Questions and Answers 3
Q.......................I have an older MX and the sail has a funny type of stitch for some of the seams. The threads are coming loose in a few spots too. Is there any way to fix this or do I need a new sail ?
A....................... This sail is an early eighties sail made in Israel. they used really crappy thread that wasn't stabilized during manufacture. The thread should actually outlast the sail by many years as it is difficult to test the thread. If the thread is much better from UV exposure than the sail material, then testing the material says the thread is OK too.
The thread is made of the same material as the sail, ie, polyester or perhaps the word Dacron is more recognizeable, which is a tradename from a manufacturer.
I am sorry to say, that most of these sails have long since been replaced with better quality products, in both thread, sewing and materials.
One easy way to recognize these sails is the triple zig zag stitch used during their manufacture. I haven't seen this stictch on American made sails, just the bad ones. Rather than having large one stitch per zig and zag, the Israli made sail has three very small sticjhes making up each leg of the zig or zag. In other words, there are three small stictches before either a zig or a zag is made.
Q......................I have some batten tips that have poked holes in the upper edge of my sails. Can this be repaired or what ?
A.......................Unless there was a crash of some sort, and the rib was forced into a position that tore the sail, I would guess the material has started to fail and the battens will continue to tear through the material. It is not economical to repair this type of failure as the basic cloth has failed. A new sail is the best fix.
Q.......................My ribs have snuck out the rear of the batten pockets. Is there a fix ?
A........................There are several fixes, and I will start from the first to my latest one.
Early planes had straight battens near the trailing edge, with small rubber tips glued on. the tips had oval holes in them, I guess for retaining the ribs with either wire or tiewraps.
The change to the MX style rear tip was made in the very early production and it is referred to as the Zee bend tip. It is fairly long, with two bends that allow it to nestle the rib just in front of the spar, and the tip makes two bends to continue back over the top of the spar. A small slit in the upper surface of the sail allowed the rib access to the batten posket.
New sails retained the batten due to tension of the material, but after awhile, the rib could merely lift a bit, disengage the bends from behind the spar, and allow the rib to creep rearwards. Ribs have fallen out of pockets on long flights. Ribs have backed into the propellor and damaged the prop, a costly error.
To retain them, the factory suggested adding two slits under the wing, turning the tips over 180 degrees, and installing the rib from the bottom. This made the installation more difficult and sometimes, holes were melted through the upper surface of the sail which looked really bad. But it di retain the rib better.
Another problem with the Zee bend tips was that they hung over the spar by a ways, and caught on anything that drug along the spar, such as wires during assembly of the plane, rags during washing, and on anything that might catch on them during handling. Sometimes they broke off making removal of the rib more difficult.
My suggested solution for keeping the ribs in the sail was to place a tiewrap over the rear spar, through a small hole melted just next to the rib. Another way was to melt tweo holes, and run the tiewrap over, through a hole, under and back over holding the rib to the sail.
The Sprint sails are also single surface, and they used the MXL C shaped rear tip. This allowed a bit of load to engage the rear tip with the spar, thus holding the rib securely in place.
This works well, but tends to offset the main portion of the rib either up or down depending on the way the rear tip is installed. Having the tips one way makes the last few inches of the sail bed up, and reversing them makes the sail bend down, acting as little flaps clear across the trailing edge.
The last and maybe the best fix, is my personnal Y tip. this tip looks like the letter Y, and engages the spar, placing the rib in the center. they are made extra long so the older MX ribs can have their tips replaced with the Y tips. These tips locate the ribs properly, require no special holes or tiewaraps.
Q........................I have an MXL and have removed all the ribs into a pile. I see there are two ribs that are called Tip Ribs. How do i find them in the pile of ribs ?
A.........................The tip ribs have a harder job holding the sail up at the ends than do the nromal ribs in the middle of the span. The sail makes a sharp angle down to the tip tube and places much more load on them.
They can be separated by merely weighing each rib. the tip ribs are sleevd almost full length to give them a bit more resistance to bending. they are easy to tell from the normal ribs.
Q........................I've installed my new MX sail but the small tubes at the end are not long enough to push the outermost compression strut out to tension the sail. Can these be fixed ?
A........................ Best bet is to buy new blank tubes and recut them a bit longer.
I pull the sail just about as hard as I can, using the compression strut to push the other way. Then mark the tubes about an 1/4 inch long. They should be cut so they are a good fit to the side of the batten at the end pocket of the sail. the cut is referred to as a 'fish mouth' cut. Check the original tubes for a pattern.
BTW, these tubes should be installed on the top of the end compression strut to have the best angle when pushing out on the compression strut.
Q........................I purchased some new sails with extra ribs. What do I do with the spoiler panels ?
A........................Cut them to fit the smaller pockets, and purchase four new crossover plates to join them together just as the original spoiler panels were joined. This looks good rather than installing the full panels and having the ends misalign and the panel ride on top of the extra ribs.