More gas

[svyolo]

I am still stuck on the wrong side of the world, hopefully for only another week. There is at least one 4 place with 100 gallons of fuel. I haven't closed the wings yet, but they are ready. I didn't do aux tanks because they added 30 lbs, and if I needed more fuel, I didn't think 18 gallons was enough. What does it take to add 50 gallons of fuel? If you put the other 25 gallons per side outboard of the struts, they would have little structural effect on the airplane. The main tanks get away with hat sections stiffening the wing skins to maintain shape. Is there any reason you couldn't duplicate that outboard of the struts?

I didn't think 30lbs were enough to justify 18 gallons of gas. I might accept 60 pounds to justify an extra 50. I know the moments would reduce the roll rate. I am not building a Pitts. I am building a back country tool. Putting it all the way out by the tips might make the most sense for loading, but worse for handling.

[Chris In Milwaukee]

Provide midline fittings for a soft ferry tank when needed?

[svyolo]

That is what I have added in now. Before I close the wings, just looking at a different option. If on floats I can carry as much gas as I want in the floats.

Alaska and northern Canada are huge places. 30 lbs per wing at the outboard end would definitely affect handling. Let alone when they are full of gas, but when they are full, I could care less because I need it and I am flying a long way out.

I talked myself into ferry tanks when I need it. Just question it one last time before I close the wings.

[rodsmith]

Phil Johnson was the builder that used aux tanks the same size as the mains. I don't know if he consulted with Bob on that or not. If interested in that I would talk to Bob first.

[mswain]

kestrel has a 4 place with 4 main tanks, sounds like there are structural mods required.

https://bearhawkforums.com/forum/bea...3-4-main-tanks

[svyolo]

I should have done a search first.

I am not sure if strut braced wings are different than cantilevered wings in this regard. Wing fuel farther out usually is no-problem structurally. I think structurally, it is preferred. Perhaps a hard landing might cause issues with the strut if the outer tanks were full?

[kestrel]

The outer wings are built lighter to match the lower bending loads. In steady air flight, span loading should reduce loads on the wing. In a perfect case, the load would match the span-wise lift profile of the wing; generally close to an ellipse. In real life there is turbulence and bounced landings. The wings of my plane were beefed up during construction to carry the extra load. 150lbs near the end of each wing is no small thing. ...the tilt of the plane when one is full and the other empty is disconcerting. It looks like it might tip over. 3+ feet of high difference between the wing tips?

Keep in mind that the skin is an important part of the structure. To install the 25 Gal tank, some of the ribs have to be removed. Those ribs help support the wing skin.

I'd at least run it by Bob before trying to duplicate, esp. on an already (mostly) constructed wing.

[kestrel]

I don't know if Phil Johnson did something similar (or even, who he is?), but my plane was built by Jim Clevenger.

[svyolo]

If it involves much more than re-skinning the wings in the middle, it sounds like it might be in the "too hard" category. Did the spar need reinforced as well?

[kestrel]

Mark can correct me if I'm wrong, but I believe it is mostly spar work.

Even if starting from scratch, I'd suggest that you think long and hard before deciding that you need 100 gal. There are cases where it can be very useful, but for most people (myself included) they are few and far between.

I'd suggest that your best path to a 100 gal Bearhawk is to buy mine and I'll put the money down on a Five. :-)

[svyolo]

I think that is what is referred to as "thinking outside the box". LOL

[yateselden]

Kestrel I like you're thought process! 🤣
By the way, I'm up and running may be back in the air this weekend, weather permitting