Hello Gentlemen:
After moving house to a new country, I am finally back to building models again. Since I am Canadian, I am trying on this next build to do the British warship of 1780 the HMS Ontario. This has always fascinated me when images of its discover came to light.
I have procured the single sheet of admiralty plans but am disheartened by the lack of information. Using Steele's and Deans books My efforts will be to accurately reproduce the drawings using Autocad and then vuild a 1/2" to a foot scale Admiralty model.
I know what you purists think but at 1/4" to a foot the mosel will be to small for my eyes. I am almost blind you see. The challenges that some have are small compared to mine. I am not belittling anyone, but my challenges are great. Besides I LOVE to build.
At 1/2" to a foot the model comes out to 40" so its not to bad.
I can let people know my progress and share some of the cad work and then build if there is interest.
Keep building
Dave

 

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Sounds like a great project Dave. Please share your progress. I am sure you will do a great job.

 

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there is a set of modeling plans done by John McKay which are very detailed.
McKay is an architectural draftsman and an authority on 18th century British ship construction. These are plank on frame drawings and based on the Admiralty drawing.
Plans are available from quarry Press p.o. box 1061 kingston ontario canada K7L 4Y5

 

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Hi Dave,

As a fellow Canuck, I am very interested in your project and look forward to your progress reports. I am quite new to model ship building - haven't built one yet, but am expecting my first kit any day now.
However, the HMS Ontario has caught my fancy - I ordered the book "Legend of the Lake" and hopefully it will arrive soon. I find brig-sloops to be quite lovely. Another that I like is the HMS Speedy.

Cheers,

- ian

 

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Here is what I have been working on so far. I have done the math and tried to explain where I got the information and then did the drawing in cad. If you notice anything wrong in my calculations or cad work please let me know.

What we know about the H.M.S. Ontario
Length of lower deck - 80'
Length of keel for Tonnage -62'
Extreme Breadth -25'
Depth in Hold -9'
Breadthen in Tonnes -226 tonnes

Terminology needed to understand old english wording
Besides thous and arts etc :) words like :
Sided - the dimension of a scantling taken as depth
Moulded the dimension of a scantling taken as width
Scantling is all timber or pieces that are part of the makeup of a ship
I will get into other definitions as they arise.
Moulded Breadth
Extreme Breadth- 2x the Bottom thickmess = 25- 2x3"
= 24.5'
Bottom planks ( not Garboard) = .0185 of the half Extreme Breadth
= .0185 ( 25)
= .232 ' which is approx 3"
Keel as by definition shall be sided 1/2" for every foot of extreme breadth
= 1/2 ( 25)
= 12.5"
Deanne states in his works that the sided dimension also includes the false keel . This is a normal practice in all shipbuilding of the time. But if you look on the draughts you will see no false keel. I don't know if Coleman didn't include it in the drawings but it is not assumed to be included. Most draughts that I have seen include it. Also Deanne states that the keel was basically square.
Moulded dimension = 12"
True length according to Steel: Measured from the back of the stern post at the level of the rabbitt , along the rabbitt to the perpendicular under the bowsprit on the level of the Hauseholes minus 3/5ths of the Breadth must equal the true length
We need a dimension here which is called the Rake of the Stern by definirion is 1", 2" to every 6 feet of the length of the post.
The length of the sternpost is 2/3 of the breadth-1/2' again Steel
2/3(25) - 1/2'
= 16.2' at the lower deck
Rake of the Stern = 1" to every 6' of 16.2'
= 2.7'
ao therfore the true length of the keel is = 81' - 3/5(25') - rake of Sternpost 2.7'
= 63.3'
Now we can turn our attention to the Load Water Line or L.W.L.
Which by definition is 3/5ths of the Top Limber Line or T.L.L.
which is for two decks or under 1/5th of the Length
= 1/5 (80)
= 16'
therefore the L.W.L. is 3/5ths (16') this is at midships position
= 9.6'
The height of the L.W.L. at the perpendicular of the stern is the 9.6' + the sheer of the forward deck or forward rise of the deck. Which by definition (Steel) is 2 1/4" for every 10' in length.
= 9.6' + 1.5'
= 11.1'
[IMG]keel[/IMG]

 (open in a blank window)

 

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What I have done next, was to check my results with the actual Draughts. I am wrong on a couple of places. Or should I say that the formulas I used were wrong.
The Keel length formula is wrong. I instead used Van Yk a Dutch shipwright, and determined that the length of keel is = 9/10 the length of the lower dec . He uses the length marked from the outside of the stem and the stern post at the level of the lower deck.. Since the perpendiculars are set up to the outside of the stem and the inside of the sternpost. We can add approx. 1' to the length of 80’. So therefore the equation now works out to 9/10 of 81' or 72.9' This coincides approx. with the draughts. The scarph is next. The minimum of any ends of the scraph is 6" and a length of 4' bolted at 6" intervals; according to Steel.
The rake of the sternpost is right, I just put it in the wrong place. The rake measures from the back of the sternpost at the keel height to the perpendicular at the height of the stern post. This puts the intersection of the sternpost perpendicular with the lower deck at the front or inside of the sternpost.
So now I turn my attention to the stem post. I have to determine my height first.
If you notice on the draughts, the stem post almost is straight at a point at the crutch of the curve of the figurehead knee. When I use the formulas to calculate the height of the stem they all seem to point to this area. Therefore I will use this as my base point
Therefore stem height = to 11/60 of the length. The length determined from the above calculations as 81' therefore the height is 14.85'.
Now I must determine the intersection points to draw the curves of the stem. ( apron, rabbitt and outside of stem) all related to the keel and scarph.
1st. I extended the line at the end of the keel 6" up ( the beginning of the scarph) past the perpendicular.
2nd I made another perpendicular 1.15' past the first one. This is the width of the stem.
3rd. I made another line parallel to the bottom of the keel at the top of the keel, extended past the perpendiculars
4th. From the intersection of the 2 lines of the perpendiculars and the bottom of the keel draw a line the height of the stem.
5th. Measure the distance from the intersection from the stem height and the first perpendicular to the height of the scarph at the top of the keel. 13.85' .Draw an arc from the top of the stem at the first perpendicular into the hull. Now draw an arc from the intersection at the top of the keel and the scarph until the 2 lines x. From this intersection draw an arc of 13.85'.
6th. Add .25' to 13.85' and draw another line from this intersection. This will give you the rabbitt.
7th Now measure down from the height of the stem to the line at the keel from the start of the Scarph. This along the outside perpendicular. 14.35' Draw an arc into the hull.
8th. Now draw an arc from the top of the scarph at the keel the same distance 14.35'
9th. At the intersection draw the arc from the top of the scarph at the front of the keel to the height of the stem. This is the outside of the stem.
You will notice it does appear right. We are not finished.
10th. Draw a line from the intersection of the lines of the beginning of the scarph front of the keel to the intersection of the lines we just finished drawing. 14.35' ones. Now draw a perpendicular line from the top of the scarph at the top of the keel, until it intersects this line.
11th. From this intersection draw an arc 8.33' and then add .25 for the rabbitt and draw another arc. Then draw another arc 9.69' and this is for the front of the stem
12th. Trim all extraneous lines for your finished shape of the stem.
13th. You will notice that the lines to the top of the stem at the 14.35' mark extend past the 2 perpendiculars. The beauty of autocad is you can trim where the lines meet. This just so happens to be the height of the lower deck at the stem. 12.22'
If you look at the draughts you will notice that the stem is so close to being vertical here. If we had left the lines of the stem curved at the perpendiculars the stem would have been raked back to the stern and this is a no no.
I am going to leave the apron for now.

 

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The next step that now needs to be addressed is the height of the floor timbers. I am not going to draw in each individual timber yet, Ijust need the moulded height.
According to Steel, it is 1/2" for every foot of breadth
1/2" x 24.5 = 12.25"
and the sided is 10/12ths of the moulded
10/12 x 12.25 = 10.20"
I drew a line 12.25" parallel to the top of the keel at 12.25"
From this line we can create the Cutting Down Line. CUTTING-DOWN LINE, a curved line used by shipwrights in the delineation of ships: it determines the thickness of all the floor-timbers, and likewise the heighth of the dead-wood, afore and abaft. It is limited in the middle of the ship by the thickness of the floor-timber, and abaft by the breadth of the kelson; and must be carried up so high upon the stem, as to leave sufficient substance for the breeches of the rising timbers. Murray's Ship-building.
Ok so the next is the curve of the Deadwood of the stern.
Take the height of the Sternpost ( 15.08') and then measure along the bottom of the keel starting at the tapered end. 15.08'. Draw a perpendicular at this point. This establishes our Deadwood size.
Now measure the distance from the waterline at the intersection to the false sternpost, to the intersection at the top of the floor timbers and the perpendicular. (17.86').
Draw 2 arcs. One from the intersection of the false sternpost and waterline and the other at the intersection of the perpendicular and the top of the floor timbers.
Now draw an arc from the floor timbers and the perpendicular to the intersection of the waterline and the false sternpost.
When the transoms are added later the exact height of the deadwood will be determined.
Now for the Apron. Measure the distance to the top of the stem (14.85').
Measure from the perpendicular at the inside of the rabbitt along the bottom of the keel. (14.85') Draw a perpenicular here to the top of the floor timbers.
Draw an arc from the intersection of the perpendicular and the top of the keel, not the floor timber line. (14.85')
Draw an arc from the perpendicular at the front of the stem and the top of the stem arcs (14.85')
Draw an arc from this intersection to the top of the perpendicular abd the floor timbers. up to the top of the stem.
Draw another arc from the intersection of the perpendicular and the rabbitt line at top of stem (14.85').
Now draw a line from that intersection to the intersection of the perpendicularat the keel's base.
Draw a line from the top of the stem curves to that diagonal line.
At this intersection draw the arc that blends in with the previous arc.
Trim lines. This is the Apron.

Automerged Post:
The next step is to determine the section line locations.
To do this, the Dead flat frame has to be determined. According to Issac Blacckburn's article of 1836, the midship bend or Deadflat is at 3/7 of the length of the ship from forward. It is measured by the length along and at the height of the upper waterline from the after part of the stem to the fore part of the sternpost. The most preferred location.
In this case the Ontario's measrement is 79.74'
therefore 3/7 x79.74 = 34.2'

Measure along the waterline from the aft part of the stem 34.2' and place a perpendicular here.
According to the Draughts, Coleman has another deadflat frame to the aft side of this. I have looked in several books, surfed the web, and could not come up with any plausible reason for this. I just have to beleave this is correct, (I don't like something I can't explain), as the draughts say " as built".
The placement of this frame can be explained thus, It appears there is a single frame located at this next location. If you take 1/2 of this frame = 5", now working towards the calculated deadflat frame, there is room for another single frame at 10" plus 1/2 again 5" of the Deadflat frame.. Don't forget there are spaces between the frames ( yet to be calculated) . So I would say the distance between the Deadflat frames is 2'.
Measure over 2' from the perpendicular you drew for the first Deadflat frame and draw another perpendicular.
Now, using the room and space method of determining the next section lines, they would be at 4' spacing. ( double frames therefore 2' plus 2' space = 4')
Draw in rest of section lines. Stop before getting to fashion frame location and Cant frames.
I haven't added the Keelson yet, not until I add transoms and Breast hooks.

 

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I had left with instructions from the fore perpendicular measure back 34.2' and put the first section line there. Amore accurate way of placing the forward section lines is to measure from the fore perpendicular to the deadflat. take this measurement and divide by the number of spaces , not section lines to get the measurement.
34.3 / 8 = 4.2875' So draw a section line at every 4.2875' from the deadflat.
To the aft section, from the deadflat measure over 2' to the center of the next section line. Mr. Coleman has a single frame here. So measure again from this section line to the aft perpendicular and then divude by the number of spaces.
44.2' / 11 = 4.018' towards the aft there is one space divided in half.
Now I returned my attention to the keel .
I want to outline my reasoning for what I did and see if it's sound by the others in the forum.
I added the rising wood here. It's moulded dimension is calculated as 0.5 x moulded depth of the keel. In this circumstance is .565' The reason I added this now, instead of making the keel the one size of 18" , is when the ship was built, a gentlem by the name of Robert Seppings, made some changes to how the rabbit was in relation to the top of the keel. His method that was followed later was to bolt the floors directly to the keel. He made the keel larger in the moulded direction and maintained the rabbit position. As I said he made these changes at the beginning of the century and my thought was perhaps it hadn't become standard practice yet in the colonies. So I made allowance for the rising wood.
I drew this line in then added the top of the floors at 1.13 ' and drew this line. Note this is measured from the top of the keel at the rabbit line. On top of the floors I drew a line 4" acroos. This represnts the limber strake and it is used later for the depth of hold.
At this point I turned my attention to the aft deadwood. The construction of the deadwood is usually done with 8 pieces. One of them is the deadwood knee that supports at the top of the deadwood the sterpost and the transoms. Where the deadwood starts to rise to the tramsoms is where the rising wood is scarphed into the first 2 pieces of wood. At the sterpost the first piece is moulded the thickness of the keel and tapers to the rising wood that is cut 3" vertical then tapers to the top of the rising wood . the next piece is again the moulded of the keel sitting on top of the first piece then cut to the scarph at the rising , there by locking it in place. The next piece is scarphed into the lower by lowering it 4" and then tapering back by the standard 3x the moulded depth. I know the front piece has a point but my thinking is if the carpenters put a square scantling on and then cut in the curve before putting on the stemson this might be appropriate.
I continued this method up arriving at the knee. I added the front piece that locks it all in and then cut to the curve , known as the cut down line.
I then added the transoms.
Here there are 4 , the deck transom and 3 fillers. I determined the size of the wing transom which is, by definition, width as 1" for every 1' of length, it's depth is 5/12 of the width, and length as 2/3 of moulded breadth. All other transoms are 7/8th of these measurements.
The deck transom situated at the deck is 7/8ths of the wing transom measurements and also " lapped under ends of lower deck planking 3 1/2" in length and 3" deep " I take this to mean rabbitted in at the planking side.
There is also a space between each transom for air. Usually 3 to 4" in size.
So therefore the wing transom L= 16.3' , W= 16.3" D = 6.79"
The other transoms are 7/8th of these measurements.
I drew in the deck transom #" above the floor measurement and then drew in the depth added 3" for air and the 3 other transoms. Until I determine the shape of the Fashion piece I can't draw this in yet.
OK I failed to mention how I got the lower deck heights.
From the top of the Limber strake measure up 9'. This is the depth of hold. It measures from the top of the Limber strake to the top of the beams of the lower deck. This vdoes not include the deck planking. Draw this line across to the stem and sternpost. The fore and aft shear is added to this. They are: Aft shear =1/5th depth of hold = 1.8'
the fore sheer is 2 1/4" for every 10' of length = 1.5'
I add this to the depth of hold measurement respectfully and make a mark. Next because there are deadflats or either side of the main deadflat, you wil notice ( ) 's around these letters and numbers it means these frames are the same. So I drew a straight line at the 9' measurement acroos these deadflats. Then I drew a curve from the aft mark of the sheer rise at sternpost to the first deadflat and another curve from the fore sheer rise mark to the front deadflat. This is the shape of the lower ( gun) deck.
I added the scarphs to the stem and apron at the standard sizes (3x moulded ) amd blending in the dead rise wood to the apron via scarph as well.
I'll explain the red lines next.

Automerged Post:
Here are the cad snapshots of what I did. (open in a blank window) (open in a blank window) (open in a blank window)

 

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I would like to explain a few ideas here. This undertaking for me is trying to establish from a set of draughts how the experts of the day arrived at their design. I do not have at my disposal their intimate knowledge they possess. They use it every day where I have to by trial and error come up with the right formula. I am making mistakes but I am learning their methods and beleave me everyone of them has their own methods or ideas so it changes. What I have to do is try to find the norms for that time period.
So bear with me and if there is something you don't understand ASK. I might be able to explain it. Don't forget, you may not be alone in your not understanding something.
Oh and if I sound like a teacher I once was, now retired. and my apologies.
Dave

 

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The next step that is needed are the counters at the stern. Deanne states from the intersection of the top of the transom and the rabbit measure across 4'.
The lower counter for this time period was usually set at 30 degrees from this point. At the 4' mark draw a perpendicular to the 30 degree line. Draw 2 arcs from the end points 7' radius. Now draw the arc at the intersections. Add 6" for the width of the timbers and redraw another arc.
The top counter is drawn similar to the lower. Measure over and draw a line 1/4 of lower counter. 1/4 of 4' = 1' Draw a perpendicular at this point. The angle usually at this time period was set at 60 degrees. Draw a line from the lower counter end to the perpendicular at the 1' mark. Again o draw 7' arcs from each corner and then draw the arc for the upper counter. Add 6" again for the width of the counter and redraw the arc.
The stern face of the master cabin was set on an angle anywhere from 70 to 85 degrees. I set the angle to 70 degrees because the sterpost is at 80 degrees and it appears to be less of an angle than that on the draughts. Not scientific but does fit. I drew a line from the end of the upper counter to a 70 degree angle. I then offset the line in cad 6" and drew a secound line inside the first one. I trimmed everything and all I have to do now are the upper deck .
The upper deck or the top limber line is determined by taking 1/5th of the lower deck length.
1/5 x 80’ = 16’ I measured and drew in the 18’ line at the deadflats and then using the deck below for the sheer rise I offset the required amout and copied the fore and aft deck . I then extended the lines to the front stem and to the aft . The lines above this that don’t extend all the way across are the highest point the frames extend to. This done by taking 1/10th of the moulded breadth. 1/10th x 24.5 = 2.45’
The 2 red lines:
These 2 lines represent the rising line of the upper height of breadth and the lower line represents the rising line of lower height of breadth. At the stern it is first located at the intersection on the lower deck and the rabbit . At the stem it is located at the height determined by taking ¾ of the height of the sternpost ¾ of 19.07 = 14.30’ Start at the stern and draw an arc from that point to the first deadflat. Then draw another arc from the forward deadflat to the 14.30’ mark on the stem at the inside of the uprights. You will notice they start off following the lower deck but rise past as it nears the stem.
Next draw in the lower height of breadth. First off I needed to determine where on the deadflats it was located. By definition it is the same as the lower wale at midships. Since I haven’t done those yet I determined that the lowest wale was 6” below the water line. I temporarily drew in the wale measured it and marked in on the drawing. I erased the wale because it complicates what I am trying to see right now. I will add later.
So I drew across the deadflats at this mark and then starting again at the stern I drew an arc from there to the lower breadth mark and then to the stem mark.
These lines are very important in the next few steps. (open in a blank window)

Automerged Post:
The Rising line of Floors
To determine this I went to Mr. Geanne, He states to draw a perpendicular from the waterline mark that intersects at the stern post. Then measure this height. Then measure from this intersection along the base of the keel to the first deadflat. This measures 40.2'
The height of the perpendicular measures 10.11'
Now Deanne says to double the base dimension 40.2x 40.2 = 1616.04'
now divide by the perpendicular height 1616/ 10.11 = 159.85'
Now add the perpendicular 159.85' + 10.11' = 169.96
Now divide by 2 169.96 / 2 = 84.98' This represents the true center of the radius for the aft rise of line.
So at the waterline intersection draw an arc 83.98' and from the base of the keel at the center deadflat not at the 40.2' mark. The reasoning here is because Deanne goes from the calculated deadflat of the ship not by the first deadflat like on the Ontario.
Now draw the arc from the intersection to the first deadflat ( not the calculated one ) at the section line and the dead rise ( 5.65 "). I trimmed all unwanted lines at this point.
You will notice at the waterline and sternpost it is slightly above. According to the draughts this where it should be.
The forward rise of line is done similar.
Draw a perpendicular from the waterline intersection and the frony stem down to thw lower part of the keel. Now measure this
Measure from the calculated deadflat position to the perpendicular you just drew.
Following Deannes description again , I doubled the base measurement 35.43x 35.43 = 1255.29'
Then taking this number and divide by the perpendicular number 1255.29 / 9.36' =134.11'
Now I add the number 134.11 + 9.36' = 143.47'
Then I divide by 2 143.47' / 2 = 71.74'
I drew 2 arcs one from the dead rise on the calculated deadflat and the other at the intersection of the waterline and the aft rabbit line 71.74' for each.
At this intersection of the 2 arcs I drew the arc from the intersection of the forward deadflat of the calculated deadflat and the dead rise to the beginning of the rabbit on the stem. This is the forward rise of the floors. I checked the draught and the position of the line seems to match. (open in a blank window) (open in a blank window) (open in a blank window)

 

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