Hull 2 Construction Details.
Congratulations, you have purchased one of the most researched and accurate skeleton model kits available for building the hull of a 1/20th scale, World War 2, ELCO (Electric Launch Company of Bayonne N.J.), PT103 class Patrol Torpedo or PT Boat. These boats were 80 feet 3 inches long and 20 feet 8 inches wide and many hundreds were built by ELCO during World War 2, These boats were mainly used in the Pacific and the Mediteranean theatres of war. The most famous of this class of boat was possibly PT109 whose captain, lieutenant John F. Kennedy, later became President of the United States.
This kit comes as 8 sheets of very fine grade 2mm Scandinavian plywood containing 122 pieces of very accurate laser cut parts, including ribs, transom and parts to make up the laminated keels, laminated deck runners, battery box, steering servo, motor mount and also parts to make a stand.
Note:Because these parts have been laser cut they have a smell of burned wood and the laser cut edges can be a bit dirty, like charcoal, and can leave a mess and finger prints around the house if you are not careful.
To finish the hull you will need to provide 4 or 5 lengths of 5/32" (or 4mm) square Balsa wood, Spruce or Ramin (4' or 1200mm long) for the chine and gunwales (deck edges) and also the covering materials which could be two layers of 1mm or 40 thou Balsa sheet then covered with two layers of tissue and dope. The deck could be Balsa or thin ply (0.8mm -1mm).
The hull is built upside down on three deck runners that provide the deck shape at the top edge but also a flat edge at the bottom. To help keep the hull straight and true during construction it is preferable to build it on a 4 foot x 1 foot (1220mm x 304mm) sheet of thick Ply or MDF which the deck runners can be glued to and you can also use it as a cutting board. Once the hull bottom is finished the deck runners can be cut through at deck level.
O.K. LET'S GET STARTED !
Step 1. Make up the deck runners.
Remove the parts for the deck runners from the sheets, (leave the other parts in the sheets until needed). On a cutting board, use a scalpel to cut through the small tags holding the pieces into the sheets, Use a chisel type blade and cut from both sides to stop any tearing. Sometimes it is also necessary to run a scalpel around the part's shape to fully release it from the sheet. The deck runners have wide slots along their length to allow you to cut it at the deck level once the hull is complete.
The middle sections of the inner sides of the two long deck runners have no slots, these form the inner deck "upstand", which will hold the superstructure in place later and also stops water getting inside the hull off the deck at speed.
Laminate (make two layers) the sections together on a large flat surface, glue the sections together with medium superglue (Greatplanes medium or Flash medium model glue). Glue only along the curved thinner sections with the notches (the bottom part in this picture >).
There are two long deck runners each made up of two overlapping layers and 7 pieces each (RUNNER-A to G) and one short bow section runner made up of two overlapping layers and 4 pieces (RUNNER-H to K).
The sections all overlap so that the joins are all in different places (for strength) and the bottom edge (when upside down) must end up straight. The runners are made from two layers to counteract the ply's natural tendency to bow. You could use a PVA or marine glue but you would need to clamp all the pieces in place on a flat surface until the glue is set. You can use scrap pieces (the push outs from the ribs) of 2mm ply in the notches for temporary alignment.
There are two sets of each group of parts for the side runners that are cut mirror image so one set has backwards writing and one set reads normally. Make up both sets with the -D-C-B-A- sections on the bottom and being able to read the -G-F-E- sections (one set will read backwards). Eventually the upstand sections need to end up facing each other and towards what becomes the access hole in the middle of the deck. The upstand is approximately 9mm (3/8") high between stations (ribs) 25 and 57 for the superstructure and about 4mm (5/32") high from 57 to 65 for a 40mm Bofors stern mounted gun. Depending on your proposed deck configuration you may want to change this later.
Long side deck runner sections: ---G---F---E---
D---C---B---A
______------deck upstand section ------
Short bow deck runner sections: --K---J-----
----I---H---
Step 2. Make up the wing rudder keels.
I know you want to make up the main keel but it's best to practice on the small ones first!
Cut out KEEL2G to KEEL2M (7 pieces) and build them up progressively, glue only the end sections not the bits that need to be cut out to make the rudder hole. Outside lines are for 8mm shafts and inner lines are for 1/4" shafts.
Make sure you keep the ends lined up and the sides are square and not leaning over (use the ruler/square) and a scrap piece of ply through the slot, make a left and right hand version, KEEL2L will be towards the outside of the boat and KEEL2G towards the centre.
Once L, K, J and I are glued together cut out the slot for the rudder hole, The cutout on KEEL2K (and H) is slightly smaller than J and I to form a semi round hole. - don't cut into KEEL2L.
Add KEEL2H and cut out for the rudder hole and then add KEEL2G and then fit KEEL2M to the open slotted end. This slot is for a propshaft strut, which can be fitted later on if required.
Step 3. Make up the wing propshaft keels.
Cut out KEEL2A to KEEL2F (6 pieces) and build them up progressively, glue only the end sections not the slots that need to be cut out to make the shaft hole. Again outside lines for 8mm shaft and inner lines for 1/4".
Assemble and make sure you keep the ends lined up and the sides square and not leaning over and make sure they are flat as you glue each layer (some bending is possible until it gets to be thick). The top (with notches) should be square to the sides but the bottom gets larger towards the main keel. Cut through the shaft slots with a fine model saw or scalpel to make the propshaft hole. Don't cut into KEEL2A
Test fit the propeller shaft as you build up the layers.
Make a left and right hand version, KEEL2F is to the outside of the boat
DO NOT FIT THE PROPSHAFTS UNTIL THE HULL IS COVERED.
Step 4. OK, enough practice now you can make up the main Keel.
Remove the parts for the main Keel from the sheets. The main keel is made up of 4 widths of ply (8mm or 5/16" wide) at the bow (front) and 6 widths (12mm wide) at the stern to allow for the propeller and rudder shafts.
Main keel sections:---H---
------G---F---E-----
---D---C---B---A---
---D---C---B---A---
------G---F---E-----
---H---
There are two lines marked on the two KEEL-E parts where a 'towing bit' may be fitted to the bow at a later time, cut a 'V' shape into the opposite side of the marks on each of these or drill a small hole through between the pieces after gluing them together
The parts of the two inner layers of the keel (KEEL-E to G) can be glued together on a flat surface - E to E, F to F and G to G. Do not glue the propeller shaft area or the rudder hole area. When glued the etched lines and text should be readable (one side has reversed or backwards writing).
Then add KEEL-A, B, C and D to one side and also glue the first pieces end to end. KEEP IT FLAT. Then add KEEL-H to the same side. Now you can turn it over and cut through the angled slots (Don't cut into KEEL-H) for the propeller shaft using a fine model saw or scalpel, the inner lines are for a 1/4" diameter shaft and the outer lines are for an 8mm shaft..
You can also cut through the vertical lines just in front of station65 which allows for a strut to be added later to support the rear end of the propshaft. Use some scrap pieces of material in the slots to keep it all lined up as you go.
Add KEEL-A, B, C and D to the other side and cut through the propeller shaft and rudder lines and then test the propshaft for size. - DO NOT FIT THE PROPSHAFT UNTIL THE HULL IS COVERED.
Glue on KEEL-H and then you can 'V' shape the keel bottom with a rough round or half round file from the middle of the keel to the etched line on the sides. The angle of the "shaped" part of the keel should end up concave (slight hollow) following the line made by each of the bottom profiles of each rib and is more concave at the bow and is almost straight at the stern. (Sandpaper glued around a piece of broom handle works well).
Step 5. Set out your Deck Runners.
On a 1' x 4' base board made of thick ply or MDF (Fiberboard) (3/4" or 19mm thick is good) set out the deck runners, the ruler is the correct length each way to set the correct distances between the inside of the main runners and the inside of the main runners and the bow runner. Keeping them very straight, tack glue the side runners down to the base board on the outside only but don't get carried away with the glue and don't let the glue soak up between the runner laminations where the upstand section is, between stations 25 and 65, or you will not be able to break away the outside lamination later. (As an alternative safer method you could tack glue a length of 4mm square timber down to the baseboard first and then glue to the outside of the runner in a few spots only.) The bow runner can be glued just at the section in front of Station 4 (STAT04). It doesn't matter if the runner are closer to one side of the baseboard or if the baseboard is narrower or larger, it's only there for rigidity during construction.
Step 6. Set out the Ribs.
The Ribs are properly called Stations and there are 20 of them in the Hull-2 kit from STAT001 to STAT65 and then the TRANSOM (or stern). The station numbers and shapes used are copied from the original boat plans and are in the correct (scale) positions (which is why they are not equally spaced or sensibly numbered). The station positions are marked on the runners. Because of the shape of the boat and because laser cutting produces a very slight angled cut, it is better if the runners up to STAT25 have their writing facing forwards and the ones from STAT29 to the stern facing aft (to the rear of the boat). The original Elco 80' boat had 69 stations plus an extra solid plate at the bow (STAT001) as well as the transom.
Punch out all the ribs and glue in place, again don't let the glue get between the runner laminations between STAT25 and STAT65 (the upstand area). Some of the rib top center sections will be cut out later to make larger openings to get your hands, motors, batteries etc in, so don't get too carried away with glue at this stage, when you glue the deck covering on there will be more glue added at each joint anyway.
Step 7. Add the main Keel.
Dry fit (no glue) the main keel into place along the centerline of the ribs, this can be a bit tricky as it is a fairly tight fit and there are slots in both the keel and the ribs to line up but the ribs will bend a fair way without breaking. Start at the bow and work your way aft. The ribs should line up with the etched line on the side of the keel (or to where you 'V' filed it to shape) and then the line along the bottom of the ribs and up the keel 'V' shaping should be smooth and gradual. Once you are happy with the fit, put a drop of glue between the keel and the bow runner and push that wedge joint fully into place, then glue the keel into place at each rib making sure it is fully "home" at each rib. New fresh superglue will soak into the joint easily but with PVA or marine glue you may have to apply it with the keel removed and you may also need to use clamps to keep it all in place as the glue dries.
Step 8. Add the Bow and Chine pieces
The purpose of these pieces is so that you don't have to bend timbers by steaming (and maybe breaking) and it also keeps the bow shape much better as bent timbers on opposite sides can have much different levels of stiffness and strength, they also stop the ribs from bending back out of position during assembly.
The BOW pieces are only a single 2mm thickness and fit to the keel and to stations 001, 02, 04 and finish at STAT06. The bow pieces should finish flush with the top of the ribs. (Later a 4mm (5/32") square timber length goes from just behind STAT04 to the stern. These lengths of timber are fitted at the side angle of each rib and will sit up slightly proud of the top of the ribs and will be filed off flush later before fitting the deck. Work your way from the bow end with clamps at the very front make sure they are fully home in their checkouts and check the rib to rib distances and rib straightness before gluing at each rib).
The "Chine" is the hard line caused by the change of direction between the side and the bottom of a boat's hull. There are 4 Chine pieces (two thicknesses or 4mm thick) called CHINE and CHINETOP (goes nearest the deck) and they go from the keel to stations 001, 02, 04, 06 and to the front of STAT09. (Later a 4mm (5/32") square timber length goes from just behind STAT06 to the stern on each side. Use clamps at the very front and you need to make sure they are pushed fully home and check the rib to rib distances and rib straightness before gluing at each rib).
Step 9. Servo Mount.
There are two STEERING SERVO mount pieces which need to be glued together, these then fit in a raised up mounting between stations 61 and 65. There are also two rudder stiffeners RUDDERSTIFF that fit beside the servo mounts and down between the ribs and almost to the boat bottom, these stop the servo mount from twisting due to the force of water against the rudders. The stiffeners are slimmer towards the stern and have slots to put the servo lead through.
Step 10. Fit the Wing and Rudder Keels
The wing propshaft keels should fit perfectly into place between STAT51 and STAT61 in the notches provided and likewise the wing rudder keels fit between STAT65 and the TRANSOM. Make sure they all fit properly (it's easier to sand any excess off now) and then glue them into place. The rudder keels have an extension forward of STAT65 to allow for struts to support the propshaft as does the main keel - if it was cut out at Step2.
Step 11. Motor Mount.
At this stage you might like to make a decision about what type of motors you are going to use and whether to use a geared or direct drive method. The MOTOR MOUNT is very flexible in the type of motors it can fit from standard 540 or 600 style motors to Kontronic brushless types and it also fits a variety of gearboxes. If you are looking at Direct Drive or metal gearboxs then the motor mount is best fitted forward of STAT51 using WEDGE-A's and WEDGE-B's and using 8" long propshafts. If you are going to use a plastic gearbox like the 'Mater Airscrew 05' then you may be better to attach it aft of STAT47 Using WEDGE-C's and WEDGE-D's. Either method should leave enough room for universal joints between motors and propshafts. Or you can mount one MOTOR MOUNT plate in each location and make up your own gearboxs.