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Letov Sluka.

Posted: Tue Aug 06, 2019 11:08 am
by Bill McCarthy
My Sluka (now in the SSDR category, was under the LAA ) employs a 90mm thin walled boom tube as the fuselage, at the front of which sits a Rotax 447. Many Sulks are now defunct due to radial cracking emanating from a forward attachment hole for the wing. I dye penetrant tested mine every year for annual inspection and any cracks found meant a write off for the microlight as the boom tube is no longer available. There is a “fix” if no cracks are found and that is to fit a reinforcing tube inside the boom tube. My Sluka is clear of defects and I am about to carry out the remedy. Since the original Sluka is long out of production ( there was a new model advertised but priced double what it ought to be) could the round section tube be replaced by a rectangular one with radiused corners, say, 75mm x 50mm. How much would be in it regarding inflight stresses. Mike Wittaker had a micro design that used square section tube many years ago - seen at a PFA rally.
A rectangular tube would be much more builder friendly for drilling and applying fixtures.

Re: Letov Sluka.

Posted: Wed Aug 07, 2019 7:46 am
by dmcnicholl
Bill, I cannot advise on the engineering aspects of changing to a square or rectangular hollow section but depending on the required length of the round tube insert might it be possible to have an insert custom machined and fitted?

If you think that might be a way forward and you want to discuss with a machine shop I'd suggest Shandwick Supply in Evanton as one possibility. (I have no connection with Shandwick supply but have seen some of their work.)

Re: Letov Sluka.

Posted: Wed Aug 07, 2019 12:39 pm
by Bill McCarthy
I have the sleeve machined (by the Queen’s men) all ready to fit - it’s just a nuisance taking the engine mountings and other fittings away. I will get round to it ! Basically, I would like to make an attempt at making a near copy of the whole microlight. I have enough aircraft quality tubing (round) of various sizes to make one but not a boom tube, hence the query on rectangular material.