VIDEO- How to make a radiused Dome to laminate ukulele backs

Note- It says "guitar backs" simply because more people search for guitar stuff then uke stuff on youtube.

In this video,
I show the way I made a radiused dome to fit inside my 15' radius dish (also used for glueing back braces and radiusing the sides).

This dome will be used to laminate guitar and ukulele backs if/when needed.

Use epoxy to glue the laminations, and use an odd number of layers.

There are a few ways to do this job however I found this quite easy to do using the drywall spackling (or any product that drys hard and sands easy).
The others methods would be
1- Buy one (I recommend buying a professionally made radius DISH)
2- Have one made with a CNC.
3- Use a vacuum setup in a radius dish
The first two options would probably cost about $100 (I'm presuming as as a radiused dish costs about $100)-
#3 costs about $300-$500 to get set up with a vacuum.

4- Make one using a router and radiused sled.- This method is also cheap (presuming you already have a router), but (a) you have to make the radiused sled, and (b) still have the problem of sanding the plywood at the end which is the hardest part.

So, I recommend either buying one or making it like this with a layer of spacking that sands very easy and makes for a perfect fit.- takes a few hours.

Luthier of luxury heirloom quality guitars and ukuleles.
https://www.beauhannamguitars.com

You have made the comment that Paulownia has the highest strength to weight ratio of any wood. On what basis do you say this? I did a quick look at some woods on the Wood Database, looking at the 'Modulus of Rupture' which is a measure of strength, and the average dried weight. I computed a relative strength number by taking the ratio of the 'strength to the weight.

For three woods I find:

Paulonia
modulus of rupture=5480
Average dried weight(kg/m3)=18
rupture per unit weight = 304.4

Basswood
modulus of rupture=8700
Average dried weight(kg/m3)=26
rupture per unit weight=334.6

Port Orford Cedar
modulus of rupture=12,290
Average dried weight(kg/m3)=29
rupture per unit weight=423.8

From this is looks like either basswood or Port Orford cedar is stronger per unit weight than Paulownia.

I've tried this.... perhaps I should share my results. I'll take some images tomorrow.

jupiteruke said:

You have made the comment that Paulownia has the highest strength to weight ratio of any wood. On what basis do you say this? I did a quick look at some woods on the Wood Database, looking at the 'Modulus of Rupture' which is a measure of strength, and the average dried weight. I computed a relative strength number by taking the ratio of the 'strength to the weight.

For three woods I find:

Paulonia
modulus of rupture=5480
Average dried weight(kg/m3)=18
rupture per unit weight = 304.4

Basswood
modulus of rupture=8700
Average dried weight(kg/m3)=26
rupture per unit weight=334.6

Port Orford Cedar
modulus of rupture=12,290
Average dried weight(kg/m3)=29
rupture per unit weight=423.8

From this is looks like either basswood or Port Orford cedar is stronger per unit weight than Paulownia.

Click to expand...

Repeating what i was told- maybe the statistic is it is the lightest wood with the highest strength ie over balsa wood? -

Paulownia is indeed light in weight, not much that is lighter. However, balsa wood, because it is so very light, actually has a higher relative strength number than Paulownia

Balsa
modulus of rupture=2940
Average dried weight(kg/m3)=9
rupture per unit weight = 326.6

Paulonia
modulus of rupture=5480
Average dried weight(kg/m3)=18
rupture per unit weight = 304.4

jupiteruke said:

Paulownia is indeed light in weight, not much that is lighter. However, balsa wood, because it is so very light, actually has a higher relative strength number than Paulownia

Balsa
modulus of rupture=2940
Average dried weight(kg/m3)=9
rupture per unit weight = 326.6

Paulonia
modulus of rupture=5480
Average dried weight(kg/m3)=18
rupture per unit weight = 304.4

Click to expand...

too late to change the video now!

Beau Hannam Ukuleles said:

too late to change the video now!

Click to expand...

"We'll fix it in post production" (as in the old saying, "We'll fix it in the mix."