Dry Climate Build Schedule

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Onoitsmatt
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Dry Climate Build Schedule

Post by Onoitsmatt » Wed Mar 22, 2017 10:08 am

Hi All,

I'm just getting underway on my first guitar build (I am wrapping up a uke build that was my first instrument).

I live in the desert where average humidity is in the low 40's in the winter then gradually dips lower through the spring and bottoms out in the mid-teens in summer then gradually climbs again to the mid-40's in winter again.

Most humidity topics revolve around high humidity issues, but I'm trying to sort out the best schedule for assembly given the low humidity here in the desert.

Do I want to try to do most of the gluing (bracing and closing up the box) in the dryest time of year, or does it matter?

FWIW, the guitar will stay in this climate, so I'm not concerned about future exposure to higher humidity levels (though during monsoon season, there are days when humidity levels can get much higher).

I understand that dry wood shrinks, as it absorbs moisture it expands. I just don't fully understand what the optimal humidity would be for gluing up and the pitfalls of doing it at the wrong time/humidity.

My shop is the garage and it is not climate controlled in any way.

Thanks in advance for you input. This forum is a tremendous resource!
Matt -Phoenix, AZ

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56nortondomy
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Re: Dry Climate Build Schedule

Post by 56nortondomy » Wed Mar 22, 2017 12:19 pm

Hi Matt, 40 to 45% humidity is considered to be best for gluing up the braces.
Wayne

Dave M
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Re: Dry Climate Build Schedule

Post by Dave M » Thu Mar 23, 2017 8:30 am

My understanding is that guitars can take increases in Relative Humidity reasonably well compared to when they are built. Everything can expand a bit, and particularly the doming of the top and back can increase to absorb this increase in width. (Changes along the grain are small). Note that the top and back plates are pretty wide pieces of wood.

However a drop in humidity, and therefore drying of the wood is more problematic. Doming can decrease to a point, but after that the shrinkage across the width of the plates, or in the height of the sides, can not be accommodated, resulting in splits.

So the answer would seem to be to try and build (and the important operations are the glueing of transverse braces to the plates) at or near the minimum relative humidities you experience.

40 to 45 % is often suggested but it really does depend on your local conditions. I am in the UK and humidity is generally pretty high so I feel 50 or so % is more realistic to build in.

Anyway best of luck with the build. There's nothing like playing one of your own.
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Dave

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Re: Dry Climate Build Schedule

Post by Jim watts » Thu Mar 23, 2017 12:30 pm

Hey there neighbor!
I build in the mountains of Northern New Mexico and try to brace my tops around 35 - 40%. That seems to work well. I have to humidify my shop to get it there though. RH typically varies from 5% -25% in the fall and spring and jumps to 25 - 50% in the summer "monsoon" season.

Onoitsmatt
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Re: Dry Climate Build Schedule

Post by Onoitsmatt » Fri Mar 24, 2017 5:08 am

Thanks for all the input! Will keep a hydrometer in the shop and shoot for 40-ish for gluing up bracing. Any other glue jobs where I would want to be attentive of RH, or just the bracing?
Matt -Phoenix, AZ

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Re: Dry Climate Build Schedule

Post by jeffhigh » Fri Mar 24, 2017 7:26 am

Gluing the soundboard and back onto the rims is the other operation to do at low RH

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Mark McLean
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Re: Dry Climate Build Schedule

Post by Mark McLean » Fri Mar 24, 2017 8:37 am

Onoitsmatt wrote:Thanks for all the input! Will keep a hydrometer in the shop and shoot for 40-ish for gluing up bracing. Any other glue jobs where I would want to be attentive of RH, or just the bracing?
Matt
From what you said in your first post, RH of 40 is the upper end of your local experience and you spend a lot of the year below that. Therefore it would make sense to do the humidity sensitive bits of the build at the dryer times of the year (which for you is at RH around 20, or less). If you do this the finished instrument will be able to survive the dry times that it will be living through. On the occasions that it cycles up to RH 40 it will not really be a problem. The old saying is "wet to dry - it will die; dry to wet - it will live yet"

And to reiterate: the sensitive parts of the build are bracing the plates (top and back), and gluing the plates onto the sides. Once you have closed the box the deal is done and this instrument will forever live with the legacy of the RH at the time you did those jobs.

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Re: Dry Climate Build Schedule

Post by Onoitsmatt » Sun Mar 26, 2017 2:58 am

Thanks again for all the input. Jointed and joined back plate and attempted to bend sides yesterday. Neither went terribly well. :?
Matt -Phoenix, AZ

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kiwigeo
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Re: Dry Climate Build Schedule

Post by kiwigeo » Sun Mar 26, 2017 9:43 pm

Onoitsmatt wrote:Thanks again for all the input. Jointed and joined back plate and attempted to bend sides yesterday. Neither went terribly well. :?
Share the pain...most of us in here have been through what you're going through. I put three side sets over the bending iron before I got the cutaway successfully bent for my current commission build :?
Martin

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Re: Dry Climate Build Schedule

Post by Onoitsmatt » Thu Mar 30, 2017 2:14 pm

Yes. You guys have been really great about sharing information. I've been reading through the entire Instrument Builder's Forum bit by bit. (On page 31 now)

The jointing went poorly in that I just couldn't get the tiniest gap to go away when candle-lighting. I had two backs that I was working on and would intermittently give up on one and work on the other. I just couldn't get either of them to line up perfectly.

The side bending went poorly in that I was expecting the wood to bend more easily than it did. I found that when hot enough it bent easily enought but I had some really bad spring-back, making most of my bends pretty useless.

Here's a photo of the sides in their current state:

Image

Which may not look too bad, but this is an OM build, not a Dread. So I've got a ways to go. I'm concerned at this point about the wood being too brittle now after a round of bending to work on it much more without snapping it in two.

I've been reading up on my mistakes and sounds like spring-back is an issue with wet wood. Which this wood was.

I'm wondering if I can revisit this on the bending iron and if so, would it be advisable to go dry or wet? If wet, I was thinking I'd just clamp the sides into place in the mould and call it good.

Any input would be appreciated.

Thanks again!
Matt -Phoenix, AZ

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kiwigeo
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Re: Dry Climate Build Schedule

Post by kiwigeo » Thu Mar 30, 2017 2:32 pm

Comments from me:

1. Jointing tops and backs. I use a long soled jointing plane to do initial dressing and then if I'm having trouble getting a good join I run a builder's level faced with 120 grit sand paper over the edge. I joint both plates at the same time placed face to face and I make sure that the two plates can't move on the shooting board.

2. Side bending. Your bending Indian Rosewood? It's one of the easier woods to bend. What thickness are the sides? If youre using a bending iron make sure the iron is hot enough so that when you spray water on the iron the water immediately sizzles into jumping beads and evaporates. I bend the waist first followed by lower then upper bouts. I spritz the wood lightly with water and if the wood is a tricky species then I use a bit of fabric softener or SuperSoft. Often a bit of patience is required. Note that youll get used to feeling and hearing when the wood is about to bend.....IRW emits a faint crakling sound as the wood fibres relax.
Martin

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Re: Dry Climate Build Schedule

Post by Onoitsmatt » Thu Mar 30, 2017 3:13 pm

Thanks Martin.

I used a Stanley No. 7 to joint (both sides at the same time) and tried touching up with sandpaper but didn't try a full length swipe with sandpaper on a long, flat surface. Just touching up the high spots.

The sides are about 2.16mm. I did get them to bend, they just didn't stay that way. Thinking maybe using too much water. For the waist bend, I had the sides almost doubled over (both ends pointing at the floor) but it would always spring back to a very slight curve.

Ok to take it back to the iron or is it too brittle now?
Matt -Phoenix, AZ

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Re: Dry Climate Build Schedule

Post by kiwigeo » Thu Mar 30, 2017 5:35 pm

Onoitsmatt wrote:Thanks Martin.

I used a Stanley No. 7 to joint (both sides at the same time) and tried touching up with sandpaper but didn't try a full length swipe with sandpaper on a long, flat surface. Just touching up the high spots.

The sides are about 2.16mm. I did get them to bend, they just didn't stay that way. Thinking maybe using too much water. For the waist bend, I had the sides almost doubled over (both ends pointing at the floor) but it would always spring back to a very slight curve.

Ok to take it back to the iron or is it too brittle now?
The sandpaper needs to be fixed to a true surface like the side of a level. Do most of the jointing with the plane and finish off with a few light passes with the level/sand paper. How are you clamping up the sides while the glue sets?

I dont think too much water is your problem with the bending. The wood shouldnt be brittle after bending....I often take a side set back to the iron a few times. Just make sure your iron is nice and hot and give the wood time to heat up before applying any force to the side. Re thickness.......I usually aim for 2mm for IRW....going as thin as 1.6 if Im doing a tight bend such as the horn of a cut away.
Martin

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Re: Dry Climate Build Schedule

Post by Onoitsmatt » Fri Mar 31, 2017 12:25 am

Thanks again.

For joining/gluing the back, I am using a flat surface and wedges with a caul on the seam to keep it from buckling.

Will go back to work on the sides soon and post pictures of my progress.

Thanks again!
Matt -Phoenix, AZ

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Re: Dry Climate Build Schedule

Post by Dave M » Fri Mar 31, 2017 3:31 am

Matt this isn't going to help, but may encourage. I have found bending the blackest of black arts! I have ended up investing in a silicone heating blanket and constructing various forms and a bending machine. Even then it is not always successful.

Keep trying. The rest of the woodwork I find much more enjoyable.
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Re: Dry Climate Build Schedule

Post by lamanoditrento » Fri Mar 31, 2017 10:32 am

Onoitsmatt wrote: The sides are about 2.16mm. I did get them to bend, they just didn't stay that way. Thinking maybe using too much water. For the waist bend, I had the sides almost doubled over (both ends pointing at the floor) but it would always spring back to a very slight curve.
Try this: Once you have got the side to bend to the shape you want, hold it in that shape under tension on your bench until the wood cools a little and the bend settles in. The spring back should be less and you can repeat the whole process again getting it closer with less and less spring back. Once you have got everything where you want, claim it to the mold and let it completely dry out for 12-24 hours.
Trent

Onoitsmatt
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Re: Dry Climate Build Schedule

Post by Onoitsmatt » Sun Apr 02, 2017 8:43 am

I revisited this blackest of black arts today. I rubbed some chicken bones together and did a little dance. Burned some incense and put on my finest head-dress.

3 hours later I got one side pretty close to the right shape. I did start to get a bit of technique figured out and found the last 30 minutes to be the most productive. I'm optimistic that the other side will go better/quicker and the touching up to be done on this one won't be too bad.
Matt -Phoenix, AZ

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kiwigeo
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Re: Dry Climate Build Schedule

Post by kiwigeo » Sun Apr 02, 2017 11:00 am

Onoitsmatt wrote:I revisited this blackest of black arts today. I rubbed some chicken bones together and did a little dance. Burned some incense and put on my finest head-dress.

3 hours later I got one side pretty close to the right shape. I did start to get a bit of technique figured out and found the last 30 minutes to be the most productive. I'm optimistic that the other side will go better/quicker and the touching up to be done on this one won't be too bad.
Good to hear.....the more time you spend at the iron the better you'll get at it. When I started I got hold of a few sets of reject IRW and spent a few hours just playing around and getting a feel for how the wood behaved on the iron.
Martin

Onoitsmatt
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Re: Dry Climate Build Schedule

Post by Onoitsmatt » Wed Oct 25, 2017 3:04 pm

It’s been a while. Thought I’d post update photos for anyone interested.

Sides bent with neck and tail block glued.

Top and back are braced with baces rough shaped. Waiting for the Humidity to drop more before closing up the box.

Thanks to all of you for your support and knowledge.

I just asked my wife tonight if $250 was too much for a certain pair of books as a Christmas gift this year for my next builds. I got the thumbs up!
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Matt -Phoenix, AZ

blackalex1952
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Re: Dry Climate Build Schedule

Post by blackalex1952 » Wed Oct 25, 2017 4:58 pm

Looks good mate! My tips...calibrate the RH metre at the RH you want it to be the most accurate at. If you need to raise RH quickly in your wotrkshop, I suggest a second hand portable evaporative air conditioner.
A leather apron is a wise investment for a bending iron operator. Try the iron both vertically and horizontally and see which way works best for you. The leather apron will prevent the problem I had..I was wearing a jacket with a nylon zipper on it. Bending away, I was getting warm, but when I went to remove the jacket the heat iron had welded the zipper closed...
The thickness of the sides relative to the species and figure in the wood all affect bending. The bending iron temperature is also something to experiment with. Some woods need to be boiled first, some soaked..I'd guess in a dry climate, there would be minimum natural moisture in the timbers, so soaking doesn't hurt at all.
One last thing comes to mind. Make sure you get the area being bent thoroughly warmed through on the flat part of the iron, then move along to execute the bend on the curved section.
Ross
"Everything I say on the topic is based solely upon inexperience and assumption!"

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56nortondomy
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Re: Dry Climate Build Schedule

Post by 56nortondomy » Wed Oct 25, 2017 5:29 pm

Hi Matt, it's a little hard to tell from the photo but it looks like the lower bout and finger braces are going to be under the linings, I might be wrong. They're usually left short of the linings. It's looking good for a first guitar. Wayne

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Re: Dry Climate Build Schedule

Post by Onoitsmatt » Wed Nov 01, 2017 1:58 pm

Thanks Ross and Wayne.

I actually have the evaporative cooler, but rarely use it for some reason. I learned the hard way about the bending iron when I noticed some threads on my shorts had melted after using it one time.

You are right about the braces being too long. I cut them all long and rough shaped them with the guitar outline drawn on, but knowing my guitar body wasn't likely to be the exact shape of the outline, I decided to leave everything long so I could shave them all back to the proper length right before closing up the box.

Thanks again for all your support and input! Hoping to close the box soon (in the next week or two). Summer humidity has finally gone away and we're getting close to the sweet spot for me to close this up.
Matt -Phoenix, AZ

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