Making your Bearhawk too light - the best way to ruin a good airplane!

[Gr8apmech]

Great read. This has helped me see some things I’ve not yet considered. Thanks all.

[Bearhawk535]

Rebuild engine mount longer seems to be a logical option to move weight out where you need it. Welding up a new mount and building longer cowling would seem to to be easier than moving several other things in the airplane.

[zkelley2]

Yup. I wish I had scales the whole time I was building to see what was going to happen. I would have had an extended engine mount made.
The good news is doing the math on floats, there's so much weight at a medium arm, you just can't get it to go out the aft limit anymore. On wheels, it's big issue. One I'm struggling with and has really limited the utility of my airplane. Well that and I refuse to fly it at a CG that would never meet certification requirements.

[whee]

Rebuild engine mount longer seems to be a logical option to move weight out where you need it. Welding up a new mount and building longer cowling would seem to to be easier than moving several other things in the airplane.

Extending the engine mount will cause a decrease in yaw stability. Maybe not an issue or maybe trading one issue for another.

[way_up_north]

you could extend the engine mount below the engine...and put a wheel on it....

subject is taboo here...but a nose wheel would move weight around.....putting the heavy tail wheel on the nose...

granted not great for landing on the beach...or sandbar...

piper-tri-pacer-airplane-hanger-antique-aircraft-rests-its-airport-142550346.jpg

[Ray Strickland]

Adding a nose wheel won’t yield as much CG shift since the main gear must move to the rear.

[way_up_north]

all very true...but you could move the mains back(just enough) to just barely do their job.....if someone was in a CG pickle...you could set it up so the nose was only barely touching the ground ... with a pilot on the seat it was positive nose down on the gear ..

[whee]

Hehe, a nose would BH would likely make Bob shutter in shame. But it would move weight forward.

If I were going to do something crazy like extend the engine mount or add a nose wheel I’d go with adding a nose locker. My current plane could benefit from one and there is almost room for one as is. I plan to mount a tool box on the engine side of my firewall. Based on the little we know about the BH5 there could be room for a pretty good sized nose locker.

[stinger]

To each his own, When I bought the plans for my Bearhawk LSA my friend and myself reviewed the W/B as per numbers given. We both determined the aircraft would be tail heavy plus I wanted a additional baggage area and door,so I built my engine mount 1.5 inches longer then the plans stated. I can sense NO decrease in yaw or stability. In general the plane flies great. I wanted my fwd C/G to be on the limit and it is. P/S scratch built. Stinger

[zkelley2]

To each his own, When I bought the plans for my Bearhawk LSA my friend and myself reviewed the W/B as per numbers given. We both determined the aircraft would be tail heavy plus I wanted a additional baggage area and door,so I built my engine mount 1.5 inches longer then the plans stated. I can sense NO decrease in yaw or stability. In general the plane flies great. I wanted my fwd C/G to be on the limit and it is. P/S scratch built. Stinger

Nice.
The ideal cg of three 4pl is 10.5" with the pilot and 30mins of fuel. That's what everyone on the 4 place should be shooting for. It means an empty cg of 9.something.
it requires a very heavy prop or a longer engine mount than stock.

[way_up_north]

I used grade 5, 6AL-4V which is can be machined in the treated condition as is about as strong as can be used for a spring.

as far as I know the sonex main gear is also titanium...but from what I remember its not easy to cut...and drill

copied from the sonex forum:

Advice: drilling the main gear titanium leg
You should definitely use Cobalt bits to drill both Titanium and stainless steel. Not knowing this I attempted to drill the gear leg with a standard bit that snapped off half way through the cut. Luckily I got the broken bit end out of the hole. I read about cobalt bits and that was how I finished that hole and made the others. Cobalt bits can be found at most hardware stores, I think I bought mine from Menard's. For the #30 and #40 I think I had to order them. I tried using regular bits in the fire wall, I think I got 2 or 3 holes drilled before needing to sharpen the bit. If I remember right I used 3 or 4 bits just to do the filler box. The cobalt cut fast and clean.

Another builders comments

I stepped up the holes using 4 different bit sizes to get to the 1/4" diameter needed: #40, 5/32", 7/32", 1/4". The smaller holes were pretty easy to drill. I used new bits and lots of WD-40, and paused whenever the bit got hot. The larger bits really heated up quickly towards the bottom of the hole. Too much friction along the sides of the hole that deep into the gear leg

DrillingLegs1.jpg

copy pasted from online...Given its strength, titanium is remarkably light. When compared to steel in a strength-to-weight ratio, titanium is far superior, as it is as strong as steel but 45% lighter. In fact, titanium has the highest strength-to-weight ratio of all known metals.

[Battson]

HI plan to mount a tool box on the engine side of my firewall.

This is an excellent idea to help rebalance the aircraft when flying heavy. Even a deep glove-box under the panel to hold the tools, much better than putting them in the trunk...

[svyolo]

I will normally have mine behind the cargo bulkhead to help with forward CG when light, but even just moving them under the front seats would help a lot if you are flying heavy. Even if they are pretty heavy they would also be pretty secure under the front seats.

[Low Friction]

Small thread hijack but in keeping with the topic.

Glad I found this thread. Planning a lightweight Patrol build. With some FF weight savings for sure. Planned on keeping all things aft as light as possible, but this thread adds some extra focus. No structural or geometry changes to the Bob kit and using an IO-360 parallel valve with a CS Trailblazer. Far easier to readjust for a nose heavy CG after the build is done than the other way around.

[500AGL]

Low Friction, you probably won't find a CG issue with a Patrol, but always fun to hear about lightweight goals. Make sure you post up some of your methods, and what IO-360 you're using.

pb

[Low Friction]

Here's my current Patrol FF plan on paper:

An IO-360-M1A appears to be a good power plant choice. 8.5:1 compression, parallel valve, 180 HP, front mounted governor, dynafocal mount engine. If I feel really aggressive a conical mount version could be used. This would save about 5 pounds. Will use cold air induction, a light weight sump, and a Light weight flywheel (Sky Dynamics). Dual P-MAGS. Trailblazer CS prop. Light weight starter and alternator. Titanium firewall. Carbon fiber RV spinner and the Bearhawk carbon nose bowl. Firewall mounted earthX lithium main battery w/ heat isolating mount.

This would be 40+ pounds off the nose ignoring the composite prop. A custom carbon fiber cowl would make that number even larger. All this makes me nervous about my CG if aggressive aft weight control is not implemented. Especially if I want to be at the forward CG limit with minimum fuel and a skinny pilot in the front seat.

Once construction commences a build log will follow along.

[500AGL]

40 lbs is a big number. What are you comparing it to, that adds up to that total reduction?

[Low Friction]

40 lbs is a big number. What are you comparing it to, that adds up to that total reduction?

This is just a rough estimate of weight off the nose if I use these parts. Wonder what the weight and balance report and equipment list looks like for a typical Patrol that is at the forward CG limit w/ a pilot and min fuel?

[Bcone1381]

I like Data, and you might too.

I have an IO-360 built by Bob that weighs 304lbs. This includes the Patrol dynafocal mount, Bendix FI system, B&C starter and B&C 40A belt alternator, standard flywheel, standard vertical sump, Vetterman X-over exhaust, a single Bendix mag, Fuel Pump, and Jihistroj prop governor on the accessory pad.

How much would yours weigh?

My ideas to save weight, no spinner, sensenich ground adjustable prop, Carburetor, no electric, solar panel to feed a battery to run the starter and radio and ditch the ADSB. It gets done quicker that way too. I'm frugal and fuel saving schemes pay for themselves, like FI, Pmags, Constant speed prop, but demands electrical and that in my arena demands ADSB. weight, weight, weight. Sometimes i wish I had gone Light Weight, but I'd rather have efficiency. Can't have both

[Low Friction]

I have an IO-360 built by Bob that weighs 304lbs. This includes the Patrol dynafocal mount, Bendix FI system, B&C starter and B&C 40A belt alternator, standard flywheel, standard vertical sump, Vetterman X-over exhaust, a single Bendix mag, Fuel Pump, and Jihistroj prop governor on the accessory pad.

@Bcone1381

Ahh....Data

Looks like your 360 is a parallel valve 180 hp design engine. Everything you list is what I'm planning except 2 PMAGs (+3 lbs), lightweight flywheel (-3 lbs), Sump and intake (-9 lbs).

Are you running single ignition? What Prop and spinner are you using? Where is your CG w/ pilot and empty tanks?

I'm not planning for the lightest overall build but want to pull weight where I can. I'll have a GX3 and other civilized equipment.

[Bcone1381]

I dont know where my CG w/pilot and empty tanks is yet. If I had a set of scales for my wheels and could weigh my wings I would have calculated it. Scales might be the least respected tool an EAB shop doesn't have. Empty Weight and CG does not have to be a mystery at the end of the build.

I have a single Bendix mag because of procrastination on the ignition decision. There are benefits to sitting back and watching and reading. If my engine ignition is dependent on the electrical system then I will have dual alternator and a single battery. If my Ignition choice was made today I think a single PMag and a SDS CPI-2. That standby alternator is light & reliable though. Maybe I should go dual SDS CPI-2? I see why I procrastinate. 24 months ago I was going with dual Surefly.

Trailblazer Prop. Hartzell Spinner both from Mark G.. That spinner is expensive but very very well built.