Thompson Belly Reducer

[John Walker Waldsmith]

First Post!

Thanks Frank for this awesome forum!

Just got a Set of the Thompson Belly Reducer... pieces... haha, thought there was more to

this. All i have is regular bridge clamps (but alot of them).. will those work or do they need to be heavy duty?

Who else has used it and whats your results like?

Thanks!

[Mike Kolb]

Hi John, welcome.  I've used the belly reducers for years and, yeah, they work... but they're not for every situation. They'll help (but not cure) a bellied top.  The trick seems to be heat + time... and more of both than the basic instructions call-for.  

I'll heat the upper & lower plates to about 180-deg, then clamp-up (real tight) and set it all aside for a couple of days.  Then do it again... then again!  After about a week (and 3 applications) ...there's a reduction in the bellying.  100%? Not usually, but any progress is better than none.  

As far as clamps go, three Ibex bridge clamps seems to work best... anything beefier might start cracking things we don't want to crack.  When all's said & done, you still might want to replace the bridge plate if you're not getting the progress you're hoping for.   Like most specialized tools, these are just a helper, not a cure-all.  Good luck.

[Andrew]

I dont remember seeing anything about heat in the instructions. Maybe thats why I couldnt get one to work for me. Anyone here tried the shaped caul set Stew Mac makes?

[Mike Kolb]

Andrew, I think they're one and the same.  StewMac sells the Thompson and gives the instructions on the website (heat included)...  which calls for 150-deg but I settled on using 180-deg.  

http://www.stewmac.com/shop/Tools/Clamps,_support_tools/Thompson_Be...

By the way (totally unrelated...)  I really dig the guitar body you use as your avatar!  I'm thinking of making a bass body that's similar for a Music Man neck that's been kicking-around here for a few years. If you made that body, can you share any construction tips?  Thanks... 

[Andrew]

Ohhhh crap you're quite right. I had it in my mind that the thompson reducer was the bridge doctor. D'oh!! Disregard. Im a doink.

I did indeed, and thank you. Its a neck-through guitar, my second build and first sale :). I used a squirrel tail compass(?) plane to remove material from the 'bevels' and arm recess/contour. I just drew the basic idear on the body and started carving til it was right. Even did some freehand routing for material removal. Finished up with scrapers and sanding, and a home made gauge to make sure the contours were a consistent depth. I radiused the top with a heavy scraper. The bowl thingies around the controls were dug out with scrapers and papers alone as I couldnt get something to do it with power safely. It was brutal lol. Ill have a tool made for that next time I do that. Basically for the most of it, i drew right on the wood, picked up something sharp, and went with the flow :). If you have any questions feel free to ask.

[Kerry Krishna]

 John and Mike,  my vera first axe was a  1971  $125 buck Fender F15 plywood acoustic. After discovering medium strings ( and only playing those on that guitar for 30 years) there was a massive belly. I replaced the bridge plate after heat pressing the top several times, then replaced the bridge plate. One year later, it was exactly the same as before I started.

[Mike Kolb]

Kerry.... sad to say I've had that happen too, but sometimes the fix will "take" to some degree... I guess a lot depends on the amount of bellying, the top thickness, the bracing... and whether the planets have aligned;)

Andrew, thanks for the info... I sent a friend request so I can pester you further about your avatar guitar body without highjacking the thread.  

[John Walker Waldsmith]

Thanks for all the help guys! I have now used them 3 times and they seem to work great! I havent had any crazy humps to fix lately but the ones ive done worked great! 

No loose braces yet... not pumped for that to happen, and inform a customer i broke loose a brace fixing there guitar!

[John Walker Waldsmith]

BTW

I--- just put boiling water in a small crock pot on high with the pieces im using for a half hour . Then add hot water to the bridge plate and top, clamp up leave for 24hrs. Good results so far.