smart version of the Keel Master out of the way by next week then can re-do the keel, false keel, stem, bow, keelson individual break out plans.

 

Joss

[Matrim]

Without further ado here is the keel master. As before I am utilising EdT's plan styles because they are just so stylish.

 

 

and since I cannot appear to get turbo cad to save it in a readable format for the web

 

 

 

 

As stated before onto the construction plans for the keel/false keel next

 

Joss

[mtaylor]

Looks great, Joss.  I think re-starting was a good thing.  Hopefully, it'll go better this time.

[Pete38]

Been quietly following along on your thread.   The restart seems to be well worth it. Looking good.

[Matrim]

Thanks both for the comments

[Matrim]

Things are progressing nicely and I am currently on the 'smart' plans. I wont upload the keel/false keel parts plan as that is quite simple and thus not that exciting. Here though is the smart sheer plan. I have also finally worked out how to get a viewable image out of turbocad. Save as a pdf. Open in pdf reader and screenshot it..

 

 

Next week I plan on starting on the framing plan.

 

Joss

[Matrim]

Time to move (slowly) onto the framing plan. I decided to not use the existing plan except as a template and then had to make a descision on the vexing question of whether to follow standard practice and having the siding decrease with each frame. On reflection that is beyond my ability so I will keep to equal sided frames except where an actual siding would enable the frame to better map the actual gun ports. Though this will make the construction easier it means there will be some more work to do in ensuring the framing plan adjustments do not upset the integrity of the design.

 

First up I validated some numbers. My Proserpine contract lists the siding of the frames as follows

 

Lower Futtocks between 9 and G sided 13 inch

9-13 + G- >= sided 12 inches

Forward and aft 11.5 inches

 

I then validated this against my own framing plan. Scaling up then down I measured each of the double frames to ensure

they matched the contract above (which they did).

 

Next up I drew in the square frames before calculating the gaps. i.e for the central frames the gap was 36.36 with 2 single frames if each is 13 inches then the three gaps would be 10.36/3 so 3.45 inches.

 

When the frame sidings changed so does the required gaps. Another noticeable difference was the section of the hull where three single frames separated the two doubles.

 

Once the frames were in it was time to check against the various gunports.

 

For the purposes of the gunports the single frames do not usually form the sides so can be ignored (1 gunport was sided by a single but I will get to that later. The next point is that allowing for the drawing method the gunports themselves might not be exact. Measuring the gunports on the  plan I was fairly happy that the width was approximately 35 inches for all the gunports. On my frame plan the measurements were as follows

 

I marked the sternmost gunport of the square frames as I and worked forward from there

 

Gunport CAD frames Original sheer

I             39.36            35.28

II            39.36            35.47

III            38.36           36.17

IV           37.36            35.45

V            32.91            34.96  (bordered on right by a single frame)

VI           36.60            35.21

VII          36.36            35.28

VIII          37.86           35.04

IX           39.36            35.62

 

As can be seen the sheer plan ports (with the noticeable exception of III) all hover around the 35 inch mark. The cad frames are both larger and generally more regular. A lot of this lies in the siding decreasing but it is also covered by the gaps making slight and increasing differences in size which incrementally upset measurements and slight movements in the station line. The adjusting sizes of the gunports as measured on the original sheer has been impacted somewhat by the measurement itself. As CAD lines are thin the thicker line drawn on the map (on the right hand side of the gunport) allows slight adjustments in size to occur. 

 

To resolve this I firstly adjusted the gunport width to exactly 35 inches with the right hand line 'losing out' I then either added diminishing sidings wherever it would push my lines badly off. Height wise the gunports appeared to consistently measure around 29.45 inches.

 

So to start I needed to finally decide which lines would be used as my target gunports - the sheer square or the framing plan ports. Here is a shot of the I gunport two with the sheer port in black.

 

 

And measurement for both

 

Frame ports 

 

 

Sheer plan gunports

 

 

 

Now the horizontal for this port is not true horizontal - using two vertical starts it matches 34 inch but measuring the full length of the line almost hits 35 (hence the discrepancy between this and the above width marks which followed the horizontal). There is nothing there really to make me prefer one over the other - something which was consistent over the other ports so I had to pick one. I decided in the end to use the sheer plan ports and not the framing ports.

 

Now the next shot is of the sheer I port and the double and single frames in that area of the ship - this is also where the gap should be the worst as it is incrementally furthest away from the central double (0) frame.

 

 

Now on the framing plan there are some large sidings adjustments as follows

 

Sternwards

 

 

Bowards

 

 

 

So I shall replicate. My next job therefore is to ensure the gunports are all the correct size and bordered by frames. If anyone has anyone opinions as to gunports sizes or the best way to resolve this then please say.

 

Anyway bye for now.

 

Joss

 

 

[druxey]

Ports are spec'd at 28" deep by 30" wide for a 32 gun ship (Steel, 1805). The sizes you quote are very close to those for a 38 gun ship (30" x 34").

[Matrim]

Cheers Druxey, I shall carry out some more validation against some of the other original plans tonight. Is that measurement frame to frame or would it include any 'interior' wood i.e gunport sill would reduce the height of the gap and could be around 2 inches plus any wood (if any was used) on the vertical.

 

I will hit the books before carrying on further to see if I can resolve the discrepancy myself.

 

Cheers,

 

Joss.

[Doreltomin]

Hello, I just wonder if this computer-aided design of a period wooden ship isn't plain misleading. Don't misunderstand me, I also work as a professional architect, busy all the day long with my 3D models, but I remember the old days of the hand drawing and I have seen how this 3D models and uncanny precision of the CAD can modify your thinking. I mean, there may be too much precision which for practical reasons wouldn't be necessary for a wooden ship, where some 1-2 cm of adjustment and deviation from the standard dimensions would have been quite normal. 

 

Then, there is something else which annoys me from a long time ago and I am not yet sure how it was on a real ships.What do I mean:

 

I know all period plans of these ships show the vertical sides of a gunport to be a true vertical, while the "horizontals" are parallel with the respective gundeck. Is it like that on their period plans because it is plainly easier to draw or was it also true in reality?

Each gundeck lid would have been custom-built and then fixed to place, a tedious and time consuming process. 

 

For the real ship I believe it would have been easier to do it otherwise. I mean, on the shipyard there must have been a logical development of the things. First, the frames were erected and put to place. Then, the external wooden skin was put to place, then the gundeck beams were fixed inside and the gundeck put over. Then, I believe for practical reasons it would have been easier for them to make a wooden jig of exactly the needed size for the gunport aperture including two "legs' to align it do the deck at the needed height, mark the place and then cut the gunport along the marks. If it was needed, the true vertical of the frame was adjusted away to make room for the gunport aperture. This way the "horizontals" would be paralel with the deck, the "verticals" of the gunports wouldn't be true verticals anymore, however the gunport lids would have been at 90 degrees each, easy to build, easy to adjust and easy to switch from one gunport to another if needed. 

 

What do you think?

Edited September 3, 2013 by Doreltomin

[Matrim]

Cheers for the comment. Other people will probably give a better answer than I can but as the decks can sweep at quite an angle it would make no sense to have the gunports true horizontal as they would then be angled as to the deck the gun was being serviced from. If the ports were true horizontal then the gun would not always be able to cover all directions as the deck drop/rise would cause the cannon to 'touch' the gunport or alternately not be able to reach it at all.

 

The sides would be vertical because the frames that erm framed them were vertical (and if they were not then the ship wrights would have a much worse time building the ship than they would coping with what are much smaller angled gunports).

 

I doubt that is a very satisfactory answer though so we will see if anyone can provide a better one.

 

Joss..

[druxey]

If port sills were all horizontal and not parallel to the deck sheer then the planking of each inside would need to be chiselled out square. In addition, the curve of the ship's sides prevents port lids from being interchangeable. You could ask why a ship has sheer and is not flat along the decks. Sheer is required to counteract the tendency for the (wooden) structure to sag and for drainage. A ship is very unlike the architecture of a building, where all items are at right angles, parallel and eight horizontal or vertical, modern day cruise ships excepted!

[Matrim]

After a further investigation I have decided my gunport approach. I checked my own copy of steel and as Druxey states the provided port sizes are as follows (for the upper deck)

 

Size            38     36     32

Deep          30''   29''   28''

Fore & aft   34''   34''   30''

 

Now I then re-measured all plans with gunports on (class amphion, amphion actual,framing plan) using the smallest possible width and the size came too for the framing plan

 

34'' wide and 29'' deep

 

other plans

 

33'' wide and 28.5'' deep

 

Now as the lines on the 'other plans' tend to be thicker this means the ship average is close enough to 34 by 29 which as seen above is the Steel width for 36 gun ships as opposed to 32.

 

Considering the ships history I do not think this is difficult to explain. Firstly Steel is providing generalities over decades of ship building and not hard and fast rules and secondly if you look at the 32 gun ships as a whole they mainly tend to be 12 pdrs or less. The Amphion class was rare in that it is a 18pdr 32 gun ship so it makes sense to me for it to have ports equivalent in size with the 36 class which also mainly carried 18 pdrs. Otherwise the armament would be constrained

compared to equivalent armed ships. 

 

Even if this assumption is incorrect my basic rule is that the ship plans are right and other data resources such as the contract or Steel can help confirm things but should not be taken in preference to consistent plan measurements without exceptionally good reason.

 

Anyway that done back to the plans. Looking over my options I am using the frame as my default but rather than favour the bow side line of the stern side I am taking the midpoint and spreading the 34 inches over that. Equally for the horizontal sides I am taking the midpoint, splitting and then reapplying the correct angle. 

 

 

 

Once the sides have been marked I then added the sills using 6'' for the lower and 5'' for the upper before (in this case) adding some decrease in siding to match the original plan structure to cope with the new sized gunport. 

 

 

I will  now start the long process of repeating this for all the other square frame gun ports.

 

Cheers all,

 

Joss