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Welding Metal Boats rev. 29

There is a common misconception that metal hulls are welded continuously throughout. This is not the case. In fact the idea is to weld as little as possible and still achieve the required strength. Welding introduces stresses and distortion that can cause cracking or unattractive finishes respectively. Let’s avoid the “Hungry Horse” look. The majority of welds in a metal boat are “intermittent” or “stitch” welded , with the exception of engine beds and othe r heavily loaded areas such as chain plates etc. The shell of the hull and superstructure must be continuously welded for a watertight boat. Professional Welders The old adage that the worst person to hire to weld a metal boat is a professional welder is in most cases 100% accurate. In boatbuilding there is a different set of rules to those of most other welding applications. So if you are a professional welder then you should study this document carefully as well. The basics: Intermittent welding : Falls into two main categories : Chain and Staggered .

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Boat Building From A Kit 1: INTRODUCTION. Throughout these instructions we will use the word metal which may apply to steel or aluminum. There will be variations between the handling of the various materials and these will be drawn to your attention as necessary. YOU WILL NEED TO READ and absorb all these instructions BEFORE you start the assembly of your kit. These instructions are intended to introduce you to building from a kit but are NOT intended to replace good metal boat building practice. If you are not already a competent welder then please seek assistance. Please refer to Trident Welding document “Welding Metal Boats” for welding details . Few of you will understand (or want to know!) the huge amount of work that is required to turn any boat plan in to a cut-to-size boat kit. Every part has to exactly match that of its neighbor, the slots need to be exactly in the correct locations and everything must fit perfectly together to enable you to complete the assembly of the hull, deck, and superstructure with a minimum of problems. Despite our best endeavors and attention to detail in developing the kit and the cutting of the metal parts, some parts may not fit or appear to have the wrong shape. Before rushing to cut and or shape parts to fit the hull, carefully check the drawings and measurements from the surrounding parts to ensure that nothing else is wrong. The first thing to realize is that the kit differs in many ways from the methods you would use to build a metal boat from scratch. The kit is far superior to anything you could achieve by starting with the plans and delivery of raw steel plate and the various profile bars that are needed to build your metal boat. Most metal boats built from scratch are built upside-down…most boats built from cut-to-size metal kits are built UPRIGHT. Not only is this a more appropriate way to assemble the kit but it also saves cost and inconvenience of having to turn the hull.

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To make sure that you take notice of one very important piece of advice, we will state it here as well as at the appropriate time:

YOU MUST TACK WELD THE COMPLETE HULL DECK AND

SUPERSTRUCTURE TOGETHER BEFORE YOU RUN ANY FINAL WELDS.

Failure to observe this advice will almost certainly ensure you will end up with an unfair boat requiring a considerable amount of filler. In any case do NOT OVER-WELD or try and run long welds at one time. 2: RECEIVING YOUR KIT. Depending on your location or delivery arrangements your kit may arrive on a flatbed truck or in a container. You should be aware of these arrangements before the actual date of delivery so you can make the necessary preparations to receive your kit. The kits are normally packed on pallet(s) and can be lifted off the transport using a small crane, front-end loader, or similar equipment. Once you have unloaded your kit you must make provision to keep it covered until assembly is underway. Make sure that the metal parts are not in direct contact with cement-based floors like concrete, as this will affect the primer. You should go trough the kit and identify each part or group of parts so you can store these in the order that they will be required. Due to the requirement of packaging for transport it is impossible for the kit manufacturer to stack everything in the order you will be using the various parts…you must take care of this. Later in this text we will suggest the order of assembling your kit so you will be aware of which parts you will need at each stage. If you do not find a particular part at this stage …DO NOT PANIC…there will be so many pieces that it will be easy for you to overlook one or two at this stage. If after several checks you find one or more parts missing then do contact the supplier of your kit so they may put the matter right. 3: ASSEMBLY SEQUENCE. FOR MOST HULLS: The first item you will need is the setting up jig. The metal "castles" that come as part of your kit will support the transverse profile jigs. The setting up jig is intended to get the assembly of your hull started and is NOT INTENDED TO SUPPORT THE BOAT during the entire building process. After you have the bottom plates tacked together you should consider adding extra support and bracing to the structure. For most hulls, the general assembly sequence is:

• Assemble the jig. • Bottom plates into the jig; line up the markings for frames and tack

weld together. • Assemble web-frames in accordance with drawings. • Position bottom longitudinal stiffeners on bottom plates (very small

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tack welds only). • Position frame over longitudinal stiffeners onto bottom plates,

starting with the middle frame, work your way aft ships and then from the middle to the bow.

• Tack-weld frames in position, observing the markings on the plates indicating the correct position of the frame. The direction of the arrow in the marking indicates the direction of the plate thickness. Always start tack welding at the bottom centerline working your way outward.

• Tack-weld bottom longitudinal stiffeners to web-frames • Insert side longitudinal stiffeners into web-frames and continuously

check the frame spacing. • Position side-hull plates starting at transom and tack weld to web-

frames only. • Tack weld longitudinal stiffeners to side and aft-hull plates. For hulls

with build-in spray-rails start at the bottom and work your way upwards.

• Position the transom and tack-weld to bottom and side plates. • Position longitudinal deck-stiffeners and tack-weld to web-frames. • Position deck-plates starting aft and tack-weld to web-frames only. • Tack-weld deck-longitudinal stiffeners to deck plates. • Position superstructure walls and tack-weld to web-frames. • Position and tack-weld roof-plates to deck.

This is the recommended sequence for most type hulls. Depending on the facilities of your workshop and building site, variations may be required or preferred. The better equipped your workshop is with overhead lifting equipment and equipment the easier and more smoothly will your job proceed. We do recommend that you read some of the literature available on metal boat building, which will answer many of those general metal boat building questions that are sure to need clarifying as the project proceeds, if only to get familiar with the terminology of parts and components of your kit. Contact your supplier for titles available in your area. FOR HULLS WITH LONG KEELS: These are unusual in that the keel structure should be assembled at the same time as the bottom plating. Take care that you do not "squeeze' in the tops of the keel, use the webs as spacers. After you have positioned the bottom plates, the keel sections and the transverse profile jigs in their correct location you may start to tack weld the bottom plates to the keel sides. FOR SAILBOATS WITH FIN KEELS: Sailboats with deep keels will have the keel installed after the hull is completed. The "canoe body" should be built from the bottom of the hull upwards in a similar manner used to assemble a powerboat hull. The webs will be arranged so you can later add the keel after raising the hull into the correct elevation.

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The idea of this method is to allow you to work on the hull deck and superstructure while the boat is lower and thus more accessible. The exact method and order of assembly may depend on the availability of lifting equipment and your general work environment. FOR POWERBOATS: In most cases you can start by laying the bottom plates in the transverse profile jigs and with the aid of the "castles" so position the plates that you can start to tack the hull plating together along the centerline. You will next be able to install the bottom sections of the stringers , frames , and webs in their correct location. 5- WHAT YOU NEED TO KNOW ABOUT WELDING Attempting to construct a metal boat kit leads us to believe that at least the basics of MIG welding are known. If in doubt about your abilities to weld, improving your skills on some scrap pieces of metal would be advisable as there are no great secrets in general steel welding but practicing would set you of to a good start right at the beginning. Welding aluminum or copper nickel should not be attempted without proper knowledge of the materials and welding sequences involved and should always be carried out in covered and clean surroundings. The metal kits are constructed in such a manner that the strength of the hull & deck is created from the build up of the frames and stringers as interlocking sections, HEAVY AND CONTINUOUS WELDING OF FRAMES AND STRINGERS SHOULD BE AVOIDED AT ALL TIMES. Especially important for all plate joints during the assembly of the hull is DO NOT APPLY CONTINUOUS WELDS. The plate joints should be ONLY TACK WELDED in three locations, on the floor , one weld at the each of the ends of the join and one in the center of the join. These tacks should be no more than 2 inches (50mm) long. If you weld the plates on the floor you will end up with a "hard-spot" in the hull plating. ( Once the plating is in the jig and the stringers and frames are in you should tack (1/2”) every 6 inches.) All parts of your kit are cut to a precision of 1/16” (2 mm) and are designed to be welded together without any opening between the parts. Some plates will need to be beveled before tacking in place or you may prefer to make the bevels after you have tack welded the plates and just before running the final welds. In all cases good metal boat building practices will prevail. After the hull & deck are COMPLETELY TACK-WELDED together, the process of finishing welding can take place. The secret of creating a fair hull & deck after tack welding is completed is to use a fairly high amperage and speed setting of your welding equipment. Welding with too low amperage and slow speed will

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create lots of heat on the spot and less penetration of weld material in the seam, causing strength problems and lots of grinding weld material away to obtain a smooth surface afterwards. This in turn would weaken the weld again. Using common sense and practice should leave you to create a smooth and fair hull & deck structure with very little distortion. IF IN DOUBT ABOUT YOUR SKILLS, SEEK ADVICE. 6. ASSEMBLING YOUR KIT. With the arrival of your metal kit, you received a packing list , or parts identification sheet, containing the names, numbers, and quantities of all the parts in the metal package. You also received one or more large-scale drawings showing all the parts as flat surfaces and more or less grouped together as they appear in the metal kit and a number of small drawings showing the assembly of the frames with the appropriate measurements. Studying the large scale drawings will give you a first insight in the position of the various parts and it becomes apparent that the numbering is as much as possible a logical sequence of the way the parts assembly progresses. Using the packing list and the drawings you can now make a check to see if all the parts are present. For ease of recognition you will find that frames etc. are numbered with 4A, 4B, 4C etc. thus every time you find a number 4 and extension A or B etc., they belong to the frame no.4. The cutting, collecting, and identification of parts during production is a manual process. This is why parts may be given incorrect numbers and even get lost, in spite of our thorough quality and quantity control procedure. Checking and verifying all parts against the packing list provided and keeping unidentified parts aside until the end enables you to identify the missing parts and incorrect markings on parts for clarification with the supplier. Apart from the plate parts, your kit also includes a selection of profiles, supplied at factory lengths, as listed the Packing list. Each bar needs to be cut to the length required in its position in the construction as detailed on the Construction Plan provided in the set of drawings. Now that you have collected and sorted all the parts, the frames can be tack-welded together by using the small drawings and the given measurements as reference. (Note: Smaller boats may have 1 Pc. Frames) Prior to welding, use an angle grinder and create a "V" of approx. 60° at the seam to be welded.

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This means 30° angle at each plate edge. Doing this will give you better penetration of the welding material, adding strength to the hull. We use the word tack-welding again as it would be tempting to finish welding the seams fully. Some models have flat or angled bars added on the inside edge of the frame plates (flanges) for additional strength. Check the Construction Plan provided. These Flanges are best fitted as soon as the frame parts are tacked together, before placing the frame in its position in the hull. On larger boats it might be an advantage to only weld the bottom parts of the frames together and put the side frames up after the frames are in place on the bottom plates. Your own judgment is important here. The Jig; Having prepared all the frames in this manner it is now time to prepare the building jig. With the metal kit you have received jig parts. These supplied parts are only initial shape supports and CANNOT BE USED AS FULL BUILDING FRAME WITHOUT SUBSTANTIAL STIFFENING AND CROSS BRACING. The supplied jig parts could be placed on a concrete ground, leveled, and stiffened. In case no solid ground is available, the use of a couple of heavy “I beam’s” picked up from a local scrap dealer could do the trick. The distance between the jigs is determined by the position of each frame (web) in the hull, whereby the jig number is the same as the frame number (f.e. Jig-part J5-2 is at frame 5). In case the "jig" parts stay in place during the entire construction, it would be advisable to tack-weld a flat bar across the top of the plates to spread the point loading and avoid possible damage to the hull plating. Now place the bottom plates on the prepared jigs or building frame and tack-weld together at a number of points. We refer here to paragraph 2 in relation to sailboats where the keel is also placed under the bottom plates at this stage. If the boat has a CVK (keel bar / profile bar) now is the time to place it in the jig , prying the bottom plates apart. Care must be taken to keep everything on the centerline and line up the frame marks on the port and starboard plates. For those of you who are new to this type of boat building, having placed the bottom plates on the jigs, it seems they are never going to fit.

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Start tack welding at the location roughly in the middle or somewhat aft of the middle after lining up the lines on the plates and position of the plates. When you now go forward or backwards from the tack-welded position you can help the plates get in shape by having some helpers pull up the sides and using a jack underneath the middle join of the plates until the seams touch. Now tack-weld at this point and go to the next position. At the bow you would probably need a hand block and tackle to pull the sides of the plates together as some tension will be experienced here. DO NOT FORGET TO SECURE THE POSITIONS OF THE CLAMPS AGAINST SLIDING AWAY. Having finished tack-welding the bottom plates together, start placing the longitudinal stiffeners at the markings on the bottom plates while lining-up the slots with the position of the frames (webs), as indicated by lines on the plates … use the large scale drawing(s) as reference. Only tack-weld these longitudinals to keep them in place for the time being. As frames will have to be slotted over these longitudinals, we recommend to tack-weld only to the bottom plate in the middle between frame positions, which allows you to align these when putting the frames in position. Then start placing the frames (webs) which slot over the longitudinals . Position the middle frame first and tack-weld it to the bottom-plates in the center, then pull up the bottom plates towards the frames until they fit snugly and tack-weld. Depending on the shape of your hull, we recommend to work your way aft first, thereafter from the middle to the bow. If you have put the frames together completely, use some temporary bracing on the upright sides of the frames, as they are likely to flop about a bit. Now we place the stringers in the slots of the frames on the sides and slightly tack-weld at some spots to keep them in position. We do emphasize again, ONLY TACK-WELDING. At this stage you have already created a strong and solid base of the hull and the time has come to bring the side plates into position. This is best done by using a simple overhead gantry or the use of a forklift truck. Pick up the side plate(s) by using a plate clamp on a chain connected to a block and tackle or forklift leg, make sure the plate is more or less in balance when it is hanging in the air and bring to its allocated position. Use a helper to put a point of the seam in the right position and tack-weld. Continue by moving the plate up or down a bit with the block and tackle until the entire side is in position and tack-welded. Place some tack-welds on the uprights of the frames as well.

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The side plates nearer to and at the underside of the bow will show some tension and can be pulled in place by attaching a chain on the outside of the plates and pulling them into position. To attach a chain and/or block and tackle to a plate, tack-weld a temporary eye or something similar to the plate. By only welding on one side of such plate(s), you can easily remove these again by bending this plate until the weld breaks. Note: In the case of radius chine sailboats, the radius chine sections are not used at this stage; we will come back to those later. Next the transom plates, swim grid where applicable, stern plates and all other plates belonging to the hull are offered up in position and tack-welded in position. Especially where rounded corners are used, offer the particular plate up to the position it is to be used and check or make the correct radius in the plate prior to tack welding. REFER BACK REGULARLY TO THE DRAWINGS AND CHECK INTERMEDIATE AS WELL AS OVERALL DIMENSIONS. Now the deck plates, superstructure, fly-bridge where applicable and all other super structure plates can be offered up to the hull and tack-welded into position using the gantry or forklift truck to lift them onto the hull. Do make sure the support stringers under the deck and cabin roofs, where applicable, are placed first in its slot(s) in the frames and beams. In those cases where professional lifting equipment and space is available, an option would be to tack-weld the superstructure together at floor level, brace temporarily and than lift the entire sub structure onto the hull. FOR RADIUS CHINE HULLS: Having tack-welded the entire boat together, you now turn your attention to the radius section(s). We have supplied you with the appropriate amount of rolled section plate to fit in the left over opening in the hull. As you checked the metal kit on delivery, you have seen they are all similar sections, just one radius rolled into them. Now you can carefully hold a section against a position on the opening in the hull and using a helper scribe the plate with a sharp tool or pencil and grind, nibble or cut the edges (of the radius plate) until the plate fits in position. On straighter hull sections you can probably pull the fore and aft ends of the plate in to contact the frames . At the longitudinal centerline (middle section) of the hull you will need to

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cut slits in the radius plates to fit them. These slits can be made with a grinder with a cutting disc on it. Tack-weld into position and continue until all radius plate sections are in place. CONGRATULATIONS, you are now looking at the shapely result of your perseverance. Of course you have run into some difficulties during the building process and maybe even cursed a couple of times but it must be clear by now why we told you time and time during this manual ONLY TACK-WELDING. Any possible mistake you may have made was fairly easy to rectify, as you only had to grind a couple of small welds away. However careful the cutting of the material was prepared and cut, the material can behave unexpectedly, for example the grain in the plate runs diagonal and will resist shaping into the required form. This will require additional effort and force to get the plate to fit. Although we aim for perfection, mistakes do occur, however the general consensus is that if you have to cut or reshape a plate (with the exception of radius plates) somewhere something is not right. You can help us improve our product by reporting minor fit problems etc. so that we can rectify the problem. Any plates that are not usable through our error will be corrected and replaced (where we supplied pre-cut materials). 7. FINISHING THE ASSEMBLY. Now the time has come to finish the welding process. See the supplied Trident Welding document : “Welding Metal Boats” for detailed welding instructions.

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Fillet Welds : Leg and throat

The following table indicates the type of weld used on various structural components:

All Standard Webs to shell or bulkhead plate Staggered All standard longitudinals to shell plate Staggered All standard flanges to webs Chain Web to shell at mast partner and chainplate frames (for 6X web height on longitudinally framed hulls , down topsides from sheer along deck beam; for 8x web height on transversely framed hulls , down topsides from sheer , and in from sheer along deck beams.)

Continuous

Floors to shell Chain Floors to frame Continuous Floors to keel bottom plate Continuous Floors to shell in way of engines Continuous Floors to shell at stern tube Continuous Floors to shell at mast step Continuous Floors to CVK Continuous CVK to stern frame Continuous Bottom Girders to floors and frames Continuous Bottom-Girder Web to shell under engine mounts Continuous Bottom-Girder Web to shell Chain Frame webs to shell under engine beds. (For at least 1.5 times the length of engine and gear , or from CVK to chine or bilge , whichever is less)

Continuous

Frame webs to shell at shaft logs Continuous

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(For at least three longitudinals wide ) Engine bed flange to web and engine bed to floors and bulkheads

Continuous

Deck longitudinals to beams Continuous Bulkheads to shell Staggered Watertight bulkheads to shell Continuous Interior decks to shell Staggered Stanchion tops and bases Continuous Cosmetic attachments such as eaves and visors Staggered All continuous welds are double continuous , that is , equal fillet welds on both sides. If access to one side is restricted , a full penetration weld with a 60 degree bevel from one side is acceptable. Weld Sizes: Weld sizes are determined by the thickness of the plate they join , and the loads they will experience. The size of a Fillet Weld is specified by the leg length. The spacing between Intermittent Welds is called Pitch. To fully define a weld you need the following :

1. Leg Length 2. Bead Length (if intermittent) 3. Pitch (if intermittent) 4. Continuous (if continuous)

For example , the web of a ¼” (6.4mm) aluminum frame would be fastened to a 3/16” (4.75mm) shell plate with 1/8” (3.2mm) fillet welds , 1 inch long , with a 10” (250mm) Pitch , staggered (not chain). Fillet Weld Sizing: Fillet weld sizes are based on the thinner of the 2 plates to be joined . WELD LEG = Thinnest plate – (subtract) 1/16” (for plates up to ½”) WELD LEG = Thinnest plate – (subtract) 1.6mm (for plates up to 13mm) WELD LEG = Thinnest plate – (subtract)1/8” (for plates ½” and over) WELD LEG = Thinnest plate -(subtract) 3.2mm (for plates 13 to 25mm) WELD LEG = Thinnest plate x 0.75 (for plates over 1”) WELD LENGTH (Intermittent welds) = 8 x Leg but not over 6 inches PITCH (OC) = 10 inches for aluminum , 12 inches for steel.

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Around the end of a member such as a frame web at a limber hole, or the end of a longitudinal , there should be a wraparound weld equal in length to the rest of the weld segment lengths on that part. (See chain weld diagram) Butt Welds: For plates 1/16” to 1/8” , the gap should be 0 to 1/16” (0 - 1.6mm) For plates 1/8” to 3/16” the gap can be 0 to 3/16” (0 - 4.75mm) Plates 3/16” to 5/16” should have a 60 to 100 degree bevel on one plate edge. Plates over 5/16” require a bevel on both plates Plug and Slot Welds There will always be areas and parts that cannot be accessed from the backside to weld. Keels , Rudders , Skegs , and “paneled in” superstructure Pylons are all good examples. To assemble these components the framework is erected and one side plated and welded internally . Then the opposite plate is installed and “plug-welded or slot-welded” . The edge of the internal stiffener must have a flange added or built up to form a “T” shape in

section.

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Plug and Slot Weld Sizes A plug weld is a round “rivet” weld through one plate to fasten to the plate below. Plug weld diameter at the base of the hole = 2x plate thickness(for plates under ½”) Plug Weld diameter at base = 2 x plate thickness + ½” for plates over ½” thickness. Plug Weld Pitch Aluminum = 4.5” Plug Weld Pitch Steel = 5” Slot Welds are rectangular slots with radiused ends. (Stretched plug welds) Slot Weld Width = 2 x plate thickness (under ¼” plate) Slot Weld Width = 2 x plate thickness with a 45 degree bevel (1/4” to ½” plate) Slot Weld Length = Same as fillet weld length on same sized plate Slot Weld Pitch = Same as pitch of fillet welds WELDING SEQUENCE The sequence of welding the structural elements of a boat is critical to controlling distortion. Three major considerations:

• Use backstep welding to minimize local distortion. • Skip around the hull from port to starboard and back and fore n aft and back • The actual sequence in which the structural welds are completed must be planned

ahead of time to ensure minimum distortion. Back Step Welding: Back step welding eliminates local distortion . For example if you simply started welding at one of a seam between to plates (butt) and welded continuously to the other end , the two plates would probably overlap before you got halfway. To eliminate this you must first tack weld the seams every 6 inches or so . Then use the backstep welding technique . Start in the middle of the plate , weld several inches in one direction then skip several inches and weld in the opposite direction . Then skip to the opposite side of the center and weld a few inches in the opposite direction to your last pass. Repeat until the entire seam is welded. On Aluminum you can weld up to 10 inches (255mm) in a single pass , then skip 20 inches (500mm) making another pass in the oposite direction. On Steel , weld no more than 3-4 inches at a time then skip 12 or more and weld another pass running in the opsite direction.

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Spreading The Welds Around The principle behind backstep welding applies to the overall weldout of the internal structures as well . So if you were welding the frames to the shell plating then you would start in the middle of the hull closest to the keel and work your way outward a few welds then skip to the other side of the hull for a few welds. Then move to the next frame fwd and aft , then return to the first frame and weld outward a little further. In this way you spread the shrinkage around in an organized fashion , radiating outward from a central point. This has the effect of tensioning the structure evenly and when this principal is applied to the hull skin it results in drawing the skin taught helping to avoid ripples etc . OVERALL FINAL WELDING SEQUENCE Keeping all the previous rules in mind it is vitally important to follow a carefull weld sequence in the final vessel weldout. Except for backbone and framing components the entire structure should be lightly tack welded together. ONLY WHEN THE ENTIRE VESSEL IS ERRECTED (OR KIT ASSEMBELED ) SHOULD THE FINAL WELDING BEGIN. Always start with the shell plate. Weld all the butt seams (transverse seams) first. Weld the butt seams at midships first then move forward and aft one seam at a time. Then begin at the bilge or chine midships seams , gradualy skipping your way forward and aft evenly , and up to the shear and down to the keel. Work evenly on both sides of the boat. Whenever pratical weld out the inner seams first (inside the hull) , then back gouge the outside seams to clean (white) metal . ( Back-gouging may be restricted to below the waterline only) Follow the backstep welding method to weld out the outside seams. IMPORTANT: Resist the urge to weld with longer passes now that the hull has been welded out inside. The same backstep MUST be used to avoid distortion. Once the shell has been completely welded out then you can break loose the tacks holding the longitudinals to the frames. This will relieve stresses and is an important part of creating a fair hull. You may need to straighten stressed members … Weld the longitudinals to the hull skin , using the sequences described earlier in this text. Next weld the transverse members (frames) to the shell plate . Finaly weld the frames to the longitudinals. (Continuous weld all the stringer slots etc.) Welds below the waterline should NOT be ground flush. Welds above the waterline may be ground flush where cosmetics are important.

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NOTES: