Battson wrote:Whee - might be old news to you, but Bob didn't design the plane with that h-stab strut. He first flew the plane without that strut and it works fine. I have [inadvertently] flown without that strut too, and it was no problem.

I wonder if the longer airframe will change the CG limits and empty CG location much? Could be for better or worse, I don't know how to figure that out.

Guess leaving the strut off is another question for Bob.

In my mind there is nothing good about the extra 2" of length. All it is to me is 2 more inches added aft of the datum thus moving everything that much aft; not a good thing. Wish I'd been told about it before I drove out to MN to make the purchase; it did make me pause when I was told about it but not much I can do about it now besides getting out the sawsall. I can't see it changing the CG limits but adding 2" to the TW arm doesn't do anything good for the empty CG.

One good thing about it being longer is that the nose shouldn't wag around as much in turbulence, you will have more elevator authority at slow airspeeds with a forward cg, and you should be able to use a smaller fin on the tail with floats, I would just make the engine mount longer to bring the cg back forward

whee wrote:
In my mind there is nothing good about the extra 2" of length. All it is to me is 2 more inches added aft of the datum thus moving everything that much aft; not a good thing. Wish I'd been told about it before I drove out to MN to make the purchase; it did make me pause when I was told about it but not much I can do about it now besides getting out the sawsall. I can't see it changing the CG limits but adding 2" to the TW arm doesn't do anything good for the empty CG.

Hmmm - I see where you're coming from, I was thinking like Bhawk that there might be some benefits.

I guess an extra 2" over the length of 177" from the datum isn't the end of the world, but if you don't like it - it will never be as easy to fix, as it is right now.

Battson wrote: .....I guess an extra 2" over the length of 177" from the datum isn't the end of the world, but if you don't like it - it will never be as easy to fix, as it is right now.

That's correct, but it isn't gonna be as easy to fix as some might think-- it's not just a matter of cutting out 2 inches and welding the tubing back together. The fuselage tubes converge aft toward each other at an angle all the way from mid-fuselage, so I'd think the fuselage has to be re-worked all the way from that mid-fuselage point.

Kind of reminds me of my old motorcycle days- they used to sell weld-on hardtail kits to convert a swing-arm Harley to a rigid frame. They were usually 2" or so longer than a stock rigid frame-- not because people wanted longer bikes, but so that the lines of the hardtail section would match the lines of the forward section of the swingarm frame. Hard to properly explain but any other old rigid frame Harley guys on board here probably know what I'm talking about.

Your right hotrod and that is that why I'm not going to mess with it. Like I said earlier, if it was as easy as cutting out the 2" and welding it back together I'd have the sawsall out already.

I'm going to accept the 2" and hope that I either don't notice it or that it improves the handling. If I have CG issues I'll just move the battery around.

Get some W&B numbers for each station from a flying Bearhawk, and do the math after adding 2" to the arm for the t/w. This won't be entirely accurate, due to the weight distribution being different with the longer tail (the tail would be lighter and the mains heavier-- or is it the other way around???), but it should give you some sort of idea of what to expect. Considering that the t/w is probably 18 or 20 feet aft of the firewall, I doubt that 2 inches one way or the other is gonna have too much effect on W&B or on handling. I'd be more concerned about control cables/rods etc fitting, if you're working off a cut list or something based on a standard length fuselage.

I did that and it is only 0.15" change. I know I'm being a baby and that 0.15 isn't that big of deal, I just think the 2" was an attempt to fix something that wasn't broken. There is no cut list or bill of materials that comes with the Bearhawk so that isn't an issue.

This is a total guess, but if the tail section "weighs" 200 lbs from the CG back (a super cub tail with fabric from halfway to the tail weighs a lot less),and everything moves back 2", then the moment has increased by 400 in*lb . The plane is said to be 2500 at gross and 16 inches, or around 40,000 in*lb. The extra 400 in*lb would appear to move the CG aft by less than 3/16" if every unreasonable assumption was made to make it look bad. In reality, the actual change is probably less than half this distance.

Is there a different reason the change would do anything other than improve stability and ground handling, if it was noticeable at all? I hadn't heard there was a perfect fuselage length that was optimal for all considerations, merely acceptable compromises for them all. I saw a BH from CA with an extra 10" in it on a recent trip, and he said it made it fly on a rail at cruise.

The tail wheel weighs about 80lbs on the scale in my install......... so the moment is nowhere near that large. I agree that it's probably not going to be a big deal, might not even be easily noticeable.

whee wrote:I did that and it is only 0.15" change. I know I'm being a baby and that 0.15 isn't that big of deal, I just think the 2" was an attempt to fix something that wasn't broken. There is no cut list or bill of materials that comes with the Bearhawk so that isn't an issue.

Just piling on...but there is probably nothing that would waste time and material more than trying to change this back...

Changing it back would equally represent fixing something that is not broken...

Carry on.

Material came for ACS today. Not much to show for 1.5hrs of work.

Keep plenty of pictures coming!

Troy Hamon wrote:

whee wrote:I did that and it is only 0.15" change. I know I'm being a baby and that 0.15 isn't that big of deal, I just think the 2" was an attempt to fix something that wasn't broken. There is no cut list or bill of materials that comes with the Bearhawk so that isn't an issue.

Just piling on...but there is probably nothing that would waste time and material more than trying to change this back...

Changing it back would equally represent fixing something that is not broken...

Carry on.

Besides, when you fly that puppy to OSH, it'll drive all the Bearhawk "experts" nuts trying to figure out what's different about that airplane...... .

That alone is worth leaving it as is. I for one wouldn't even think about changing it for a lot of reasons.

MTV

mtv wrote:Besides, when you fly that puppy to OSH, it'll drive all the Bearhawk "experts" nuts trying to figure out what's different about that airplane

Best reason to leave it be I've heard so far.

The Fedex man stopped by today:
image by whee8e, on Flickr

Notice the shock strut isn't the typical profiled tubing. I asked Mark if he could make them out of round tube and he said that they do have that as an option so that is what they did. Makes the strut stronger in the case of a side load.

IMG_1286 by whee8e, on Flickr

IMG_1287 by whee8e, on Flickr

The tailpost was drilled by VR3 when they made to tubing kit and I guess something changed because the upper rudder hinge doesn't match the hole.

IMG_1288 by whee8e, on Flickr

IMG_1289 by whee8e, on Flickr

My dad came by and dropped off the brake him and my grandpa built. Not bad for almost free and it will do all that we need I think. They mostly followed some plans from Zenair.

IMG_1293 by whee8e, on Flickr

He also helped me install some new lighting. I only had 4 CF lights in my garage and it was terrible. I was going to buy some T8 fixtures but my brother came by with some T8 fixtures that came from a remodel job he is on. Again, not bad for free.

IMG_1294 by whee8e, on Flickr

Just a short note about those extra 2 inches....

There was an interesting article in Kitplanes Magazne about the liabilities a seller may have in selling a non certified " homebuilt plane " .

The article is titled Legalities Protecting the builder from subsequent owners.

Here is the link:

http://www.kitplanes.com/issues/31_10/exploring/legalities_oct_14_21106-1.html

It discusses the need to comment and disclose any changes from the kit manufacturer's or designer's original parameters.

If you build your airplane properly, and especially if you build a kit aircraft, follow the kit manufacturer's builder's manual precisely, and don't modify the airplane in any way that affects either its structural integrity or its handling qualities or other flight characteristics, you probably won't be negligent in the construction phase.

Then, if there is anything about which you ought to give a warning or warnings, beyond what is included already by the kit manufacturer, you're well on the way to being protected from losing a lot of sleep after you sell the airplane. The one last step in protecting yourself would be to insert a provision in your contract of sale to Buyer #1 that compels him to use your contract form and language when he sells the airplane, and insists that all subsequent buyers do likewise. If you do this, you've taken another major step toward protecting yourself from them, even if they don't do as they've promised.

Just something to keep in mind if and when you ever sell the current project. Since your project is a cool BearHawk, I'd say it may never end up being sold and turn out to be a life time keeper eh . I love the pictures Whee. Please do keep posting...everyone is loving this thread.

Had a distraction in the garage today. Glad it was just a pull cord that I had to replace.

being the old motorcycle rebuilder/rider guy that i am, i am betting that it makes an improvement to the handling....just a guess, but longer bikes work better and handle loads better....thats a cool bird Jon.....!

Thanks Jo.

Not much visual progress. My dad was over yesterday cutting out parts. My grandpa was over helping out and my 2y/o son was in the garage with us for a while so we had 4 generations out in the garage.



I have to admit I'm a little nervous to start welding on the fuselage. I can see myself blowing a big hole in the longeron while welding the gear attach fittings. Glad there is some work to do before the welding begins.

It were me, I'd get some scrap tubing & tabs and practice practice practice.

whee wrote:
IMG_1289 by whee8e, on Flickr

I don't think this was drilled wrong. Isn't that a floating hinge? The rudder rotates inside that coupling, I don't think its fixed in that location. Can't you just move it down to the location vr3 drilled the attach point?