I tried to output ot console with two variations, but the build
failed:

'ERROR = "END OF STATEMENT EXPECTED"
Dim tsql As String = "SELECT FT_TBL.FullDocNo, FT_TBL.DocType,
KEY_TBL.RANK FROM FullDocuments AS FT_TBL INNER JOIN
CONTAINSTABLE(FullDocuments, SectionText, 'ISABOUT ("SearchTerm1"
weight (.8), "SearchTerm2" weight (.4), "SearchTerm3" weight (.2) )' )
AS KEY_TBL ON FT_TBL.FullDocumentID = KEY_TBL.[KEY] ORDER BY
KEY_TBL.RANK DESC "
Console.WriteLine(tsql)
Dim adp As SqlDataAdapter = New SqlDataAdapter(tsql, conn)

'ERROR = ')' EXPECTED    -    SEARCHTERM1 WITH SQUIGGLY UNDERLINE.
Dim tsql As String = ("SELECT FT_TBL.FullDocNo, FT_TBL.DocType,
KEY_TBL.RANK FROM FullDocuments AS FT_TBL INNER JOIN
CONTAINSTABLE(FullDocuments, SectionText, 'ISABOUT ("SearchTerm1"
weight (.8), "SearchTerm2" weight (.4), "SearchTerm3" weight (.2) )' )
AS KEY_TBL ON FT_TBL.FullDocumentID = KEY_TBL.[KEY] ORDER BY
KEY_TBL.RANK DESC ", conn)
Console.WriteLine(tsql)
Dim adp As SqlDataAdapter = New SqlDataAdapter(tsql, conn)

I then tried a series of queries in Management Studio.  They all
executed successfully, but the last one which included variables and
weight values yielded 0 results.

SELECT FullDocNo
FROM FullDocuments
WHERE CONTAINS (SectionText, 'gold')  *** 1670 results ***

DECLARE @SearchTerm1 nvarchar(10)
SET @SearchTerm1 ='gold'
SELECT FullDocNo
FROM FullDocuments
WHERE CONTAINS (SectionText, @SearchTerm1)  *** 1670 results ***

SELECT FullDocNo
FROM FullDocuments
WHERE CONTAINS (SectionText, 'silver')  *** 501 results ***

DECLARE @SearchTerm2 nvarchar(10)
SET @SearchTerm2 ='silver'
SELECT FullDocNo
FROM FullDocuments
WHERE CONTAINS (SectionText, @SearchTerm2) *** 501 results ***

SELECT FullDocNo
FROM FullDocuments
WHERE CONTAINS (SectionText, 'copper')  *** 619 results ***

DECLARE @SearchTerm3 nvarchar(10)
SET @SearchTerm3 ='copper'
SELECT FullDocNo
FROM FullDocuments
WHERE CONTAINS (SectionText, @SearchTerm3) *** 619 results ***

SELECT FT_TBL.FullDocNo, KEY_TBL.RANK
FROM FullDocuments AS FT_TBL INNER JOIN
CONTAINSTABLE(FullDocuments, SectionText,
'ISABOUT ("gold" weight (.8), "silver" weight (.4), "copper" weight (.
2) )' ) AS KEY_TBL ON FT_TBL.FullDocumentID = KEY_TBL.[KEY]
ORDER BY KEY_TBL.RANK DESC  *** 2067 results ***

DECLARE @SearchTerm1 nvarchar(10)
SET @SearchTerm1 ='gold'
DECLARE @SearchTerm2 nvarchar(10)
SET @SearchTerm2 ='silver'
DECLARE @SearchTerm3 nvarchar(10)
SET @SearchTerm3 ='copper'
SELECT FT_TBL.FullDocNo, KEY_TBL.RANK
FROM FullDocuments AS FT_TBL INNER JOIN
CONTAINSTABLE(FullDocuments, SectionText,
'ISABOUT (@SearchTerm1 weight (.8), @SearchTerm2 weight (.4),
@SearchTerm3 weight (.2) )' ) AS KEY_TBL ON FT_TBL.FullDocumentID =
KEY_TBL.[KEY]
ORDER BY KEY_TBL.RANK DESC  *** 0 results ***