YTL-710 in 1:10

[PATMAT]

A new project! We're going to get a new 45' Navy YTL (= 45' Army ST) tug! (I figure if the Navy owned it, it's a warship...).

YTL-710 is the tug that Tom Hershey modeled and described in the November 1987 Scale Ship Modeler-- "The Navy's Cutest Tug". I've only found specific evidence on the Web of three 45' YTL's in the Navy...709/710/711. I'd like to find more, but there seems to be enough photographs available of 710 to document her condition at least in the mid-80's. So that's good enough for me!

And we've seen another one of these before-- see RMAY's thread:
http://www.rcgroups.com/forums/showthread.php?t=666749

[PATMAT]

Where to start? Well, if you'd like to build off a nice fiberglass hull, there are several available from Microglass up to 1:16 scale.

I think we're going to need a bigger bathtub...
But this one will be a tad larger... more on that later! But a scratchbuilt hull will be needed. And where better to start than a set of original builder's drawings from Paddlewheels & Props? ("Diesel Harbor Tug").

Note that such drawings do not show how to build a model! But there is nothing like original drawings to work from to get your details right.

My first step is to ignore the drawn hull lines and sections... yes, many just photocopy/enlarge/reduce these to use directly as templates to make frames... but I want to get the geometry in CAD where I can do a lot more with the lines. And for that, I go directly to the Table of Offsets... a rather confusing table that once decoded, lets you draw all the body plan sections. But watch out! The data is recorded in feet-inches-eighths... and in this table, redrawn in 1951 from the original early 40's drawings, several lines are off by a foot. Who knew? And I wonder if there are real tugs out there with the deck a foot higher than planned- which is what this error produces!

Note that the sections do not necessarily represent actual frames on the ship. The naval architect follows standards and divides the hull shape into usually 20 stations (only 10 here) for calculations on volume/displacement/stability etc. Others will create drawings as needed for each of the 33 actual frames used on this tug... but we modelers can usually be happy to use the body plan's stations for a model's frames.

Also, these lines represent the "molded" shape- the volume INSIDE the hull's plating or planks. No big deal on a ship with thin plating, more of an issue on a wood planked ship, where the hull planking is quite thick.
>>> Oops, wrong- of course it's important! The lines reflect NEARLY the outside of the hull for a steel ship... but the modeler needs to offset this line by the substantial thickness of his planking on the model when creating the frames.

The lines also reveal things like the deck's crown at center, and knuckle or bearding lines. Many ships have near-vertical plating from the gunwales and down for a bit-- easier to weld rub rails onto-- and the line where this transitions to the curved hull shape is the "knuckle".

My next steps are to take the drawn lines (drawn at 1:1 scale, BTW!), scale them as needed in CAD, and then develop the actual keel and ribs' shapes. I'll also lay in a datum plane which represents the building board, as the hull will be built upside down with the ribs attached to the board.

[PATMAT]

Before cutting the first scrap of wood, I need to determine what equipment is going in and how it will fit. Here, the prop, shaft, Pittman motor, and 12v 12Ah battery are laid in (approximately). I can check them against the body plan to be sure they'll fit between their frames at the height I choose.

With this established, I can strike lines for floor boards etc., and lay out exactly where those will connect with the frames.

[PATMAT]

OK, well maybe I'll cut a little wood...

Before committing to a design, it's good to know that your design-specific techniques will work. So I made one trial rib here, using my new little band saw.

On the Dearborn, the ribs were built up from laminated strips over formers. That got me away from the rough edges of plywood, and provided a nice wide rib that I could drive planking spikes into easily.

I was thinking about that for this build, but I want to try something else out- ribs built up from "futtocks", just like on real wooden ship. And again, I use CAD to lay out the futtock pieces, cut them from 1" wide strips of 1/4" poplar, glue them up, then cut and sand them.

Just like the glue-lam ribs, these will finish nicely and will happily accept glue, spikes, or more likely, wooden "trunnels" (pegs) to secure the planks.
Pair will be jig-assembled with a deck beam, set on the building board, and then mated to the keel.

But first, back to the drawing board-- now I need to design all the rest of the ribs' futtocks, and any special features like ledges for floors.

I think many of use tend to cut our frames too wide (in the beam direction), and too thin fore/aft. Plywood lends itself to this practice, but we really don't need the beam-width for strength in the finished hull- the skin really provides all the strength (like a "monocoque" in a race car); the frames and keel are just there to help form the planks. Hey, think of how strong a fiberglass hull is with no keel or ribs!

These 1/2 x 1/2 inch ribs are much stiffer than plywood when flexed in the fore/aft direction- good for stability during planking... and the beam-thickness is plenty for holding shape in-and-out. Additionally, they're easier to bevel when fairing the hull, and will finish sweetly.

[PATMAT]

Broke the blade on my new band saw (I hear that the factory ships with cheap blades, no surprise). But that put a hitch in my giddyup for a bit. Then I smelled something funny- no, not me, I took a shower... it's the sump pump! Motor locked, it's pouring outside, yikes! Well, had to take care of that...

But no complaints. I got a couple fresh blades, and it's back to work. In fact, I'm so happy with even this puny 9" bandsaw, I'm wondering how much I'll be using the old scroll saw any more...
Ripped about seventy 1/2" x 1/8" pine planks... a little thick so I can take them down when the new thickness sander shows up.

Then back to the ribs... much more to do! And all the while, I'm scheming on ways to build a slick building board... not sure I'll go too fancy, wonder what it will be...

[PATMAT]

After planking and glassing, I wonder if I can replicate a little of this "aging" in the hull?

[PATMAT]

Ribs!

[PATMAT]

woo-hoo, got my thickness sander today from Micromark, now I'm going to be a plank-makin' monster.

It's not without issues though. I know this isn't a tool review site, but in case you're interested in one of these:

- It comes out of the box literally dripping with oil. Going to be a while before my wood comes through without grease marks.
- There's a jack screw to adjust the sanding table height... it has a big hex head that goes click click click as you turn it against the angled table, so you can't use turn of the screw for micro-adjustments. I used a dial indicator on the table and some pivot point ratios, a pain...
- Changing the sanding drum takes a number of tools, including snap ring pliers fer cryin' out loud.
- The vac system works well, except that the connection puts the hose in the way of extracting the wood on the out feed.
- And of course, feeding and kick-back is all under manual control.
- Byrnes and Proxxon make well-regarded sanders too, though they're over $100 more. Not sure if they improve on these issues, except that changing the paper is easier for sure.

[Reid]

WOW!!! i had no idea you had sooooo many cool tools!!!

[PATMAT]

Wish I had one more tool- a joiner! That would let me build fixtures like the one here with a whole lot more squareness.

This is the beginning of the YTL's build board. I usually make them special for a build and toss them when done-- too special and/or all used up. Thought I'd try to make one this time that was potentially reusable-- I could even paint it "green"!

The board here is actually narrower than the hull, but that suits my new multi-use uprights just fine. The horizontal bars are adjustable, being fixed with clamps. The vertical part is screwed on to that, and is cut to fit the camber of each frame's deck beam. The problem is that the lumberyard stock, even "S4S", is not particularly square, so the frames need shimming to stand square to the table... a joiner would let me fix that, but the wife knows I just bought the sander!

The table is a white laminated shelf board. It takes pencil lines nicely and can be erased.

[PATMAT]

On a model this size, it's not a bad idea to fair the frames a bit before installing them... otherwise, it's a lot more work and harder too when they're in place. Especially when the ribs are 1/2" square hardwood!

For each frame, I check the angle of the waterlines crossing that frame. On the example here, the angles varied from 20� near the keel to 27� near the gunwale. I set the table on my sander to 20� and took off the offending material in a flash. Then adjusted it a little more and whittled away some more near the top. Final fairing will be touched up in situ. Of course, I can also mark out the positions along the frame for a more precise tailoring job, but this is plenty close.

[PATMAT]

I like seeing a fair sheer in the raw ribs...

Due to the woeful lack of a joiner to true up my uprights, I went through each station and sanded and shimmed until all ribs stood upright. Then I can drop in the keel without having to spring the ribs this way and that, which never ends up well...

[Reid]

AWESOME!!! that is slick!

[desron48]

looking good pat ......... ....joe

[PATMAT]

Now it's time to start planking!

[JIM BAUMANN]

--that is impressive methodology and very nicely documented!

Sure is big!--MOST of my collection could be accomodated within your hull!

JIM B

[PATMAT]

Cant as in tilted!

The counter stern of most tugs is built from "cant frames", angling out from the last regular frame, usually around the aft perpendicular. Spent most of the day building these. After planking, some of the upper beams will be cut away for access to the steering gear.

Out of view of the camera is my 4 foot pipe full of ammonia and several planks a-soaking. After the 1/8" thick planks get all rubbery, I'll form them around a paint can and let them dry... then they'll get wrapped around the cant frames.

You'd also find cant frames around the bow of age-of-sail ships... and I don't mind learning from our sticks-and-strings brethren when it comes to planking tricks. Even though I'll cover all this wood with fiberglass, it's good to build solid, and to make use of any good tricks in the more difficult areas.

First off- where the planks are highly sprung around the bow- it's a lot easier to attach them to the stem if a rabbet is laid in to accept the plank ends. Then, use a clamped chock to lock the end in while the glue sets. After setting the bow end of the plank, it's easier to wrap it around the following frames. Here, I'm pegging them with trunnels made from 2mm round toothpicks.

Next, the garboard plank (the one closest to the keel). It's important, because all the rest of the planks start from its edge. It's also tricky to shape, especially at the bow... there's a tendency to try to wrap it up the stem, and it's hard to say where it should actually stop. Trick: Lay in some masking tape, and let it fall where it likes. Where it crosses onto the keel, make a mark with your fingernail- that will make a fair pattern for cutting the garboard.

As I'm no planking expert, I'll try not to offer too much more advice on it, and maybe I won't show the rest of my planks in too much detail!

[GregK1962]

Hey Pat she is lookin real good!!! Have you figured out how you are going to duplicate the unique skeg design on these yard tugs?

Greg Knipp

[PATMAT]

Thanks Greg!
Skeg- sort of! The skeg is a V-shape intersecting the bottom of the hull, with a faceted transition to the stern post.
After planking the hull, I'll make half-V-frames to either side of my flat skeg, and sheet over them. The faceted aft face, either more sheet or carved balsa.

Pat

[PATMAT]

...to invest in clamp makers!

After soaking a few planks in ammonia, I formed them and let them dry. After that, it was easy to apply them to the stern.

Been applying other planks as well. Many r/c modelers (me included) will eschew "spiling", the art of tapering planks to fit a uniform number of them along the length of the hull. That's a tedious task best left to the glass-case crowd, where their art IS the planking. But if you just lay straight planks from gunwale and garboard towards the bilge, you'll end up with a funny looking football shaped hole (rugby ball, perhaps, in the UK) to fill with acutely tapered planks. So this time, I'm taking time to at least roughly taper the planks... I'll probably still need to finish up with some odd planks, hope to minimize that though.