H17 alternative mast

I don't trust the crack in the polyester of my comp-tip mast. When I bend it I can see a little water come out of the crack.
The mast hight is 8.43 meter....
Is it possible to use the mast from a Dart 18 for example...maybe even the sail?
Used masts for the 17 are rare to find.

Pictures, please.

The Comptip can be repaired. (If it's fiberglass, it can be fixed.)

This is what it looks like...




Maybe a carbon layher with resin for about 20 inches?
Its half way the comptip....

I repaired my H18 mast using several plies of carbon. It was cracked in the middle of the comptip on the front of the mast. It was similar to the first picture in your post, not as bad as the second. You won't really know how bad the damage is until you start grinding away at the crack to see if it's all the way through the mast or not and to see how far it extends. You're going to have a little bit of an issue dealing with the groove for the luff track. You'll have to match the groove profile pretty well with your repair, or you may have to trim away the plastic luff track in the area of the repair.

The best way to bond the carbon would be to use a vacuum bag. I didn't have one, so I improvised by using black electrical tape. Use a utility knife to punch a series of holes in the roll of tape. Then wet out the carbon and lay it up on the mast. Once you have it where you want it, wrap the electrical tape around the mast. This will compress the fibers against the mast and the excess resin will squeeze out of the holes in the tape. Once it cures, peel off the tape and give the mast a quick wipe with acetone to take off the tape residue.

It's worth a shot at a repair. Worst case scenario, you end up having to replace the comptip, so you still shouldn't need to replace the entire mast.

sm

The first photo and the second are from the same spot. Only sand it a bit to make it more clear.
It is on the backside of the mast. I think that is less negative then it would have been at the front side because of the tention from the halyard.
If the water comes from inside the comptip I think the inside foam is soaked. Is it no "closed cell structure foam"?
Are these comptips still available?

The inside of the comptip is hollow, it just has plugs on each end. You're not going to know for sure how extensive the crack is until you start grinding, but if a significant amount of water came out of the crack, that would likely mean the crack is completely through the mast. A crack anywhere on the mast is bad news, especially with a rotating mast since the loads on the mast will change significantly as the mast rotates.

From what I recall when I repaired mine, I think I ended up grinding back the crack at a taper about 1/2 way through the mast (didn't want to go all the way through so I had something to lay the new glass against. Then I added glass to build back up to original thickness. Then I added several large carbon fiber patch plys over the whole area.

Your Hobie dealer would know for sure, but as far as I know, comptips are still available for the 17. Anyway, I think it is worth attempting to repair. Fix it as best you can, rig it up on the beach, and sheet in the main hard. If it holds, you're probably OK.

sm

I will try to do the repair first. I found a used H17 mast and can buy it for 250 euro/285 dollar.
That is nice to know if the repair would not be okay.
Don't know if I should grind it for about 5 inches in a square a little lower then the surface of the mast and fill that spot first with carbonsheet and resin. After that one or more layhers of carbon around the mast. I don't want to make the part much thicker then the rest of the comptip if possible.

A handy way of cleaning out the luff track after repair is to wrap your abrasive paper around a pencil (or dowel) and insert it into the sail track with the tails of the paper protruding out of the track. The pencil acts a a bolt rope. Use the tails to slide it back and forth in the area you need to sand/clean out. Take care not to open up the track width.

Thanks for the usefull tip!

So far...the repair was succesfull.
After a season of sailing in all winds the comp-tip is still oké.
A thing that I am worried about is the movement of the hulls in waves compared to eachother.
Is a little movement normal or will this mean that the beams might be cracked somewhere?
I planned to inspect this during the winter period.
How do I get the beams from the hulls?

Some movement is normal. Hobie 17s are not stiff boats due to all the clearances required for the assembly of the crossbars to the hulls. That said, the parts can loosen up over time and become even sloppier as the boat ages. The crossbars can also crack. So total disassembly is a good idea in order to get an understanding of what issues your boat may have.

The disassembly process varies slightly depending on the age of your boat (specifically what type of tramp the boat has). But the general process is to loosen and remove the trampoline from the tracks in the sides of the hulls. Then use a 5/16" hex wrench to remove the four socket head bolts at each inboard corner of the crossbars. After this is done, you can slide the hulls outward, away from the crossbars (there is an aluminum casting attached to each hull which engages the end of the crossbar.

Things to check ...

Aluminum castings are securely fastened to the hulls. There are two or three screws which hold each casting to the hull. There are also two "prongs" at the bottom of each casting which engage the hull. If the casting is loose, remove it and check the fit of the prongs to the hull. You may need to rebuild the hull where the prongs pass through for a tighter fit. You may also need to rebuild where the screws install or switch to larger screws as the holes can become stripped out.

Aluminum casting to crossbar fit. Check for excessive slop between the crossbar itself and the casting.

Crossbars cracking where the socket head bolts pass through. The bottom of the crossbar will develop a fore/aft crack right where the bolt hole is located. The reinforcement plate on the rear crossbar was upgraded to a large size to help spread the load.

Crossbars cracking at the outboard edges. A crack can form near the tramp track at the outboard edge of the crossbar. The crack runs parallel to the track.

Crossbar cracking at mast step. Look for a fore/aft crack originating at the hole in the center of the crossbar for the dolphin striker post.

sm