Scale Need advice on acceptable practices on splicing spars, etc.

[Dave1953]

I am building my first giant scale model ( 1/3 scale Balsa Super Cub) and am seeking advice on splicing, reinforcing, etc. Sometimes I run across a situation such as splicing a false spar or something similar and the plans do not call for any reinforcing but I think it would make things stronger by scabbing a piece over the splice as long as it don't interfere with anything else, is it proper to do so? Another situation that has arose is say the notch cut in a rib that the main spar goes into is not a tight fit is it ok to glue a one inch piece of 1/4" square balsa in the corner to reinforce the joint ? I know that every extra piece adds weight but I am of the opinion that I would not mind having my plane a little heavier knowing it is a little stronger. Any advice you experienced builders can give is appreciated.

 

[dhal22]

You should be good on all your ideas. A Cub will have plenty of lift as far as worrying about weight. Post some pictures.....

 

[Snoopy1]

Normally a splice if done properly does not need any extra support. As long as the splice is 5 times longer than the thicknesses of the wood it is just as strong if not stronger. But the two surfaces must flat, smooth, square and glued with a good Wood glue and clamped until dry. And the joint must be ever so slightly thicker than the wood was.
A rib my be loos on the spar joint as long as there is no gap. If ther is a gap take some shavings from a plane then cut it so it looks neat and push it in to the gap and then glue it. Done

 

[Ironrob]

Look up “scarf joint” if you want to get an idea of what to do. Put the spar pieces on edge, side by side with an overlap the length you want for the joint. Cut the bevel with a razor saw, down through the overlapped area and the pieces should fit together perfectly.

 

[sailr]

This should give you a lot of ideas:

https://www.google.com/search?q=r/c...8KHfV5AuUQ9QEwBHoECAUQCg#imgrc=TB49IEBO57vXyM:

 

[Bartman]

Normally a splice if done properly does not need any extra support. As long as the splice is 5 times longer than the thicknesses of the wood it is just as strong if not stronger. But the two surfaces must flat, smooth, square and glued with a good Wood glue and clamped until dry. And the joint must be ever so slightly thicker than the wood was.
A rib my be loos on the spar joint as long as there is no gap. If ther is a gap take some shavings from a plane then cut it so it looks neat and push it in to the gap and then glue it. Done

for that to be true though, i believe no sanding is allowed, the parts have got to be cut or machined to fit, sanding loads the wood grain up and prevents full penetration by the glue.

 

[Bartman]

I am building my first giant scale model ( 1/3 scale Balsa Super Cub) and am seeking advice on splicing, reinforcing, etc. Sometimes I run across a situation such as splicing a false spar or something similar and the plans do not call for any reinforcing but I think it would make things stronger by scabbing a piece over the splice as long as it don't interfere with anything else, is it proper to do so? Another situation that has arose is say the notch cut in a rib that the main spar goes into is not a tight fit is it ok to glue a one inch piece of 1/4" square balsa in the corner to reinforce the joint ? I know that every extra piece adds weight but I am of the opinion that I would not mind having my plane a little heavier knowing it is a little stronger. Any advice you experienced builders can give is appreciated.

if you hold a piece in the air that you were thinking of adding to the build and it doesn't float away, then it was too heavy to go on your plane!

but seriously, if it isn't necessary to repair a poorly fitting or broken piece, try not to add stuff so it turns out as light as possible.

 

[TonyHallo]

Best time to put your plane on a diet is during the build.

 

[dhal22]

You take care of the grams and the ounces take care of themselves. Or something like that.

 

[Dave1953]

You take care of the grams and the ounces take care of themselves. Or something like that.

Thanks to all who responded. All advice has been taken under advisement.

Dave