Fixing Anti Flutter Weight

[Skippydiesel]

Hi,

My aileron anti flutter weights, have been drilled in the wrong place. I must redrill, but to do this I must fill the first holes.

Melting lead, to pour into the first holes, is not in itself a problem (as a child I made lead fishing weights). However I am concerned that in so doing I may cause a greater problem.

My concern is, will the hot liquid lead cause partial melting of the weights? - making the problem worse?

I have been considering placing the lead weight in the freezer for a few hours befor attempting to pour the molten lead into the drill holes - is this a good/bad idea/necessary at all?

Has anyone else faced this problem?

[GraemeSmith]

I have some (very) limited experience in repairing yacht keels. Partly casting new lead into old almost never works. The interface between molten and cold never flows to provide a "bond"- or the heat of the molten causes unexpected escapes as the molten lead follows any imperfections in the block of lead. I suspect your freezer idea would ensure the new lead did not "bond" and would leave it prone to falling back out at some point. Because of all these difficulties - we used to recast the whole keel.

Faced with what you describe - I would be inclined to make sure the hole was clean and bright. Run a reamer or coarse file "badly" through the hole to rough up the surface inside the hole and then make a pour of West Epoxy with a small amount of Colloidal Silia fibers for "tooth" and to give it a little thermal flexibility and then filled with fine lead shot. Seal one side with tape and then slow pour (to avoid bubble entrapment) and "fill" the hole. With a high enough density of shot and just enough resin to act as a binder and glue I think you would get close enough to the correct density as makes no difference.

This is just an idea. I have a lot of faith in epoxy with which I have considerable experience. It is how I would approach it and if it looked OK after repairing - I would personally fly it. But I have never carried out this idea. It is just that. An idea.

It may well be that buying new lead blocks is cheaper than the cost of the epoxy materials, lead shot and the faffing around!

[Skippydiesel]

Thanks Graeme,

I also had your second idea; fine/small lead shot (which I have) with high strength epoxy (Devcon, which I have), mixed to a putty consistency (lots of shot : small amount of epoxy). This would not "pour", so would have to be packed/rammed into the drill holes. I would hope the packing would eliminate voids and result in minimal weight loss while maintaining very near the original gross weight (ready for adjusting as per Sonex plans instructions).

Purchasing new weights? - possible but time consuming.

Casting new weights? also possible. The ones I have were made/cast by the first builder (who also miss drilled them) and are close to perfection.

I am leaning towards the epoxy fix, for all of the reasons you articulated.

[sonex892.]

Hi,

My concern is, will the hot liquid lead cause partial melting of the weights? - making the problem worse?

I have been considering placing the lead weight in the freezer for a few hours befor attempting to pour the molten lead into the drill holes - is this a good/bad idea/necessary at all?

Has anyone else faced this problem?

I think you are overthinking it Skippy. I think you will be wasting your time with chilling the lead, I'd be more worried about the lead cooling too quick and starting to set before reaching the bottom of the 3/16" hole. I guarantee pouring molten lead into an existing hole in the weight will not melt what you have. Obviously you will need to block off the bottom of the hole. I cut a little deep on one of my balance weights and needed to add a bit of weight. I just built it back up with a blowtorch by melting more lead into it to build it up, then filed into back to shape with vixen file. It was quite easy.

[Skippydiesel]

Thanks all - I have gone with the epoxy: lead shot option - looks good!