I have a 2013 R-29 with a custom-made Sunbrella cover for my dinghy to match my Sunbrella Bimini and cockpit walls. King Canvas in Seattle made it, and it fits well. I purchased it for several reasons, including to keep the exhaust off the dinghy, the water out of the dinghy, and to protect the dinghy from the very hot sun while in San Diego.
I cannot say whether it has kept the standing water out of the dinghy, although I tend to believe it probably did due to lack of discoloration where the water regularly collected, and the amount of rain that fell could have filled the dinghy many times over :!:
I am confident it has protected the dinghy from the sun, although that was not much of an issue in BC and Alaska as compared to SoCal 🙂
I believe some of the exhaust penetrated the Sunbrella, based on how much dirtier the dinghy was inside at the end of the summer, and my cursory inspection. My first impression is that the Sunbrella may have diffused the residue. Much to my amazement, it has not seemed to collect that challenging residue on the cover, which surprises me a great deal, and I was very disappointed when taking the cover off to see how dirty the dinghy was.
I have not yet tackled cleaning the dinghy, which will probably indicate whether the dirt is exhaust. My very brief effort to clean the dirt off was totally ineffective. Since then, I have relocated to Seattle for a few months and have been away from the boat for almost 3 weeks, visiting my family in several locales. I need to remove the cover and spend time cleaning the dinghy; hopefully it will not be as challenging as it was previously!
The cover has been on my dinghy since May 31, and the boat has traveled @ 2800 nautical miles with it on through Sept 30th. I only took it off to check the dinghy after my trip to Alaska was over and should have been checking it regularly, but was counting on my kayak as a back up in case of an emergency. I presumed the dinghy was staying clean since the cover does not have the dark stain the dinghy collects uncovered.
As my trip progressed I chose not to use the dinghy, beginning with being quite tired after long days piloting on the way north, then as a solo anchoring out much of the time and not choosing to venture out in it or to shore alone. I took my kayak out very little, but plan to more if around others.
I wish I had specific data for you, and plan to pay closer attention in the future, both as a safety check and to ascertain whether Sunbrella is a good fabric for the dinghy cover 🙂