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  #16  
Old 10-02-2019, 04:10 PM
GH41

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If I understand correctly you are using the brass tube sections as an internal bearing surface for the sliding CF tube. Sand blasting the OD of the brass would probably give it enough bite but this may be better and easier. You mentioned trying West System products. Did you know that West makes a carbon/graphite filler commonly used to restore rudder post bearings? You could eliminate the brass all together and use a proven bearing surface. I assume if you have West you are near the coast. SailDesign probably knows what I am talking about.
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  #17  
Old 10-03-2019, 06:22 PM
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I can't say it will work in this mixed material project, but my favorite, go to, product of choice for difficult "bonding" jobs is the normally commonly available PC-7. It's a lot like JB Weld but a little thicker when mixed. I once glued the bottom of an empty/fired .22lr shell to a rock (for the heck of it) and it stuck amazingly well. Your brass tube does need to be as roughed up as possible. Even better would be to find a way to "lock it in" so the "glue" isn't doing 100% of the work, holding the tube in place, if possible.
PC-7 is more than strong and hard enough to replace the brass tube. Yes, it can be drilled. I'd put a smooth on the outside "rod" thru the location first (before adding the PC-7 or before covering that part which you can get to the easiest), lightly greased so it can be pulled out when set up good. You can even go a little undersized on the rod and drill to size the next day.

Last edited by LoneWolfSS454; 10-03-2019 at 06:30 PM.
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  #18  
Old 10-07-2019, 01:08 PM
Whizfish
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Adhesive to bond brass to Marine Tex

Hi,
Not able to follow what you're doing but I do have experience with marine epoxy. It will bond like a glue to certain surfaces and not to others. However it can still be used. It just has to be done differently. To get tubing to bond to a surface, you will need to create a "bracket" of sorts. What comes to mind first is laying a piece of glass cloth over the tubing and coating it with epoxy. What makes it hold is creating a large surface area for bonding. I have used it to repair a split bumper cover on a car by roughing up the inner surface, laying a piece of glass cloth over the split, and coating it with epoxy. I've rebuilt cracked screw stand offs inside plastic sewing machine housings by using thickened epoxy around the outside of the stand off. And, of course, it's great for boats. Getting your tubing to stick should not require sinking the entire piece. A few straps of cloth should do it. Be sure to scrub off any amine blush that forms on the surface any place you've already tried to glue.
Don
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  #19  
Old 10-07-2019, 02:47 PM
TTE Phil

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Did you get it to stick ?



If the part you are using is inexpensive, try changing the surface of the brass part. Score it in all/both directions, heat it up and solder it. I'm guessing epoxy would stick to solder after you score it (after soldering) and clean it.

Or change your brass piece to copper.

Maybe it would work ?
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  #20  
Old 10-08-2019, 03:16 PM
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As GH41 stated above, I am using the brass liner as “an internal bearing surface for the sliding CF tube”. Thanks so much for all the suggestions, I now have some really good ideas to get the grip-vs-slide ratio that will best engage the CF rod that the clamping fixture inside the shoulder section needs.

It has been a bit like a composite version of Goldie Locks and the Three Bears –

The first gripping surface of resin impregnated CF chop was too harsh. It gripped well, but would not slide easily when loosened. Poppa Bear

The current gripping surface with the brass liner is actually too slick. It slides great when loosened, but I have to crank the cam fitting down really hard to keep it from moving from side to side. Baby Bear.

What I am looking for is Momma Bear that does the right blend of both.

Corny, but you get the picture.

Another issue is that the finished mechanism consists of two cut out sections of the brass tube that need to stay adhered to the wall of the clamping fixture. Right now with JB Weld, they are in place, but it is not a good solid weld. I am pretty sure the brass liner will come loose after some use.

I just received some of the PC-7 that LoneWolfss454 recommended and look forward to trying it out. My hopes are that it will bond better to the brass sections. My plan is to bore holes through the brass liner to do two things-
1. Give a better mechanical lock to the thin brass plate.
2. Give some better adhesion when clamped against the CF rod.

I am also intrigued by Whizfish’s idea to use an intermediate “bracket” layer of sorts that bonds well to the brass surface and on the other side with the resin filler. To me it’s the same principle of multi-layer electroplating.

I was intrigued by GH41’s idea of perhaps using some of the graphite filler, but fear it will be too slippery to clamp well.

Another option will be to make another clamping fitting out of just the PC-7 to see how it works.

Lot of great ideas – just have to make the time to try them out.

As always – thanks for the ideas! I will post progress (and setbacks).

Last edited by Gobber; 10-08-2019 at 08:50 PM.
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  #21  
Old 10-08-2019, 03:49 PM
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Gobber, I can't "see the full picture", in my mind of what you're trying to do, but have this general thought for the brass tubes to adhere in a strong way. If you soldered, silver soldered preferably, some brass "tabs" to the outside of the brass tubes, it would give the "epoxy" something to "lock onto", hopefully preventing them from moving. If it's possible for the tabs to be jammed snug against one or more surfaces around them, that would be even better.
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  #22  
Old 10-08-2019, 08:46 PM
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LWSS454- I really like the idea of adding silver soldered tabs that the resin can lock onto. If undercut a bit, that should give a really good mechanical lock.

So here are some better pics.
Please excuse the rough finish of everything as this is a work in progress.
I figure it’s best to get it functional before making it pretty.
Hope this gives a better description of the piece.

Here’s the overall stock.


The shoulder piece in the lower off hand position.


Here it is in the higher prone position.


Here is the internal clamping mechanism.
It is a section of CF oval tube with a slot cut out to act as a C clamp with the two sections of brass liner.


Here is a shot vertically down the internal C clamp fitting.


Here is the gap that slides past the mounting posts of the CF rod.


The stock body will get a final layer of carbon fiber once I have used the stock for a while and have all the fine adjustments to the shape worked out.
I like to use it for a while to make sure all the rough edges are smoothed off.

Last edited by Gobber; 10-08-2019 at 08:51 PM.
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  #23  
Old 10-08-2019, 10:41 PM
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I’ve run into problems with some epoxies if the temperature is too cool. My basement where I do most of my work is alway 67 degrees or less.

I found if I put the work under a heat lamp, my results in general improve greatly.

As temps get closer to 80, results are best in my limited experience.

It sounds like an obvious one, but I did have a couple jobs that were not working out well. I called the epoxy mfg. it turned out 5 degrees F made all the difference in the world.

Last edited by BadaBing11; 10-08-2019 at 10:46 PM.
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  #24  
Old 10-08-2019, 11:47 PM
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Gobber, From your last images, I got it now.
What I was talking about was to cut, make actual small tabs from flat brass material (see the red outlined - colored "Tab" in my crude image below & the side views of both tabs installed), then silver solder them onto the brass tube. If you don't have any flat brass strip material on hand, you could flatten a piece of your spare tubing, cut the primer end off of a rifle shell (an empty/fired shell of course) and beat it flat, etc. If need be, you can even put a thin layer of silver solder inside what ever you use, to strengthen it, soldering it flat/together. I would think a rifle shell, flattened might be thick and strong enough, but I've never cut the end off and flattened one before.
Since you'll have opposing forces on your brass tube (up + down), I'd solder two tabs on as shown in my crude image. Using a similar angle on installation of the tabs, they'll work together to stop the tube from moving in either direction (up or down) once embeded in the epoxy. Don't make the tabs too large or they could break the epoxy up into "thirds" (it could break into 3 pieces if the tabs are so large they keep the epoxy from forming a good & solid single chunk of material). Of course, if the tabs are too small they may not do much. From what I see that you've done, I think you'll know what size to make them.
The curved bottom cut on the single tab I drew is to have a good surface area (contact patch) once on the round tube, for strength via a longer soldered joint. I almost forgot, the slot you have would be facing to the left of the (yellow) tube in my crappy looking image.
Attached Images
File Type: jpg Tube and Tabs.jpg (47.5 KB, 24 views)

Last edited by LoneWolfSS454; 10-08-2019 at 11:49 PM.
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  #25  
Old 10-09-2019, 12:17 PM
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Quote:
Originally Posted by BadaBing11 View Post
Iíve run into problems with some epoxies if the temperature is too cool. My basement where I do most of my work is always 67 degrees or less.

I found if I put the work under a heat lamp, my results in general improve greatly.

As temps get closer to 80, results are best in my limited experience.

It sounds like an obvious one, but I did have a couple jobs that were not working out well. I called the epoxy mfg. it turned out 5 degrees F made all the difference in the world.
Truer words were never spoken!

Just this morning I was applying a layer of tooling gel to a project and my garage was about 68deg. From past experience during the summer when my garage was about 76deg, it took 2-3 days for the gel to cure. This time I put a heating lamp on the piece at about 16Ē away and the surface was tac-free within 45min! Just ordered an IR thermometer to be able to better control the temp.

Something as simple as a heat lamp and cure times go down that much.

LoneWolfSS454-
Your diagram is GTG! It ainít got to be pretty, just get the idea across. My first thought was to lay on a good drip of silver solder and then use a dremel to give it an undercut Ė thus making a sort of mushroom shape cross section for the epoxy to lock onto.

I like the idea of angled tabs that guarantee a strong mechanical lock. Iím thinking thatís the way to go on the next version.

I will also drill a pattern of holes through the brass liner to see if the added epoxy surface will give me a better grip when tightened down. If not, I will try the resin / CF chop mix that I know gives good grip.

Good Stuff!
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  #26  
Old 10-09-2019, 01:17 PM
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Thanks, I think you're on the road to success!
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