Here is an area that may not get the attention
it deserves in our 30+ year old airframes, yes, the floorboards! After many
years the original plys of wood may have become weakened or possibly soaked with
gear transmission lubricants or hydraulic fluid from a brake master cylinder or
Here are some ways and material sources that
have been used by Beechcraft owners to get a renewed and possibly stronger board
in place as opposed to their 30+ year old materials.
Here is Bob S.'s handiwork after he went in to fix a leaking
master cylinder and couldn't bring himself to reinstall his ratty old weakened
boards. Bob reports using 1/4", 5 ply Baltic birch.
There are mail order sources for the wood but the shipping
will be expensive. Try some local lumber yards first. The plywood comes in 5'x5'
sheets. Its identical to what another local used but paid about $65.00 for. Mine
cost about $20.00
Pics courtesy of Bob S., of Arizona! Thanks
When I did the floorboards of 23W, I used 1/4" Birch plywood
from Craftsmen Supply
My local Craftsmen Supply place cut me a new board, using my
old one as a template and it was perfect. I just drilled the holes and gave it a
couple of coats of polyurethane varnish. Here is one of my boards, yeah, I know,
the other one is on the to-do list!
Other folks thoughts are as follows for material options:
Okoume or Marine plywood A full sheet purchase may be
required. If the sheet is cut into (2) 4' x 4' pieces it can ship UPS.
Be sure you get the 1088 grade no matter which thickness you
choose, (6mm will be the same as original thickness). The lesser grades can have
voids in the laminations and still meet the grade specs.
BeechTalker John L. Adds the following thoughts:
Greetings Mike...Great CSOB write-up as your
usual. I have an inexpensive source for the plywood. I have been in the flooring
business for over 35 years and we use a high quality, Russian/Birch plywood as a
subfloor for vinyl flooring installation. It is 5 ply and 1/4" thick plywood
with no voids.
A 4' x 5' sheet should retail for about $20.00. Anyone wanting to do this
modification might just check with your local flooring store!
BeechTalker Geoffrey R. Adds the following thoughts:
Okume Plywood in 1088 is functionally the same as Baltic Birch plywood. They
are both 6mm 1/4" 5 ply hard wood plywood.
I used very little materials
- 1 5x5 sheet of plywood
- Plastic insert for #6 screw 1/4" length
- #6 x 3/4" oval head screw with captured washer
- #6 x 3/4" flat head wood screw
- 3/32" x 3/8" flat head rivot
- T50 x 1/4 Staples
- 1 Qt of Teak Oil
The holes in my floorboards were all squished and enlarged. To prevent this
in the future, I installed the plastic inserts. These stand proud just a bit, so
you are tightening down on the insert, not the wood.
To attach the floorboard to the aircraft, I used a screw with a captured
washer to eliminate yet one more moving part. I found a few loose ones under my
floors and I'd rather not have loose parts there.
On the back of some of the floorboards are blocks. Mine were oil soaked so I
made new ones. The factory attaches them with staples, I used #6 wood screws
recessed into the plywood.
I had not expected this project, so I don't have any tinnerman fasteners and
had to reuse the old ones. The rivots can be a pain to remove from the fasteners
and I'd suggest buying new ones before you start the project.
For now, I'm going to reuse my insulation since it is in good shape and will
staple it with 1/4" staples.
I cut, assembled, and coated the wood in two evenings and is not really a
project I enjoyed. The old oily wood is nasty to deal with and it gets on the
new wood when templating for holes, cuts, etc. I used Teak Oil which works well
for hardwoods, applies easily, dries well, is repairable, and doesn't smell as
bad as polyurethane.
I used a variety of tools, more than I expected, and this was a lot more work
than I expected.
- Table Saw
- Chop Saw
- Scroll Saw
- Belt Sander
- Palm Sander
- Cordless Drill
- Staple Gun
Bonanza owner Ken R. from Wichita, KS suggests
Gilfab 4004A, a thicker (0.041" vs. 0.250") honeycombed composite product
used in commercial aircraft flooring.
Bonanza owner Mark K. used the Gilfab product in his
floorboard makeover and has generously contributed his 337 Form and the DER
structural report. The structural report has quite a few pictures (in B&W) of
his floorboard install. The back of the 337 for a Gilfab install is
HERE. The DER
approved Structural Substantiation report for Gilfab is
If you're unsure how to approach the mechanics of the removal
and replacement of these boards, something to consider would be having
your A&P remove them for you. You then take them to a wood shop that sources the
plywood, they make the cuts and place the holes based on the existing board as a
template. You refinish them and submit them back to your A&P for inspection,
approval and re-insertion.
A side note for the gentlemen: Women are
scientifically known to have a more acute sense of smell than men. Period, end
of story...... They will more easily pick up on the oily, stinky smell of those
30, 40 or 50 year old ancient floorboards, soaked in hydraulic fluid leaks and
gear transmission oil overfill leaks. Do yourself a favor and get those old
floorboards out of there if you expect your female travel companion(s) to enjoy
the flying experience as much as you do. Right after changing my old greasy
floorboards, the first time my SO (Significant Other) got into the plane she
noticed the "stinky oil smell" was gone! Just DO IT!
If you've got floorboard material solutions worthy of CSOB
E-mail me with the details!