Some of you may be interested in advice I received when I proposed fitting the delron stop to my RV7.
"While the proposed modification appears very neat and tidy, and would of course work in the sense that it would limit the rudder travel, I do have some technical reservations about it when compared to the original rudder stop from Vans’ design team. These relate not so much to the action of the stop in limiting rudder travel when the pilot is controlling the aircraft, (although the same arguments apply in that case) but rather to the stop’s function when the rudder is slammed against the stops by air loads on the rudder, ie when affected by wind gusts or by another aircraft’s slipstream from the rearward quarter whilst on the ground, or if any inadvertent tailsliding occurs during aerobatics.
1. Due to the fact that the stop acts at a lesser moment arm from the rudder hinge axis than in the original Vans design, for a given rudder ‘slam’, with the internal design of stop the contact forces will be increased in direct ratio to the reduced moment arm. In other words, if the stops were at half the effective moment arm compared to the standard design, the forces on the stops would be twice those with the standard design. These increased stop forces are experienced not only on the stops themselves but also, on the principle of equal and opposite reaction, on the rudder hinges which react the stop loads. This means that with the proposed internal stop, not only must the internal stop cope with higher loads than the external stop, but also both halves of the associated rudder hinge (ie the part on the fuselage and the part on the rudder) have to cope with increased forces. These forces act in the approximately fore and aft direction ie tending to rip the hinge bolt out of the hinge bracket, to pull the bracket off the back of the fuselage and the rod end off the front of the rudder spar. This is of particular concern because the rudder hinge brackets are held in place only by rivets through the tailpost (fin rear spar) which would be placed in tension by the stop forces. Rivets are lest effective as fasteners when placed in tension, so the design is already not very good as regards dealing with the stop loads – it does not seem a good idea to significantly increase the tension loads on them and there may well be early cracking of the fin spar, rudder spar, hinge brackets or failure of the rivets themselves if more highly loaded in this way.
2. With the Vans stop, the rearward load on the hinge due to the stop reaction is shared equally as tension in three of the rivets attaching each hinge bracket to the rear spar (the ones closest to the fold in the bracket - the other three, closest to the edge of the flange won’t contribute much, due to the flexibility of the flange). In the internal stop arrangement, the stop loads will apply a levering action to the brackets tending to focus all the tension on the rivet on the opposite side to the stop that has made contact. This will greatly increase the likelihood of a local failure at this rivet position.
3. With the Vans stop, the stop itself is not attached to the rudder hinge bracket but separately to the fuselage. While not so tidy, this arrangement means that any disruption of the stop does not affect the integrity of the hinge itself, so while overload of the stop might compromise its action as a stop, it would not affect the hinges or cause any immediate flight safety issue. In contrast, with the internal stop, damage to the stop could well affect the rudder hinge.
In view of the above, while elegant in one way I am not in favour of the proposed mod and suggest that you stick to the standard design, unless you can show by analysis or test that the increased loads are well within the capabilities of the structure, per the design code CS23 paragraphs 675, 395 and 415 which can be downloaded here:
https://www.easa.europa.eu/system/files/dfu/decision_ED_2003_14_RM.pdf
I am sorry if this seems like a lot of fuss about a five-minute off-the-shelf mod but unfortunately not all such aftermarket tweaks are a good idea. Vans’ design team have a great deal of experience in details of this nature which is why their products are so excellent."
I am led to believe that the RV10 is different in its construction. Builders of other models may certainly fine the above advice useful. Make of this as you wish.