Comp tip installation

Replacing my comp tip. What kind of Sikaflex should I use and what should I coat the comp tip base with other than Bondo, 5200?

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ADDICTION
1989 HOBIE 18 SE/sx wings
HOBIE ALTER SIGNATURE MODEL

Never install a CompTip with a soft adhesive like 5200. You need to use thickened resin, bondo or other hard filler. There is a lot of flex force on the joint. You need to keep the parts fixed and stable. I prefer Bondo. Its easy to work with and hard as a rock.

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Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Thanks Matt. I was hoping you would reply. What about the Sikaflex for the foam plug? What type/product number Sikaflex should I use? Any other methods or product suggestion for sealing the new foam plug?

_________________
ADDICTION
1989 HOBIE 18 SE/sx wings
HOBIE ALTER SIGNATURE MODEL

5200 on the plug

Goop up inside the mast with the 5200 and then insert the plug. Push to the depth (9"?) If you have one of the little metal plates shaped like the extrusion... goop up the visible side of the foam plug, insert the plate flush and then goop up the plate.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

You may wish to drill a small airhole to allow you to push the comptip in after you seal in the foam plug. Otherwise, the comptip will act as a giant plunger and push the plug out. A rivet hole at 8 1/2" if the plug is at 9". Seal the hole with a rivet and rivet condom (rivet seal cap, I don't know the formal name).

The aluminum section of the mast has a 3/8' hole with a plastic plug. Hobie comptip replacement instructions say something about filling the space between the top of the mast plug and the bottom of the comptip with epoxy foam. There was no foam in this void when I removed the old comptip. What is the purpose of filling this area, do I need to?

_________________
ADDICTION
1989 HOBIE 18 SE/sx wings
HOBIE ALTER SIGNATURE MODEL

That is for quicker installations for retrofits in the field. The foam plug coated with sikaflex / 3M 5200 seal takes time to cure, so slows the process by days. If you install to soon, it gets pushed out of place by the air pressure.

Actually (our forum friend) "Hammond" designed a 2 part foam injection for this when he worked here at Hobie Cat years ago. You Drill the hole, glue in the tip (air vents out the hole), then follow with the foam injection plug through the hole. Much quicker!

Has to be a 2 part (A&B) closed cell floatation foam (West Marine sells it).

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Careful with the two part foam. Think expanding foam in an enclosed space with one escape route. If you do this, do it outside on a warm day (check the foam temperature and humidity requirements). Wear eye protection and tape off anything you don't want covered in foam. Really, it is best to let a dealer do this for you. What ever the cost, it will be worth it.

Hammond is correct... shoots like a geyser under pressure. You have to cover the hole with a gloved finger. We had a dealer miss that step... he "use to" have a beard.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Like I said, when I removed old comptip the area between the plug and the comptip was void of any foam. I waited 2 days for the plug/5200 to cure, new comptip is installed. Why do you fill the void with foam? Do you have too? The old one from the factory was not.

_________________
ADDICTION
1989 HOBIE 18 SE/sx wings
HOBIE ALTER SIGNATURE MODEL

Again... the foam reference is from dealer installations of the CompTip. The factory didn't do that... they did as you saw. Sealed, cured and then installed.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Thanks Matt. I think I'll just plug the hole with a plastic cap like when factory new and skip the foam.

_________________
ADDICTION
1989 HOBIE 18 SE/sx wings
HOBIE ALTER SIGNATURE MODEL

I recently reattached the comp tip on my H18... this was my first time, so here are some thinking points:
* I used a step drill to drill out the rivets -- it has only one cutting edge, advances slowly, and is very easy to control
* while I had a few inches of sweep at the top of the mast, it was still pretty difficult to get the tip out of the mast
* 20 minutes with a heat gun cooked the (factory?) adhesive loose, but I still needed to strap the mast one way and ratchet-strap the tip the other way
* whatever was used to minimize galvanic corrosion between the tang and the mast is rock hard and no solvent would soften it (I sanded a bit and tried not to take off too much mast)
* dry-run your assembly process -- have everything neatly prepared and at hand, you won't have much time after you mix your adhesive
* I used Bondo, and mixed it lean for hardener, and still had almost too little time
* a second person would really have helped with tip insertion and cutting overall time (as noted, an issue due to pot life)
* inserting the rivets and caps was surprisingly difficult, even with a dry run -- aligning holes for the tang, mast, and tip was tough (pot-life, again) - I used an allen wrench to lever alignment as needed
* after I had the rivets started, a few were still stubborn to completely seat against the tang (pot-life, again) -- I used a 5mm 1/4-inch deep well socket as a hollow mandrel to drive the rivet/cap by their flange without bending the rivet
* I used this as an excuse to buy an air-driven hydraulic rivet gun, I wouldn't have had time (maybe strength?) to get all those rivets popped manually

The result is nicely stiff and looks acceptable. The tang doesn't sit absolutely flat in one place, and one of the rivets is somehow slightly cocked in the bore. I am confident that this will be serviceable, but I will keep an eye on it; Hobie did it better. I sailed last season with a loose comp tip, and was impressed with how well adhered it was even when 'loose.' Generally, the bondo/adhesive has some 'stiction' involved, but it seems to provides axial bending stability essentially as a columnar shim that creates an interference fit, and there's 10-12 sturdy rivets holding that joint in above and beyond that. I'm not sure how many comp tips really fail from getting loose, there's quite a lot holding that joint together.

Thoughts for next time:
* keep acetone away from the sail track on the comp tip (mine softened considerably where I left an acetone-soaked rag sitting on it - it did harden back up after time, but I had to file a bit to get alignment back (removed material leaves it weaker)
* use a slower-fired adhesive, pretest pot-life in actual conditions, and assemble on a cooler day in the shade (pot-life, again)
* have a couple 3/16" punches on hand for better leverage alignment for the tang, mast, and tip
* bar clamps might help the tang sit flatter (that would probably help with alignment, as well)
* I used sturdy packing tape between the tang and the mast and trimmed around the tang after it all set up - there's probably a better way

I put this off for way longer than I should have. It wasn't a big deal, and could have been done all in one afternoon with time to spare.

Randii

Has anyone tried the evercoat foam for filling the mast
http://www.evercoat.com/cache/ex_q75_w5 ... 100654.jpg
its a closed cell polyurethane..

Hi all, Hobie maintenance greennhorn here. I have a couple of clarifying questions

So when you guys say bondo, you mean bondo fiber glass resin?

Also, on my 89' Hobie 16 my comp tip is attached via two large, flat Philips head screws, not rivets (i dont see holes where rivets would have been). Should I just insert the comp tip with the resin then insert the screws while its drying?

Additionally, what is the foam plug you guys are talking about? And is the mast filled with expanding foam from the factory, or is that an upgrade you guys are doing?

Right now I'm thinking my process for tightening-up/ reinstalling the comp tip is as follows:

1. take (2) screws out
2. work comp tip out of mast
3. put layer of epoxy around comptip insertion area and let dry
4. sand down comp tip insertion area until it cam be inserted with a snug fit
5. insert into mast with another coat of wet epoxy
6. insert screws and let dry

I know that was a lot, so thank you for your responses and advice!