Hello, I own a nylon internal frame backpack, brand name of Kathmandu (a brand from New Zealand). Unfortunately I have had mishaps with food and the like and it has sat, dirty, for awhile now. I feel guilty about mistreating this pack as it has suited me well, but I have no idea how to go about cleaning it! All the advice that I've read so far details how to clean external frame or frameless backpacks. I cannot seem to remove the frame from this one as it is sewn in (I believe, I do not have it at hand right now to take a look at it). How would I go about cleaning this? Thank you for your time.