Model Builder: October 1977

¢ special waxes are formulated in the d RICH, By ROD CARR ® The crush of the competition season has delayed our outfitting of the East Coast 12-meter that we promised to start. However, David Mainwaring, guiding force of Heritage Marine, P.O. Box 554, Need- ham, Mass. 02192, has been kind enough to release an excellent writeup on the construction and outfitting of fiberglass hulls. His research and experience in all things polyester is summed up for the benefit of all of us who have worked with the pun- gent, itchy stuff. Dave is a Model Builder advertiser and should be contacted directly for further information on his line of scale and competition models. For now, dons his cap as guest columnist. he THE FIBERGLASS MODEL YACHT BUILDER’S GUIDE, BY David L. Mainwaring This is a guide to assist the model builder in building model sailing boats from kits with fiberglass hulls and associated components. FIBERGLASS Fiberglass is the common name for glass reinforced plastics, GRP. The strands are produced in a nonwoven cloth called matt and in a woven cloth called fiberglass cloth, boat cloth, tooling cloth and woven roving. After the cloth has been saturated with resin and the resin cured (hardened) we have fiberglass. Fiberglass matt and cloth are sold by the yard in small lots by retailers, and by the pound by wholesale suppliers. Matt and cloth are designated in thickness by referring to their weights. Matt is weighed by the square foot, with 3/4 to 3 oz. matt being most common. Cloth is also weighed, but unlike matt, it is weighed by the yard. Thus, a 9 oz. | cloth has the same glass content as 1 oz. matt. Matt and cloth have dif- ferent handling characteristics and different conformability, as well as different impact and strength factors. Working with matt using brushon resin ‘requires skill and experience to avoid developing one big mess of glass fibers and resin. You will find, with a little practice, that matt conforms well when worked with a resin-covered surface with a constantly wet brush. A matt called surfacing matt can be used to work the regular matt in place and squeeze out air bubbles and excess resin. This matt is hard to obtain, other than from wholesalers. A layer of cloth 40 works well for surfacing if you can stand the added weight. Fiberglass cloth put up in tape form is widely available. It is a convenient way of getting high quality cloth in small quantities. It is important for the glass resin combination to have as high a glass content as possible for strength. Fiberglass cloths used in boat building must have a special treatment called Chroming to make the glass compatible with the resin. Do not use industrial or auto grade fiberglass cloth unless it is treated. Fiberglass (GRP) laminates will absorb water through the capillary action of the glass fibers. The problem of water absorption and surface abrasion is overcome in the molding stage by adding a specially formulated resin known as gel-coat. AIlthough gel-coat is available clear, it is usually pigmented to give the surface resin a molded-in color. Polyesters and lay-up resins can be pigmented, giving the part a solid color throughout. This is an inexpensive way of molding color in, but it presents two problems… hidden air bubbles within the laminate, and exposing glass strands. RESINS Polyester resins are formulated in many make-ups. To change the liquid resin to a solid you must add a hardener to catalyze the mixture. Whenever resin is referred to in this manual it is intended that it be properly catalyzed before use. The resin you choose for your model should be preaccelerated. This resin will commonly have a purplish hue in the liquid stage and may change color to indicate states of cure. Resins should be at room temperature (60°-90°F.) for curing. Among the polyester resins available are the air inhibited types. Lay-up, spray, and gel-coat resins are formulated so their surfaces will not cure readily while exposed to air. This is advantageous if several layers of glass are to be laminated over a period of time. However, it may present a problem to the unsuspecting who finds the surface of his resin ‘forever tacky”. Sometimes, applying a layer of hard bowling alley wax will solve this problem. Gel-coats, therefore, are not used as a finish coating on completed boats because they are air-inhibited. Finishing resins or hand lay-up resin is commonly a waxed resin. When resin, they will move to the surface as the resin cures. This is an advantage if this is the outer surface. If you want to bond to this surface, you must first sand it thoroughly and then prepare the surface with acetone or polyester solvent. Polyester resins may be thinned with acetone and styrene. The common polyester hardener is methyl ethyl ketone peroxide (MEK60). Resin and hardener must be handled most carefully and in strict accordance with the manufacturers’ instructions. The amount of hardener or activator in conjunction with the room or ambient temperature determines the jel time and the cure rate of the resin. The jel time is the period that the resin remains liquid until it turns to a jelly just before curing hard. Resin has a ‘pot life’ and is only. workable for the time before it jels; this may vary from seconds to several minutes. CAUTION . DO NOT use too much hardener. Styrene will thin the resin and become chemically part of the cured resin. Acetone will thin the resin but will evaporate during cure. Acetone will change the characteristics of the cured resin and may result in brittleness and other unwanted characteristics. Polyesters may be filled with a number of components from sawdust to pecan shells. Most common fillers are Cabosil and micro-balloons and macro-balloons. This filling may make the resin thixotropic, and filled resin may vary from a slurry to a heavy paste. Macro-balloons and micro-balloons are used to make a foam-like putty which will work as a flotation foam. Polyester will bond nicely to polyester. We stress that surfaces must always be cleaned and prepared for bonding. The bond between two fiberglass parts, such as keel and shell or hull and deck, will be enhanced if the interface between bonded surfaces is filled with a layer of saturated matt, cloth, or filled resin. Polyester resin is frequently used to bond to wood as a glue. However, among wood glues, polyester rates poor. The initial bond to wood may look all right, but it has a history of delaminating. We will not rule out its use for model building. However, there are better wood glues, and the best of the waterproof glues are the many epoxies. Fiberglass is not at its best under tension. Spread or distribute any tension load over a wide area. The same goes for compression loads which should be spread out also. This fiberglass found in models will tear if pulled on, so always spread the load… more on this later. You must remove all waxes in MODEL BUILDER weight, load spreaders are used to distribute loads over a wide area of the flat surface. A sectional shape, called a Tee or Top Hat, will greatly strengthen a flat glass panel. This works on the same idea that an Ibeam works in steel construction. A piece of cardboard, plywood, spruce, or another fiberglass component is used to form a right angle to the flat surface. A piece of glass tape or matt is placed so as to form a right angle with the flat surface being the top of the letter T. When molded in place with some activated resin, the finished Tee section acts as a solid brace equal to the height of the Tee. The cardboard former or plywood may be removed if it was waxed before the resin was applied. For still additional strength, form what is called a Top Hat, which is a double-Tee section with a cap between the tees. Cut in half, it would look like a top hat. The former used to build the Top Hat can not be removed. Using Tees and Top Hats can strengthen a hull or com- ponent without using up significant hull space. You may use bulkheads of polyurethane foam to make tee sections and leave the foam in for flotation. Do not use styrofoam or any styrene-based foam; it will dissolve away in resin. Once again, remember that surfaces must be prepared for gluing or bonding to them. TOOLS order to bond to fiberglass and you can reverse this and coat surfaces with hard floor waxes during building to protect surfaces from accidental spills. Also remember to use only resin-resistant tape, such as Scotch brand Cellophane tape which is inert to resins; regular masking tape may be used, if not in contact with resin or solvents. OCTOBER 1977 Fiberglass has the outstanding feature that when molded in curves it has very high strength imparted to the part because of the curves. On smaller models the curves of the hull provide sufficient strength for the model. On larger models you will need stiffeners. These may be ribs or bulkheads which add support to the hull. These can be of the aircraft framework type. Another stiffening method is to make a sandwich. Here the strength of the GRP is achieved by laminating a lightweight core between two layers of fiberglass. G.R.P. LOAD SPREADING Flat surfaces or slightly curved surfaces, such as the bottom of a Star 45 model, have only moderate fiberglass strength unless sandwich construction or several layers of glass are used. To avoid this added The average kit builder will need few special tools. When working on hardened fiberglass parts, we recommend the Dremel Motor Tool. With this you can sand, carve, cut, trim, grind, and much more. It takes the cussing out of trimming fiberglass and cutting holes in hulls. Other than that, the usual assortment of clothespins of the spring variety, sharp modelers knives, rubber bands, a few coarse bastard files and a couple of mill files, and a supply of 3M-ite wet-or-dry sandpaper; Nos. 220, 320 and 600 will be adequate. SAFETY Always work in a well ventilated area. Resins, hardeners, and solvents are flammable and toxic. MEK60 is impact sensitive. Some people are especially sensitive to any and all components. Avoid excessive skin contact. Avoid inhaling concen- trated fumes. Wash well and keep skin clean from these chemicals. Always follow manufacturers instructions. DO NOT SMOKE or have open flame around when working with fiberglass chemicals. Select an appropriate work area. Protect furni- ture, floors and other surfaces from Continued on page 95 41 spills and spatters to prevent permanent damage from these sub- stances. Remember that the fibers of the fiberglass are irritants, and commonly cause skin itching and irritation. When sanding, use a barrier cream or gloves, protective clothing and sanding mask, and careful clean-up methods as you work. Fiberglass is just that, GLASS, and it will cut if you are not careful. When you sand, cut or trim anything made from fiberglass, keep in mind that it can be as sharp as anything known to man. SOME ADDITIONAL HINTS Your fiberglass hull and deck probably are fresh from the mold. If so, they may have mold release still on the surface. PVA mold release looks like a flaky film and washes off with water. Wax and other mold releases will require scrubbing with detergent. If the edges of the parts have not been trimmed, trim them when the time comes for assembly. Stick with using name brand products in your model building. Look for proven modelers products and industrial adhesives. Very important: Prefit and trial fit all parts before installing them. Don’t install anything until you check your building plan and building schedule Your building schedule is the list you make of all components to be assembled before you begin to build to make sure you don’t put something together in the way of something else. For example, you must be able to install the radio gear into the hull, so don’t assemble components in such a way that it will block installation of that radio gear. FIBERGLASS HULLS Fiberglass boat hulls are available in different forms. A one-piece hull is supplied molded in one piece. A two-piece hull has two half-hulls which must be joined together by the builder. Hulls may come with edges reinforced and a mounting lip molded about the sheer edge. Often they come with a “straight’’ sheer; this means the modeler must put in a shelf or sheer clamp or gunwale strip in order to mount the deck and support the edge of the hull. In the two-piece hull, trim the halves carefully. Hold the parts rigidly together with clamps or tape and laminate in a strip of fiberglass across the inside joint, between the halves. When the resin cures you. will have a one-piece hull. . Before proceeding further, you will need to build a cradle to hold the model in place while you finish building it. If your hull is of the straight sheer type, it will require a deck mounting shelf to be installed; pro- ceed as follows. After trimming the sheer, laminate two strips of 1/8 x 3/8 spruce about the inside edge. shelf to support the deck. You may use other sizes and woods to fit your individual needs. Take care not to distort the hull at this stage. If necessary, brace the hull externally to hold its shape. Do not try to force the wood strips too tightly to the hull. This will distort the hull at the clamping points. Use a thixotropic resin to bridge the small gaps between the wood strips and the fiberglass. Another method is to use a small strip of fiberglass between the wood strip and hull with the saturated glass strip bonding to both the hull and the wood. On a racing model, remember weight should be kept at a minimum. Choose your building technique and materials with this in mind. Locate the points at which the chain plates and various fittings will be attached to the hull and deck. Locate and install load spreaders and back up blocks for such items as shrouds (stays), head stay or job rack, mast step, back stay and any other item which will need to be fas- tened after the boat is assembled. These back-up blocks or load spreaders are generally blocks of light weight wood, such as spruce, which are bonded to the hull or deck so that when the fitting is screwed or bolted down to the fiberglass, the -pull is taken up by the block of wood. Remember that unless the load is widely spread out, fiberglass, especially thin GRP as in models, can not stand tension loads. Arrange the blocks to spread the load or to put the fiberglass in compression loading. an The bottom of your model must support the weight of a heavy keel located on a long lever-like fin, so it will need some sort of strengthening or “load spreading”. If the keel is bolted on, the hull will need a keelson installed inside the hull. The keelson is sometimes called the hog, or occasionally the keel. To do this, you laminate a 1 inch wide strip of glass tape down the centerline inside the hull bottom. While this is still wet, laminate three or more 1/8 by 3/4 inch strips of pine or spruce on top of this strip right down the centerline. You could use several layers of the 1 inch cloth laminated in place of the wood strips, but they will weigh more. This keelson will give you the hull thickness to hang the keel on and support fore and aft. Load spreaders will still be required on each side of the keel bolts. The “STAR 45” calls for the keel fin to pass through the bottom of the hull and be glassed permanently in place. The keelson of wood is needed only under the area below the mast step. . Check the beam measurements of your particular model; it may be necessary to spread the hull slightly or even to push it together to get the beam at the desired measurement. Ne ete ae | hope to utilize more of Dave’s material in the near future. | understand that complete copies are partof the kits that he sells, so if you buy a copy of the directions, you’ll be pleasantly surprised to find that a boat comes with it! With the regatta season in full swing, there must be a few of you out there who take a black-and-white photo or two when you are not racing. Why not send me a clear print that shows us the action in your fleet? | can’t be everywhere, and if you want to see what’s going on elsewhere, don’t sit on your duff and wait for the other guy to do something about it!!! While reading one of the other modeling magazines | came across a well presented article by Jerry Julian on making buoys for sailboat race course markers. I’d like to add yet another way of skinning the cat. This technique was suggested by Ted Robertson, formerly of the Buffalo Club, and the first AMYA A-class Secretary. The sketch is really selfexplanatory. Items needed are: 10 inch inflatable beachballs (I used some from Radio Shack) D-rings from a craft shop large enough to let 8 oz. lead weights pass through. 16 oz. lead primary anchors. 8 oz. lead tensioning weights. 1 roll 3/4 inch glass fiber filament tape. Upon construction, one needs only make sure that the balls are clean and dry before attaching the D-rings opposite the inflation nipple. Tie plenty of light polyester cord to the primary weight and wrap it around the primary. To launch, drop the primary weight and let it unwind on its way to the bottom. Then slip the secondary through the Dring and plop.it into the water. Presto, a taught moored buoy, that works no matter what the depth of the water (if you have enough cord), | made a plywood box with a handle and the whole array of 5 or 6 buoys, weights and all fits right in. As an added help to the regatta director, we set two windward marks of different colors and use the one dictated by the prevailing wind at the one-minute-to-go start of the count. For depth perception ease, | do think that the balls should all be the same size. We have found the system to have a couple of advantages over Con TINVED ON PAGE S53 2 7 7/7 the buoys with the flags. The major one is that boats absolutely cannot Snag or get hung up on them. We’ve even tried to snag keels on the mooring lines, and have been completely unsuccessful with that. Since the whole shebang fits in a box, it does make the trip to the lake a good deal easier on the Fleet Captain. urs oh hs Remember SPOT, the darling of the STAR 45 class, that appeared in these pages back in December of 19752 Well, she is still alive and quite well. | sailed her in the 3rd Annual Class Championship Regatta (ACCR) … When will AMYA decide to call that a National Champion- ship so that non-sailors will know what we are talking about? … For the third year in a row she won the event and now proudly wears ’77 gold chevrons on her main. Before the rumors get out of hand, it is true that she was the inadvertant cause of the sinking of the second place boat … got caught to weather by a gust and whacked John Krick’s boat a good one. John continued to sail the course and was near the finish when his boat sank by the stern and threatened to disappear. He got her running again and pulled out to a strong challenge to SPOT. John’s boat was fiberglass, while SPOT is: one of the “old-fashioned” wooden hulls. Maybe wood does go better, Vince Santoriella was awarded SPOT’S DISH, an engraved silver bowl perpetual trophy that is given to the highest finishing rookie at the ACCR. Class Secretary Al Hemmalin set the site of next year’s event at Marsh Creek, PA, so start planning for ‘78. The STAR 45 ACCR is the only event that has remained a “fun sail” rather than a thinly disguised fight. My hat is off to all the skippers who took part, the Hemmalins who ran it, and to John Rosebery, of the Tri-State MYC, who provided boat, buoys and a lake full of water, Ill continue to field questions for a stamped, self-addressed envelope, or in care of Model Builder, to: Rod Carr, 7608 Gresham St., Springfield, VA 22151. And remember to send in your annual $5.00 dues to the American Model Yachting Association, 2709 S. Federal Florida 33444. Highway, Delray, 8