[Spinnaker]

Did you shear them going in or coming out?
If you broke them going in, then they should be fairly easy to get out with some sort of extractor. You can buy screw extractors at any hardware store. If you broke them trying to get them off, the most likely case, then be sure to apply plenty of penatrating oil and let it soak in for awhile. The bolts were probably seized due to corrosion and will still be difficult to get out. When you drill them out to use an extractor, try to drill all the way through to the bottom and then spray in some more penatrating stuff and let it soak in for a few hours to help free up the threads before you use the extractor on it. I like to start with a smaller size drill bit first, because it is usually hard to get it exactly in the center of the broken bolt, and it is easier to keep the smaller bit from walking around. If the bolt is protruding above the surface, file it flat and then center punch the bolt to help you get it in the center. If the first drilled hole is slightly off center you can angle the next size drill bit slightly to get it back on center. If the bolt is broken flush, or below the surface, just try to center punch in the center as best you can. If the punch mark is off center, angle the punch towards the center and hit it again to move the mark over towards the center.
Here is the most important part of drilling out the bolt. Drill with a VERY slow RPM on the bit and use a lot of pressure and lubricant. The mistake most inexperienced people make is that they run the drill bit in there at high speed and then they work harden the bolt from friction. This makes it even harder to drill out the bolt and the frustration level escalates. When you are drilling the bolt, you will be able to see and feel the drill bit cutting the metal. Metal chips should be coming out at all times. Use sharp bits. If the drill bit spins in the hole and no chips come out, the bit is dull and/or you have work hardened the metal. Once the metal is work hardened, it is a lot of work to drill through the hardened layer.
After you have drilled out the bolt and let some penatrant soak in, insert the extractor and apply some pressure to it, but don't force it. You don't want to strip out the threads on the hole because the bolt and the threads are most likely fused together from corrosion. It should take at the most, medium hard pressure to get the bolt out. If it doesn't want to budge, then apply more penatrant and maybe even a little heat from a torch to get the threads to free up.
Be patient and take your time to do it. It usually isn't that hard to get the broken bolt out but you have to be careful not to screw up the original hole and threads. If you have access to metric taps, then chase the threads with a tap after you get the broken piece out to clean up the threads.
Remember to be PATIENT and take your time. If you get frustrated, just take a break and come back to it later. You don't want to have to buy new struts or have to fix a stripped out hole. If the worst happens, do a search for "Time-Serts". Good luck.

BTW, when you put it all back together be sure to use some antiseize on the bolts to prevent this from happening again.