While R’ Gil Student’s blog, Hirhurim, is one of the finest Jewish interest blogs on the net, when the subject is eruvin, like many others, he consistently shows a partiality. In this post I will illuminate what transpired in the comment section of a post on Hirhurim titled, “The Weirdest Eruv on the Block.” In one of R’ Gil’s prior posts regarding the Flatbush eruv (see the comments to Flatbush Eruv II) he claimed that pirtzos esser is me’d’Oraysa and therefore the mechitzos encompassing Brooklyn are deficient. In the course of that exchange he was shown that Rav Moshe Feinstein zt"l and 99 percent of the poskim maintain that a pirtzos esser is only d’rabbanan. No longer sure what Rav Moshe maintained, R’ Gil fell back on Rav Ahron Kotler zt”l (see comments to The Weirdest Eruv on the Block). Not surprisingly when he was shown that even Rav Ahron would allow the mechitzos circumscribing Brooklyn he summarily deleted that comment. So much for being open minded. What follows is the dialogue - note the last comment which was deleted.
R’ Gil Student commented - It doesn't matter. Eruvin without mehitzos are perfectly acceptable.
Reply - For many reasons there is no comparison between an eruv consisting mostly of tzuras hapesachim with an eruv made up of mechitzos. For one we don’t have to rely on shishim ribo as a heter.
R' Gil Student commented further - If Brooklyn is, indeed, a reshus ha-rabim, then the mehitzos they are using for the eruv are insufficient to enclose the area according to R. Aharon Kotler (I don't know about R. Moshe Feinstein) because they have breaks of more than 10 amos. If Brooklyn is not a reshus ha-rabim then an eruv of tzuros ha-pesah is sufficient.
Reply - Rav Ahron Kotler zt”l would agree that if a tzuras hapesach closes a pirtzas esser and it’s not crossed by a rabbim, even a pirtzos esser does not negate the mechitzos (see Mishkenos Yaakov, O.C. siman 122 p. 144). Since the Brooklyn mechitzos are at the waterfront there is no rabbim traversing the pirtzos. Never mind that Rav Aharon is a daas yachid and even Rav Moshe Feinstein zt”l didn’t agree with him concerning pirtzos esser (see Igros Moshe, O.C. 2:89). To begin with, this whole issue really has no basis since there is no question that the first Flatbush eruv relied on some kulos such as tzuras hapesach min hatzad. Therefore, there is no question that the new Flatbush eruv is superior.