Hi Mike,
I built a custom garage for our R27 so I can offer details about the R27 as well as some other suggestions, some of which I included by design, some of which I added after getting the boat inside and some of which I wish I had thought of but am too late for now. I have pictures of all of this and will post them soon (tomorrow?)
1) The R27 is 35' 10.5" on the trailer (with the swim grid). I know this because I have exactly 36' between the door and the landing at the back of the swim step. It is a tight fit but it works! I actually have a slightly larger trailer than normal that was meant for a C28 but modified for the R 27 (It's a long story). I have had the boat in with the standard trailer in the garage so I know that arrangement as well. There is some ability to adjust the OAL by adjustIng the location of the winch stand but you need to manage the tongue weight when making changes.
2) If you back your boat up to the wall it can be a pain to get around it and get on the boat both sides. I chose to put a 3 ft landing against the wall at the height of the swim step (48 in. for the R 27). This adds three feet to the interior of the building. I highly recommend doing this if you can add the additional length. I also put stairs up to the landing on both sides. This makes access to the boat from either side very nice. I also put an exterior door to the outside at the height of the landing. While not absolutely necessary it was convenient for the building design so I chose to do it. Code requires a railing on the landing and stairs. I chose to put a removable rail for both. When the boat is on the water the railing is in place, when the boat is in the garage I remove all rails for easier access. The interior of the garage is 15 ft wide.
3) Heat and Insulation: Because of the layout of our garage the port side wall is insulated but not the starboard side. This was simply a matter of cost. Fully insulated may be better but I chose to heat the boat and not the garage. The boat garage has no heat but is adjacent to a heated garage. It never drops below freezing in our climate even if no heat is added to the boat. To keep it dry I use a portable ceramic heater in the boat cabin and leave the engine access under the step open to keep the engine warm. I can always choose to add heat to the whole garage in the future is needed after I quit making changes to the space!
4) Power: I put a 30A Marine supply outlet near the port side just under the edge of the landing. I also am reconfiguring to add 120v outlets on each side of the landing to power for tools etc. while working under the swim grid. They are currently on the walls which is not as convenient. The boat is left connected to 120v AC continuously (batteries charging) while in the garage.
5) Water supply: I have a hose bib under the landing on the port side for supplying fresh water to the tank and to provide water for cooling during engine tests (see below). Ideally this hose bib would have been on the starbard side for the R27 but the port wall is insulated so I used a frost free hose bib there making potential freezing a non issue.
6) Grey (and black water) drainage: I added a dump port to our septic system in the floor of the garage under the landing for grey and black water drainage. It is nice to be able to dump and flush the system while in the garage. Ranger added an extra Y valve to the boat to aenable the macerator to pump the black water into to the septic tank. They also built a friction fit manifold to collect the grey water from the shower, head sink, and kitchen sink which I run to the septic tank. This all allows us to use all the water systems on the boat while in the garage. Very useful when doing fall cleaning/flushing of all the systems.
7) Engine cooling water supply: I feed the regular fresh water hose directly into the seawater strainer (with the cover removed) for engine cooling. A standard garden valve on the end of the hose allows me to control the water flow while I the boat. It will overflow however but I let the excess water run to (clean) the bilge and get pump out via the bilge pumps (see engine ancillary drainage below).
8) Engine cooling and exhaust drainage: This item I unfortunately did not plan for for adequately. When doing maintenance on the boat you often need to start the boat to test your work or to warm the oil. For this purpose I have added an exhaust hose (standard auto repair shop high temp exhaust hose with a piece of muffler pipe to fit boat exhaust outlet) to a dryer vent under the landing. This exhausts gasses and cooling water out the building.
9) Ancillary drainage: In addition to the exhaust drainage there are drainage requirements for the bilge plug, the bilge pumps, and the prop shaft cooling. I didn't plan for these adequately. I would recommend a zip drain in middle of the garage floor if I were to do it over. In my case I am using a bucket to catch the bilge plug water, modifying the grey water manifold to collect bilge pump water, and adding a large tray under the prop to catch the prop shaft cooling water. Note that a zip drain in the floor would also allow you to wash the boat while in the garage!
With all the above features I can do all maintenance items with the boat in the garage! Very convenient. While clearly not necessary I highly recommend these features if you are building from scratch anyway and have the luxury to add what you need for the boat. Let me know if you want more details.
Curt
