This question to Bob...

[fairchild]

Did you intend us to route the rib form blocks directly off the master rib model--
so that the wing's completed thickness would be an extra .100 in (4x.025) thicker
than the mylar drawing ? ( I was intending on doing it with a copy bit this way)

OR-

Do we need to reduce the form blocks thickness by .050 on all 4 sides so the completed wing's thickness matches the mylar sheet #4 ? (form block + rib and
skin added on top and bottom = mylar dimensions)

Also--- when I am sanding down my master rib model-- should I sand to the
outside of the line in the mylar, to the center or to the inside of the line?

I dont want a dimensional error on the ribs to intrude into the surrounding
parts so that I later run out of slack later.

I asked the question about form block size on the bearhawk forum but no
one else knew the answer either--- so I will pass on your insights to them
so we wont have to ask again ! Sorry to bother you but I dont want to cause
an error right at the beginning ! Thank you ahead of time !
Tim

Sent this to him by the e-mail box on his plans page.
Will post answer when i see it ! On hold till I can understand the correct way forward.
Tim

[Archer39J]

I'm calling it, dwg #4 represents the exterior profile of a completed wing, skin and all. I don't really know, but I'll bet 10 internet dollars on it

ETA: Actually, false. If you look at dwg 3 you find this:

wing form dwg.PNG

No internet money for me today...

[Chris In Milwaukee]

Sold! As described earlier, it honestly doesn't matter. Cut the form to whatever size you choose, inside or outside the line, and run with it. Whatever you start with, be sure to finish with it. It really is that easy.

If we use Eric Newton's build manual as the standard, it will tell you sand just until the line disappears.

For the new folks who haven't yet heard this said about a Bearhawk, we're building an airplane, not a watch

~Chris

[Archer39J]

Sold! As described earlier, it honestly doesn't matter. Cut the form to whatever size you choose, inside or outside the line, and run with it. Whatever you start with, be sure to finish with it. It really is that easy.

If we use Eric Newton's build manual as the standard, it will tell you sand just until the line disappears.

For the new folks who haven't yet heard this said about a Bearhawk, we're building an airplane, not a watch

~Chris

Darn, and I already had it spent

Yeah, these aren't precision machines. Inside or outside the line shouldn't matter as long as it's consistent. "Beat to fit, paint to match, engineer as-built" as the saying goes...

[Chris In Milwaukee]

Darn, and I already had it spent

Yeah, these aren't precision machines. Inside or outside the line shouldn't matter as long as it's consistent. "Beat to fit, paint to match, engineer as-built" as the saying goes...

Yes, yes! That was a saying that I first heard from SportAir Workshop instructor Buck Greenlaw. Words to live by!

Another great saying from Earl Luce when he taught me gas welding 4130, when building a steel tube aircraft you "Measure it with a micrometer, mark it with a grease pencil, and cut it with an axe."

[fairchild]

OK--- here is Maria's response ( I think she is the one who drew up the plans--- so I count her as the "smartest guy in the room" here-- :-)

Tim. Drawing #4 is the form block, so you shouldn't subtract anything from it. When cutting the form block aim for the middle of the line, do not cut to the inside because then there is no prof you have the correct form shape. The Bearhawk Book shows to use a I inch thick form block. Please read over the Bearhawk Book thoroughly and study your plans closely. Thank you for your question, Maria Barrows Harris So- it Is as I hoped logic would indicate-- that the outline in the mylar IS the form block. That arrangement makes our end much easier I think..... I can simply use the duplicating bit to cut the form blocks right off the 2-nd master rib model. Then im off to the races. ALSO -- i did notice that on page 4 (mylar) the front and rear spar lines have the "center-line" abbreviation beside them. So- I think it is safe to assume that line represents the CENTER of the spar sandwitch. So that will enable me to calculate how long the rear tail is on the nose ribs. (and taking into account how many layers of plates are stacked under it against the web ) That should be where the 2 little removable spacers come into play so the tails are longer where there are fewer plates stacked. Might make them out of 2 strips of 1/8 aluminum with pairs of counter sunk wood screws so the bearing on the router bit doesnt feel any bumps as it rolls over them. I should be good to now make my plates to cut the blanks out and then the form block. I MIGHT experiment with coating the corners of the form block with minwax wood hardener to see if that toughens the corner to better stand up to hammering or air hammer flow forming. I can go kick some sheet metal backside now ! :-) Tim

[whee]

I don't think Tim will take this the wrong way but I kinda had to chuckle about this. Tim has to be the 5th or 6th guy in the past few months to ask a bazillion questions about building the form block and banging out ribs. I'm probably one of the cheapest guys on the forum but if building these parts is really as hard as you guys make it sound I would have sent Mark a $3500 check for ribs and spars the day after I ordered plans. Build on ya'll, I'll follow along with interest.

Chris, you need to stop flying the Maule and start working on your plane again.

[Chris In Milwaukee]

Chris, you need to stop flying the Maule and start working on your plane again.

Don’t I know it! Getting skis put on Friday morning.

As for building, well, this is the state of the makeshift shop at the moment. I’m going to have to make room in the basement to work this winter, methinks.

[jaredyates]

You need to get yourself a Fred shed and store your stuff!

That's a line from the frequent TV commercials of Bearhawk builder Fred Spain, who also happens to sell sheds.

[fairchild]

Chris--- you need to call up Arthur Twosheds Jackson ..... remember him from montey python ? Wow - i thought my shop was a little jammed up---- :-)
Whee : I guess we all have different tendencies in the way we approach problems. Everyone makes fun of me. My typical mode is to find something that is so hard
no one wants to do it. I spend a week making a tool to accomplish the job- and when the tool is used it only takes 5 minutes to do it. but it took a week to make the tool.
I grew up making tools as I needed to do whatever one of a kind project presented its self. That was my dads role model I guess. (smartest man I ever knew- but I never
understood that when I was younger)

i feel like there are a lot of parts in this wing- that have to interlock like a huge erector set. Sometimes on something like this - if you make an error right at the front end-
that can force you to carry that error all the way through--- and it seems like you never get away with it---- it always bites you somehow somewhere . a little error later on might have far less impact than one at step 1. The other thing is--- I have to admit -- I do love to make a tool to make a product im building come out better in some respect. It may or may not
have any impact on building--- I just like doing it that way if I can.
and a final thing I remind myself of repeatedly--- I try to make a thing twice as good as it needs to be- because often I make it only half as good as I should have. And still there is a can with some crumpled up duds.

I think the wings are going to be fun. Will be fun to see if I can build a wing as nice as cessna or piper. I expect skinning will be one of the harder parts. Time will tell.
I can move forward now though making ribs ! Yeah !

BTW----
Regarding Eric's building CD's ---- are they the same as his on-line web pages ? or are the CD's more detailed ?

Tim

[Chris In Milwaukee]

It’s always a good time thinking about a better mouse trap. I’ve thought (and overthought) a lot about this airplane. The conclusion I’ve reached is that the spacing between the spars (and therefore wing attach points) and keeping the assembly square are probably the biggest deal. But if you’re scratch building, you can even easily account for that. There’s enough flexibility in the dimensions of all those parts that you’ll be fine if you’re off by a line’s width.

Eric’s web site is a small, small portion of what’s in the manuals. Definitely worth the purchase. An amazing learning experience. Everything we’ve discussed here will make perfect sense after your first pass through them. And you’ll find something new every time you read them again.

Once you get started, you’ll see that it isn’t overly complicated, just monotonous. I’m at the spars part at the moment. Plenty of hours spent, and many more to go.

[sjt]

IMG_5146.JPGIMG_5147.JPG
I followed the build practice that Maria mentioned in post #6. I found the 1 inch mdf material at a place that caters to cabinet makers. If you use the 1 inch material you can route 45 chamfers on either side to decrease the number of form blocks required. I think my sheet was about $50. The 1 inch sheets are a little bigger then 48 inches.
stan

Also, Bob would recommend you make all of the nose and center ribs without accounting for the capstrip material. The ribs can be adjusted to the correct size at assembly time.

[Bcone1381]

When I flanged my Rib lightening holes, I used Glenn Patterson's instructions using MDF dies to form the flanges. I formed my lightening hole flanges after had formed my outer flanges. The MDF die method works, but there are a lot of MDF parts to fabricate before those holes get flanged! When the ribs came out of the hole flanging process, they looked like potato chips, and required straightening.

Shortly after I finished the lightening hole flanging, I saw Chris in Milwaukee's method.... rubber pressing his flanging holes in his Rib Party thread. Go to post 29 in the thread below. I consider the entire process that Chris used to be an industry best practice.

https://bearhawkforums.com/forum/bea...ib-party/page2

Note in particular that Chris flanged the lighting holes before he put the outer flanges on the ribs. He used the Rubber Press. There is no apparent distortion, and the parts count for making the rubber press dies merely consists of putting a chamfer on your rib cutting die that you already have resulting in a significant time saving and improved quality.

My suggestion is to Rubber press everything you can. Rib Lightening Holes, Aileron nose ribs, Flap Nose Ribs, Pocket Ribs, maybe aileron and flap ribs. The nose ribs and main ribs are too large to rubber press with a 20 ton press.

[Chris In Milwaukee]

Thanks for the shout out :-) It really did work well! I credit John Snapp (@N3UW) with the process. Beautiful stuff!

[JimParker256]

Eric, just curious... Did you ever finish the Patrol-specific build guides? I still think a Patrol-specific set of guides would be extremely helpful, and would be happy to proof-read, or whatever other assistance you might need with it. (Just sayin... :-)

[fairchild]

BCone---- I was thinking about making my rib forming blocks from 2 sheets of MDF - either 1/2 +3/4 or 3/4 + 3/4

Also thinking about the idea of pressing the flanged holes with the rubber -press method. Im thinking of why not let the rubber - at the same time-
press the outer edges down. I expect it could/would fold them down part way- maybe 1/3 of the way. i would guess that most of the distortion might be
induced at the first portion of the bend. So if that first portion was bent vis rubber---- that might make it easier. Then I would finish the edge bends
with it in the MDF sandwich and mallet or flow forming tool. I think my ribber is about 12 by 18 so I can do the smaller rib parts.
Do you think that will work ?

SJT- I may try taking 2 pieces of 3/4 and gluing them together to make a 1.5 inch blank. Yes- thats a good idea to use both sides so you dont have to make a seperate left and right.
Might also try minwax wood hardener on the corners ( if it is still made) to make them tougher when using the air hammer.
Tim