Adding sugar to adjust SG

[Torin Price]

I have just juiced my grapes from my Dad's vine. Living in Scotland the grapes tend to be a bit sour but this year they're as sweet as they have ever been due in part to the warmest summer on record. However my SG reading is at 1.047 and some research has suggested to aim between 1.060~1.090 for a wine. I'd like to make a dry red out of the juice.

Firstly what would people suggest as a SG to aim for? Secondly, to increase the SG how can I calculate the amount of sugar to add?

Bonus question the grapes come from Kippen, Scotland. Kippen used to host the worlds largest indoor grapevine and these come from a cutting of it. Does anyone know what variety of grapes these are?

 

[marc1]

Gros Coleman according to the page I found :

https://theweevine.org/2017/07/30/making-wine-from-kippens-famous-big-vine/

 

[DaveDiamond]

I used the calculators on Brewers Friend to work out some quantities. A little tedious because the ABV calculator uses SG, and the Sugar Calculator uses Brix, so you have to convert SG to Brix, then you have to convert ounces to grams and gallons to litres.
Rounded off slightly, 29 grams of sugar per litre raises the SG by 0.010 points.
1.045 is 5.91%
1.050 is 6.56%
1.060 is 7.88%
I didn't go higher when taking notes, but the calculator for ABV is here https://www.brewersfriend.com/abv-calculator/
The Sugar to Brix calculator is under Wine Tools if I recall correctly. Edit- here's the link https://www.brewersfriend.com/wine-calculators

 

[hottpeper13]

Table sugar is 46 GU's per pound per gal.

 

[Closet Fermenter]

I’m sure there’s a way to target this out exactly using algebra, but I’m not that particular. The issue lies in the fact that if you’re targeting a certain volume for your carboy (say 5 gallons) and you take a reading, you can easily determine how much sugar should be there to raise the SG to your target. However, when you add the sugar, the volume will increase. Now I suppose that you could just use a larger mixing container and add more sugar until you get there, but you might have more than will fit into your fermenter. Possibly, you could divert the excess to another smaller fermenter. Or, you could just get close enough and live with it as I do. Pursuing a particular sg can seem like chasing your tail.