Slim THTLP

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JensToft91
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Re: Slim THTLP

#16 Post by JensToft91 »

I'll be buying the other PU glue I used before. This one smells really bad. I'm not really comfortable about it.
I can't but PL Premium in Denmark. The one I used before is SikaBond 545, and was recommended in a forum as an alternative to PL - glue. It nearly doesn't smell.

ecut1
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Re: Slim THTLP

#17 Post by ecut1 »

The foaming glue looks like "gorilla glue" I used one time to glue some old barn wood to a metal frame. The stuff is amazing! I'm not sure it would seal very well though. I'd probably scrape all that dry foam off and silicone the joints up.

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Seth
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Re: Slim THTLP

#18 Post by Seth »

I agree, the glue you're using now, Jens, does look like it cures the same as Gorilla Glue brand PU adhesive. Not sure if that's a brand you're familiar with or not. No matter.

If you're able to get it, from it's description, SikaBond Construction Adhesive is more like the PL Premium mentioned in the plans than the SikaBond 545 is.

I'm pretty sure the thick PU construction adhesive is recommended for it's gap filling abilities and properties. It'll fill gaps and cures into a very durable barrier, sealing the gap and preventing potential air leaks. Standard PU glue is a great adhesive, but fills gaps with a not-so-durable foam.

If your cuts are all perfectly straight, all panels are 100% completely uniform in their width, and there's absolutely no gaps to fill... you'll be fine with most any wood glue. But, when it's time for the last side to go on, if you have ANY doubt that it will seal to every panel and create a 100% leak free bond, look for something thick and goopy that will fill voids and cure into a durable state.

Leaks will seriously hinder a horns performance. Even small ones. (small leaks or small horns :mrgreen: )
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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Bryan Cox
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Re: Slim THTLP

#19 Post by Bryan Cox »

This is obviously anecdotal, but I built my first Otop 12 with Gorilla glue (PU foaming glue) and have had no issues several years later. I scraped off the excess foam with a chisel and sealed the joints on both sides with silicone caulk.

I'm not saying the PU glue is as strong as PL Premium. However, I am saying that it hasn't failed me yet.
Otop 12 x 4 (Delta Pro 12-450a) 2x melded, 2x straight
Titan 39 x 4 (3012LF) 20" wide

JensToft91
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Re: Slim THTLP

#20 Post by JensToft91 »

Thank you for the answers. I will look for your suggestion, Seth.
The annoying thing is, that they have many different, but similar construction glues here in Denmark. All from Sikabond.
I sent them a mail, and asked them which one compares :-)

I think it's Sikabond - 118 Extreme grap, because it can be used outdoors.

JensToft91
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Re: Slim THTLP

#21 Post by JensToft91 »

Hi again

This was recommended from Sika. Sikaflex 111 - Stick and seal
https://www.youtube.com/watch?v=hguPauq6O50

Does this look right?

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Seth
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Re: Slim THTLP

#22 Post by Seth »

That was a pleasantly quick response from them. However, none of the ones shown at the end of that video appear to be Polyurethane.

Tell them you're looking for a Polyurethane Construction Adhesive. If you can't find it, don't worry about it. Just make sure everything is sealed up air tight.

I sure that driver comes in early!
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

JensToft91
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Re: Slim THTLP

#23 Post by JensToft91 »

I'll ask. The sikabond 545 is looking good though. But I can't apply a bead nearly as thick as the PL Premium videos.

Seth - have you seen my post on DaveMacKay's build thead? I'm sure you'll love the link i added.

JensToft91
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Re: Slim THTLP

#24 Post by JensToft91 »

This is the only PU glue they have in Denmark because of environmental regulations.

Sikaflex 11 FC+

https://youtu.be/wQ7SkTO8mzw

Do you think this will be better than the Sikabond 545?

JensToft91
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Re: Slim THTLP

#25 Post by JensToft91 »

I'll keep the Bond 545. It's expanding, and leaves a hard rubber-like surface with small bubbles inside. I'm 100% certain, that this stuff is airtight, and will fill small gaps.
Thanks for the suggestions anyway.

JensToft91
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Re: Slim THTLP

#26 Post by JensToft91 »

The curved back-panel is starting to fuck with me now, as illustraded in the attachment.

I think the solution will be to fasten a panel on the outside of the box, and remove it when the whole thing is done. I guess this is the perfect use of the little triangular spot that's not used in this horn. I will be able to remove the screw inside the mouth, and the other screw in this triangle on the outside.
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JensToft91
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Re: Slim THTLP

#27 Post by JensToft91 »

Well. It worked! There's still some bending at the MDF i put on top to measure it - but i has helped tremendously. It will be quite annoying to work with though.
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JensToft91
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Re: Slim THTLP

#28 Post by JensToft91 »

I'll have to eat my words. It actually ended up helping me. It creats a fine stand, so i can screw the panels from underneath.

I've cheated a bit, and attached panel 7 before 6. I couldn't see any reason i should be able to do this.
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JensToft91
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Re: Slim THTLP

#29 Post by JensToft91 »

That's it for tonight.

I'm really happy with the centerlines i drew for the braces. I measured the brace, and marked where it's supposed to fit. I then used the brace to unwarp the panel.
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jimbo7
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Re: Slim THTLP

#30 Post by jimbo7 »

JensToft91 wrote: Wed Jan 19, 2022 3:44 pm That's it for tonight.

I'm really happy with the centerlines i drew for the braces. I measured the brace, and marked where it's supposed to fit. I then used the brace to unwarp the panel.
On my first build I made the mistake of cutting my braces to the plan's dimensions then forcing them in like a wedge. Caused the mouth to bulge out. Nobody noticed it, but lesson learned.
BFM builds:
XF212
T24 BP102 24"
2x SLA's 6-5" mids, 9- gt-302's
2x AT 14" MCM 55-2421
TrT 5" MCM 55-2421
AT 18" JBL GTO804
2x OT12 flat array
2x SLA Pro 2-Alpha 6's 2-Goldwoods
2x T39 24" 3012lf
Simplex 10 BP102

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