Dunbrody by Mahuna - FINISHED - 1:48 - Cross-Section - Irish Famine Ship

[Mahuna]

Nicely done scarphs, Frank. However, I believe keel scarphs were always made in the vertical plane.

 

Thanks Druxey.  I thought the same thing about the direction of the scarphs, based on my reading of the Desmond and Crothers books.  However, this is just one of the discrepancies I've discovered between the Dunbrody plans and those books, so I'm planning on following these plans.

 

Hi Frank,

 

Good start, you have my full attention, I also bought a copy of plans for a future build.

 

Owen

 

Thanks Owen.  I've taken a lot of measurements from the plans to build a Table of Scantlings.  If you're interested send me a PM and I'll forward the Excel file to you.  Similarly, if you want any of the drawings I've done in TurboCad I'd be happy to share them with you.

 

 

Excellent work Frank  

 

I beg to differ with Druxey,Vertical scarphs for English ships,but the French scarphed keels horizontally,as this ship was built in Quebec,the latter style may have had some influence in design.

 

Kind Regards

 

Nigel

 

 

Thanks Nigel.  That's a very interesting point, since as you say the ship was built in Quebec.  However, the naval architect (Colin Mudie) who designed the Dunbrody replica ship was working from scantlings and survey documents only, so it may also be that this is his interpretation of how the ship was actually built.  If you can recommend any books on French and/or British ship design from the 19th century I'd be very interested.

 

 

Hi Frank,

 

The keel looks great and also thank you for the very nice step by step photos showing the sequence.  

 

Cheers,

 

Nigel.

 

 

Thanks Nigel.  I think showing and explaining the steps helps the reader understand the process I'm following (right or wrong), and hopefully will prompt someone to point out a different or better way of doing something, which I would greatly appreciate.

Edited April 2, 2016 by Mahuna

[mtaylor]

Frank,

 

I saw several here:  http://www.aamm.fr/boutique/index.php?main_page=index&language=en....On any page, click on the flag on the upper right to get English.  Not all the books have an English version, however.

[NMBROOK]

Hi Frank,Mark beat me to it This is the only source I know of the period,all my own material for both English and French vessels is much earlier in time

Kind Regards

 

Nigel

[AON]

I believe The Seventy-Four Gun Ship by Jean Boudriot, Volume 1 of 4, Hull Construction, pages 102 through 106 of 131 is a very good reference of the French construction.

[Mahuna]

Thanks Mark, Nigel, and Alan.  I'll try to get a look at those sources, but they don't sound like they refer to merchant ships from the mid 1800's.  At any rate, I've committed myself to following the Dunbrody plans, whether or not they're historically accurate.

[albert]

Hi frank, great start.

[Mahuna]

Part 5 - Dunbrody’s Frames

 

The Crothers book describes a “Long and Short Floor” System for building square frames.  Its principal feature is the staggering of floor butts in adjacent frames and the absence of first futtocks butts over the keel.  The Dunbrody plans appear to employ this framing approach. 

 

The cross-section view of the frames from the Dunbrody construction plans show the frames as having parallel sides, with the sided dimension of each higher frame timber decreasing.

 

       

 

Each of Dunbrody’s frames contain the following components:

            Floor

            4 Futtocks (2 on the Starboard side, 2 on Port)

            2 Rising Timbers (Top Timbers)

           

In addition, every other frame contains 2 bulwark stanchions.  From the plan, it appears that these stanchions are part of the forward frame of even-numbered framesets.

 

The joints between the Floors and the Futtocks, and the joints between the Futtocks themselves, are strengthened by frame chocks, 4 for each frame.  The joints between the topmost futtocks and the Rising Timbers are strengthened by the use of a simple scarf joint. 

 

Since the frames are paired into framesets, and since the joints between components are offset from one frame of a pair to the other, it seems to me that the use of chocks and scarf joints is overkill.  The two books (by Crothers and Desmond) that I’m using as additional references show frames that are paired, but nowhere do they show the use of chocks or scarf joints within these frames.

 

In conversations with others and within my own thinking I keep revisiting the idea of eliminating many of the chocks and scarf joints, since most of the framing detail will be eventually hidden.  The chocks and scarf joints add a couple of hours of work for each frameset (if all goes well, more if they cause rework).  Nevertheless, my goal is to build Dunbrody as she is depicted in the plans that I have, so I intend to be true to those plans as much as possible.  I also feel that focusing on getting this joinery correct is (hopefully) going to make me a better modeler.

 

The first order of business in modeling Dunbrody’s frames was to develop a method for drafting each frame.  A set of layers was used to allow printing different views.

 

The first layer is the template itself.

 

                        

 

No drawing is done on this layer – it is used as a guide for locating the various components that need to be drawn.

 

The right edge is aligned with the Y axis at 0, and the base is aligned with the X axis at zero.  The vertical lines are the buttock lines and the horizontal lines are the waterlines.  The diagonals serve two purposes:  the brown lines labeled D1 through D6 will determine where the chocks and scarf joints are placed.  Along with the other diagonals they will be used to mark the moulded dimension at the point the diagonal crosses the outer frame line.  The numbers to the left of the each diagonal indicate the moulded dimension at that point.

 

The next layer is the Drafting Points layer, which initially is blank.  This layer is used to plot the points that will be the basis for drawing the curves for the outer and inner edges of the frame.

 

Each face of the frame has a layer:

 

The Aft Layer is the aft face of the aft frame of the frameset.

The Middle Layer is the forward face of the aft frame or the aft face of the forward frame, as required.

The Forward Layer is the forward face of the forward frame of the frameset.

 

The Aft Layer and the Forward Layer are initially blank.  The Middle Layer has permanent lines that indicate the Cutting Down line (the level area at the top of the frame where the Keelson and Sister Keelsons will be installed) and the dimension of the notch that will fit over the keel.  It contains a semi-circular arc that will be the limber hole in the frame, and it also contains the centerline used for mirror imaging during drafting and for aligning the center of the frame during building.

 

                        

 

(The above image is enlarged and cropped so these details are more visible)

 

The remaining layer is the Pinning Template, and is used to place the pins for each frameset (more about this below).

 

As part of the planning for the build, the values for waterlines 1 through 6 were determined for each frame.  The values indicated that frames 27 through 37 are identical, so that the same drawing can be used for each of those frames.  In addition, the sheer changes only for those frames at the extreme forward end of the sectional model, and will be barely noticeable at 1:48.

 

                   

 

I’ve developed a process for making these frames that I’m comfortable with.  The process is highly dependent on the ‘Pin-Indexing’ approach introduced by Ed Tosti in his Young America build.  This approach has helped bring my modeling to another level of accuracy already, and I intend to employ it whenever the opportunity is there. 

 

As mentioned above, the frame drawings include pin locations as a separate layer within the file, which I refer to as the Pinning Template.  The Pinning Template is printed separately and glued to a piece of MDF (medium density fiberboard).  The idea is that this MDF-based template can be re-used without the holes being enlarged due to subsequent uses.  The middle 11 framesets of the model are identical, so those templates will be re-used often.

 

                        

 

After gluing the Pinning Template to the MDF, the holes for the pins are then carefully drilled.  The accuracy of this drilling will be critical to the success of the building process.  The following photo shows the template glued to the MDF and drilled.  The holes are a tight slip fit for the pins, allowing flexibility for removing and re-inserting the individual components as necessary.

 

                        

 

The next topic will describe the frame construction process.

Edited April 6, 2016 by Mahuna

[captainbob]

It's looking good, Frank.  You should be making sawdust soon. 

 

Bob

[Elijah]

Nice start! She's gonna be great !

[Mahuna]

It's looking good, Frank.  You should be making sawdust soon. 

 

Bob

 

Soon??  I've made a whole lot of sawdust just trying to get the process right.  Lots of fun, though.  Here's the current state of my scrap box - I expect it will keep growing over time - I hope I have enough Madrone!

 

                         

[Mahuna]

Nice start! She's gonna be great !

 

Thanks Elijah.  I looked in on your build and I'm very impressed.  Welcome to a great hobby - I only wish I started at your age instead of waiting to start many, many, many years later.  Better late than never, though.  

[AON]

I think you uploaded the wrong image... those pieces do not look like scrap to me

Edited April 6, 2016 by AON

[druxey]

Thanks for the clarification over the direction of the keel scarph, Frank.

[Mahuna]

I think you uploaded the wrong image... those pieces do not look like scrap to me

 

LOL!!  I wish you were right.  There was a lot of trial and error in trying to get the build correct.

[Mahuna]

The process for building the frames is fairly long and complex, and I'm still trying to put it down in a form that makes sense to everyone who looks in.

 

In the meantime, I've completed the first 7 framesets or frame pairs and I wanted to see how they look on the keel.  The frames are NOT permanently in place, they're simply laid on the keel.  The notch in the bottom of each frame is fairly tight, so it holds them in place.  As I install them permanently I may need to loosen the notch here and there for proper alignment.  I'm still thinking through an effective way to make sure they're correctly aligned when installed.

 

Here's what they look like in their temporary install:

 

                                    

 

                                    

 

Thanks everyone for the likes and comments.

[druxey]

Are you sure you don't want to build the whole hull? Looking very neatly done, Frank.

 

One way to ensure the frames are plumb is to glue a temporary cross-spall across the top of the frames and mark the centreline. This will ensure symmetry across the hull. Two set squares will ensure plumb as well as at right angles to the keel.

Edited April 7, 2016 by druxey

[Mahuna]

Are you sure you don't want to build the whole hull? Looking very neatly done, Frank.

 

One way to ensure the frames are plumb is to glue a temporary cross-spall across the top of the frames and mark the centreline. This will ensure symmetry across the hull. Two set squares will ensure plumb as well as at right angles to the keel.

 

Thanks Druxey.  I've been thinking about using cross-spalls (EdT seems to use them frequently), but I have a question on glueing them 'temporarily'.  Can you explain the type of glue you use and how you separate them when the frame is securely in place?  There isn't going to be a lot of room between frames, and I'm afraid any jostling in trying to get a cross-spall off may upset things.

[Mahuna]

Part 6 – Frame Installation

 

I was going to begin the description of the frame construction process, but I’ve been thinking a lot about the installation of the frames, and I think I’ve come up with a workable approach.  I’d appreciate any comments, suggestions for improvement, cautions, etc., that anyone cares to make.

 

The frames are separated by approximately 5 inches (actual), which would be slightly less than 7/64 at 1:48 scale.  This doesn’t leave a lot of room for clamping.  I do have some small machinist’s clamps (from Lee Valley woodworking) that I’ll use.

 

                        

 

I decided to use a flat piece of wood mounted vertically on the shipway as a clamping fixture.  The wood is 3/32 thick and I made sure that it lay flat and that the bottom edge was flat against the shipway.  The length of this fixture is just greater than the span of the frame at the second futtocks (this is the extent of the largest sided dimension of the frame).  I cut out clearance for the keel and the pieces holding the keel.

 

                        

 

As Druxey already suggested, I want to use a cross-spall to check that the frame is perpendicular side-to-side.  In thinking about how to secure this cross-spall, I decided to pin it to the frame, using the lower of the two pinning holes at the top of the frame.  This will position the cross-spall within 1/8 inch of the string used to mark the centerline, making it easy to line up the centerlines.  Since most (possibly all) of the frames will be of the same width at top, I can reuse the cross-spall.  Pins will make it easy to mount and unmount the cross-spall, so I cut some pins down to a length that will not interfere with adjacent frames, and CA glued them to the spall so I wouldn’t lose them.

 

                        

 

The ends are marked S for starboard and P for port, to avoid any fit issues, and the centerline is marked on all four sides of the spall.  The following photo shows the spall attached to a frame.

 

                        

 

A test mount of a frame, aligning the centerline of the cross-spall with the centerline string seemed to work.

 

                        

 

So, hopefully this is the approach I will use for mounting the frames.  As I said earlier, though, I am very open to any comments, criticisms (I know they’re constructive), or suggestions.

 

[markjay]

Frank, it's looking real good. Hope I can get away for the next meeting. When and where?

[mtaylor]

Hmm... I think you'd need to leave quite a few spalls on to constantly make sure nothing has shifted.   Might I suggest that you put them on top the frame?  A lot of the builders do it that way so they can get the spalls off.

[Mahuna]

Frank, it's looking real good. Hope I can get away for the next meeting. When and where?

 

Thanks Mark.  I'll be sending an email out in the next day or so.

Edited April 8, 2016 by Mahuna

[Mahuna]

Hmm... I think you'd need to leave quite a few spalls on to constantly make sure nothing has shifted.   Might I suggest that you put them on top the frame?  A lot of the builders do it that way so they can get the spalls off.

 

Thanks for the suggestion Mark - I'll need to think that through.  I'm not sure I could use the pinning approach for the spall if I left them on, so I'd need to come up with a way to attach them on top as you said.  Any ideas on what kind of glue, how much to use, and how to get them off?

[mtaylor]

On the Triton cross-section, a lot guys do it that way.  I did too.  Just a small drop of PVA.  Once some planking is in place a bit of alcohol on a paper towel on the joint should pop it loose.

[EdT]

As suggested, Frank, pva glue is easy to soften with isopropanol.  I made my spalls of soft pine and glued them with Titebond (pva).  Those and the softwood spacers I used between frames were easily removed using a single edged razor blade lightly tapped into the glue joint.  A bit of filing removed any glue traces.  I could have used isopropyl, but it leaves the glue residue gummy for a while, making immediate removal less easy.  But either would work well.  Keeping the spalls in place will be useful later until some sort of ribbands or logitudinal planks can be added.

 

Ed

[Mahuna]

Thanks Mark and Ed.  I'll abandon the 'pin' approach and use the PVA glue.  I tried using a small spot on the spall, which is made of poplar, and it came off easily.

[druxey]

Looks like you've already answered your own question!

[Omega1234]

Soon?? I've made a whole lot of sawdust just trying to get the process right. Lots of fun, though. Here's the current state of my scrap box - I expect it will keep growing over time - I hope I have enough Madrone!

 

Rejects.jpg

Hi Frank

 

Super progress so far. She's going to look great and like other's have said, why stop at building a cross-section? I'd be tempted to build the whole hull. Come to think of it, if you could just send me your scrap box of discarded frames........hehehe!

 

Cheers

 

Patrick

Edited April 9, 2016 by Omega1234

[Mahuna]

Hi Patrick:

 

Thanks - I'm happy with the progress, even with all the do-overs.  I had to add two whole frame sets (4 frames) to the scrap pile today when I discovered that they were off.  This led to a revision in the way I'm assembling them - I hope it solves the problem.  And, at this point, don't even talk to me about doing the whole ship!     If I tried that I don't think I'd get very many of my 'punch list' done.  I wish I made the kind of progress you're capable of.

[Omega1234]

Thanks Frank!  My ships are a fraction of the size of yours, so progress is always going to be quicker for me, though.

 

Stay positive with the framing and I'm sure you're going to overcome the gremlins that've crept in.

 

I look forward to your next update.

 

Cheers and all the best!

 

Patrick

[Mahuna]

Part 7 - Frame Construction

 

The frame construction process can be broken down into three general phases:

1.    Forming the individual components of the fore and aft frames.

2.    Adding the chocks to the fore and aft frames.

3.    Assembling the fore and aft frames and joining them for the frameset.

 

Since there are many individual steps in each phase of frame construction I will treat each phase as a separate topic.

 

Phase 1 – Forming the individual components of the fore and aft frames

 

Step 1.  After printing multiple copies of each fore and aft frame drawing for the frameset (at least 2 copies, more if rework is needed), the components from the frame drawings are then cut out and glued to the appropriate stock, using an Elmer’s School Glue stick.

            The Floors and First and Second Futtocks use 11/64 stock.

            The Third and Fourth Futtocks use 9/64 stock.

            The Rising Timbers and Stanchions use 7/64 stock.

 

                        

 

Step 2.  The locations of the holes for pin-indexing then need to be prepared.  The process begins by making a very small pilot hole (really not more than a pin-prick) with a small awl.

 

                        

 

            

 

            

 

This pilot hole is then used to accurately locate a center punch, and with one tap of a small hammer the hole is enlarged to the approximate size of the drill for indexing.

 

                        

 

                        

 

Step 3.  The components are then cut out on the scroll saw, leaving approximately 1/64 of waste outside the lines.

 

                        

 

Step 4.  The holes for pin-indexing are then drilled, using a #63 drill in the Sensitive Drilling Attachment of the Sherline milling machine.

 

                        

 

Step 5.  Any rough edges from the cutting or the drilling are then cleaned with a fine sanding stick (220) to eliminate small particles that may affect alignment in future steps (learned through experience!)

 

Step 6. The initial detailed shaping of the floors is performed:

a.    On the disk sander, the ends of the floors are trimmed down to the joint lines and the bottom of the floors are sanded to the outline

 

                                     

 

 

b.    The floors are temporarily pinned together with the pattern facing out for each floor.

 

             

 

                          

 

c.    The notch in the floors to fit over the keel are cut out and shaped with a file  - I use files for most of the shaping required for the frames.  I use coarse (00 and 0) followed by medium (2).

 

 

A spare piece of keel material is used to check alignment with the rabbet and the centerline.

 

                         

 

                         

 

d.    The limber holes are then cut.  A line is drawn for the each side of the limber hole, using a Starrett No 14 square, which I’ve found to be a valuable tool in this build (I’ve had it for years and rarely used it until now).

 

 

 

Using a small saw, a stop cut is made on these lines - the outside edges of each hole - then some of the material is pared out from between the stop cuts to make a groove. 

 

                         

 

                         

 

                         

 

The shaping of the limber holes is completed using a round escapement file.

 

                          

 

                          

 

e.    The boundaries of the cutting down line are marked on the top of the floors.  The top of the floors are flattened to accept the keelson and sister keelsons, following the lines marked off for this area.

 

 

f.      A centerline is marked across the top of the floors. The floors are then unpinned and the mounting hole for each floor is drilled in the center of the top of the floor using the #63 drill.

 

 

(For this build, I keep my Sherline Mill set up as a ‘drilling station’, using a mill vise for clamping and a piece of waste material for drilling the pinning holes)

 

            

 

This completes the prepping of the floors, which is most of the work in this phase.

 

Step 7.  The individual frame components are trimmed for an accurate fit.

 

Futtocks 1 (for the Aft frame of the frameset) or Futtocks 2 (for the Fwd frame) are pinned to the pinning template (both port and starboard futtocks).  Then the floor is pinned to the template so that it slides down to overlap the futtock, and a line is drawn on the futtock to reflect the outer edge of the floor.  This marks the butt joint on the futtock.

 

             

 

The joint is then trimmed to the line using the disk sander.

 

This process is followed for each butt joint in the frames.  The scarf joint is marked the same way, but is finished to the line using files.

 

This completes the first phase of Frame Construction.  The two frames of the frameset are now ready for installation of the chocks.