If you are moving from model to High Power Rocketry then the construction of the two types of rocket are quite different, In HPR materials are stronger and all the joints you make have to be a lot stronger .

Dry Fit & Prepare

Even more important in HPR than model rocketry is to test fit (dry) all parts of the rocket, any areas that need sanding to give a good fit should be sanded with a fine wet and dry paper ( Wet and Dry leaves less scratches than the equivalent sand paper ). All areas of the rocket that are to form part of a joint should be rubbed down with fine wet and dry to ensure a clean grease free surface to which the glue can hold ( Don't forget to clean with a clean dry soft cloth to remove any dust from sanding).

Phenolic Tube

Once happy with the fit of all parts, the spiral groove in the Phenolic body    tube can be filled ( unless you have a new quantum tube ). I use Ronseal two part wood filler, this comes in a tin the space in the lid of the tin contains a foil packet that has the catalyst for the filler, this is the easiest to use filler I have found, easier to sand than car filler, it also gives a smooth and strong finish and   have never had a problem with it. It cures fairly fast and hence you should only make up a quantity about the size of a pea (this means a minute amount of catalyst so patience is required when mixing to ensure the correct amount) the mixed filler should be applied to the groove using  a small flat object I find a flat screwdriver with a blade approx 0.25" works well, remove surplus filler while still soft and reuse to fill groove further up, this is one reason for only needing a pea size piece (it goes a long way). In the picture below ( in the Fin Joint section) you can see the filled spiral groove on a phenolic tube.

Fin Joints

Fins on model rockets are joined to the outside of the body tube with a butt joint, on HPR you will mount the fins through the body tube onto the motor mount, so the fins have a but joint to the motor mount tube and are also joined with a fillet of epoxy to the inside and outside of the body tube, also the glues used is no longer model or white glue but 5 min -> 1hr epoxy. The longer the drying time the stronger the joint.

The fillets in the gap between the body tube and the motor mount can be difficult to do, The way I have found it best to do is to use a straw to suck up enough epoxy for one of the fillets insert the straw in to the gap and blow the epoxy out in to the gap holding the rocket at such an angle as to let the epoxy run into the v formed by the fin and the body tube or motor mount tube. It is also possible to use a kebab stick but on models such as the PML Quasar this is near impossible due to the small size of the gap.

To make a neat finish to the fillet place a length of masking tape so one edge of the tape is where the edge of the fillet will be on the body tube. Place a second length of masking tape so one edge of the tape is where the edge of the fillet will be on the fin. The gap between these strips should be parallel and is where the fillet is to be placed. Apply the epoxy along the gap between the lengths of tape ensuring the epoxy just goes up to the tape, the trick is not to put to much there should be just enough to flow up to the tape but not bulge above it to any degree, the epoxy should be just in contact with the tape the full length of the fillet. before the epoxy has cured and is still slightly liquid remove the strips of tape. The slight ridge of epoxy formed by the tape will (providing it has not been left too long) run out to soften the joint to from a smooth transition to the fin and body tube. See Diagram bellow

Insert pic of tape on fin fillet

Finishing

Once construction is complete you will want to paint your rocket, There are lots of ways to paint the rocket so I wont go into that in too great a detail. However I can not stress strongly enough unless your model has a good finish to it before painting it will not have a good finish once it is painted. Here we go with the filler again Ensure all joints, groves or fillets have a perfect finish spend extra time now and you will save it later, ensure the model is perfectly smooth, finish the rocket with a rubbing all over with 2000 grit wet and dry, then before painting spray it all over with a filling primer that is suitable for your paint ( ensure you mask off any areas that need to be paint free i.e. connectors between sections of body of the rocket ).

Fitting Black Sky Rail Guides

To fit the black sky rail guides the help on the Black sky WWW page was not too great when it came to a 2 stage rocket as per my Thunder and lightning so here is how I fitted mine.

EXPAND HERE HOW TO FIT RAIL GUIDES