Ballast tube in wing inspiration

[cadzilla]

I've been doodling how to put a ballast tube in a built up wood wing and just come up blank on what would be a good solution. I just hit a wall.

So, I could use a picture of what you've done, maybe a pointer to another web site, or just a good write up. Anything.

Thanks;
RichK

I could be wrong.
Your mileage may vary.
Always wear a seatbelt.
Don't drink and drive.

[jtlsf5]

I used to use 1/2" ID cardboard tubes (I think they were from model rockets). Starting at the wing root cut out enough ribs to take the length of tube you want to install. Best place is just ahead/behind the spar, as close to the CG as possible. The tube should install through and flush with the last rib, and be capped on the outer side of the rib with a piece of ply.

Get some 1/2" OD brass tube and fill with melted lead. I use a 2 X 4 drilled to take the tube, use an old tin can and butane torch to melt the lead, and definately do it outside. Once the tubes are filled, cut to length to give your self slugs of the desired weight. For partial ballast, use 1/2" hardwood dowels as spacers. The spacers should go into the tubes first followed by the ballast. You want the weight as close to the fuse as possible.

JT

[Batmanwpg]

If this is a RES type wing, why not install the tubes with access being gained by opening up the spoiler? I prefer to make my tubes from fibre glass on a piece of pipe.

[cadzilla]

About how long did you make the tubes? Did you wrap the tube tight against the shearweb with carbon tow ?
RichK
I used to use 1/2" ID cardboard tubes (I think they were from model rockets). Starting at the wing root cut out enough ribs to take the length of tube you want to install. Best place is just ahead/behind the spar, as close to the CG as possible. The tube should install through and flush with the last rib, and be capped on the outer side of the rib with a piece of ply.

Get some 1/2" OD brass tube and fill with melted lead. I use a 2 X 4 drilled to take the tube, use an old tin can and butane torch to melt the lead, and definately do it outside. Once the tubes are filled, cut to length to give your self slugs of the desired weight. For partial ballast, use 1/2" hardwood dowels as spacers. The spacers should go into the tubes first followed by the ballast. You want the weight as close to the fuse as possible.

JT

[jtlsf5]

About how long did you make the tubes? Did you wrap the tube tight against the shearweb with carbon tow ?
RichK

The tubes were typically 12" as supplied, and that was what I used. In cases where I needed more capacity (on a foam wing, not built up), I put one ahead and one behind the spar. I don't think I would go any further out than 12", as you would start affecting turn efficiency by placing weight too far out in the wing.

A 12" x 0.5" diameter tube filled with lead calculates to a little over 15 oz. With one on each side, this would net you about 30 oz. I don't know of many wooden structures that would be happy with nearly 2 lbs in the wing. This puts a lot of stress on the rest of the wing, and structural integrity of the entire wing is at risk.

I didn't do anything to tie the tube to the spar. With a number of ribs supporting the tube there is little tendancy to move. You could always add ply doublers to the rib portions that contain the tubes for added security.

I would also fully sheet the portion of the wing that you put ballast tubes in. Pure open structure relies solely on the ribs for strength; sheeting gives significant added strength to the entire structure.

JT