On Sunday, August 10, 2014 9:10:41 PM UTC-6, Six-Seven wrote:
Here is an update and questions on the original thread about needing a strut part - the fill valve. We now have not one but two different (used) parts from an L13 I am working with at this point. Pictures and Blanik manual documentation can be found at http://aviation.derosaweb.net/Blanik



One replacement part is the original Blanik type that connects to the Blanik T-handle fill apparatus (and then to a nitrogen bottle) via a sort of ball and socket affair. The internal valve itself is held in check inside the fitting by a spring that is part of the assembly and depressed by the T-handle. There appears to not be any rubber seal of any sort in the fitting or the adapter, just a metal on metal seal. The original fitting leaked big time at this ball/socket joint while the new one leaks just a little. We tried to fill the strut to ~450PSI but no joy with this assembly.



Now onto valve style #2. This uses a standard Schrader valve insert like on a car/cycle/bike. I heard from a couple of quarters that this is a US adaptation so that they didn't have to buy the Blanik fill adapter. The question is how to marry this with our nitrogen bottle. I was able to locate the correct brass fitting for the bottle's hose end (flare) that gives me 1/8" NPT which I can adapt that to most anything. But what do I do at the Schrader valve end? The idea of holding a standard chuck against the valve at 450 psi doesn't seem quite rational. Is there such a thing as a screw on chuck? Can't find one from any of several sources (Napa, Grainger, McMaster, etc).



Questions

======

- Is it possible to safely hand-hold 450 psi at the valve?

- We assume the strut should be filled without having to raise the fuselage to unload the strut. Yes? We tried it both ways and it didn't matter.

- The manual (see http://aviation.derosaweb.net/Blanik) alludes to filling the strut with liquid "only in the vertical position". Has anyone done this? Is the strut X% hydralic fluid and Y% nitrogen? How much is X and Y?

- The manual says at fully inflated the distance X (Fig 301) on the strut should be 13mm (about 1/2"). This location is conveniently located under the strut boot. Sigh.

- Does it appear that the strut is just BAD? Can it be rebuilt?

- How have you filled the strut?

- Anyone know of a back issue of Soaring mag. that deals with all this?



Any advice is welcome.



Thanks, John

Perhaps others can confirm. I seem to recall an anecdote about there being a bleed hole that the seal passes if the strut is fully collapsed. Thus you need to extend the strut while elevating the tail before filling because if you do it when filling it may be possible for the strut to expand fast enough under high pressure to launch the glider several feet into the air once the seal moves past the bleed hole.

Frank Whiteley