Trial Beam Repairs If you’ve read other articles on Repairing Loose Beams but found them a bit daunting, then consider these alternative trial methods, all of which you may find easier. The first two were sent in by John Peperell (JP) our Club’s Technical Officer. Neither method needs any dismantling, and leaves all other options still open. John only recommends these methods if your boats spacer tubes are not damaged or shortened due to prolonged wear or serious corrosion inside the cross beams.

JP Trial Method 1

Method-1.This uses 2mm thick aluminium plate with a central hole drilled to fit snugly around the loose insert’s head. The Insert head projects 2mm above the beam surface so the final result will leave the plate flush with top of the insert’s head. This method does not need the spacer tube or insert removing. Gap filling adhesive/sealant directly under the plate is optional when fitting after final alignment. As you can see, the central hole of the plate matches the outside diameter of the insert’s head, so use a drill size of 15.5mm. A hole this size should require just a gentle tap to fit perfectly. But check your own boat’s insert head diameter before selecting the drill size. Note that the bends in the plate are made well away from the edge of the central hole to prevent distortion and weakness. An alternative plate material to use would be 2mm stainless steel. This would be stronger, but far more difficult to cut and drill.

Boat frame alignment has to be carried out before riveting anything in place. Rig the bare boat frame up with all bolts and any new plates in position but loose (bolts not tight, plates not riveted). Set both hull beams level using a spirit level on each. Pack up as required. Measure opposite diagonals to check the frame is square. Tighten all bolts. Drill and fit stainless steel pop rivets where access is visible, then remove affected beams and re- fit upside down to fits remaining pop rivets.

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Note. With both JP methods, access may not be possible to drill or pop rivet with the beams in position. You may have to put some gap filling adhesive/sealant under the plates and leave overnight to dry. Next day the plates should be stuck firmly in place. You can then remove the beams to drill and pop rivet them.

JP Trial Method 2 This method also has the advantage of no dismantling being required. It’s simple and non destructive, but like method one, should be restricted to beams that show only slight movement of the inserts and little wear or corrosion of the internal spacer tubes.

Because the 2mm thick aluminium plate, doesn't need bending it may be structurally stronger. The central hole diameter should need to be the same 15.5mm (check yours first). Again, if you used stainless steel it would be stronger, but much more difficult to cut and drill.

Boat frame alignment now needs to be carried out before riveting anything in place. Rig the bare boat frame up with all bolts and any new plates in position but loose (bolts not tight, and plates not riveted). Set both hull beams level using a spirit level on each. Pack up as required. Measure opposite diagonals to check the frame is square. Tighten all bolts. Drill and fit stainless steel pop rivets where access is visible, then remove affected beams and re- fit upside down to get access to remaining pop rivets. Note. With both JP methods, access may not be possible to drill or pop rivet with the

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beams in position. You may have to put some gap filling adhesive/sealant under the plates and leave overnight to dry. Next day the plates should be stuck firmly in place. You can then remove the beams to drill and pop rivet them.

SG Trial Method 1 My Own Trial Method 1 described here is untested to date, but simpler than SG-1 or SG-2. No special riveting tools are needed. It’s also reversible and non destructive, but requires the insert removing, then refitting. It still leaves other options available, and involvesthe least cutting, drilling or grinding. The spacer tube remains in situ unaltered. This method uses thinner 1.2mm thick stainless steel plate which need cutting and bending. The loose insert is removed, then pressed through a new plate and glued/sealed in place. The adhesive/sealant used, should be the slow setting, gap filling, solvent type.

Fig 1: Extracted insert and new plate.

Fig 2: Insert pressed into new plate.

You'll need these tools• • • • • • • • • •

Vice. Bench Grinding Wheel (or file). Electric drill. Drill bits, sizes 4mm and 9.5mm, plus a 10mm or larger and a countersinking drill bit (or large standard drill bit) A 10mm car mechanic's socket. Fine toothed hacksaw. Spirit level. Pop rivet gun – To pull 4mm or larger rivets. Hot air gun or gas gun (may be required). Adhesive/Sealant – waterproof, solvent type.

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You'll also want these materials 1. Some off cuts of 1.2mm stainless steel sheet. This can be purchased for around £5 per 2kg weight in random sized pieces from eBay. The offcuts I received comprised 5 sheets at 1.2mm thick, mostly about 150mm squares. Much more than you'll need. Use only 1.2 -1.5mm thick stainless steel for this method to avoid making the beam too oversized. 2. Stainless Steel (or Monel Metal Pop Rivets) size 4mm diam. x 9mm length. I normally use 4mm diameter stainless steel pop rivets. These are large enough, and leave an option to up rate the diameter later, if required. 3. Gap filling sealant (Any solvent base gap filling sealant/adhesive should do). Cut the stainless steel plate to the dimensions given below. The flat area between the dotted bending lines is usually about 17-18mm. Make it fit the contour of your beam.

Smooth off any sharp edges and round off the corners. Grip your plate in a vice with some scrap wood

Fig 3: S/S Plate - 1.2mm thick. behind it (Fig 4) and drill the holes in the positions and sizes shown in Fig 3. Use a slow drill speed and heavy pressure. File the burrs off after drilling. Remove the insert from the worn cross beam hole. You may need to use a hot air Fig 4: Drill through into waste wood. gun or similar to heat the internal spacer tube to expand it. The inserts can be difficult to remove. I found that a suitable sized rod inserted through the opposite end of the beam hole may allow you to tap out the insert from behind. Articles “Beam Repairs (1)” and “Beam Repair (2)” cover this in more detail. Bend the plate to the contour of the cross beam. Hold the plate hole over the beam hole and insert a 9.5mm drill bit into the frame to help centralise the plate. This will keep the holes in line while you mark the bends.

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You'll need to take particular care with all marking and bending. A cardboard template marked and scored to test the bending lines may help to get your bends exact. Bend the plate over in a vice by gently tapping it close to the vice jaws.

Fig 5: A light chamfer allows the insert’s head to sit down flush to the plates surface

Fig 6: Sketch, shows radius at back of insert's head and the thinner lead in section.

Before pressing the insert into the plate, countersink the outside edge of the central hole Fig 5. This will make space for the radius at the back of the inserts head to sit tight to the plate surface, Fig 6. Pressing the insert in. Clean the plate and insert with acetate. Then, just before pressing the insert into the plate, smear some adhesive/sealant under the insert’s head. Fig 7: Press the insert through into a 10mm socket. Open your vice and place the end of a The plate should already be bent to fit the beam’s contour. Photo is to illustrate the method only. 10mm socket on the back of the plate directly behind the hole. Slowly and carefully tighten the vice to press the insert through the plate and into the socket behind, Fig 7. Wipe off surplus adhesive. The insert is now an interference fit which makes it almost impossible to remove. Repeat for the other worn holes. Fit the repaired plate into the beam and test fit the beam back into the hull beam brackets. You may find that the repaired cross beam is now tight in the hull brackets. This is

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because the beam will be 2.1mm wider if repaired on one side only, and 4.2mm wider if repaired both sides. The frame brackets can be knocked apart slightly using a hammer via a length of wood held behind the bracket’s fixing holes. For reference- The “standard” internal distance between hull brackets is – 85mm. Note: If you think the internal spacer is too worn (e.g. the beam squashes up as the frame bolt is tightened), consider eliminating this wear by, 1- Replacing the alloy spacer tube with a new, slightly longer one. Or 2- adding a suitable stainless steel or alloy packing washer at one end of the spacer. The latter is just about possible with one insert removed. Squashing the beam in a vice at 90 degrees to the frame bolt angle may be help to position it. Standard measurement for the spacer tube is 77mm length x 12.5mm O.D. x 9.5mm I.D. = 1.5mm wall thickness. You can now locate the new plate with it’s original insert, back onto the beam with some suitable adhesive behind it. Assemble the boat frame. Check the frame is level and square, then fit all framebolts and tighten as normal. Leave overnight (or as per adhesive instruction) until set. Finally, remove the beam to drill and fit the stainless steel pop rivets.

Remember, this is a trial. I don't envisage any problems, but please let me know if you find any, so that I can pass your information [email protected]

Syd Gage Catapult 506 END.

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First published April 2014 Last update Dec 2016