10/23 Raptor Video

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

Status
Not open for further replies.

ifthen

New Member
Joined
May 9, 2021
Messages
2
I'll pick at this nit, Ross, and go you one better :). Actually, the fact that the original empty weight WASN'T pulled from a hat, but was pulled from the empty weight of a Velocity XL-RG, which is the closest extant canard type aircraft, makes the "overweightness" issue even worse. Had it been pulled from a hat, there would have been zero basis for assuming that it was a reasonable #, so missing it by 90% or thereabouts wouldn't be completely insane.

But since it was based on an existing aircraft that can be built at that empty weight, the "overweightness" is even more egregious. I make the assumption that even though Raptor is a slightly larger aircraft than a Velocity XL-RG, the theory was that "BUT CARBON" was going to eliminate all the excess weight in the Audi engine, pressurization, and poor engineering. Obviously, that's not how things work (and wouldn't have worked, even with good engineering and a TIO aircraft engine).

When anyone asks me if they should build a COZY out of carbon, because they'll save a bunch of weight over fiberglass AND it'll be stronger, I ask them how many COZYs have had structural failures in flight (the answer is zero) and how much lighter a Berkut is than a Long-EZ (the answer is 100 lb. to 200 lb. or so heavier).
Berkut has only has carbon wings, canard spar caps (because you embed the antenna) and strake skins. The fuselage mimics the laminations set forth by Rutan for the long EZ. (7781uni, DB090 biax, Divinicell or balsa core, DB 909 Biax, 7781 uni). D.R. was careful to use the original EZ laminate schedule as closely as possible. The changes to carbon were in the wings (uni in the long EZ laminations) over the stock EZ blue foam cores initially, and then fully molded wings and strakes. Honestly, The original laminations and foam cores were impossible to beat for weight, because Rutan is, in fact, a genius, but the stiffness and strength of the carbon wing was about double. It makes sense: when you have 2 ply core 2 ply, and they have the same arial weight, it weighs the same. all you can do is reduce a ply and D.R. was wisely not every going to do that. The EZ laminations were sacrosanct. By the time the project had eveolved into Mobius, we were molding complete fuselages in one piece, in carbon. The most impressive piece I have ever seen. It took two weeks to lay up. This included roll overs, all hard points and we bagged it out of the canopy openings. The extra weight was really mostly a factor of the gear system (Shirl Dickey- Eracer) and the added weight and complexity of the 360/540. I will tell you though, that the power to weight and speed was...adequate. Especially with the 540 and constant speed prop. It would pin you to your seat. The 360 versions could also touch 260-270 MPH and the 540 would do it all day. They could return over 40mpg @ 180 as I recall. It would run out of elevator up trim at about 270. Great airplane, just hard to build. Harder than most people had time or skill for.
 

Victor Bravo

Well-Known Member
HBA Supporter
Joined
Jul 30, 2014
Messages
9,723
Location
KWHP, Los Angeles CA, USA
Although I have never been in the Berkut, it was always my understanding (back in the day, from R. Riley) that the carbon versions were stiff as hell... if you flew through what was "mild chop" for a glass Long-EZ the carbon Berkut would pound you like Mike Tyson. The stiffness combined with the Berkut's very high cruise speed was uncomfortable on many more days than other composite airplanes.

This was THIRD hand info; again I have not ever flown the Berkut and only have a couple of flights in any canard (One in Klaus' Vari-Eze and one in Verne Simon's Long-EZ).

Getting the s**t pounded out of you because you're penetrating choppy air at 200-230 knots in a light/stiff airplane doesn't sound like fun to me.
 

proppastie

Well-Known Member
Log Member
Joined
Feb 19, 2012
Messages
5,259
Location
NJ
Then you should be flying a Long, not a Berkut!
right now I fly a Mooney and it is a lot more comfortable at 120 kn than 140 kn when it is choppy also it helps to get above the clouds where it can be really smooth when it is bumpy low.... but for the normal $100 lunch we usually do not go far enough to justify the climb...
 

Daleandee

Well-Known Member
Joined
Sep 11, 2015
Messages
1,575
Location
SC
The Quicksilver and other ultralights don’t get a choppy ride. Penetration speed is slow, so you get gentle rises and drops.
True that. In my little Challenger I could slow to 55-60 mph and it would just kind roll up and down the thermals & light chop. What I'm flying now tends to take the bumps more like a VW with worn out shocks on a dirt road ... 😁
 
Status
Not open for further replies.
Top