noob questions about RMH

been watching a lot of videos and reading a lot of posts on permies

i have a few questions

1)  i'm having a hard time finding refractory-quality brick locally at big-box stores.  all i'm finding is lower-end firebrick rated for around 1700F, when what I really want is brick rated for 2300F+  i want to build something to last, and don't want it cracking as i assume would happen with lesser bricks

2)  question about routing flue through a mass.  my concern is that somehow, if the pipe run is too long, or takes too many turns, it might slow down the thermosiphon action.  is this a legitimate concern, and if so, what are the practical limits in this respect?  

3)  does the top of a typical steel barrel in the rocket->barrel->mass configuration get hot enough to bring a pot of water to a rolling boil in a reasonable timeframe (or at all)?  

thanks for your time

Find and read the book "The Rocket Mass Heater Builder's Guide: Complete Step-by-Step Construction, Maintenance and Troubleshooting". Here is a link https://permies.com/wiki/57365/Rocket-Mass-Heater-Builder-Guide

I found that many of my questions were answered.

Hello Weston and welcome to the RMH forum!

1) I would agree to source out the higher rated firebrick. Do know that however that even it too will eventually crack. A lot of the time this won't be an issue as the brick still holds together as it never shears perfectly straight and it irregularity will still hold itself in place. Best to know now that some may need to be replaced over the years.
Masonry supply and wood stove shops will carry this higher rated brick. Sometimes you can get lucky and find second hand ones from craigslist. Lumber mills sometimes have them. Call around and see what you can find. Gearing up to build a RMH

2) If you go with a piped mass then there are some standard published limits given as guidelines for both 6 and 8" systems (generally 20-40 feet). It also depends on the number of bends you put in your pipe which puts a lot more drag on the gas flow than a straight run. If you go with a bell (a big open chamber where the gasses are allowed to stratify), then the size and shape are not as limiting, especially when accompanied with a bypass.

3) Short answer, yes. Water can be brought to a boil in a very quick period of time if that is one of your main goals in designing your stove setup.

Hi Weston;   Welcome to Permies!  And Welcome to the Wonderful World of Rocket Science!

Lets see if I can answer your questions.
1) You want 2700F heavy fire bricks and you probably will not find them at a box store.
You need to locate a Masonry supply house.  
I don't know what larger city you are near, but pretty sure they will have one.
Masonry supply house will have firebricks in full and split, and they will have #50 sacks of fireclay.  
One company that is popular out west, is Mutual Materials. Here is a link, https://www.mutualmaterials.com/branches/missoula-mt/
Look to see what might be in your area.
Firebricks are around $2.00 each and fireclay should be about $10 a sack.

2)Pipe run on an 8" J tube is apx 50'  with a 5' deduct on every 90 degree turn.
A 6" J tube is 30' .  

3)Most barrel tops run 500F-800F  One of my early builds  was 1100F
So yes, they will boil water.  They also will melt plastic handles and such, so care must be taken to use suitable containers.

Last but not least. Buy the builders guide!