To set up a custom search engine for this forum in Edge, copy-and-paste the following into the browser's URL bar:

edge://settings/privacy/services/search/searchEngines

Click "Add search engine" and fill in the following fields:

Search Engine -- GreyNomads

Shortcut -- gn 

URL -- https://www.google.com/search?q=%s+site%3Athegreynomads.activeboard.com

Then click the Add box.

Now you can type the following shortcut into the URL bar:

gn caravan

The browser will automatically resolve it to ...

https://www.google.com/search?q=caravan+site%3Athegreynomads.activeboard.com

I expect that other Chrome based browsers will have a similar feature. Other browsers have a different approach. I can add to this thread if someone needs help with Firefox.