Aluminum sheet required

[TTAero]

I found this pdf with sheets required to build bearhawk wings. I was wondering if anyone knows if this is accurate (or pretty close ) for the Patrol? I am in California working for the next few weeks and not near my plans to break it all down, but it just hit me that I could swing by spruce while I’m down here and carry my material home myself.

http://mybearhawk.com/wingneeds.pdf

thank you!

[geraldmorrissey]

I would get;
2 sheets 4x8 .032 for spar webs and ribs
3 sheets 4x8 .025 for ribs and misc.
1 sheet 4x12 .125 for reinforcements, or buy the one piece spar web reinforcement from Mark if and when it becomes available.
This will get you started and leave enough stock to build a resonable scrap pile. You may have some excess, sell or better yet give it away. Try to get plastic coated stock. Might be a good time to pick up some steel, expensive to ship.
Gerry
Patrol #30

[TTAero]

Thank you. I bought the spar and hydro formed ribs from Mark. I’m sorry I should have been more specific. It’s mainly the skin call outs in that list I would need. I’m trying to grab stuff while I’m here , but also I’m concerned about rising prices of material. The plan was to weld out the fuselage this summer and build wings during the winter.

[sjt]

b1.jpg PATROL
Always buy the 12 foot length. The 032 is wrapped completely around. Other 12 foot sheets can be split into 6 foot lengths. One six foot length for left wing, the other six foot lenght for right wing.

I believe the patrol has 020 bottom skin. I know some builders use 025 for the bottom skin.

I would also buy the alodine ,acid, and epoxy primer in case it needs a hazzard surcharge packaging.

I also bought some 016 for the Aileron pocket rib covers. You do not need much, I think a 4 x4 foot sheet maybe?




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sjt patrol 284

[Fly Alaska]

This is a great diagram from how to cut up sheets for skinning a bearhawk patrol wing and found it very useful. In looking at my set of plans, the .025 skin measures wider than 48"... is that just a issue with the drawing (i.e. not to scale) or do I really need a sheet wider than 48"? Also the plans call for .020 for the bottom skin, but I have seen .025 mentioned in various placed... any thoughts on that? Thanks for any info you can give me. I am a first time building and brand new to the bearhawk community.

[TTAero]

Great info. Thank you!

[Fly Alaska]

This is a great diagram from how to cut up sheets for skinning a bearhawk patrol wing and found it very useful. In looking at my set of plans, the .025 skin measures wider than 48"... is that just a issue with the drawing (i.e. not to scale) or do I really need a sheet wider than 48"? Also the plans call for .020 for the bottom skin, but I have seen .025 mentioned in various placed... any thoughts on that? Thanks for any info you can give me. I am a first time building and brand new to the bearhawk community.

[sjt]

The .025 skin wraps around fuel bay. It is less then 48 inches. In the cut diagram above I include a black and white photo from Bob's book. It shows the bottom skin as 020. 025 would add some strength but at the cost of more weight. Always buy 12 foot sheets. You can split it into 6 foot by something less then 4 foot for fuel bay. The 025 wraps
the same as the 020 across the top. The only sheet different is the 032 piece at the root. You will have to have bought a 12 foot sheet for that piece. I drew the 032 differently on my diagram to show that you can not use 6 foot lengths as was done with the 025 and the 020.

The 020 bottom skin goes from tip to the fuel bay. It does not go under fuel bay. You will have to do maintenance on fuel tank and there is a panel that can be removed on the bottom of the wing so that the fuel tank could be removed.


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[SpruceForest]

BLUF: We ran into the same issue when the second KFDK-based Patrol build started, so decided to bite on the sheet stock and mill it up on my cabinet saw. You might see what Spruce will do for you on splitting a sheet with another builder if you know of one, or just do what we did: mill up the extra set of spar caps and run a classified ad to find others in the same boat. An alternative for you is to look for someone in your home area that did the same thing.

Discussion:

We have what amounts to a perfect storm in aluminum demand and available supply right now... Russia are off-line, super-tight capital market for investment in other sources, we have issues with our domestic mills, and we are still recovering from the 2020-2022 worldwide 'whiskey and bad decisions' event, so absolutely the worst time to buy anything made of the stuff.

Your problem on ordering up all that aluminum is going to be the main and rear spar caps... DAMHIKT. For the Patrol, main spar caps strips are 0.125 x 1.000 and rear spar caps are .063 x 0.750.

Cap strip material has risen in price to the point where it is about as expensive to buy a full 4' x 12' sheet of .125" and 0.063" materials (generating three full sets of caps from the 1/8" sheet and 6 full sets of rear caps from the 1/16" material) versus paying $1200 plus shipping (~$600 or more) and an indefinite 'out of stock' status from AS or $1400 plus shipping (~$600 or more) from Wicks. Current price of a 4x12 sheet of 1/8 and 1/16 delivered to KFDK was $1700 from Wicks, so a no-brainer.

And just to add a little sting, my order for caps that delivered in June 2022 ran $775 delivered from Spruce, and I considered that pretty steep for the stock I received.

[sjt]

I did not do it this way But -- In the case of the rear spar you might ask Bob about doubling up 032 for the rear spar. 032 can be shipped rolled 062 can not be rolled.
There is another option for the rear spar. I know Aircraft Spruce sells 2024 angle 3/4 angle in 1/16 . You could rip off one of the legs -very waist-full. But if you only need a single 12 foot strip???


The cheapest way is rip 4x12 foot sheets - with a very thin kerf blade. I have never tried ripping 1/8 with a circular saw. Then find another builder. Different Bearhawk models have different width capstrips.

p.s.
When I have ripped aluminum with a circular saw it required a second person to hold a vacuum and remove the 1million chips that are flying everywhere.

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Big box stores sell straight edges. I bought several and used the new 2024 sheet as a straight edge reference and then used gorilla glue and a long strip of MDF to make my very long straight edge. The 2x2 piece of steel was only used to glue up the MDF and short straight edges. Circular saws need clearance so the MDF has to be longer then 12 foot so that it can be clamped and not interfere with circular saw.

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[Steve W]

I used a 16’ table. Drilled and screwed (on the bottom of the saw) a 2’ 3/4” angle 1/8”wall parallel to the blade of a new DeWalt circular saw with 1 1/16” cutting gap. Used a quality aluminum cutting blade. Cut all the 12’ strips for the Patrol and sold the rest to a nearby 4 place builder. There was a 1/32” width discrepancy between the two ends of the remaining sheet. I lost a couple of teeth on the blade so be prepared to have a second on hand. The long gate on the bottom of the saw works extremely well for accuracy.

[Steve W]

I posted this back in 2015:

Phil, I got a small piece of thick aluminum angle 3/4X3/4" 18" long and mounted it to the bottom of a good quality circular saw. After squaring it to the blade, I drilled several small holes through the saw bottom plate and the angle. Confirming it was parallel to the blade, I screwed it together with a couple of #6 screws. With a quality non ferrous blade, I cut all the 1/8" cap strips and the .063 for the Patrol a bit wide than required and finished them of on a router table. Think I used 2 blades to complete the job. The angle acts as a gate/guide and after finishing all the required cuts, the remaining sheet was within 1/32" compared from end to end. I then got the table saw out and ripped two groves in a 12' piece of 2x4 and slid the capstrips in so they could be cleaned up with a vixen file.

1 Photo

[SpruceForest]

I believe the 032 option was discussed and found AOK by Bob as mentioned, but those that have looked at it suggested that trying to manipulate multiple layers of 10' plus of 032 x .75 would be a lot like working with cooked spaghetti, given it's 1/8 the stiffness of .063 stock in bending.

A more pertinent question might be if the 1/8" caps on the main spar can be doubled out of 1/16" stock, which would get all cap stock out of one sheet of 4 x 12 x 1/16" stock? Still more expensive than a group buy on 1/8" and 1/16" sheet.

On the angle stock, you need 4 pieces of 1" x 1" x 063 to get 8 x 3/4 wide caps out of the material, and that takes a good table saw for the work. I did exactly that for my caps, but if Wicks or Spruce gets angle back in stock (a big if... both are showing out on most stock sizes), that is about a $500 ($257 material + $240 shipping) versus $500 for a sheet of 1/16" plus truck freight... maybe $1K or a bit less? Big issue is angle is massively expensive right now. I did a quick look at using 1.5 x 1.5 x .125 split for caps, but that gets into truly ridiculous cost even before truck freight.

Re: our sheet buy which we hope becomes a group buy:

Aluminum has arrived from Wicks as of this AM. Think we will come in somewhere around $380 per set for main spar caps and $100 for a set of rear caps, plus shipping & packaging out of KFDK to group member address. Carlo is doing the leg work on packaging and arranging truck freight service, so no issue if it makes sense to ship from MD to wherever. When we get a final price, I'll put that in classifieds.

[sjt]

If I had to use 032, --- I would -assuming it is an allowed process - glue the predrilled 032 strip to the rear spar. Then drill the holes thru the spar. Then glue another 3/4 strip - that had not been drilled- on top of the first strip. And then drill from the other direction. The glue would have nothing to do with the strength. It would just hold it together long enough to rivet.

I think the circular saw method is cheapest. Just do not assume the other bearhawk builder has the same capstrip width. The patrol has 1/8"x1"x ~12' Other bearhawk models may not be 1".

I do not have good records from the time of making center spar blanks. It is possible that with the correct layout of a 12 foot 032 sheet I might have had enough material to make 032 strips.



You need more then the 12 foot 032 sheet for the root skin and flap spars

In addition:
Probably (two or three ) 8 foot 032 sheets or maybe two 12 foot 032 sheet
8 032 full size center ribs rib 2, rib 5 and a double rib 1
2 false spar behind fuel tank
2 main spar (could be made using 8 foot sheet)
2 rear spar
several smaller ribs around fuel bay
aileron spar


Bob suggests that you glue the #4 drawing mylar to a piece of 032


my point is that if you either needed 3 8 foot 032 sheets or two 12 foot 032 sheet you would be better off getting the two 12 foot sheets.
You might want a strip of 12 foot 032.