First I'd say you've installed a professional forum the solution. This is a powerful full-fledged forum solution which brings lots of functions and features. Also, wpForo has built-in Phrase system so it inserts in your database all forum phrases in wp_wpforo_phrases table so it may increase your database + 1 MB. But the main size change comes from the user profile data. wpForo creates forum profile data based on your users in the wp_wpforo_profiles table, so the size may be as much as the count of your users.

I don't think wpForo may increase your db size +30MB, it's something impossible. There are only two cases if this may happen:

1. If you've migrated other forum data to wpForo and the wpForo is not empty.

2. If you have thousands of users and the forum profile table has become big.

In both cases all is ok and you have nothing to worry. I don't think the 30MB is the size you should think about that.

So i have a issue the database went from 8mb before the forum to 42mb after

Do you mean your SQL database increased by more than 30mb after adding wpForo?

Are you talking about an empty wpForo forum or did you migrate from a different forum to wpForo and 42mb is the size of the whole database?

any thoughts? has anyone run into this? 

thank you

Tom