Cross brace

[Tim Mace]

My new homemade Mandola that I crossbraced(my first)gave a loud pop this wk/nd and Mon I found that the the cross had been violated.This damn thing sounds great but now has only 3 wings and some leftover material.

What should I have done to prevent this tragedty(humor)?What is normally used at the cross(mid)road to reenforce the joint?

[Ned Knepp]

Tim, I've never braced a mandolin with an X brace so my experience with guitar tops is different. The forces on a pin bridge are more up than down, as with a tailpiece/ bridge comibination. When I use an X brace, I make a very tight joint and bridge it with a spruce cap.  

 

Do you have pictures?  Maybe what you needed is a longer cap? 

 

Ned 

[William F.Eden]

Did you not show pictures of that Mandola when you were building it Tim?????????????

[Tim Mace]

yep...I had a tight joint but no cap.Also I extended an added brace from the mid.bass side to the tailblock area

and now I'm wondering if I hadn't added that 5th piece would this have occured.I guess the pull forward could have caused stress in a way I hadn't considered..oh well ..back to drawing board.It still plays well for now.

Time will tell..........next time stronger supported joint.I've seen molded covered joints that look like epoxy and in some cases cast/gauze looking material applied.What do you think?

[William F.Eden]

 If i were building that Insterument i would have made the xbraceing longer and had the braces coming close to the sound hole on a longer angel but still crossing under the bridge .If that was not posible i would put a cross brace  in the back area of the bridge.I don't know if you used quarter cut braceing or not but it looks form the picture that you didn't have enoff wood left on your top brace?? You make your joint mortis on both pices the same thicknes and I also take a pice of cloth from an old t-shirt and glue it over the joint . P.S Iam not trying  to tell you what to do but just trying to help.good luck Bill.''''''''''''''

[Tim Mace]

You're probably right...what ever caused it cracked away from joint so there's still something attached in there.

[Ned Knepp]

Sorry, Tim, I forgot you posted pictures before.  If it were me, I'd think about pulling the back and repairing the bracing with a cap.  Like Bill, I probably would have shifted the X closer to the soundhole and put a brace or two across the lower area , like a guitar BUT I haven't tried making a Mando like this. If it sounds good as it is now, I wouldn't do more than repair and test. I doubt if adding a cap to the X will make any difference to the sound but it should help the strength of the joint a lot. 

 

You already practiced your building skills, now you get to practice you repair technique. What fun!

Ned

[Tim Mace]

It's playing too good for now ..I wanna see what kind of problems arise but will make that joint stronger next time.Thanks for ideas.....

[Tim Mace]

Having little experience w/calculating or preplannig for things like bridge/crossbrace  location vs scale length I had intended for the bridge to rest in the strongest area possible which looks like just behind the midpoint of the bracing.I've seen so many

failed tops on mandos and figured a supported area would maintain the slight curvature built into the braces.I'll keep in mind about moving x fwd

and use floaters between tail and X.I really think the 5th brace was pushed fwd from string tension..So far no exterior signs

of stress!

[Tim Mace]

Here's what top looks like......