Bearhawk 4? or 5? with IO540-D4A5

V

Vince

New member
Hello,

I am considering a Bearhawk build, been trying to decide between the 4 or the 5. I am pretty sure that I would like the io-540-D4A5 because of its unleaded fuel capability, since I will be then limited to around 260HP, would like to know from anyone if thats enough HP for the BH5

Is it fair to say that it would be a higher performing BH4 than an underperforming BH5?

Thanks in advance...

Vince
 
I had that same discussion with Virgil when I was deciding.

From what I can remember, if you finished a 5 the exact same way you would do a 4, then it won't be much heavier. I might be mis-remembering, but I think it is in the range of 50-75 lbs.

Also, from what I understand, the 5 would probably be a few mph faster.

The struggle will be to actually build it like you would have a 4. The temptation to add all the bells and whistles will be there.
 
That IO-540 can be bumped up in HP. Lycon's CNC port and polish adds 5 HP/cylinder. Cold air induction adds another 15-20. Just my opinion, I would go with the 5. The extra width is really nice, it is a fill 4 seats with big people haul a ton of gear plane.
 
I can't think of any reason a 5 is faster than a 4 without using more HP. You can use a heavier angle valve on the 5, and burn more gas to go a little faster.
I am perfectly happy with my 4, but would build a 5 if I was to do it again. And I am thinking of buying a tubing kit for a 5 fuselage and converting sometime, just not right now.
 
svyolo said:
I can't think of any reason a 5 is faster than a 4 without using more HP.
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How much does the longer tail of the 5 factor into this? With a longer arm, the tail doesn't have to provide as much down force to create the same moment arm. That could translate into less drag. With all the other factors involved, it would be hard to predict the outcome, but I think Virgil has found that the 5 has a slight edge over the 4. That may be at the same weight though. With the 5's higher useful load and gross weight, the performance numbers at full gross with equivalent power are likely better on the 4. It seems that if you don't ever use the extra useful load of the 5, the 260hp should be almost the same in a 5 vs. a 4.
 
The Five airframe compared to the Four airframe is less than 30 pounds heavier. The IO540-D4A5 is our small engine option on the Five and big option on the Four. That being said you will have an airframe that is a few pounds heavier empty but with a much more effective tail and great performance. You will be a few faster in the five due to the more aerodynamic windshield and decreased incidence in the horizontal tail plane. 260hp makes a great engine in either airframe, but you will gain a lot more airplane for just a bit more in funds to build the five with the same engine.
 
Bearhawk Aircraft said:
The Five airframe compared to the Four airframe is less than 30 pounds heavier. The IO540-D4A5 is our small engine option on the Five and big option on the Four. That being said you will have an airframe that is a few pounds heavier empty but with a much more effective tail and great performance. You will be a few faster in the five due to the more aerodynamic windshield and decreased incidence in the horizontal tail plane. 260hp makes a great engine in either airframe, but you will gain a lot more airplane for just a bit more in funds to build the five with the same engine.
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I forgot about the windshield, but the tail has even less incidence? All things being equal, engine, prop, the 5 is faster for the same fuel flow?
 
I had the same serious debate. But it's easy to run the BH5 light with the extra space when you need it, but with BH4, if you need extra space, it's not there. The only penalty is the dollar cost difference in the kit, fabric covering, interior materials. But what you get in exchange is so much more capability.

BTW, I've had the same debate over the years with the 206 vs 182 debates, and I've owned several of each. But the 206 is much heavier and slower on a HP basis than the 182. But those cargo doors were awesome though.

The BH5 design is interesting in that you don't suffer the performance of the larger cabin. To me, it was an easy choice.

FYI, I also went with the IO-540-D4A5 (actually a C4B5 but with changes to make it -D4), but added the EFII, streamlined induction, 9:1 cylinders to get it to 290-300HP while burning 92 Unleaded. But it took work, or you could simply drop in a IO-580 and get 310HP, but need 100LL.
 
Vince said:
Hello,

I am considering a Bearhawk build, been trying to decide between the 4 or the 5. I am pretty sure that I would like the io-540-D4A5 because of its unleaded fuel capability, since I will be then limited to around 260HP, would like to know from anyone if thats enough HP for the BH5

Is it fair to say that it would be a higher performing BH4 than an underperforming BH5?

Thanks in advance...

Vince
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4 vs. 5 I’m building a 5 and certifying it with 4 seats… more cargo capacity, also look at MOSAIC advantages…

John
 
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