Illustrated steps for replacing broken or damaged spar joint ferrules. Hardware illustrations are schematic and not to scale.
Steps 1 through 7 are below.
Step 1 Disconnect the end cap
Pull the end cap and its cylindrical insert out of the spar tube a few inches. The thick black elastic is attached at the insert tip; keep the two thin external lines attached to the cap plate.
The next section shows how to draw out and secure the elastic while loosening the knot.
Step 1 (Continued) Hold the elastic and loosen the knot
Pull enough elastic cord from the tube to leave several inches of slack between the tube opening and the end cap. Clamp the locking pliers onto the elastic just outside the opening to prevent it from retracting.
Let the end cap rest to the side, keeping the two thin external lines attached.
With the cord secured, gently loosen the existing knot. If needed, use needle-nose pliers to work it open without cutting the cord.
I recommend photographing each step as you go. Your photos will provide a useful reference when reassembling the spar.
Once the knot is untied, release the locking pliers and allow the elastic to retract into the tube. We will retrieve and rethread it during reassembly. After the cord clears the damaged joint, slide the sections apart to expose the connector that needs replacement.
Step 2 Identify the damaged joint
In this repair, the connector was bent. When I tried to collapse the spar for storage, the sections jammed and would not pull apart. The damaged joint also prevented the spar from fitting and working properly.
The pointing finger marks the damaged area. The enlarged cutaway illustrates how a bent connector can bind inside the tube.
A connector may also break rather than bend. The lower illustration shows a fractured ferrule. Either type of damage may require replacing the connector.
Step 3 Remove the old ferrule pieces
The connector piece in the tube toward the outside of the antenna has the tighter fit and may be harder to remove.
Use a 3/8 inch threaded rod to push the connector out. Once enough is exposed, grip the ferrule with pliers and remove it.
The piece on the center side should come out more easily. Look inside the tube for any remaining fragments and try to retrieve them.
If the connector is difficult to remove, try the alternative methods described below.
Step 3 (Continued) Another removal option
If the connector remains stuck, clamp locking pliers firmly onto its exposed end.
This damaged connector will be discarded, so marks on it are not a concern. Keep the jaws clear of the spar tube.
Hold the pliers approximately at a right angle to the tube. Use a rubber mallet to tap the metal jaw area, directing the blows away from the tube opening. The illustration shows the mallet moving from left to right. Use light, controlled taps. Stop if the tube begins to split or the pliers slip.
If the connector still will not come out, the next section describes the last-resort method used in this repair.
Step 3 (Continued) Last resort drill method
When the other removal methods did not work, I drilled into the damaged plastic connector. I worked slowly until it came free. The illustration shows the removed connector still attached to the drill bit.
I used a 5/16 inch bit, slightly smaller than 3/8 inch. Check the clearance inside your spar before choosing a bit.
Keep the bit aligned with the connector and clear of the spar wall. Do not let it cut into or strike the tube. Work slowly, pause frequently, and stop once the connector comes free.
Drilling can generate enough heat to burn your hand. Secure the tube without crushing it, keep your hands away from the rotating bit, and allow the tube and bit to cool between attempts. Wear eye protection.
This was the last resort that worked in my repair. The photo documents the extracted connector; it does not establish a universal bit size or drilling depth.
Step 4 Insert the replacement ferrule
The replacement ferrule is black plastic with a raised center ring. A faint lengthwise groove marks the end to insert first. This shallow line runs from near the center ring toward the end, stopping a few millimeters short of the edge. It can be difficult to see.
Insert the marked end into the spar section that retains the ferrule. This replaces the connector removed earlier. The marked end has the tighter fit; the unmarked end should slide more easily into the adjoining section. Keep the ferrule aligned with the tube. When fully seated, the center ring should meet the tube end.
In my repair, the ferrule went in only partway. I brought the exposed ferrule end into contact with concrete while keeping the spar straight, using that contact to seat it until the center ring met the tube end.
Use caution. This impact method can break the ferrule or damage the spar tube. Stop if the ferrule tilts or cracks, or the tube deforms. This describes the method I used.
Step 5 Thread the elastic cord through the sections
Before threading the cord and reassembling the spar, check that each wire clip is in the correct order and position. From the outside end toward the center, the order is blue, green, red, yellow, gray, then black.
Step 5 (Continued) Thread and secure the elastic cord
1. Start with the first spar section. Pull the elastic out to its working stretch without overstretching it. Clamp the locking pliers onto the cord immediately outside the tube opening. This keeps the cord from retracting and leaves the exposed length loose for threading.
2. Feed the loose end through the second section. When it emerges, hold it firmly before releasing the pliers at the first section.
3. Pull the cord through, then clamp it again immediately outside the second section’s opening.
4. Repeat this process for the final section: feed the cord through, hold the emerging end, release the previous clamp, and pull the cord through. Clamp it at the final tube opening.
5. Leave the pliers in place with the exposed cord secured, ready to attach the end cap.
Step 6 Thread the ring and end cap
Keep the locking pliers on the elastic at the final spar opening so the cord cannot retract. Slide the separate cylindrical ring onto the free end of the elastic first.
Next, pass the free end through the cord hole in the end cap. Keep the two thin external lines attached.
Slide the ring and cap together into position. Two lengths of the same elastic should remain visible: the cord coming from the spar and the free end returning out of the ring.
Step 6 (Continued) Prepare the cord for knot tying
With the ring and cap assembled, the cap plate sits at a right angle to the cylindrical insert. Fold the extra free length back alongside the cord from the spar, ready to tie the knot outside the ring in Step 7. Keep the cord secured with the locking pliers, and leave the cap outside the spar tube until the knot is finished.
Step 7 Tie the elastic knot
We need to tie two inner turns resembling a taut-line hitch, with the final outside hitch omitted. The illustration shows these turns on the end-cap assembly. The cord loops are exaggerated for visual clarity.
Tighten the turns into a compact, secure knot, leaving as little free tail exposed as practical while retaining a sturdy knot. Keep the locking pliers in place until the knot is complete. The tightened knot should resemble the compact attachment shown below.
Step 7 (Continued) Seat the end cap
Once the knot is complete and secure, remove the locking pliers. Guide the free tail and knot into the spar tube, then slide the end cap back into position. Keep the two thin external lines attached to the cap plate.
The completed assembly should now resemble a working spar.
Source: BuddiHEX Repair, Changing the Spar Joint Connector, by Daniel AF4OZ.