View Full Version : rocket -vs -4 structure

01-07-2010, 08:52 PM
Hi Guys Im building a -4 and was working on the foward fuse and started wondering. What is differant about the HR structure wise. I understand the basic differances , but are the longerons a larger size, skins thicker,larger rivets,bigger engine attach mounts,larger firewall angles? what are the wing skin thickness? extra spar caps? empanage skins thicker? Just wondering
Thanks Dan Weseman

Steve Barnes
01-07-2010, 10:30 PM
I can't speak about the Harmon or Fredricks, but the Super Six has thicker fuselage skins. longer fuselage. heavier duty engine mount. more stringers in the wing, (like the 9) titanium gear, larger rivets and tighter pattern in some areas, also heavier brakes for the heavier airplane. Since I didn't shorten the wings, my plane flys in the standard and utility catagory, because the extra weight. It's every much as a delight to fly as the standard six but more stable. The empanage and wing skins remain the same as does the VNE.

Steve Barnes "The Builders Coach"

01-08-2010, 06:58 AM
what dose your airplane weigh empty,do you have a CS prop on it ?

pierre smith
01-08-2010, 08:10 AM
...in the front cockpit than the -4. Notice that it's cowling is about the width of an -8, with a lot more shoulder/elbow room.


01-09-2010, 09:20 AM
The Rocket fuselage is 4" longer between the wing rear spar attachment bulkhead and the rear seat bulkhead. This means the fuselage longerons, cockpit side skins and bottom skin are all 4" longer.

The fuselage main spar bulkheads are 3" wider. John Harmon provides new forward fuselage bulkheads in his HR2 fuselage kit.

The bottom side longerons between the firewall and main spar bulkhead are formed from 1/8" plate. The side skin and bottom skin are a butt joint along the bottom of the fuselage using the longer width of this forward bottom longeron.

The firewall is wider, so the steel brackets in the corners of the firewall and the engine mount are different. I don't know if the steel brackets are made from thicker material.

The top rear deck on the fuselage tail cone is made higher so the canopy blends into the back of the fuselage. This mod has been done on a couple of RV-4's. I suspect John Harmon has the upper fuselage bulkheads available. This works because the RV-4 tail cone is not changed from the rear seat bulkhead to the rear bulkhead below the fuselage longerons. The RV-4 bulkheads above the longerons are cut off, and John's upper fuselage bulkheads are inserted.

There are numerous additional changes outside of the fuselage.

The wing tips are cut 7" shorter and the wing root is 1 1/2" shorter. The wing ribs are moved closer together to accommodate these changes.

I hope this helps.
Jim Ayers
HR2 sn 269