Season's over! I'm gonna strip the paint, fair the hulls, and repaint her this winter. So now's the time to deal with the tramp pulling out of the groove in the hulls. Do I just build up more glass/carbon over the top of the groove, and then route it out again? What kind of router bit(what's guiding it?)? Fill the slot with something so as to not slop epoxy in there? Better ideas?
As you can see from the pics, I attempted to modify the tramp so it didn't need the groove(ala Tiger), and it was moderately successful. But the tramp is more bouncy than it would be if it were firmly anchored to the hulls alon its edges, so I'd like to return to the orginal concept.
Advice? Thanks gentlemen!

Dave

Why not consider adding another layer of fabric on the tramp bolt rope instead of working with the slot. It would seem easier to increase the diameter than reducing the slot.

Dave,
I have had the same problem on my older Stealth. We solved it 2 years ago (or rather Greg Goodall did) by cutting off the existing bolt ropes and replacing them with the next size up. We then had to increase the size of the 'feed' part of each slot to get the new rope in and also had to run a piece of sandpaper wrapped around a drill bit along the slot to ease it in about 4-5 places. It took a while but I was VERY pleased with the result as the tramp is much tighter than it had ever been before and has never pulled out since!

You're the only Stealth I know of with a groove in the hull for the trampoline. Most have a series of mushroom plastic thingies screwed in the top of the hull to strap the trampoline to.

The simplest option would be to go to a larger bolt rope, maybe widening the entrance of the groove so it can fit.

Another is to try is to slide a big diameter rope inside the groove with small dyneema line spliced and stiched at regular intervals to make loops. You can then lace the trampoline to the loops. You would have to reduce the trampoline width however in order to get tension...

Or convert to the mushroom method.

John,
My concern was that the hull in the vicinity of the groove was flexing, allowing the bolt rope to escape. That's why I was thinking I needed to add material to the hull to stiffen it up. Although, when I got the boat, it was already pulling out, and I didn't really investigate why, I just wanted to make the boat functional.
So maybe I don't need to add thickness, just increase the bolt rope diameter? Can you describe how you enlarged the feed opening?
You might have saved me a bunch of work, thanks!

Pepin,
I'd be ok with the mushrooms, particularly since I now have grommets in the tramp. But it seems like I'd need to be securing them into some reinforced section of the hull. I doubt riveting into the foam sandwich would hold.
Your other idea seems doable as well, although I don't have a totally clear picture of what you're proposing.
I guess I need to gently pry on the groove and see if it is
indeed flexing excessively. Thanks guys, and I do recognize that some of these remedies you've offered me before, when I first got the boat from Gary.


Dave

Dave,

Before I may or may not jump in on this topic.. would you mind mentioning that this issue was fully disclaimed when you bought the boat from me?

I did not enjoy the same treatment from the previous owner, seller.

GARY

Pepin,
how would you retrofit the " magic mushrooms"? I dont even know where I can get them..

I like a tight trampoline, so I would look into converting to lacing. Easiest way is probably to make a boltrope with a strip of cloth and some webbing loops. This goes into the slot in the hull. Have the trampoline re-cut and stitch webbing loops on to it so they match the loops on the part installed into the slot. Lace together and it should be solid. Expect to replace the webbing loops now and then.

Those can be installed with rivets or self taping screws.

Those need access from the inside to thread a bolt onto them. But they look nicer

Most boats have those mushrooms on the rear beam. Lots of Stealth have them on the top of the hulls so the trampoline is slid into the groove on the front beam and then laced around.

The links are to the Marstrom shop, but you should be able to get your favorite local merchant to order them.

They are also used on Hobie Getaways. You should be able to order them from your local Hobie dealer.

What local merchant
The hardware stores here would not know where to start if I asked for something like that. Ordering from Marstrøm used to be a chore (and $$$) but I have not tried for a couple of years. I had to lean on a guy I know who worked there to get the last order completed

What reinforcement is neccesary to install these. The loads are not insignificant even with a backing plate.

Dave,
We just kept offering a short piece (about 4") of the new bolt rope up to the slot to see what needed 'easing'.

To open up the feeder part of the slot we used a combination of a Stanley knife, round file, half round file and some sandpaper. Once we got the size we needed, I took off just a fraction more and we then made good with gelcoat filler. When dry, this was sanded fair and the job was done!

This was when we discovered that the slot also needed to be eased in a few places, so we used a broken drill bit (I think it was about 8mm) and wrapped it in sandpaper and slid it down the slot. It took a while but we just kept working away at a few high spots in both the slots until the sample piece of bolt rope slid easily along the length of the slot.

I suppose the whole job took a little over an hour and a half. Have fun!

Gary did indeed let me know that this was a problem with the boat, and I hold him harmless. I had a ton o' fun with the boat this season, I've got no complaint. I just think I'd like the tramp better if I can once again secure the sides to the hulls.

Dave

I think the Stealth do use polypropylene (or polyethylene?) backing (same material as a kitchen cutting board) glued in place before hull joining for the stress points. But I'm not sure there are any for the shrooms, you would have to ask John.

Hobie 20 "eyelet post" P/N 4122 0001 ~$3.00
riveted (6-8 MONEL) to rear beam

I can tell you that the problem with this tramp groove on this specific boat is that they are split lengthwise, allowing them to easily spread apart. The tramp pulls downward and sideways on the groove and this spreads the split tubing to the point of splitting it in the bottom of the groove.

Look in that groove to find the lengthwise split and evidence of my gluing it. I desalinated it with water, dried it with alchohol and a warm air dryer before gluing it. I also pried it open to ensure good glue penetration. Once the entire split was glued, I clamped using a series of several rope wraps around the entire hull and a length of dowel to twist the rope to squeeze the slot closed. This was left to cure for 24 hours before being unclamped.

The result as a re-split on the glue line as soon as I applied my body weight to the tramp. The way the tramp pulls on the edge of the groove is much like the lever action of a can piercing opener like what was once used to open a can of beer before we had pop-tops.

I don't know if you'd want mushroom buttons on top of the hull because it would hurt your pelvis if you sat on one. I would not expect there to be adequate backing beneath the foam sandwich hull to support the buttons. I don't believe that mushroom buttons would be at the proper angle if you glued them into the slot.

The groove is probably unidirectional pulltruded fiberglass tubing. If that's the case, gaining strength across the section will be nearly impossible unless they are completely filled with epoxy or better yet, bridged over with a patch. Doug Sanborn and I brainstormed this problem and came up with the following solution:

A series of loops hanging out of the groove, with composite bandages bridging the slot in between each loop location. The loops should be Amsteel since metal sail slugs would fatigue from repeated flexing. Amsteel has the tension strength, abrasion tolerance to do the job. Take the largest size Amsteel that would allow you to fold it in half, tie the bitter ends into a knot that can be slid down through the slot and situated at each desired location. I think I tested a piece of 3/16" and a piece of 1/4". Can't recall which was the better fit. I seem to recall that 3/16" would probably be tight enough and 1/4" was a very tight fit.

The next step I am not convinced would be necessary but it would be to fill the slot with thickened epoxy.

Finally, take a strip or two or three of 2" or 3" wide woven glass cloth over top of the groove, in all the locations where there is not a loop of Amsteel in the way. You could use a layer of Kevlar cloth for abrasion resistance, followed by a top coat of fiberglass cloth.

I would mask the Amsteel loops so that they don't get any epoxy in the portion that will need to flex.

Those epoxy impregnated woven fiberglass (and Kevlar) "band aids" could be a single strip with a hole cut out for each loop.

Gary

In order to reduce the strain on the tubing and transfer some of the load back to the hull skin, would it be possible to create one or two 'bridges' down each groove? You would have to create an additional opening to feed the trampoline and have appropriate breaks in the boltrope. Additionally, if required you could also reinforce the inboard part of the groove on the outer surface by laminating with unidirectional carbon and epoxy. This could be faired in and painted but shouldn't be too obtrusive as it would be hidden by the trampoline.

Cheshirecatman

That's great Gary! I was pretty sure more material was needed, but my idea of just beefing up each side of the groove might not be sufficient. The concept of bridging the groove between loops would certainly provide the strength to overcome the inherent weakness of the design. Now I'm trying to conceive a slick way to mask the loops so as to minimnize fussing, and provide a clean appearance when completed. Stuff the loops into some stiff platic tubing(like a straw) that the epoxy wouldn't stick to?
A lot easier to finish would be to fill in the groove, glass over it, and then secure mushrooms of something else into the now filled groove. But you're right, that the angle of the hull probably won't work for the mushrooms. And anything solid(eyestraps or?) is gonna be a pain to sit on. Still open to suggestion.....

Dave

You could dip the loop ends of the Amsteel in melted candle wax (or even butter) but you would need to be very careful not to let those treated areas touch any of the portions that you want to have the epoxy adhere to.

It might be slightly easier to use some sail slugs that fit snugly in the groove. As long as you don't fill the groove with epoxy then you would still be able to replace them if they were to fatigue and break. You could cut away the "band aid" bridges to start over again with replacement.


http://www.sailrite.com/core/media/media.nl?id=3609&c=603010&h=96311ce087aa7abe9032
"sail slug without rocker"

Sail slugs like this are available in up to 1/2" diameter. Using these you could forget about the worry of the Amsteel fiber rope wicking up some epoxy. Try Sailrite for sourcing them. They own the image that I just pimped off of the www.

The two possible down sides that I anticipate are that the hard prong could pry against the edge of the groove, creating the leverage I mentioned that resembles a can opener and perhaps that he metal could eventually fatigue. I think that 18 or 30 of these things could easily support all the forces without ever fatiguing over a period of several years of use. These slugs should correspond to some grommets on the tramp. If the tramp and its existing grommets are too wide, consider "shrinking" the width by "taking up" a "Z" hem somewhere down the length of the center of the tramp.

In short:

Sand off the paint along the groove, 2" on each side of the groove.

Insert sail slugs every so many inches along the groove, to situate them between the spacing of the tramp grommets.

Lay one or more layers of2", 3", or 4" wide woven glass cloth or unidirectional glass cloth that has the "warp" at 90º to the length of the groove. This will be impregnated with two-part epoxy of course. These layers will bridge the sections of the groove in-between each of the sail slugs.

Fill and shape with epoxy mixed with lightweight filler.

Whet sand and paint to keep the UV light off of the epoxy and to keep a smooth surface.

We should probably cross post this to the I20 tramp groove thread because I don't recall anyone ever mentioning applying these superficial "band aids" between slugs to keep the groove from spreading open.

Gary

Another solution would be to fill in the groove with epoxy/filler, cover the top with some glass tape, gelcoat to make it look nice and then screw an aluminum C track on top. Just slide your trampoline into the C track (you will have to make it smaller however). The epoxy filled groove will give the track a good footing and this will look clean for less effort than building a set of loops.