Approximate number of hours to scratch build to the equivalent quick build kit

[Stefano]

Thanks, everyone, for your valuable information. I appreciate it.

From old threads on the forum to this thread, I am seeing 2000-3000 hours to build to the QB kit level of completion. Since I won't include learning/research time in my calculation and since I intend to buy those component parts that are the most difficult and time-consuming to build, 2000 hours is what I will prepare for. I realize that will be about the half-way point in my total project.

Since the QB kit is selling for $86k before shipping and sales tax, I will use $92k as my actual cost to buy it. If I budget high at $32k to scratch-build (with some purchased component parts) to the QB point in the project, that leaves about $60k in savings to compare to my extra 2000 hours of build time.

That looks like $30 per hour. But I have to make quite a bit more than that and pay my taxes to have a net income of $30 /hr.

The only other issue left is how much longer will I have to wait to be flying my 4B. Given a kit lead time of up to 18 months, I would need to average about 26 hours per week on the project up to the QB level to break even time-wise. That is possible in the beginning, but not probable for the entire 18 months. Still, 6-12 months delay is fine with me given the savings.

[SpruceForest]

You can scratch-build pretty fast if desired... this is Carlo's build right at six months from receipt of plans... and this included engineering the wet wings. Full time job with an aviation advocacy group as an A&P-IA plus 4.25 other airplanes to take care of (2.25 his/2 spouse) and that recently acquired wife. I remain in awe.

The real reason for the shots? The alternate build jig knocks a lot of time off building up the spar and rib assembly, plus gives really excellent access (which makes riveting way easier). The skinning jig is vertical, and is being welded up of 1/4" industrial shelving and rack stock.

IMG_0490.jpg IMG_0488.jpg IMG_0487.jpg IMG_0489.jpg .

[Frank]

One thing to consider maybe is that the factory parts and assembly are sometimes different from plans built. Compare, for instance, factory nose ribs to plans nose ribs. Or factory skin stiffeners versus plans which do not include these. I wonder what other differences there are between factory and plans. In general, I think the factory parts could be considered superior to plans built parts.

[Frank]

Particularly mine.

[SpruceForest]

That may be the case for the Bearhawk factory parts, but most definitely NOT for the Cessna, Piper, and other light aircraft manufacturer parts I've see on the airframe side of things. My goal has been 'better than factory' based on those supposedly 'blessed by the manufacturer' airworthy parts.

[Stefano]

One thing to consider maybe is that the factory parts and assembly are sometimes different from plans built. Compare, for instance, factory nose ribs to plans nose ribs. Or factory skin stiffeners versus plans which do not include these.

Hi Frank. Could you be more specific about these two examples? What is the difference between factory vs plans nose ribs? Where are the skin stiffeners added that are not included in the plans? Has there been any known problems with the plans-made parts that the factory parts solved?

[Frank]

Plans nose rib flange stop before reaching the nose and is trimmed. Factory nose ribs have a flange across the nose, and is not trimmed.
Plans lightening hole flanges are a straight 30 degree press. Factory lightening hole flanges are different from plans, look more like Vans lightening hole flanges.
Three skin stiffeners (to address canning) are now standard on all factory wings. So far, Bob has only drawn a single skin stiffener as an option on Patrol plans.
These are the only differences I am aware of. There may be more.
Regardless if one method is better or not, scratch building to the quick build stage would not be exactly "equivalent."

[gregc]

I suspect the rib difference is due to the fabrication process. I think the factory ribs are hydroformed by a third party.

[Stefano]

Regardless if one method is better or not, scratch building to the quick build stage would not be exactly "equivalent."

I see. Scratch-building and buying some parts may close the gap? I found this thread with some other solutions to the oil-canning problem:

https://bearhawkforums.com/forum/bearhawk-general-discussion-news/67123-wing-skin-thickness

Interesting about skinning the wings warm. I live in a climate that has hot dry summers. It may be best for me to plan to skin the wings in July-August. Maybe even throw an electric blanket over the skin?

[svyolo]

I had somebody in the local EAA chapter mention skinning the wings "warm". I can't wrap my head around that. Once the holes are drilled, QB or scratch built, I would think the shape is set in stone. The ribs might move a bit, but not the spars/skin interface.

[jaredyates]

There sure are a lot of planes flying around doing fun things whose skins were installed without going to all that trouble.

[Frank]

I asked Bob about the skin stiffeners. He said he's not seen any cracking or other problems on his planes due to the canning/flexing of the wing skin. I asked if there were drawings for the wing stiffener option (other than what's already available for Patrol plans) and he said he'd get back to me on that.

[Bcone1381]

For the patrol....

http://bearhawksafety.com/Patrol/february2020.html

[Stefano]

Is the same wing planform and airfoil used on the 4B, Companion and Patrol? (Not including differences from wing tips and VGs)

[David Swartzendruber]

Is the same wing planform and airfoil used on the 4B, Companion and Patrol? (Not including differences from wing tips and VGs)

Yes, and the Model 5 is included in that group as well. Structurally, the 5 and the 4B wings are the same and the Companion and the Patrol wings are the same.