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HBMS Amphion 1798 - 32 Gun 18pdr Frigate


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#31
Wintergreen

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Joss, I know exactly that feeling of not being satisfied with the status of the work and to many deviations from what one wanted it to be...

(I'm in the same mental state with my Wasa, although I haven't hit the delete-button yet...)

 

Edit;

And of course we anticipate some great work from your drawing table in the near (?) future ;)

Take your time!


Edited by Wintergreen, 14 April 2013 - 06:26 PM.

Cheers from Håkan

__________________________________________

Current build:

 

Previous builds

Gallery: BB Regina Build log: Regina by Wintergreen

Billing Boats Dana

Billing Boats Wasa

Upcoming projects: Shalom, HMS Euryalus


#32
mtaylor

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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.


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#33
prodas

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I liked it, I congratulate you for the initiative



#34
Matrim

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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



#35
Matrim

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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

 

Original.jpg

 

and here the new trace

 

NewWorking.jpg

 

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)

 

full1.jpg

 

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

 

Insideworks1.jpg

 

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

 

InsideWorksMismatch.jpg

 

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

 

 



#36
Garward

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


Best regards,
Garward


Is under construction Montanes

Ready models Golden Star Corsair San Francisco II
Bronze 24-pdr canone Le Fleuron
Bronze 24-pdr canone Le Fleuron (second version)

#37
druxey

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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.


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#38
Matrim

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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



#39
Matrim

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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

 

LengthOfBreadth.jpg

 

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.

 

Straighten.jpg

 

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

 

Difference.jpg

 

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

 

rotate.jpg

 

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

 

AftPerpendicular.jpg

 

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

 

Placing.jpg

 

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

 

GunportOnFrames.jpg

 

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.

 

GunportClean.jpg

 

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

 

Joss

 

 



#40
Matrim

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

 

A1.jpg

 

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.

 

 



#41
druxey

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This is looking good, Joss!



#42
Matrim

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

 

Joss.



#43
AnobiumPunctatum

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Joss,

 

your drawings are looking really good.


Regards Christian

In the shipyard:
  Naval Cutter Alert, 1777 - Scale 1/32

To be continued: HMS Fly, 1776 - Scale 1/48


#44
mtaylor

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



#45
Matrim

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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 - 

 

A5-RearLine2.jpg

 

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) 

 

A4-RearLine.jpg

 

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)

 

A2-CapRailLeft.jpg

 

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

 

A2-CapRailLeftFull.jpg

 

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

 

A3-CapRailCentral.jpg

 

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)

 

A6-CapRailAtFrameHeight.jpg

 

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..

 

A7-Aaa.jpg

 

 

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

 

 

 

 


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