Wooden wing spars
Robert Ollerton
wing spars (metal ones too...). Its in the "Acceptable Practices" book.
There are some limits on where the splice can be made, and how long
it must be. If its in the way of some other wing
component, say
a rib, then you have to make a choice of modifying the wing component and
document it with a 337, or getting a new spar(prepare to sacrafice 2
chickens at the alter, pray to Mr. Money).
The procedure is done with a combination of doublers, glue, nails,
magic, etc.
I would guess that a repair towards the outer third of a wing would
be much more possible that one that was in the inner third or
at the strut attach point.
To know for sure, you need to strip back the covering, ribs, and hardware
bits and get an A/I thats familure with wood spars to inspect it.
--
Robert P. Ollerton
San Diego: 6 cars, 3 airplanes, no house
olle...@cerf.net Bob_Ol...@priacc.com
Robert Ollerton
You are not allowed to use "Todays" glues on a certificated
airplane. Yet. The Acceptable Repair Practices book specifies
the choices. Thank the ever forward looking FAA.
Charles K. Scott
mck...@VNET.IBM.COM writes:
> I have a friend who is wondering if wooden wing spars can be
> repaired or if they have to be completely replaced if damaged.
> In his case, he has a spar broken outside the last wing rib,
> if that makes any difference.
They can be repaired, there are specifications in the AI repair manuals
that describe what angle of cut must be made for the replacement piece
to be glued on. Basically it's a gradual angle cut often called a
scarf joint which allows for a long glue joint. Most of todays glues
bond with a stronger joint than the surrounding wood so this is a safe
repair. It's the getting to the break that is the problem.
Corky Scott
PS, you should of course be using the same type wood as the existing
spar
mck...@vnet.ibm.com
repaired or if they have to be completely replaced if damaged.
In his case, he has a spar broken outside the last wing rib,
if that makes any difference.
Matt McKrell, 607-752-5140
guy byars
|> On glues:
|>
|> You are not allowed to use "Todays" glues on a certificated
|> airplane. Yet.
Are you *_SURE_* about that? I'm using T-88 on my wood wings and the A/I has no
problem with signing it off? While my project was a factory prototype and never
certificated, the A/I indicated that it would be ok even if it were.
Would you please site your source?
Guy Byars
Robert Ollerton
I dug up the book, and I stated the title incorrectly (too many
beers at the company picnic)
"Acceptable Methods, Techniques, and Practices"
"Aircraft Inspection, Repair, and Alterations"
AC43.13-1a/2a
Published by our pals at the DOT/FAA. Available from
just about any Airplane part/book store.
Sorry for the incorrect title in my previous posting.
David York
>On glues:
>
>You are not allowed to use "Todays" glues on a certificated
>airplane. Yet. The Acceptable Repair Practices book specifies
>the choices. Thank the ever forward looking FAA.
>--
the gentleman in charge of this project at Oshkosh last year. He seems to
really be doing his homework - attending Oshkosh to review the latest
techniques and materials and how to repair them. I know that glue and
glueing techniques were on his list at that point. I also understand that
he is working with Randolph, Stits, and the other fabric process companies
to get the latest in those areas too.
He told me that AC43.13 will probably be replaced with SEVEN manuals, each
covering repair techniques for a specific area - wood, fabric, composites, etc.
I don't know when they are expected to be published.
Dave York
|-|-| "BELLANCA" - At Home In The Air"
----O---- My 1950 Cruisemaster project - "at home in the garage."
00nzwi...@bsuvc.bsu.edu
> What Glue are you allowed to use on Certificated Aircraft wood
> structures? Its in the part 43 Acceptable Practices book that I just
> carried back to the book case 5 seconds ago...
>
> I am afraid I can't spell them very well, one is Weldwood and the
> other is (excuse my spelling) Resorsonal which I believe is
> made by DAP. Both are hardware store items, weldwood is a powder you mix
> with water, the other is a two part liquid/powder.
> San Diego: 6 cars, 3 airplanes, no house
> olle...@cerf.net Bob_Ol...@priacc.com
>
My local hardwood dealer informs me that Elmer's Waterproof Glue is in reality
Resorcinol and that they changed the label because no one seemed to know what
Resorcinol meant.--
Nyal Z. Williams
00nzwi...@bsuvc.bsu.edu
rdick...@unicomp.net
In article <19941014....@almaden.ibm.com>, <mck...@VNET.IBM.COM>
writes:
> I have a friend who is wondering if wooden wing spars can be
> repaired or if they have to be completely replaced if damaged.
> In his case, he has a spar broken outside the last wing rib,
> if that makes any difference.
You may repair wooden wing spars as you have been told in this
group. You have not said what type of spar (solid wood, laminated
or box type) is being repaired and whether or not it is in an
experimental or certified aircraft.
Repair of a wing spar is considered a major airframe repair and
requires a form 337 be filed. Also replaceing the wing covering
on a fabric covered aircraft is a major airframe repair also
requireing a form 337 be filed.
Wood types acceptable to the repair are discussed in AC43.13.
Spruce is the standard by which all woods are judged but douglas
fir, hemlock and some other woods are acceptable substitutes
provided they meet the grading requirements set forth in AC43.13.
As far as glue types go, "modern" glues are acceptable for use
provided that the FAA or the military has previously accepted
the gluing system. You may also get approval of the glue system
by making up some sample test blocks of spruce or other similar
material and perform destructive testing for the FAA.
If you are repairing a homebuilt, then what the heck! You can
use any glue you feel safe in using. I suggest that you read some
of the various articles on glues. Many glues, such as epoxies,
have some drawbacks and may not be suitable for use.
One more thing. The wing spar is probably the most important
component of the wing and repairs must be done exactly right!
Since your break is on the outer rib bay, a repair may not be
extermely critical as has been pointed out by another reply
article. Yet, ask youself this question. "Would I fly in an
aircraft that I knew had a spliced spar?" Let your conscience
be you guide!
Good luck,
R Dickerson
The Aeronca Man
Ken Bickers
In article <37q6co$k...@noc.cerf.net> olle...@nic.cerf.net (Robert Ollerton)
writes:>From: olle...@nic.cerf.net (Robert Ollerton)
>Subject: Re: Wooden wing spars
>Date: 16 Oct 1994 03:24:08 GMT
>There are acceptable procedures for repairing (splicing) wood
>wing spars (metal ones too...). Its in the "Acceptable Practices" book.
This thread raises an issue about which I have been looking for additional
information.
I am building an airplane that utilizes wood spars and ribs constructed from
Spruce. While I don't have any desire (or ability) to redesign the airplane,
I would like to be able to calculate for myself the loads and gross weights
that the designer has specified. So my question is, does anyone have the
formulas for calculating the loads that spars and ribs can take? I assume
that these formulas are a function of gross weight, wing area, wing span,
and anticipated top speed, along with the width and depth of the spars
and capstrips (and perhaps assorted other factors). Or perhaps someone
could point me in the direction of a reference book that has these sorts
of formulas.
Thanks in advance. Ken Bickers
Tim Kramer
Mechanics" by Egor P. Popov. Keep in mind that this is not an easy subject and
that there are no "standard formulas" for wing strength that you can plug in to.
For the most part you'll be dealing with static loads, which is only part of the
problem. The material in Popov will lead you in the correct direction.
Hope this is helpfull,
Tim Kramer
N30450 C-177A
Robert Ollerton
structures? Its in the part 43 Acceptable Practices book that I just
carried back to the book case 5 seconds ago...
I am afraid I can't spell them very well, one is Weldwood and the
other is (excuse my spelling) Resorsonal which I believe is
made by DAP. Both are hardware store items, weldwood is a powder you mix
with water, the other is a two part liquid/powder.
T88, I have been told, is an excellant glue to use on wood. A lot
of A&Ps would rather have you use it and get a better bonded joint,
and look the other way. I have been to several wood working sessions
at Sun-n-Fun and it gets lots of praise. By the way, there are some
two part glues that get brittle with heat and age that were sold
are I believe are still available. They have caused several fatal
accidents. I believe they were of an Alphatic (sp?_)base.
As was previously mentioned, the FAA has a very good person working on
rewriting the part 43 procedures and getting them updated to allow
for all the new materials that are available. For instance, Dacron
fabric and composite materials are not covered. The type clubs for
wood structure aircraft (Bellanca in my case) have been fairly involved
with making suggestions and reviewing the new procedures. I would
bet that T88 becomes an acceptable repair material.
This is mostly off the top of my head and its been awhile since I
was active with wood. If you need more detail I can try to dig
into my notes.
Hope this is more helpful than confusing.
bob.