Duct raising

hello, a couple of weeks ago I posted a question regarding raising the main rectangular duct trunk up 4 inches to gain headroom in my basement. Thanks to all who responded. Raising the main trunk will be the easy part. It's the transition piece that I am unsure of... . I will need to get some sort of galvanized 4" riser. If I make one myself, how long should the riser be? In other words, to help the airflow, I don't think I should use an elbow. My thought was the riser should gradually taper up 4" over a couple of feet. Also, if I screw this up, any ideas what it would cost a sheet metal guy to make one of these? The duct is rectangular 18" x 10". . Thank you for your time.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

maybe 50 bucks.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 07 Aug 2007 09:45:26 -0400, JohnnyC wrote:

Just call the sheet metal guy first. Should take less than an hour.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.