• The Biplane Forum is a large global active community of biplane builders, owners and pilots. From Pitts to Skybolts, to older barnstormers, all types are welcome. In addition to our active community, our content boasts exhaustive technical information which is often sought after for projects and maintenance. This information has accumulated over the 12+ years the forum has been in existence.

    The Biplane Forum is a private community. Subscriptions are only $49.99/year or $6.99/month to gain access to this great community and unmatched source of information not found anywhere else on the web. We are also a great resource for non biplane users, since many GA aircraft are built the same way (fabric and tube construction).

I-strut refabrication

Beej

Creator of this place
Staff member
Administrator
Moderator
Joined
Jan 1, 2006
Messages
6,482
Reaction score
1,411
Location
Austin, TX
I am planning on using the I-struts from the salvaged skybolt I have. I got all wings rigged,and then tried seeing how the I-struts looked in situ. I wasn't expecting miracles, but the differences were intriguing...as you can see in pic A, either my incidence angle was off or the orginal builder was off. Seeing this gap very rapidly coaxed me into triple checking my incidences. All was fine. The incidence differencefortopv bottom wing would have been a full 1deg on the original plane, that, or he had some sort of washout going on?


pic A
20071223_170810_Dscf0234GAP78.jpg



Just for peace of mind, I decided to lay out sample ribs and the I-strut to convince myself hisangle of incidences for top and bottom were out. They were out approx 3/8 - 7/16.


pic B
20071223_170910_Dscfparaellel02.jpg



The next problem: As you can see by in pic C below, the box section comes up short, and is of course long the other end. This means his sweepback angle was probably nearer 7+deg rather than 6.5deg. I cannot accurately confirm my wing is the one correct [not that it matters now anyways], but I do know that I had spent days marking out the original sweep back jig [the bench] and then added concrete bags for ballast, so I feel comfortable with the accuracy.


pic C
20071223_171032_Dscf02strutHole.jpg



So...I would like to try and salvage these I-strutssomehow.


1. Is there any way to safely increase the box section length in pic C?


2. I intend on heat bending the box section to reduce the gap in Pic A.


3. I am assuming trying to grind off the wholebox section to salvage the streamline tubing is maybe a non starter...
Or should i simply make new ones? [streamline tubing - $40 per ft!arrgggh]
 

Latest posts

Top