>>754
https://en.wikipedia.org/wiki/Flat-iron_gunboat#Description
In contrast to their failure as coastal defence gunboats, the occasions when they were used for coastal bombardment were more successful;
Argentine gunboats were used in 1890 to bombard rebels during the Revolution of the Park,[5] Greek gunboats bombarded Turkish forces during the Greco-Turkish War of 1897
and both Bustard and Excellent (formerly HMS Handy) were part of the force that bombarded the Belgian coast during World War I.[4]
According to Professor Andrew Lambert the Royal Navy flat-irons succeeded in their task of deterrence, and were a key asset to the capability of coastal offensive operations.[7]

海防艦としては失敗作だけど沿岸要塞に対する艦砲射撃を行う砲艦としては役に立った
最初のレンデル式が登場したのは1867年で戦艦を持つ余裕のない国のユーザーが多かったけど、19世紀末になると魚雷と水雷艇の方がもっと安上がりで人手も少なくて済むので作られなくなった