Gluing on the bridge but the wings won't cooperate

[nkwak]

This is more of a rant but I'm wondering if this is a humidity issue: I'm ready to FINALLY glue the bridge on my first build down but I'm doing dry fit after dry fit to see if I have the radius on the underside just right. I mostly do but for the wings which seem to be curving up so that I can slip a sheet of paper beneath. I'm assuming that since the wings are less than 1/8" thick they're more prone to curving up. I've done many dry fits with both a huge C clamp and Stewmac bridge clamping caul and the design just wouldn't work with the shape of my bridge so I made my own out of walnut scrap, some hardware and double-sided tape. It clamps the tail of the bridge better but not the wings.









PS: the tape is for positioning and I've got some hot hide glue ready to go for the actual gluing. I just can't get the joint to 100% contact because of the wings.

[nkwak]

Well, I did stain the bridge. It's made of Honduran mahogany whereas all the other dark woods are Indian rosewood. Maybe that would introduce more moisture into the wood? I stained it a couple of months ago. I think your point of sanding the ends down more is probably more likely. I simply taped a piece of 180 grit sandpaper to the top and despite primarily using a circular motion I did also fall into the bad habit of going back and forth. That might have done it.

[Kevin Sjostrand]

Neil,
When I sand the bottom of my bridges, I only go forward and back on top of the bridge area and I have always gotten a great matched fit. Is it possible that the dome on your top has changed since you sanded the bottom of the bridge, or did you just do it? Perhaps I missed that.

Kevin

[nkwak]

That's a good idea, Kevin. I was sanding side to side and in a circular motion. I've been overdoing it over the past few weeks.

[Darryl Young]

If you are using the top of the guitar as the "caul" to sand the radius in the bottom of the bridge, be sure you are controlling your humidity very well. Remember that the radius of the top changes as the humidity changes. The bridge is likely the strongest brace you will glue to your top and whatever the curvature is when you glue it.....that will be the "normal" positon.

There are different opinions on this subject but some folks sand the bridge on a template that has the ideal radius you want to use on the guitar (the same radius used when gluing the braces to the top). Then when the humidity in your shop is at your target building percentage, glue the bridge on the top. This lets the stiff bridge help set the ideal radius on the top at the correct humidity.

There are argument both ways on which method should be used. I tend toward the second method. No matter how you get the proper radius sanded in the bridge, I think everyone would agree it's best to glue the bridge to the top under ideal humidity conditions.

[nkwak]

Mahogany? I wouldn't. Too soft, too likely to split either along the pin holes or saddle slot. There's a reason makers have used ebony and rosewood -- and this is it.

Oops. I meant to say Honduran rosewood. Sorry.

[Dan Bombliss]

You can always chalk fit if there's a question about your fit.

Draw chalk on your top where the bridge will go, and just push pressure on the bridge, and be careful not to drag or move it. The chalk that shows on the bridge are high spots. If the chalk covers everywhere you have a good fit. So if it is very spotty, or predominant in spots, just hit those with a scraper or such, and check again.

I chalk fit my bridges, fingerboard extensions, dovetails for neck resets, and just about anything else I wonder about.

-Dan

[Kevin Sjostrand]

Neil,
How did your bridge gluing turn out?

Kevin

[nkwak]

I haven't done it yet, Kevin. Other things have taken priority, though I still do mull over the guitar from time to time.

Basically, I felt that I needed to clean up some mars in the top first and the masked area where the bridge is to go. I already drilled a pair of pin holes so I'm committed to the placement but I just felt that it was now or never to take care of some dings in the French polish and having a clear footprint in the finish before gluing the bridge down. I also noticed that the underside of the wings were rounded off a little too much so I've been attending to that. FWIW I don't think my bridge's height will suffer too much from that.

[nkwak]

*phew!* This certainly is a learning process. I took a crash course in hide glue and had to do over because the viscosity was not where it needed to be. Hopefully the second time around leaves me with strong enough of a glue joint. If not then I'm going to have to break out the iron to steam it off and do over.