Pappy said it right. Heat cautiously as you could ruin the sinew if you get to hot. Sometimes prop twist will happen if the sinew is thicker on one side,thus pulling uneven. If this is the case it will be more stubborn to remove as you will be fighting the sinew. I had that happen on one sinewed bow and after trying unsuccessfully to straighten, I ended up adding a little more sinew to the weaker side of the limb. If you are still plenty thick you might be able to slightly correct just by scraping appropriately