Murray, the S/Hawk has the cabin raised approx 13".
Murray, the S/Hawk has the cabin raised approx 13".
Not knowing exactly what Allan has already done, this is what we do to a standard Raf, probably worth less than 2 cents...
Have the Raf sitting on the front 3 wheels with ballast in the cabin, and place a support under the tail wheel. Cut the keel approx 4" behind the lower mast.
Slide the engine and redrive down the mast 6".
The "L" brackets that attach the rods that go from the redrive to the seat belt attachment bracket have to be turned upside down and mounted under the seat belt attachment bracket.
If living in a cold area, using doors, and having a stab without fins, undo the rudder cables and slide the rear keel back 6 to 8 ".
Make crush plates to attach the now lowered and maybe moved backwards rear keel to the front 4" that was left behind the mast, allowing for prop to keel clearance. This will have the rear keel with an upward rearward slope to give any fixed stabs approx 3 degrees negative AoA.
Next is a definate must as well. Move the axle back 4" by shortening the rear trailing arms, and placing a plug into the top of the axle to mast strut with a 3/8" unf tapped thread. Wind all the way in a 3/8" rod end with a lock nut. The rod end is attached to the lowerest section of the brackets that were slid down the mast 6". There is usually a dimple to center the 3/8" drill.The new rod end can be used to bow the axle a little as per the Raf construction manual.
If the rear keel was moved rearward, the rudder cables need an alloy rod/welded chain or cable extention.
Boy!!!!! what a difference this makes, particularlly moving the axle. With the machine now closer to CLT there is not as much nose down push of the high thrust line and the nose comes up too early and you have to push the stick so far forward to place the nosewheel back onto the ground the the rotor disc angle is so low that it takes forever to get the rotors up. You get airspeed quickly but not RRPM. It is my opnion that every Raf with the weight of a stab out the rear should move the axle back a few inches.
If I had enough interest I would package together the required bits and instructions with picsf or sale. Anyone seriously interested?
Allans machine looks like a dog when he takes off.
Allan has to drag the tail wheel on the ground for sooo long to get his rotors up.
Allan needs a little more rotor diameter. I would suggest Robs 30' blades with the taper etc and reducing the torque tube offset from the Raf 3/4" to 11/16". I took towers up to Bond Springs for him to try but silly boy did not take advantage of the opportunity!!!!! LOL
Robs rotors with the VR-7 airfoil at the tip would be great for Allans heavy machine with that ej-25 quad cam, but that would require the torque tube offset to be reduced from the Raf 3/4" to 5/8".
Allan is currently flying the 29 footers, with a disc loading that is too high. They are extremely tip dragy at that higher rrpm.
S**t, I did not realise how much testing and work I have done living and operating Rafs for 7 years, to achieve an acceptable level of pitch stability.
The above is a cheap, simple and quite a quick Raf modification. The last one we did in NZ had excellent pitch stability. Stick fixed testing showed very little pitch movement with power changes.
IMHO you do not need to lift the cabin. Certainly up 5" to sit the cabin on the keel instead of under it would be all that is required.
Geez, better get going to shift that axle back on another Raf!!!!
Aussie Paul.