NACRA 5.2 - Trampoline - Jib Strops - Center Tube

Just checking again.  Anyone have experience with this?  Thanks!

Nacra added that longitudinal tube likely for a good reason. I'm guessing that it's because without it, the main and rear beams may deflect enough to not be able to keep the trampoline tight enough. Just a thought.

If the main beam deflects enough from tramp tensions, the beam could fail under the mast's compression upon it. That beam is put into column-compression and must remain in a very straight column in order for it to withstand the compressive forces that the dolphin striker's stays act on it, every time there is vertical mast compression put onto the striker.

@cat-scratch Thanks for the input.  Defiantly need to consider that.  I wonder how successful it has been for those who have removed it?

I have a Nacra 5.2 with the center beam. I considered the same thing when I bought my new trampoline a few years ago. I decided to stick with the center beam on the purchase for the new trampoline mainly for 2 reasons.

1. It does provide a good place to rest your foot on has you begin to fly a hull.

2. I believe it is critical to the structure of the boat. I think the cross beams could potentially twist if they are not completely locked into the cradle. It also may take some of the load and share it between both of the cross beams. 

I agree it is nicer to move across the trampoline without the beam but you may be sacrificing the structure integrity of the boat. When I purchased my 2nd Nacra 5.2 a few years ago one of the spots that had hull damage was where the front beam punched through the side of the hull at the Bearing Tang. It was the end of the Dolphin Stricker bar that went into the hull.  It may have been caused from a loose beam strap or just to much flex in the cross beam vs the hull.  

In the attached picture you can see the missing Bearing Tank next to the front cradle.  I fabricated a new Bearing Tang and attached it yesterday. Maybe I can share a picture later. 

Good luck with your decision!

Does anyone have any suggestions

on the repair of this rudder tip?  I was going to insert screws or wooden dowels into the center of the rudder and then attach to some thin piece of board. Once I got something structural then I was going to fiberglass around it to the shape of the matching rudder.

Thank you.

@leadbetter

Merely a mild case of road rash. 🤣 

What I would do is either use a piece of purchased G10 'glass, or make your own G10. 

Use a dremel or a oscillating multi-tool to cut a slot into the center-line of the rudder's core (vertically oriented), wide enough to key-in the G10 with epoxy for a good anchor. Trim the G10 to the original rudder's profile. Then build up some filler on both sides of the G10, or you could use some Divinicell structural foam as well. After  a bit of filling, you'd want to lay on some 'glass/epoxy for the skin of the repair, so you'd want to scarf that skin onto the existing skin with a 10:1 - 12:1 scarf joint. E.I.--- sand back the edge of the existing 'glass skin to give plenty of surface area for the new 'glass skins to adhere to the existing  'glass skins.

I'd use something like a 4 oz. crow's foot (H4 weave) in multiple layers.

Alternatively, you could just use a high-density filler/epoxy to shape around the G10 that you inserted, then fair to profile, and likely not worry about a new skin, though you might eventually get some cracks forming between the old glass and the new repair if you don't add an additional 'glass skin.

For ease of laying-up the new 'glass skins, I would add just enough filler to allow for a nearly flush molding surface to the scarf-prepared existing skins, bringing the filler to a sharp, feathered edge near the leading edge of the G10, providing some lateral/medial surface area on the leading edge of the G10 for good skin adhesion to the G10. Then lay on your 'glass skins. Then after cure, add more filler to fair a proper foil-shape.

I know.... sounds complicated. But it's not. Just a few steps.

I've made my own G10 'glass (or even CF) sheet with any old fiberglass cloth scraps I've had laying around, and epoxy or even polyester resin, or vinylester resin. I've made very flat G10 sheet by waxing a flat mirror or glass pane and laying up on that (I have saved some old mirrors for that purpose). Or, put down plastic sheeting on a flat table and laying-up on that, though the resulting surface may have slight wrinkles due to the plastic sheeting not being perfect. Cheap plastic packing tape works well as a release surface as well.

Make your G10 thick enough so that it doesn't bend too easily as you're filling around it on the damaged rudder repair. Perhaps three or four layers of 1708 (biaxial) fabric (or similar) would do.

If your G10 base molding surface is very flat, then the top surface of the G10 will come out reasonably fair if all your 'glass layers are the same size without any overlaps. Put some plastic sheeting over your layup after complete wet-out and squeegee the excess resin out with plastic bondo spreaders. Leave the plastic in place until cured.

The cool thing about making your own G10 is that you can form it to conform to any shape or contour.... beam pads or clamps, cleat bases, tangs (using CF), etc. My old H18 front beam had a crack form at the mast step. I made a thick piece of G10 (fiberglass insulating layer, then CF layers) formed around the beam, shaped it (sanding off sharp edges) after removing it from the beam, then epoxied it to the beam under the mast step. Worked perfectly.

Thank you for the advice! I just picked up some scrap G10 from my local surfboard fin company, (True Ames). Just need to get a few more items before I begin. 

@leadbetter Thanks!! Appreciate the advice!

I just wanted to confirm the orientation of the G10 slot I need to cut into the rudder.  Here is a picture of what my plan was with the G10.  I am going to cut the G10 with a matching slot to fit into the rudder.  It will insert approximately

one inch into the rudder, does this look like what you had described? 

I'm also installing the deck lids and had to grind down about 1.5 mm on 2 sides of each lid to help fit the contour of the deck. The old lids were made by Viking and the new ones are by Seadog. It would be great if the lids were made of a more flexible plastic as they don't bend very easily. 

Does anyone know why the rear transom of the Nacra 5.2 was never painted or gel coated? I painted my old 5.2 rear transoms black with spray paint years ago which looked more finished.

Yeah, that's perfect if it's aligned with the vertical center of the rudder blade and is on the same centerline plane, which appears to be in the photo. Didn't really have to be one inch, just enough for the epoxy to make a good bond with both the rudder and the g10. 

The lid frames are not to be bent! If you do bend them to the deck contour, the lids would never screw on correctly. Fill in the gaps with some thickened epoxy with white or gray pigment added. You could tape the bottom surfaces of the frame with packing tape, then place the epoxy filler on the bottom taped surface and stick it on the deck, filleting the epoxy to a nice contour. When cured, remove the deck lid frame, remove the tape, then adhere it down with your favorite waterproof goop and screws.

Why not just epoxy the lid to the deck? You might loose or break the lid, and newer lids that you may purchase years later may not fit the older installed frames.