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Thread: My first U.L. an MX Sprint, need some maintenance advice

  1. #1

    Join Date
    Sep 2015
    Location
    old 15 acre homestead on N.D. prairie
    Posts
    45

    My first U.L. an MX Sprint, need some maintenance advice

    I just took possession of this on Sunday and just got the Rotax 447 stripped to block. I've done a lot of work on 2-stokes and upon inspection found a little too much scoring in the rear cylinder so its coming apart to check cylinder clearances and the least it will get is new rings depending on how worn it is. It's been hanging in a barn for about 8 yrs. and in surprisingly good condition. The fabric seems good, but I was wondering if there is a treatment or wash that will help restore its luster and clean it at the same time. There are a couple very small 1/4 inch at the biggest tears on the back of the ailerons and one on the rudder, so if somebody has a favorite glue or patch method for these small blemishes I would greatly appreciate hearing them. If there are serial#s where would they be as I was wondering how to find out what year it is. It has a belt drive and points in the engine if that's a clue. Also is there a consensus on using pistons from MFSupply? I'm in my mid 60's and finally managed to get something to fly as I had to quit working about 9 yrs. ago my dreams of an old air knocker were dashed. Anyways, prob'ly seeya on this forum again. Cliff

  2. #2

    Join Date
    Jan 2013
    Location
    Central Texas
    Posts
    7
    Cliff, the fabric may look good, but you have to be careful as looks may be deceiving. Over time the sail fabric may become weak. You don't want it rupturing or splitting in flight. I thought I read something years ago about a testing tool to measure the strength of the sail fabric- some sort of tool which would measure the strength of the material by pressing a probe into and against any given area of fabric. If the fabric held at a given pressure without poking or punching through the fabric, it would pass as flight capable.

    Can anyone verify this? It's been such a long time ago that I heard about such a thing.

    You may wish to consult a sail maker if you can find one in your area. Years ago, for me, there were a couple of sail makers in my area who made new sails for Quicksilver MX ultralights.

    I would also consider replacing the drive belt(s) for the propeller before attempting flight.

    Hopefully someone here with more expertise than I will post here about what to do and how to check or test your fabric to insure it is still safe for use in flight. What area of the country are you in? I am in central Texas. I used to fly my own Quicksilver MX back in the mid 1980's, in Michigan, and lately have been toying with the idea of getting another ultralight.

    I also just sent you a PM (Private Message) regarding this subject. Check your private message mail box here. Hope to hear from you.

    Rick.
    Last edited by Rick G.; 10-01-2015 at 12:57 PM. Reason: corrected spelling errors.

  3. #3
    Dana's Avatar
    Join Date
    Jul 2011
    Posts
    942
    The expert on all things related to old Quicksilvers is Mark Smith at http://www.trikite.com/. He was a Quicksilver dealer back in the day and still sells parts for the older models and their engines. There is also the "Quicksilverultralightowners" Yahoo group with a lot of knowledgeable people posting there (including Mark).

    Quicksilver used to sell a fabric punch tester; it was a spring loaded deal with a small tip; you pressed it on to a specified load and if it went through, the fabric is no good. The Maule fabric tester used on standard aircraft with doped fabric is similar but the numbers are different. The cheap and dirty method is to push as hard as you can with your finger tip... if it breaks through, the fabric is no good.

    Nothing more than a mild detergent should be used to clean the fabric. If it's badly faded, it's likely no good as UV light is the primary thing that destroys both the color and the strength. If the fabric is good, small holes can be patched with sailcloth repair tape which you can get from an marine supply store; larger tears need to be sewn first and then patched.

  4. #4

    Join Date
    Sep 2015
    Location
    old 15 acre homestead on N.D. prairie
    Posts
    45
    I should have given you guys a little more background on me. My childhood was like an apprenticeship in rebuilding old aeronca champs,my dad did'nt like cheifs as bigger guys found it more of a tight fit and they were'nt as good to hunt out of. Any way we recovered,modified and generally did complete restorations as his one of many hobbies. I was a very lucky young man to have learned so much about aircraft and flying at my young age,so flying was'nt much of a novelty, but more associated with lots of cleaning parts and hand sanding frame tubing. But I always vowed I'd have one when I retired. Well, life always throws them curves and I was dis-abled in 07, short of a full pension for retirement so my finances have not allowed me to pursue my privates and a real plane. To ease your worries about the sprint the fabric is quite good being it was under a roof all the time and well cared for. The guy I got it from has a 150 so the MX kinda got sidelined for his kids but they show no interest and he sold it to me. I have ordered new bearings, pistons,belts,points condensers, you name a replaceable part and it's on it's way. And any A&P prob'ly has a fabric punch in his tool chest,but if I thought it was in need of testing I would replace without question. If my memory serves me right there are 4 test grades with the punch,last being fail. I'm not familiar with the type of fabric on the sprint, that's why I was asking for some repair advice. It's flyable the way it is but I'm just a little bit picky about preventive things. Another question I have is how picky are they about the weight as when the instrument pod is mounted I'm 1/2 pond over. It's not much,but I've seen some inspectors that would'nt let that fly, so it's most likely my luck of the draw. Thanks for the advice guys and I'll tell you how I make out with this state registration.

  5. #5

    Join Date
    Nov 2013
    Location
    Redding, CA
    Posts
    11

    Dacron sail cloth testing

    Here's a video with some useful information on inspecting dacron sail cloth. The last segment is particular to the Quicksliver tester but in the middle segment (4:25 on the clock) it says that Quicksilver recommends a minimum of 41 pounds with a Maule fabric tester.

    https://www.youtube.com/watch?v=1WEO6l8LxHs

    Here's another one specific to the Quicksilver tester

    http://eaavideo.org/video.aspx?v=666091412001


    Regarding pistons, I've used SPI moly-coated pistons with good results. The moly coating seems to mostly wear off after about 50 hours or so, so I'm not sure whether it's really a benefit or not in the long run. Mfgrs supply sells Weisco pistons which I haven't used. From what I gathered from cruising the sled web sites, the SPI pistons seemed to be preferred by the racers. Whichever pistons you use, it's important to be very aggressive wit the honing. You need deep hone marks to hold the oil. Ranier Ultralights (www.ruleaviation.com) has the right type and grade of hones to do a good job. I've also had them rebore cylinders oversize with good results. If you've not had previous experience operating a 2 stroke engine in an ultralight, I highly recommend this video as a starting point.

    http://eaavideo.org/video.aspx?v=626943072001

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