WTB aluminum stringer stock

I am digging into my new/old Orlando clipper project. It has members which
are riveted to the inside of the hull and run lateraly. There is one every
couple of feet. It is shaped like 3 sided box with a flange on the two open
edges of the 3 sided box. The flanges lay face down on the hull skin and get
riveted every few inches. It looks to be about 3/32 thick and the box
width about an inch and about 3/4 inch flanges. In addition the whole
piece of stringer has a long gentle curve to fit the curve of the bottom skin.
I am sure this is heat treated alloy and I believe it was fabricated from sheet.
(does not have the look of an extrusion ) This boat was built in an aircraft factory here in orlando after the war.
One of my stringers is cracking on both ends. the cracks started from the rivet holes. Looks like a fatigue problem.

Does anyone know if this material is still made by anyone ???????
I have looked in aircraft spruce, wicks and airparts with no luck.

If I have to I can make it from sheet using a home made form block.
But I would rather buy it and then work a gentle curve into it.

Any ideas ??????

Tim

 

Sounds like a top hat stringer. On aircraft these are pretty much always folded or pressed from sheet. The alloy will probably be bent in the soft state then heat treated. My guess is that the alloy will probably be 6000 series, most probably 6061-T6 as you're in the US. This won't bend easily in the T6 temper state, but if annealed then re-hardened it can be formed into pretty much any shape you like.

On aircraft it is often possible to perform a local repair, without replacing an entire component. I'd suggest finding your local EAA (Experimental Aircraft Association) chapter and asking if they have a sheet metal guru (most have). I'd suggest a visit to Lakeland, not far from you and home of the EAAs second largest airshow, and ask around amongst the homebuilt aircraft people there. They are usually a helpful bunch, in my experience. If you ask the EAA using this link: http://www.eaa.org/chapters/resources/contact.asp they will probably be able to give you contact details for the Lakeland Chapter.

Jeremy

 

Hello Jeremy !

We are on the same wavelength I see ! I have been an aircraft mechanic
and am currently helping restore a 1934 Fairchild 24 c8c what yall would
call a uc-61 I believe.
The only kind of hat type stringer I can find here is a sine-wave shaped one
and it is too thin of a material. I have seen stringers like this on old bigger
planes like a dc-3 or a c-123 or something I cant remember exactly what.
It appears to be maybe 3/32 thick. They way it failed it looks like whan they
made it the ends didn't quite follow the hull curve exactly and the last few
inches were under tension when they compressed it to rivet it - like not
relaxed like it should have been. There is an aircraft junk yard here in town
I will call to see if they have any bigger fuselages scrap. If there were too
many holes that would ruin the idea of using a salvaged one. There is another place which build airboat hulls - all welded.
The part has a gentle curve to follow the hull - not a lot. If I have to make it from scratch I have 2 senarios ---------

1. Use annealed 2024 , fold it on the metal brake (if its not too small to
do in the brake ) . Then , by hand, streach it with hammer and dolly
to get curve. Heat treat. Install. ----- may be a problem to streach
such a complex cross section by hand.

2. Cut a piece of plywood to match the curve of the hull. Bend a piece
of 3/4 by 1/4 steel to match the curve and drill it for countersunk wood
screws into the edge of the wood. This would form a hard edge. grind a bevel
on the edge of the metal to make a suitable radius for a 90 degree bend.
Hole saw holes behind the edge to C-clamp down onto the face of the steel.
Cut out a blank of aluminum and clamp it down to the hard face. Work the
sheet gradualy down back and forth till you get both sides down to 90 degrees. This would make the 3 sided box with the perfect curve to fit
the hull. Maybe take it off and anneal it. Put it back on and clamp on a
short support (maybe a drill press vice) to fold short sections of the skirt
to form the brim of the hat where the rivets would go. anneal and heat
treat. install.

I am concerned that if I try method #1 when I try to streach the finnished
stringer , it will have to be streached different ammounts on the inside of
the radius , the middle and the outside of the radius. I suspect it would
get pretty distorted since I cant do all this at once. I have streached and shrunk angle by hand with a mallet and dolley - but you basicly only work
one of the surfaces. This thing has 5 surfaces !

I am thinking method 1 would be best.

Yes, I go to lakeland every year. They lost 75 aircraft last time to a bad
tornado ! The day after I was there. I thought we were getting one that day too, but it didn't.
I know quite a few of the antique rebuilders in the area but not many know how to make parts from scratch. Reillys in Kissimmee would have been the
place but they are out of business. The practically built warbirds from scratch
there. Just used the old parts for patterns. I might e-mail the TinMan
Kent White - the best sheet metal man who ever lived (www.tinman.com)

Are you into airplanes there ? I have followed the restoration of several
Hawker Hurricanes there in GB. Would love to do one. Not many here.
I know where there is one but they would never sell it and I couldn't afford it if they would ! Maybe in the next life !!!!!!!!!!!!!!

Cheers !
Tim
PS. I cant figure out why people think I am not searious about doing the things I do..... I sound searious don't I ?????
I guess most people just throw things away without even trying to repair them. The longer I live the more I would rather
have something old I have overhauled than some brand new junk that cant even be dis-assyembled !

 

I have seen simular stiffeners in a gregor welded aluminum hull that were welded in on the edges of the flanges and some of them were cracked also. I am pretty sure gregor just used 5052 grade. In the 5052 grade at .090 or .100" thick it would be easy to brake up on a press brake with narrow dies . Being that small and light it shoud be easy enough just to wedge them in to the hull curve?
These here where an 1-1/2" tall and wedged in nicely.
Tom

 

Aluminum supply

I found T-6 and 5052 at a place named: A.C.M.E. Industrial Surplus in Sanford, FL. 407-328-1280
They also have Titanium and all sorts of goodies. I ignorantly thought I could use bars of Zinc for my anode set-up (on my 1969 Marinette Houseboat--all aluminum.) ACME has lots of it. I have too many questions about anode protection, but that's for another thread I guess.) ACME is worth a visit though.
I had an outboard motor bracket (1/2" thick aluminum-T-6-framing ) welded together by these other guys who actually make air boat hulls. They are known for proper aluminum welding (and I couldn't hire anyone to weld that thick.) This air boat manufacturer is called Alumitech Airboats in Orlando: 407-826-5373 or check www.alumitech.net
Good luck, Roger--Mt. Dora. Check out my headache: http://s1216.photobucket.com/albums/dd377/projecthouseboat/
Specifically the question about the thru-hull fitting.

 

5052 is an alloy generally used for architectural applications. Sheet metal work is often done in that alloy because it works well. It'll work OK in your boat. The T-6 designation is a measure of hardness not an alloy description. You probably will not find 5052-T6 But there is plenty of 6061- T6 in circulation.

 

Ok, thanks in Lakeland. Yeah it was 6061 (T-6 harness) that I used for that thick frame I used to shore up the inside of the transom area (the frame is in-turn inked to the stringers.)
http://s1216.photobucket.com/albums/dd377/projecthouseboat/?action=view&current=19c55308.jpg
http://s1216.photobucket.com/albums/dd377/projecthouseboat/?action=view&current=10797836.jpg
http://s1216.photobucket.com/albums/dd377/projecthouseboat/?action=view&current=98b05f04.jpg

 

The “T-6” is the temper designation. Nothing to do with hardness.

The “T” refers to heat-treatable alloys. The 5000 series is strain hardened NOT heat treatable, and has the designations “H”, or “O”.

FYI, T-6 means it is solution heat-treated or cooled from an elevated temperature shaping process and then artificially aged. This designation also applies to products which are not cold worked after solution heat-treatment, or in which the effect of cold work in flattening or straightening do not alter the limits of mechanical properties.

 

What I wrote is actually the case; T6 is a description of the alloy temper, not hardness. In this case, T6 refers to an alloy that has been solution heat treated and artificially aged. The big change from this process is to increase the tensile, shear and bearing stress limit of the alloy significantly. It doesn't change its stiffness (Youngs Modulus) but does make the alloy significantly more structurally efficient (in terms of weight per unit strength).

Unfortunately, whilst it's easy to anneal alloy from the T6 temper back to a weaker state where it's easier to bend without cracking, it's not so easy (at least for an amateur) to re-heat treat it to get it back to T6, as requires careful temperature control through the whole heat treatment process over a prolonged period of time.

 

aluminum work

Rsimon:
I have been to acme regulary. It is a great place to find raw materials for
projects - and they are great folks there. Only down side for aluminum is
a lot of surplus stuff does not have the ID stripe left on it so you can't tell what it is. Sometimes you don't need to know though. If you plan to weld or heat treat it you do !
I have also been to Alumitech too. We had a fuel tank made there last year.
They weld Al there every day so they should be OK at it. Though the welds
in your pictures seemed a little bloby and uneven - but it was hard to see
that closely ....... If you need to weld 1/2 inch aluminum you need some
pretty big current. There is a place on south orange avenue near Kaley
.... there is a barbecue place there on the west side of the road. Right
behind the BBQ is a machine shop that can Tig weld that thick. They use
miller dynasty 350 inverter Tig's which should so-to-town on mere 1/2 inch !
They are nice folks too. Check them out. small but fully equipped shop.

I looked at your pics, ... hard to visualise your instalation from the drawing.
Are you putting a V-8 on end up inside the box and running the lower end
out the slot in the back ?????????
It it a auto type v-8 ? or a normal style but huge outboard ?????
- and the box like a hardpoint to distribute the stress and vibration out ?

I always wanted to try a 1400 HP pt-6 gas turbine GPU but I havn't seen any
of those cheapo - or at all ..... your boat wouldn't hold a big enough fuel
tank for that !

Seariously though .... I would have thought a big diesel might be good on a
houseboat. Maybe the cummins that dodge uses on their ram pickups.
They can be jacked up to 900 HP if you want ! Or just chug along easy
for the next 30 years !

I think no one has a stringer ready made to match. I will have to hand
form. I may have to build a heat treating oven. Put an electronic heat
control on it. (programable type) They are cheap at skycraft !

Looks like a neat rig ! I am considering welding up an aluminum transom "insert"
to take the place of the ply in my clipper. Depends what the existing
wood looks like !

PS Garry at Aluminum supply is also great to supply less-than-sheet sizes
of aluminum. Have not been impresses with Jenks metals on sand lake.
They don't want to fool with small stuff. Alro in castleberry is OK but more for steel. They have some aluminum but not as much as acme. They are higher than acme as well.

Interesting project ! More Pics !

 

The box-like structure hanging off the back of the outside of the boat (transom) is where a regular outboard motor (Evinrude 150HP) will attach. The bracing on the inside is tied to the stringers. Did you see how bad the hull was? That was an unexpected surprise.
The 1/2" thick plates have already been welded (by Alumitech.) Where is this small place behind the BBQ place? Also, I think I have heard of the Aluminum Supply company. Your right about the aluminum not being labeled though at A.C.M.E. Pics are ongoing on that site.

 

aluminum...

Aluminum supply is about a block North of the old tangerine bowl.
It is on the same street as the automotive paint store except about 200
feet north of it. I think the street is Atlanta ave.
The machine shop is on south Orange ave just south of Kaily. West side
of road. Watch for a bar-be-cue place. Pull in there. To the right and behind of it you will see some steel buildings. The machine shop is the one nearist the rear of the bbq place. I had their card somewhere but I can't find it. Talked to the owner. Nice people. He has four Miller Dynasty
350 tig/stick welders. That will Tig up to 1 inch aluminum. That should do
anything your boat should have I would think. (?)
So the structure is just a way to put on a big motor and not distroy a weakened transom. I couldn't really see the picture clearly enough to see
the transom was really bad. I was thinking of a fix like that you might take
a full sheet of 3/8 6061 and make a plate which would cover the inside of the
transom area all the way out to the edges. Then take some aluminum channel about 1.5 by 1/4 maybe and turn it on edge. tack it arround the
perrimeter- all arround all 4 sides. Then take it out to the welding table and
add several verticles where the motor clamps go - then some horizonals in
between them. Like a waffle. Then weld all that to the 3/8 sheet. Then take a thinner sheet of say 3/16 and cut out a similar matching part as the thick plate. Drill holes in the thin plate which correspond to the channel
bar's locations. Drill a hole say every 2 inches. Lay the thin plate over
the bars and weld through the holes - welding the thin plate onto the beams.
That would give you a stiff honeycomb type structure which could fit
into the space used by the transom wood. You could even add a piece of
1/4 thick 2 inch aluminum angle to the perrimeter on the inside arround the edge. weld it to the new plate. Let the flange face foreward . Then use
a double row of solid bucked rivets to rivet the angle's flange to the last few
inches of the hull. That should hold the new plate 360 degrees arround the
hull. Then maybe a couple of big ( 3 feet) gussets from floor to transom
rite where the motor attaches.
If you can visualise what I have not very clearly tried to paint a picture of
???????

I may try this if my transom wood is bad. - a lighter duty version for my little
boat ! I was immagineing something like a heavy duty version of
aluminum honeycomb. It is incredibly stiff for its weight.

Next time I pass the machine shop I will get another card for you !

Best wishes and keep constructing !
Tim

 

The design is to beef up the area that did not originally intend on having an outboard attached. The transom is 1/8 thick aluminum (the boat, a Marinette, is all aluminum.)
This is the concept of the outboard motor bracket. http://i1216.photobucket.com/albums/dd377/projecthouseboat/ed71f5a9.jpg
The bracket/box will bolt through the transom to a bracing system like what I've done here: http://i1216.photobucket.com/albums/dd377/projecthouseboat/19c55308.jpg
And the result with the help of some local machine shops and welders:
http://i1216.photobucket.com/albums/dd377/projecthouseboat/98b05f04.jpg and inside:
http://i1216.photobucket.com/albums/dd377/projecthouseboat/10797836.jpg and
http://i1216.photobucket.com/albums/dd377/projecthouseboat/d068cc84.jpg

On a separate question, see my post on the "Boat Design" thread about "Propane hot water heater location--rendering." What do you think?

 

RS:
The welding place is called "Badger welding" and is behind Cecil's BBQ .
Just get directions to Cecils and you are there !
WoW ! 1/8 inch transom ! The hull must be thicker than that. In aluminum aircraft
when they have that situation sometimes they overlap several layers of skin so the
total thickness effectively tapers. Might be 3 or 4 layers at the motor mount and
maybe each layer ends 2 feet from the previous as you move rearward away from the
engine area. This kind of lets the stress and vibration spread out across the whole
structure.
I see the big arms which connect the transom to the bottom of the hull. Have you considered a web type shear plate triangle (maybe 1/4 sheet) welded up against
the face of the arms. Maybe to better resist the motor torque on the arms which
would tend to lift the front of the arms and the also the bottom ?????? You could
bend a small flange on the bottom of the plate which could be riveted to the bottom.
Just a thought .....
The fellow at Badger (Cliff) was very nice to me. I was just poking my head in to see
the place !

Tim