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The Unofficial Bearhawk FAQ

Tools and Workshops

 

Introduction by Del Rawlins

By its very nature as a plans-built aircraft, the Bearhawk will require quite a few different tools that most "do it yourself" types won't have in their inventory. Fortunately, because of the simplicity of the design, the list of special (read: expensive) tools has been kept to a minimum. Quite a bit of the plane can be built with nothing more sophisticated than hacksaw, file, and tin snips, for builders working with a lean budget. Conversely, if one can afford more sophisticated equipment there really is no limit to the amount that can be spent on the conveniences that will make the project go together more quickly and smoothly. A substantial portion of the Bearhawk e-mail list traffic has been about required tools, ideas for getting by without spending a lot on them, and non-required items which can make a homebuilder's life simpler. The following tools have been recurring topics on the list:

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Sheetmetal Bending Brakes of Large Dimensions by Del Rawlins

To fabricate the wing spars, you need at least an 8 foot brake, capable of bending .032 2024t3 along its full length. Brand new, such a tool runs about 3 grand (that's three_thousand_dollars) from an American manufacturer such as Tennsmith or Connecticut. I am unaware of any imported brakes of this size. This being the case, not many Bearhawkers are liable to have one in their shop. Since it is only required for bending the wing, aileron, and flap spars, Bear-Tracks recommends that you try to find one you can use locally, like at a high school shop. Many builders have their spar webs bent by a professional (don't have them bent to the plans dimension, they have to be bent to fit your ribs), and at least one builder has had success getting them bent at a shop specializing in heating, ventilation, and air conditioning work. And for the ultra ambitious among us who must do everything themselves, there is a set of plans available to build an 8 foot brake.
 


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Smaller Metal Bending Brakes by Del Rawlins

If you already have one of the 8' brakes mentioned above, skip this section (and I'm sure you are aware of being envied among homebuilders). If not, you should still consider buying or making some sort of smaller brake(s) for doing the rest of the metal bending on your Bearhawk. 4-6 foot brakes in varying capacities are available at prices ranging from a few hundred to over $1200, any of which would be worth having around. Additionally, it is possible to make your own brake. There is a book called "The Racer's Guide to Fabricating Shop Equipment" which sells for about $12. It contains instructions for and photographs of a 5 foot metal brake which you can build yourself from commonly available steel stock (you will need to have access to an arc welder).

The above mentioned book also contains instructions for a lot of other useful tools, including a hydraulic press which I built. I made a set of forming dies (essentially a press brake) for making the heavy 4130 fittings and they worked beautifully. Pictures of my press, dies and the parts I made with them can be seen in the other improvised tools section.

And the cheapest brake of all can be built for less than $40 total investment. It is limited in what it can do, but is just the trick for bending the rib stiffeners and attach angles from 2024t3 sheet. It is an off the shelf unit, modified to handle aircraft material and best of all it doesn't take up any space when you aren't using it. Pictures and a description of it can be found on the tools section of my own Bearhawk project page.
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Drill Presses by Del Rawlins

A good drill press is another necessary item that you cannot build the Bearhawk without. Don't do like I did and buy a cheap imported press (made in China by slave labor). While I managed to make it work well after a bit of tweaking, it was a pain in the butt and I would have returned it except the cost of shipping it back to Bellingham from Alaska would have exceeded the cost of the unit. When I moved I ended up just leaving it in my shop when I sold it. It has been recommended to me that when shopping for a good drill press, try to find an older Delta press; apparently the new Delta stuff is also made in Taiwan and may not be as good. A good place to look for one might be a High School that is liquidating its shop program (which seems to be common these days). If you want a new press, I've had pretty good success with the JET floor model (Taiwan) that I bought when I moved. It isn't perfect, but it is way nicer than my previous press.
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Scotchbrite Polishing Wheels by Del Rawlins

On April 8, 1996 Russ Erb wrote in response to the question:
>Finally, the books recommend using a Scotchbrite wheel to polish the
>edges. Is it effective?

Scotchbrite wheels are WONDERFUL! You can get the appropriate hardness from Avery tools. They have a 6" wheel for a bench grinder, and smaller 2-3" wheels you can put in a drill or drill press. It gives a smoother edge than a file. I use it, and everyone I know using aluminum in EAA Chapters 1000 (Edwards AFB) and 49 (Lancaster CA) uses them. Highly recommended. The smaller wheel works good on lightening holes. Bob Barrows mentioned using a flap wheel on the lightening holes, but I'd be concerned it would remove too much material.
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Metal Cutting Bandsaws by Del Rawlins

It seems as though most of us building the Bearhawk from plans own and use some variant of the ubiquitous 4"x6" taiwanese bandsaw, which is available for $200 or less from a variety of sources such as Harbor Freight and Grizzly Industrial. No matter whose version you buy, they all seem to be pretty much the same thing, although there are also more expensive versions available (such as from Delta) which may or may not offer any extra features. The one universal recommendation seems to be buying a better blade than they come with; my saw is fitted with a 24tpi Starrett blade from MSC.

These saws have been discussed regularly on the email list, and here are a couple of the more useful posts:

On September 3, 2004 Budd Davisson wrote:

I've mentioned this before, but the group is growing so fast, I'll do it again:

First, I'm on my second Taiwanese metal cutting bandsaw. The first one only lasted 28 years, a half dozen airplanes, a couple of cars and God knows what else.

Second, make a four inch square table out of 3/16" or so to replace the little bitty table thing or the big floppy one that comes with it. It'll make it much easier to cut out parts and you can remove it in seconds by pulling the two screws in the middle.

bd


On September 6, 2004 Tom Walter wrote:

No recommendations really on what saw to buy... but
most of us probably have the $199 harbor freight band
saw.

Budd recommended making a new table out of 3/16" steel
plate (or was it 1/4") larger than the original. Just
easier to cut out pieces when it is in the up right
position with a better table.

On my saw the gear box was full of swarf (metal
chips) when I got it. Cleaned it out, and used 90W gear
oil in there. Seals held fine, and oil helps in
transferring the heat.

Spend money on good saw blades. Course 10 tpi for
aluminum, much finer (24?) for cutting thin wall
tubing. I remember "alway three teeth on the work"
but for aluminum the larger gap helps clean the blade,
and for thin wall tubing you never can have enough
teeth!

On the "pressed steel stand" they wobble all over the
place. Nothing some scrap 3/4" plywood will not solve
once bolted between the legs in four places. My older
model had a shelf built into it, so was pretty steady.
Newer ones had thinner steel leg stampings.

Check out the details on:
http://www.frugalmachinist.com/bandsaw.html

Lots of great tips that he used to improve his band
saw. Also lots of good information on his web site.

Hmmm... just spotted a tip about a budget band saw
welder for $149. For that price, darn temping.

Tom


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Bench Grinders by Del Rawlins

>> Hi Guys,
>>
>> I'm going to pick up a bench grinder (6" I think). What type of
>
>If you haven't bought the grinder yet there is one thing I'd look
>into. The cheap and even not so cheap grinders have large electric
>motors between the grinding wheels. The expensive ones like Baldor
>and other good brands have longer slender motors. Spend the extra and
>get a good grinder. The large diameter motor gets in the way all the
>time on the cheap ones. A good grinder will last a lifetime and and
>over time you will pay for one anyway buying two or three cheap ones.
>Jim


For the ultra cheap, you can try a setup like the one I built for a wire wheel. I use a nice Baldor buffer for my scotchbrite wheel, but I also wanted a wire wheel grinder so I combined some on hand and scrap parts to create the following beast:



The 1/2 hp motor and switch came from an old drill press which a former employee ruined, and all the steel was leftovers from other projects. The wheel for the stand was abandoned for a number of years in the tire shop in Cordova. I may fill it with concrete (or lead) at some point to give it more stability, but for now it is nice to be able to move it around as needed (I work in a small shop). Total investment is a cord, box for the switch, the adaptor and wire wheel. Time spent building it mostly doesn't count when you figure that I would have built a stand for a store bought grinder as well, and that was most of the work.

If I had wanted to spend a little more time/money, buffing arbors are available for $20-$50 which can be bolted to the top of a stand, and then run from a low mounted motor with a V-belt. That gets the motor totally out of the way and provides a second drive end. If you don't have an old industrial motor laying around like I did, a possible source is an old washing machine, but you might want/need to build a housing for it.

One of my ambitions in life is to own a big honkin' Baldor bench grinder, but for now I am pretty well set up for what I am doing (I use a 1" belt/6" disc sander to perform grinder duties):



 

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Other Improvised Tools by Del Rawlins

Most homebuilders share 2 things in common. One being a drive to do as many things as possible themselves, and the other being insufficient financial resources to purchase every tool needed during the construction process. This naturally leads to a lot of experimentation and resourcefulness in creating equivalent, field expedient tools to perform various tasks. These are a few of them, presented in the hopes that other builders will be able to benefit.

This is a C-Frame fixture for dimpling skins and setting rivets. Versions of this tool are available from Avery and elsewhere, but as far as I know, none of them can reach the center of a 48" wide skin like the Bearhawk uses. I made this out of scrap steel which I had on hand. It has a 25" throat, which means it can reach a little beyond the center of a standard 48" sheet of aluminum.

 

These are my bucking bars. The one on the left is 3/4" steel, made using the pattern found in Bear-Tracks. Next is my rendition of a "heel and toe" bar, with a lead filled handle for extra weight. The third is something I made up because I ran into a situation on another project where I thought it would be useful, and the last was the scrap left over from the 3rd bar, and I thought it might be handy at some point. The leather cases are plain cowhide and serve to protect the polished surfaces from getting scratched up in my toolbox.


Neither of these tools were my idea, but they are useful for jigging and welding tube structures. The upper tool is an adjustable tubing clamp/jig as seen in Tony's books and elsewhere. The second tool started out as an ordinary vise grip pliers, but with the teeth ground smooth can be conveniently clamped to a tube wherever needed to provide a rest to stabilize one's welding. Thanks to Bruce Frank for this idea.


As seen elsewhere on my site, I built this press to form steel fittings for my Bearhawk project. It is more elaborate than required for that function, but is useful for other chores in the shop as well. Instructions for building this can be found in "The Racer's Guide to Fabricating Shop Equipment" by Steve Smith.
 

 

 

 

 

 

 

This is one of the press brake dies that I made for use in the above press. Pictures of parts made with this die as well as pictures of the other dies I have built may be found in my project pictures section.

 

 

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Tool List by Del Rawlins

One of the more frequently asked questions on the Bearhawk list is "what do I need in the way of tools?" This is an attempt at creating a "suggested list" of required and optional tools for wing construction. Please bear in mind that this is only my idea of what is needed and if you have any comments, feel free to send them to me at del@rawlinsbrothers.org or post them to the Bearhawk list. Kit builders will most likely need some of these tools, but since I am building from plans I don't really know which. If you are building from a kit you should contact the manufacturer for a list of suggested tools.


Required tools:

Drill Press
Fractional bits through 1/4"
#40, #30, #21 drill bits
Punch set, 3/32", 1/8", 5/32", center punch
Large fly cutter or other adjustable lightening hole cutter
Offset handle aviation tin snips (left and right)
Soft mallet or dead blow hammer for forming ribs
3X rivet gun and appropriate bucking bar(s)
Hand drill (air or electric)
Source of compressed air for above
Means of cutting/sanding form block accurately (a handheld jig saw and bench mounted belt sander work well)
Hand files with cleaning brush
Optional tools:

Router and bits (for cutting aluminum)
Rivet Squeezer (air or hand)
Deep throat dimpling tool (otherwise must use dimpling blocks with rivet gun, not recommended)
"Rivet fan" spacing tool
Scotchbrite deburring/polishing wheels
Unibit Step Drills
Benton Holzwarth added the following suggestions:


Del -- much easier to second guess someone else's work than
to do the initial bit--

I looked around the shop, noting the differences between
your list and my inventory/experience and things recommended.
(Note that some of the recommendations are from RV guys, who
have more Al work to do than we do.)

- safety goggles and/or consider a full-face shield
- fluting pliers (see Beartracks or pay $$$)
- 45/90deg angle drill or attachment ?
- 2# sledge (used with yoke to set -5 rivets)
- Chapter 1000 benches, but built 8' long (Hi Russ!)
- 1/8"x1" angle Al extrusion inset into bench edge for
straight-edge router cuts (I have an 8' shear (w/ 3/8" kerf!))
- cordless drill
- H/V band saw ($140 at HarborFreight)
+ the 'Deep Throat Dimpling tool' is AKA a dimpling/riveting yoke, the
one from Avery (?) has a shoulder on the upper piece to accept a
rivet gun (neat feature.)
- hole deburring tool (Avery)
- micro-stop counter sink cage and cutters
- "pop rivet" dimpler (dimpler set used 'blind' w/ pop-rivet tool
- rivet cutter
- back-riveting set and backing plate (RV specific?)
- 2nd air reg & water-sep mounted at bench or on wood block.
Can be handy to be able to set air pressure at tool, so you want
it close by. I run my system at 95-100 psi, but variable action
on drill works best with 40-50 psi, or adjust pressure at rivet gun
for best control, plus extra stage of drying. (Oil *always*
added at tool.)
- 8' brake for spars (try to borrow or hire.)
- smaller brake for other pieces (use previous, depending on availability)
- smallish shear
- ULTRA FINE SHARPIES
- nibbler (I used a hand nibbler to cut the non-round rib lightening
holes. In retrospect it was a *hassle* smoothing out the bite marks.)
- re: Bench Grinder - mine is mounted on a piece of plywood. It doesn't walk,
sitting on the bench (it's NOT a Baldor!) and can be moved close to hand
when I'm sitting nestled in a mess 'o tubes. (I.e. PORTABLE grinder.)
- Grinder wheel dressing tool
- angle/die grinder ? (for tube fitting)



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