Tell us what you did today on your Bearhawk Project

[Deftone]

After work keeping me busy for a few days I finally got my master form completed. Now working on the router forms. I have the day off work today so hopefully will have them all finished.

I guess that also means time to order my 0.025 and 0.032 sheets. Where is everyone buying from? I have tried locally and online and nobody can come even close to the price at aircraft spruce.

[Chris In Milwaukee]

I bought mine from TW Metals. While the quote is from 2010, this is what I paid for my metal:

https://groups.yahoo.com/neo/groups/...iles/Materials%20Quotes/

Note that quote is for two airplanes worth of metal (4 wings). Not sure how the price of aluminum has done lately, but it'll give you another data point.

~Chris

[Deftone]

It's interesting so many people had luck with TWmetals. My quote from them was terrible, roughly 70% higher than spruce and wicks

[Chris In Milwaukee]

I wonder if it was quantity driven? I bought a *lot* of metal at that time.

[Olm]

At last my ribs and spars are formed, also formed flap spars and elerone spars! Than the top and the bottom part of the fuselage farm are welded. We use stainless steel tubes for fuselage, and russian aluminium d16at for the project.

[Deftone]

Working on the rest of my router templates, about to get my beater forms done. Got a little frustrated with the nose rib router template, not real happy where the leading edge cutout transitions to the flanged part, considering making it again, but for now moving forward.

[Chris In Milwaukee]

If you're not happy, now is definitely the time to fix it before the metal is bent. :-).

[Chris In Milwaukee]

Wrapped up the right side ribs today.




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[Chris In Milwaukee]

Happy to! Routing templates?

[Chris In Milwaukee]

Take a look here and see if there's a good view:

http://bearhawkforums.com/forum/bearhawk-patrol-plans-build/19435-having-a-rib-party?p=19541#post19541

I can take some other pics if they aren't enough detail.

[Deftone]

The pics in that link we exactly what I was looking for, thank you!

[Pat Fagan]

Well I didn't do anything on my Bearhawk, but I did sign into the group for the first time in what looks like two years. Ooops. I'll try to do better in the future. Pat

[Battson]

Good to have you here, Pat.

You're one of the 'Originals'! I remember spending hours day-dreaming, looking carefully at photos of your plane half a decade ago.

[rv8bldr]

I did my tailwheel training on a Stinson 108-3 and really liked the horizontal manual trim handle. When I built my RV-8, I put an electric trim in it, and while it does work good, I really missed the manual trim.

I have been deliberating for months on what approach to take for my scratch built 4 place (well, mostly scratch built; I have the excellent assembled spars and rib kit from Mark as well as the tanks 'n such). I didn't particularly care for the vertically aligned trim wheel, and even though I am planning a two axis autopilot, I didn't really want an electric trim. I was also a little uncomfortable with the trim sensitivity with the servoed tabs, even when the trim tabs were halved in size. A few weeks back someone posted a picture of the push/pull non-servoed tab that Pat Fagan had done and decided that was for me.

Below are a few pictures of the system I have come up with. I made a bent tubular trim wheel mount tube which gets the sprocket above the level of the ceiling crossmembers in the cockpit. I just made the handle out of a piece of tube.

trim wheel.jpg


I made a bellcrank assembly down near where the horizontal stab is attached so I can get at the nuts and bolts for maintenance. The empty fairlead tube you see is a remnant from when I was going to do the normal trim tab mechanism. I'll be cutting that off.

trim bellcrank.jpg


And finally here is the trim tab with the clevis fork. I am going to fabricate a small piece of sheet that will go around where the cable exits the elevator. This will allow the attachment of fabric in a clean manner. The cable itself is held in place with an Adel clamp attached to a nutplate I put in the elevator rib. Hey, I built an RV. I am an EXPERT at installing nutplates... :-)

trim tab.jpg

[Chris In Milwaukee]

Very creative! Well done!

[whee]

Looks great rv8bldr! What push/pull cable did you use? Are you using one trim tab and if so is it the big one?

[rv8bldr]

I'm using the A-930 Push/Pull cable, 60", from Aircraft Spruce. I'm going to use a single, small trim tab and see how that goes. I have already made and installed the other trim tab on the right elevator (hinges and all), My plan is to weld that in place (right at the trailing edge) such that, if I ABSOLUTELY have to, I can make two cuts with a cut off wheel and turn it into another functioning trim tab.

All that being said, I'm betting that a single, small trim tab with +- 2" travel will be plenty. I think I read that Jared says his trim tabs move +- 3/4", so I am cautiously optimistic :-)

Cheers

[whee]

Thanks for the info rv8bldr.

The BH I flew had one large tab and I wouldn't want any less trim but I don't recall how much travel it had.

[rv8bldr]

Thanks for the info rv8bldr.

The BH I flew had one large tab and I wouldn't want any less trim but I don't recall how much travel it had.

Hmmm, not exactly what I wanted to hear Anyone have Pat Fagan's email? I would like to ask him about his trim system as I got the impression he had only used one tab. I don't know if it was the full size tab or the smaller one.

Cheers all

[swpilot3]

For what it's worth I took a picture of Pat's plane at Copperstate this year. It has two trim tabs.

[Pat Fagan]

RV8bldr, you will be very happy that you installed this system. The work looks very much like what I did which has worked very well. I had two large trim tabs on my original build but I cut them down on the rebuild but still have both in use. I don't recall now if the bell crank ends were mounted together on top of the bell crank or one on top and one on the bottom. Were it me I would go ahead and make the other functional now. If you opt to do it later you'll have to uncover the elevator to run the cable. I could stand to reindex my system for more up trim with full flaps when empty but haven't yet bothered. Don't know how it would feel with just one tab. It looks like your bell crank bracket is .032. So is mine, however, my bell crank bracket spanned a wider part of the rear fuselage than yours and knowing eyes felt it might allow some flexion which is a serious no-no in the trim system. I had to add some braces to ensure my bracket wouldn't flex. It looks like yours will be stiff enough, but give it a look with that in mind. Along the same lines I think I would feel better about using a cable that has a positive locking attachment feature instead of one only held in place with an Adele clamp. The cables I used had a groove around the barrel on both ends so it is impossible for the sheath to slide. I'm not an engineer, but I wonder if you should add a gusset to the arm supporting your trim wheel. There is some moment there but I don't know if that is an issue. Also, think about how you can achieve some adjustable drag on the system. I use a bell crank and handle in the front rather than a wheel. That part of the system is unchanged and yet with the new trim setup I needed to tighten up the drag to keep the tab set in flight. Bob never signed off on my system but simply warned be sure there is no flexion in the system. On my original build I had an incident which bent the original style push rod. Bending it back to shape weakened it enough that I experienced trim flutter which is a frightening experience. Anyway, nice work, Pat

[rv8bldr]

Hey Pat,

Thanks a lot for this reply. Very helpful, although now I have more work to do and more parts to buy :-)

Yes, the current bellcrank is .032 with a bent flange to give it strength. However, I'm going to make a new one out of .100 with a smaller flange. I will put one rod end bearing/cable on top and the other underneath, securing both with the same bolt. This will guarantee the tabs move the same and won't cause a torque load on the bolt at the bellcrank (the bolt should just be in shear).

The cables themselves have the groove you mention, and that is where the Adel clamps are attached. I experimented by trying hard to slide the cables in the clamps but just wound up moving the whole airplane back and forth on it's wheels :-)

As far as drag in the system is concerned, there is actually a fair amount of drag as is, but I will think about some kind if tension adjustment mechanism.

I don't suppose you'll be bringing your Bearhawk to Osh this year?

Thanks again

Mark

[whee]

You can look at the pictures of Pat's system in this thread: http://bearhawkforums.com/forum/bear...rvoed-trim-tab

I think he did a minor revision after those pictures were taken but I don't know what he changed. You can see that he has a cable going to each tab. With 2" of travel you might get away with one small tab but I don't really know. I just wanted to share my experience.

EDIT: I see Pat posted before me. I'm so glad he is here and provided answers to our questions. Thanks Pat!

[rv8bldr]

Thanks a lot, Whee, for your thoughts and help on this. Looks like I have yet another order to put into Aircraft Spruce (which really hurts with the exchange on the Canadian dollar right now :-)

Between your experience and Pat's suggestions, you have probably saved me from a huge ARGH!!!! once I started flying.

Cheers

Mark

[marcusofcotton]

Thanks for the info rv8bldr.

The BH I flew had one large tab and I wouldn't want any less trim but I don't recall how much travel it had.

Important data point noted. Thanks!

[Deftone]

Today I made new nose rib router templates, much happier with the result this time! I then spent the rest of my time cleaning up all the MDF dust from making the forms!

Tomorrow I will be ordering my 2024 for the ribs, after all my research I still couldn't find anywhere that could beat the price from aircraft spruce.

[Chris In Milwaukee]

I'm glad you got it the way you wanted it this time! If I had to do it over, I would have made a master full-sized routing pattern (which I did), and then used it on my router table to match-cut another full-sized form that I'd have cut on the spar lines to make forward, center, and aft rib routing patterns. But instead I made them separate. Would have saved a lot of sanding! But what's done is done, and moving forward!

But I've got a master routing pattern for every rib style that remain untouched, and I used them to build the actual routing forms. If I need to build new routing forms for some reason, they're there and ready to roll.

[Deftone]

I also considered the full size routing template, I was worried that by cutting at the spar lines I could mistakenly end up with a form that was too short once it has been cleaned up and sanded, perhaps it would have been ok?

I have noticed that now that I am over the initial burst of over-excitement at starting a new project I am producing much higher quality pieces. I guess I am now taking more time to think out the form rather than diving in and making dust. Still having fun though!