NOT Gorilla Glue! Watch This Before Building a Foamie!! BEST Adhesive

[@BennyTheButcher2]

Late to the party here. But just finished my foamie and want to offer my advice. Any polyurethane adhesive (gorilla glue and most construction adhesives) create a mechanical bond to the two pieces being glued. You absolutely must create a rough, or uneven, surface to the pieces being adhered. When done correctly the connection will be many times stronger than the material being adhered. Try sanding the XPS foam at the connection point with a very coarse sand paper. If possible, I recommend rough sanding first and following up with a docker after (I used a roller docker with steel pins made for docking pizza dough). For adhesive I really like a couple construction adhesive designed for outdoor applications: Loctite PL Max (caulking tubes only) and Loctite Power Grab All Purpose (available by the gallon). They are fast acting, easy to work with, and clean up with soap and water.

[@thelwood]

Thank you for your response! And yes, in the trailer we roughed the foam up with a wall paper remover in some parts and 80 grit sandpaper in others. The end to end demonstration more accurately shows the foam without any film over it. The foam fusion still provided the deepest bond.

[@carrolbrooks2143]

@@thelwood Another helpful hint: Use The Vacuum Bag System, Used In Fiberglass/Carbon Fiber Lamination, You Can Also Use A Screen Printing Technique for Burning Screens. Build an oversized Frame and attach Neoprene Wetsuit Material. To Pull The vacuum Straight Down From the Upper Surface To Evenly Distribute the Pressure on the Upper Surface. I Believe they use this "Dry Mount" Technique to mount poster prints to Foamcore for picture frames!?!! 😉🙃😜

[@davidelliott5843]

Car body panel PU mastic is amazingly sticky and the resulting rubber is tough. I’ve successfully repaired kids school shoes. You won’t find a better test than that.

[@jamesmorton7881]

Latex paint, will bond EPS sheets, and is friendly with hot-wire cutting.

[@MrIgottap]

⁠@@jamesmorton7881was going to recommend latex paint as well. Roughing up the surfaces to be bonded before application will provide even better adhesion.

[@grndiesel]

Wood glue didn't cure because the foam is water tight. Wood normally draws moisture out of the glue, which allows the glue to dry. Something to consider with any kind of water based product if you're working with synthetic materials that do not "breath".

[@patrickbodine1300]

Breathe. It is what you do. Breath is what it is.

[@birdnv4547]

Just a thought - the aircraft and boat guys use a 2 part epoxy (West System) which you can get at a marine supply store or aircraft supply house (Aircraft Spruce) then they sand and put a layer of fiberglass over the joint - the result you can stand on or jump on without breaking. Sanding both surfaces of a joint is critical. I made wing ribs this way and flew it for years - about unbreakable if you need great strength. Good video and fun project - thanks for making :)

[@thelwood]

Sounds great! Great information, thanks!

[@sda141]

Yes! I use epoxy in my art projects and I was thinking the same thing

[@mr.e7022]

Doesn't the epoxy melt the XPS foam?

[@montiemorrison5637]

@@mr.e7022 No, epoxy is good for EPS and XPS, old school polyester resin will melt both.

[@rjhinnj]

I’m an aircraft builder also… I mentioned west systems epoxy in the comments for another tutorial video… also Aeropoxy would work (Aircraft Spruce).

[@LaOwlett]

It's usually not the spray paint that melts the foam, it's often the paint thinners used to make the paint thin enough to spray. If you spray the foam from far enough away, most of the thinner will evaporate as the droplets go through the air before it hits the surface. You'll have to test the safe distance for each brand and color on sample pieces. People who make costumes use XPS a lot, they have some tips and tricks that you don't hear about within the community of large project builders.

[@thelwood]

Thank you! Great information!

[@LaOwlett]

@@BLAlley The paint itself is almost never going to react with the foam, It's the propellants that rapidly evaporate. You want to spray from far enough that the propellant mostly evaporates before it lands on the project but not so far away that the paint starts to dry in the air.

[@LaOwlett]

@@BLAlley I've used it. There's a happy medium where it subtly melts and bonds to the surface. This is different for every brand and even every color of spray paint so you need to test a scrap piece. Feel free to invest in a spray gun or use a paint brush. Most people are interested in using spray paints because of their price and availability, ease of use... That's why I explained the why and how to avoid damaging an XPS project.

[@LaOwlett]

@@BLAlley It's a bad idea in your own opinion. No one is preventing you from doing it your way. Not everyone has the money to be picky. Move along.

[@LuckyTown77]

​@@LaOwlett your channel has no content. It is moving nowhere.

[@peterloichtl4512]

Good video about gluing foam. This is useful for me. Most of us are not willing to go through that much work, even if we need to know. As you know, there are many ways to skin a cat. You can glue foam with hot glues that normally melt foam by priming foam with latex paint, the paint will keep the foam from melting. Depending on the heat of the glue, you need up to 5 coats of latex on the bare foam. This works perfect when using fiberglass resin to glue foam or for fiber glassing large surfaces of foam because the wet fiberglass melts unprimed with latex foam.

[@thelwood]

@peterloichtl4512 great information!

[@Fulcrum205]

A 1/2" fillet of thickened epoxy and bamboo skewers dowels will make MUCH stronger joints than just butted glue joints. The foam kayak guys use the skewers Fillets are common in boat building (foam and wood)

[@thelwood]

Thanks! We did add a few skewers here and there. But with the relief cuts for the curves and only using 1 in foam, they were prone to blowing through the foam or ending up between the relief cuts. So we ended up just using the adhesive and then once it was wrapped with the canvas it was super strong. I will look into the fillet method.

[@brettmoritz3698]

​@@thelwoodJackman Works uses the fillet process on the Upside down boat!

[@RandomAxeOfKindness]

Doweling is easy with foam, and it makes a big difference. Even a bunch of toothpicks can really strengthen long joints.

[@mercedescherokee6853]

Experts like burt rutan have been making airplanes with foam and fiberglass construction with extreme strength, they use a form of epoxy I believe then lay fiberglass over for a high strength exterior

[@chrisdaniel1339]

If you need to make walls or counter tops or other large panels invest in a vacuum pump and vacuum bags to clamp the wood skins to the foam core to create super strong, super lightweight foam core composite panels. You can get 1/16" real wood veneers or use very thin plywood to lay up on each side of the foam, place this lay up in the plastic vacuum bag and seal the edges, install the connection port for the vacuum pump to the plastic bag, then turn the vacuum pump on and get as close to -29.92 inHg or -14.696 psi as possible. Since all the air has been removed from the bag the atmosphere is pushing from all directions clamping your lay up together with a uniform force of 14.696 pounds per square inch. If your layup panel was 96x48 and you wanted to just use concrete cinder blocks to apply a clamping force to your layup while it cured you would need a whopping 67,719 lbs of cinder blocks to equal the clamping pressure of using a vacuum bag with a full vacuum applied. One other hint, if you need to make a composite panel that will hold more weight increase the thickness of the core and keep the skin thicknesses the same, for example a 2"-3" thick foam core is going to be massively strong that if you were doing a van build you could clear span from side to side for use as a bed platform with the only support being a cleat running down each side wall and no center support. I hope this helps

[@thelwood]

Great ideas! I have a vacupress but I haven't tried using it with foam, just veneer and mdf

[@Tonisuperfly]

Excellent tips, thanks!

[@erikdossett3636]

Re: Surface prep - I use a hand held wire brush - it's fast, it's effective. But - thanks for the tests!! Great to know the Foam Fusion is good. I've been on the Foamie Trailer page forever (decades? lol) - and yet you have taught me new things :) .

[@thelwood]

Wire brush is a great idea!

[@Tonisuperfly]

Excellent idea

[@craigmonteforte1478]

I really like he concept and the overall look of your Teardrop Camper i spent 35 years as a ProfessionalWoodworker and i’ve always done similiar resting on products i’ve worked on myself i one time years ago had a Finishing issue with using incomparable Clear coats or TopCoats that actually bubbled the other finishes thankfully i discovered that in a test and not on my Final Furniture Peice ! in working with Foams i’ve discovered you need to stay away from products that use products that end in Line as the drying chemical i like using Adhesive Caulks designed for the Marine Industry and often i prefer 3 M 5200 it’s expensive as hell but has a tenacious bond with almost anything it is the usual choice Trailer companies bond the “Screwless smooth exterior Panels onto the frames with one draw back to 5200 is it’s usually Permanent a positive is it sets up under water and is available in a few colors i’ve seen it trolled onto the exterior of a WoodenBoat Hull embedded with a Fiberglass Mat and then GelCoated on top of that to make a no Soak leak free hull it looks great and really tough ed up a very old boat again it was expensive as it was purchased in 5 gallon Pails that are a few hundred dollars per pail

[@thelwood]

Thank you! And thank you for the excellent information! That adhesive sounds amazing:)

[@windmolenfarm8030]

I have done a lot of projects with foam and fiberglass using 2 part epoxy which glues closed cell foam together great and seals fiberglass cloth to foam very well with no delaminations when done properly. Epoxy can be expensive but doesn't take a lot for a project like the "foamie" trailer. I suspect the stuff you liked, the foam fusion would work well also. The epoxy makes thefiberglass very stiff and hard but needs to be painted well with a UV barrier paint to keep from degrading over the years outside. But it makes an outstandingly rigid and protected outer shell for the trailer. Great presentation!

[@raydreamer7566]

There is a term called glue starved. This term relates to two smooth surfaces being glued together with a Non-etching glue( glue does not melt or etch the surfaces to be glued ) and have been clamped together to tight and all of the glues is squeezed out of the area that was to be glued together. IF the two surfaces to be glued together are sanded to make a more pores or rougher surface allowing the glue to have more surface area to stick to the glue joint becomes MUCH stronger. Even by running a pen or dull nail scratching parallel lines inside the surface to be glued will increase the glue joint dramatically because the two pieces that are to be glued together to have MORE glue staying into the joint surface area.

[@thelwood]

Thanks for the info! On the teardrop we sanded at 150 and ran a wallpaper remover it. The side by side joint in this test represents this best since both surfaces were cut. I was impressed with how deep the bond was through the shiny surface using the foam fusion. Have a great day!

[@dogdazetravellergarrett1367]

Appreciate your time explaining the differences in brands of adhesives and their effectiveness 😎👍

[@AstroLanderRV]

The foamie scooter trailer is so dang cool! I feel very inspired seeing it.

[@thelwood]

Thank you!

[@davidphelps7763]

As a retired cabinet shop owner I have have a fair amount of experience with glues.. I see in your butt joint to flat panel you are glueing a raw edge to a flat panel with appears to be a finished surface.. Try coating the raw edge with glue and allow to dry and then reapply for finished joint.. We used a lot of melamine glue in the shop that is like a vinyl base.. I believe you can use waterborne contact cement for glueing panels together..

[@thelwood]

Thanks for the suggestion! I definitely do that with wood glue when I am doing butt joints, I will give it a try on the foam!

[@americanme9933]

If you hold the spray paint back farther it allows the ingredient that eats the foam to evaporate off before the paint hits the foam.

[@thelwood]

Good to know!

[@Fulcrum205]

Forgot to add. PL makes a foam specific polyurethane adhesive. It comes in a caulk type tube. It worked well when I insulated my garage door with rigid foam

[@thelwood]

Good to know! Thanks!

[@RHawkAdventures]

Drywall screws make good clamps use the coarse thread versions, provides some extra strength as it grabs some glue going in. some foam has plastic coat that will peal off. Kabob sticks also work good put on some glue.

[@thelwood]

Those are great tips! We did use a few kabob skewers but with only using 1 in foam and having kerf/relief cuts we put one through the kerf so it was visible. After that we decided it was best to just use the tape. By the time we wrapped it all in canvas it was plenty strong. Thanks for you tips!

[@thetinysideoftiny7625]

Fantastic video Lucy. Super valuable for anyone building a foamie!!

[@thelwood]

Thanks, Tom!

[@WoodcliffCommunity]

Thank you so much! I appreciate these types of videos because it saves so much time for us DIY types in testing ourselves. Much appreciated!!

[@thelwood]

Thank you!

[@digitalmunky]

Build a clamp with foam and dowels using EVA for the faces to prevent slipping and marring.

[@tarawakefield4383]

That foam fusion seems amazing!

[@thelwood]

It would have been a nightmare if we had used the original plan of gorilla glue!

[@SethDowns]

Didn't you know that one of your biggest fans is an amazing material scientist and glue expert?! If you need a "Home Depot" solution, I would expect a product like Loctite PL300 to work well. Any of the urethane based adhesives will foam--that's why I avoid them for wood projects too!

[@thelwood]

Awesome! Thanks Seth!

[@thelwood]

I will consult you for all of my glue needs/ questions!

[@SquareRootOfMinus1]

Hey Seth - great tip. I did get some PL Foamboard adhesive. Planning to bond foam to aluminum. Now, will it work with EPS - the white “lumpy” foamboard - made with beads (as opposed to the smooth XPS.) ? Thanks much.

[@jongonegone1262]

loctite marine adheisive sealant, sold in caulk size tubes, cost about $15.00 per tube. really good stuff, works with many foams.

[@jdinthekeys]

Thank you for making this video! I appreciate your commentary and effort completing your testing.

[@thelwood]

You're welcome and thank you!

[@kansaIainen]

Dissolve the plastic in acetylene until you get a thick syrupy glob. Put it in the seam to be glued and you get a really strong joint.

[@FuhrChris]

Elmer's makes the cheaper form of the Gorilla Glue. The secret is to mist water over the glue before you attach the second piece. If you try for a spiral of glue on a large sheet of foam and the glue line crosses itself (making a closed circle) you seal in the misted water which will still be there when you pop the two sheets apart. (Glue spreaders are hard to work with because you want a very thin layer.)

[@thelwood]

Great information! Thanks!

[@slightlybothered2011]

Glitter grabber primer paint Works great as an adhesive for pink foam

[@thelwood]

Interesting! I will have to try it out, thanks!

[@mymai5859]

Glidden Gripper Primer paint

[@MiniLuv-1984]

That was crude but adequate testing - which is all that is required. Thanks, Foam fusion is the glue for me! One thing I want to experiment with is lining the EPS foam with aluminium sheet (1mm or thinner). First I need to get some foam fusion and see how well that bonds the aluminium....

[@epicsurvivors1399]

They sell those

[@MiniLuv-1984]

@@epicsurvivors1399 The ones I've seen are with open cell foam - "foamboard"

[@usedcarsokinawa]

Great video. I’m getting ready to make a foamy camper and I need to glue 3mm ply on foam before fiberglassing. Gorilla clear as it’s available here locally in Japan. Thanks

[@dougupah8778]

Regular gorilla glue works great on foam, dont add water/spray water to the foam, thats for wood application, the wood will absorb the moisture out of the GG before it can bind with the other piece of wood. Gorilla glue will expand much more when you add water. Try it without the water, completely different results. I have no affiliation with GG but have used it many times with foam with good results. Your video was very informative, thanks for the Foam Fusion mention, had never heard of it before but will definitely look for it.

[@thelwood]

Thank you for the information! I will give it a try without water. But I definitely will be sticking with foam fusion as I can be messy... so the crystal clear color when it dries is awesome! I am happy you have been successful with GG. I definitely recommend you check out the foam fusion, the bond is amazing and it is so easy to clean up!

[@denisemartel3352]

Outside grass carpet glue is great

[@obsidianjane4413]

I liked this test video. Very good work. Considering you are going to be covering the foam in a composite fabric that provides the strength, you really only need something that will hold the pieces together and is easy/similar to the foam to sand.

[@TheBeardedDog]

Great comparison of glues. I wish I would have known foam fusion when I built my trailer. I got pretty good with the Gorilla glue though. One adhesive that is a pain to work with, but works incredibly well is Great Stuff expanding foam. I used it in places that were impossible to clamp except by holding it. It sets up very quickly, and works as well or better than the Gorilla glue as an adhesive.

[@thelwood]

That's very interesting! I have never heard of it. I will have to check it out! Thank you!

[@НиколайАлексеевич-в6к]

Церезит Хейнкель, особые условия в Северной Америке. (Ceresit СТ 84 Express PLUS) я на пенсии ничего не продаю ничего не покупаю👍

[@astrobouncer487]

@@thelwood I have worked extensively with foam for years building things out of them, using polyethylene, ldpe, styrofoam, xpanded (xps) foam etc. One thing to know about great stuff is it will indeed keep expanding, sometimes for years. You can test this yourself by painting and sealing a small 1 to 5 inch glob of it after a week or more of it drying. Cracks will appear in the paint as it bulges outward from the expanding pressure. I even tried waiting 6 months to paint things made from expanded foam, and they still expanded.

[@thelwood]

@@astrobouncer487 thank you for the information!

[@jeffheeg1019]

Have you tried ratchet straps for clamping? Really excellent securing curved forms

[@thelwood]

Ratchet straps are great! I used them on my wooden teardrop! The reason I didn't in this one is because the sides were already cnc cut before I got involved and the roof had to go between the sides instead of on the top (which is how I would have done it) and then ratchet straps would have made life much easier! Thanks for the tip!

[@dagan07]

Very useful demo, Thanks!

[@thelwood]

Thanks!

[@shaunhall960]

Thanks a bunch Lucy! I will try using this in my build.

[@thelwood]

You're welcome! Enjoy your build!

[@sparksmcgee6641]

Also hot glue guns are probably stronger than everything except the foam glue and maybe even that since it will work over the plastic coating around the exposyareas.

[@katiekumcgil]

just a tip for people youll need to give the xps foam a sand before glueing ,and ive guys have great results from D3 wood glue and sanding then coating the xps foam with cotton canvas and d3 wood glue and roll it in with tiny roller then they used quite a thick almost tanking paint ontop for a rock hard outer finish

[@ex-engineer6657]

Thanks! Practical, not too technical (like Project Farm) and friendly. First time viewer, now subbed.

[@thelwood]

Thank you!

[@kevinnguyen5588]

I'd go for marine epoxy. It literally bonds to everything.

[@Pablo453]

Thank you for making this video. Very practical and helpful.

[@thelwood]

You're welcome, thanks for watching!

[@theaussienurseflipper.8113]

With the gorilla glue original, you only use a little bit you get a credit card and scrape it so you there's a thin layer. I used to buy this clear glue from one of those cheap shops in Australia. It clear, bit had not of smell to it and was warm on the skin, took a few hours to dry but it would never break where the glue was. They stop selling it, I was so annoyed.

[@thelwood]

That is a bummer! Thanks for the tip on gorilla glue!

[@brendenellasfunadventures4186]

I bet it’s super lite on sturdy with the thin wood for stiffness

[@Terry_1111]

Nice experiment design and excellent review! I enjoy your channel very much! Thanks for sharing all that you do!

[@thelwood]

Thank you so much!

[@solarguy6043]

I have built a foam and fiberglass kayak and found that epoxy produces a bond that is stronger than the foam. And if you mix up some epoxy and fine sawdust or wood flour to make fillets, the strength more than doubles.

[@thelwood]

Great information! Thanks!

[@racrx7]

I’ve always used the regular gorilla glue with great results. Yeah it’s a pain to work with and lots of clean up trimming involved. I also have used different wood working techniques for gluing and joining the foam boards, such as finger joints, lap joints, mortise and tenon, scarfing etc, with strong results. All this being said, I will definitely try the “Foam Fusion” glue!! Thanks for the video 👍🏻

[@thelwood]

Thanks! Yes, gorilla is so messy! And definitely woodworking joinery to increase surface area is definitely a great idea!

[@OutnBacker]

With any foam construction, the foam itself will always be the weak point. Having built a few trimaran pontoons with foam core under eglass skins, the only issues I ever had at the beginning was foam tear-away. Ben Hoza's comment is spot on: Rough the surface to increase glued area. I did it differently by slotting the mating surfaces (table saw cut) and inserting wood splines into the slots along the entitre run. Ordinary yardsticks work great. Basically, it is the same thing as using splines to join two plate or corners in woodworking. For a foam trailer, the spline is perfect for adding strength against high wind resistance at the corners.

[@thelwood]

Great advice! Thank you!

[@epicsurvivors1399]

That submarine worked good for awhile with it's foam core

[@Mr.Alwaysright-z8q]

Expanding foam works better than anything you tested.

[@dannyfubar3099]

Excellent post, thank you for sharing.

[@robertwilliams8974]

Great demo. Thanks Lucy!

[@williamcampfeild3]

I ABSOLUTELY LOVE YOUR VIDEOS, I'm a 48 year old disabled man and I'm going to be homeless with my dog in 4 months, I only have SSI check to live on and I want to build a self contained foamie trailer that I can pull behind my scooter at 45 mph. Any kind of help would be GREATLY APPRECIATED, I have no clue as to what to do and I have a small budget.

[@thelwood]

Finding a base trailer that will work well be the hardest part. This one was welded it out aluminum. I have seen trailers made with bicycle tires too. Once you have the base trailer, then building with foam isn't too hard. I would look for the 1.5" or 2" foam to make it more ridged. You definitely want the xps stuff (pink) not the Styrofoam style (white) stuff. Good luck!

[@williamcampfeild3]

@@thelwood ty for the help 🙏 keep me in your prayers 🙏

[@___Noah]

I learned from a completely different channel that the spraypaint won't eat the foam if you stand back a little farther. The propellant is the chemical that reacts with the foam, and it is mostly gone if you get a few more feet away.

[@KF-bj3ce]

Very informative. Have fabricated foam air ducts successfully but always needed to handle with care. Thanks

[@AaronHendu]

Have you thought of adding a biscuit joiner to the mix? I think it would work AMAZING...I am in the midst of building my own foam bicycle camper and I think I might actually start the foam over, since I'm not very far in, and incorporate some wooden biscuits into the joints. That combined with foam fusion would be a winner combo, IMO. I'll be ordering the foam fusion...I already started with wood glue, but like I said, I'm not very far into it, so I think it's best just do it again.

[@thelwood]

Biscuits are a great idea! They typical help with lining things up more than strength in wood, but in the foam they would probably add significant strength! I have a festool domino joiner. They are longer than Biscuits and next time I would throw some of those in too!

[@garethbaus5471]

You could try inserting short lengths of steel wire as pins, it would create a similar mechanical joint without having to cut slots for biscuits or dominos.

[@DanSwanson2070]

I use PL Max construction adhesive. Perfect for XPS foam like Foamular

[@Lollygagger-k4p]

Epoxy is the way to go. All corner joins should be splined with rough cedar lathe, which requires a larger groove, thus allowing more epoxy into the groove, around the wood, and increasing the gluied surface area. Any interior cabinet or shelving structure ahould be likewise constructed and splined to the interior walls for added rigdity. Reinforce all interior corners with fiberglass. Best to just glass the entire interior, which makes the whole structure a one-piece build. Cover the whole exterior in fiberglass with at least double reinforcement at all corners - preferrably well radiused. Trailer and piggy back campers endure gale forces and vibrations each time they are on the road - for hours at a time, and days on end.

[@richharris9036]

Might I suggest using great stuff spray foam. It worked fantastic on my foam boat.

[@Paul.Douglas]

Purpose of the video aside, I LOVE your shop!

[@mattharvey8712]

Bravo ......yep polyurethane.......sika adhesive.........lowes in cement section .........flexible and paintable ........cheers

[@gorgeousdzastr]

I'm curious if the "shiny" side where the adhesive is applied was "scuffed" lightly just to sake off the sheen. Just as you would do cleaving two pieces of "pvc" to join. Love the videos.

[@thelwood]

That is a great thought! We did sand off the shiny surface and score the foam on the trailer. It would be interesting to see if there would be any difference in the test. The edge to edge joint was without the shiny surface so that is probably the most accurate to reflect that scenario. And foam fusion made a really deep bond on that one. Thanks for watching and for your input! I appreciate it!

[@gorgeousdzastr]

@@thelwood Quite welcome... great minds think alike ya know lol

[@johnsavage7507]

As someone who builds modles with this foam I can say most definitely. A fine grit sand paper works well.

[@Charlemagne1367]

Fine grit is 100 and 120, correct ?

[@SolarMillUSA]

@@Charlemagne1367150-220 is perfect

[@josephdupont]

Also, you use wooden skewers that you use for shishka. Bobs I used to stick that in through the phone to give it reinforcement

[@smile768]

Great science! Imagine if they taught this in school? People would make all kinds of stuff. Good demonstration between cohesive and adhesive failure. (You want cohesive failure, not the glue failure)

[@thelwood]

Thank you!

[@gregoriancatmonk6904]

Has anyone tried spray foam instead of glue and then sanding down until smooth? What about using woodworking joinery?

[@garagemonkeysan]

Great video. Just the info I was looking for! Mahalo for sharing! : )

[@MIDNIGHTSUNALASKA]

Thank You So Much.!!! I appreciate your through work.

[@thelwood]

Thank you!!

[@ThePlthompson]

VERY helpful test you did, thank you!!!

[@thelwood]

Thanks!

[@TreDeuce-qw3kv]

The substrate/foam is the weak point. No connective adhesive material will overcome the inherent material weakness of the foam. As suggested by others, here, a fillet at the joint in combination with a structural overlay(fiberglass/carbon fiber) will provide the strength required for shear, deflection, and connectivity.

[@abundantYOUniverse]

Really good thanks. I build full size foam airplanes.

[@thelwood]

That's awesome!

[@Digitalmanne]

I like a spiked roller to texture the surface. It helps the glue penetrate the foam.

[@thelwood]

Great idea! On the teardrop we did a combo of sand paper and a wall paper remove to scuff up the surface

[@peterdubyoski4622]

On our rockets we use super glue with activation spray. Fins are reinforced with glue fillets.

[@jerryg957]

Gorilla Heave Duty Construction Adhesive worked great for me.

[@thelwood]

Good to know! Thanks!

[@danpease8395]

It's like opening Christmas presents

[@crawford323]

Thank you for your efforts with all your testing.

[@webyankee6558]

No matter what you do with glue the foam is not going to be strong enough. What you need is to attach a fiber glass matt to the foam to give it a lot of support and strength.

[@Wingnut_Stickman]

Use urethane foam, polyester resin won't eat through it. That is the foam that fibreglass composite makers use.

[@retiredtom1654]

Nice, complete, and clear to understand your instructions... video

[@thelwood]

Thanks!

[@KlingbergWingMkII]

The Dow foam has a coating on the factory surfaces that must be sanded off in order to get a good bond. I use it in my aircraft designs with epoxy.

[@thelwood]

We did sand the trailer, the edge to edge joint best represents the bond without any film. I was impressed with how deep the foam fusion bonded even through the film. Epoxy is great! Just wanted a one step, non fumey option. I bet your aircrafts are really cool!

[@capitalggeek]

For theatrical props, I've had good luck using Super77 adhesive. I also use bamboo skewers to help keep parts aligned. You can also use coarse drywall screws to hold it while the glue cures. Hand-screw only, obviously

[@joshua43214]

Super77 is Gods gift to adhesives. Love the stuff, hate the price...

[@sunseeker8457]

Wouldn't cutting small lines (scoring) the joints where the glue would go stick better has the glues would go inside the form some??

[@scottwilliamherman9384]

I'm intrigued by how well the foam fusion appears to have glued the plywood to the foam. I wonder how well it would work to bond canvas to the foam? Did you by any chance try out the foam fusion as the "base layer" for the poor man's fiberglass (in place of titebond)? If so, how did it work?

[@thelwood]

I have not tried it. I think it would work extremely well. So far it seems to work well with all porous surfaces

[@scottwilliamherman9384]

@@thelwood Thanks for getting back to me so quickly. I think I'll give it a try on some test pieces like you did with the other glues, to see how well it bonds with canvas. I also want to see how it bonds with the fabric they use as a headliner in camper shells for truck beds, as that's what I want to line the interior of the cabin with (so I can stick Velcro anywhere). Another question, since you've built both a plywood and a foamie teardrop, do you prefer one method over the other?

[@jamesmorton7881]

Latex paint works like a charm. can be hotwire cut.

[@Monstamonkey]

Tape is enough for foam. But if you want to clamp or use straps you can put "sacrifice" pieces between the foam and clamps/straps. Or even leave excess on the edges under clamps/straps to be sanded or shaved off later with a surefrom file. The latter is what I do when gluing up blanks for surfboards.

[@thelwood]

Great advice!

[@normprice4210]

Would it be possible to drill and add dowels across the joints Possibly gluing the dowels in place

[@thelwood]

Yes it is! We did put a few BBQ skewers through a few parts. But since we cut kerf marks every inch to bend the foam roof it was difficult to get into the foam and not blow out where the kerf was. Definitely dowels will make it stronger! If I were making another foamie I would use 1.5 or 2 in foam. That would make it much easier to add dowels or dominos :)

[@CMAenergy]

I've heard to use just expanding foam insulation Supposed to work wonders

[@MHLivestreams]

it's basically bubbly super glue. Same stuff.

[@Chemist1076]

Great experiment

[@thelwood]

Thank you!

[@psdaengr911]

For joins that don't require sealing and don't permit clamping but need structural strength quickly, spray cyanoacrylate might work as well as it does with wood end grain.

[@obsidianjane4413]

Superglue dries very hard which makes sanding and shaping the foam afterwards difficult. You wind up with ridges and dimples where you try to sand the seam but take more of the surrounding material instead.

[@LaineyBug2020]

Use dovetail joints and cover all the foan in drylok. Prop makers use these techniques all the time.

[@thelwood]

Great idea!

[@amandahugankiss4110]

I have seen the addition of finger joints to increase glue surface.

[@thelwood]

Finger joints definitely increase strength!

[@detroitdan8487]

I had very good adhesion on face-to-face gluing with latex paint. separation quite often broke at the foam. Found that out gluing 1 inch foam pads for a TV stand.

[@thelwood]

Interesting! Thanks for sharing!

[@davidelliott5843]

Cover the outside and inside with a non stretchy fabric and resin. Denim shirt fabric would be cool. Blue face outside chequer face inside. That would be insanely strong.

[@lenturtle7954]

You will get better results if you rough sand the smooth foam first .

[@Seafariireland]

Excellent lesson!

[@stevecarlisle3323]

The best product to use for this project would be, Regular SOPRA-ISO is a closed-cell polyisocyanurate foam insulation board laminated with a glass-fibre-reinforced organic facer.

[@josephdupont]

Use nylon screen and use glue to hold it on or primer

[@patrickday4206]

I've used spray foam to bond foam together worked great messy though

[@thelwood]

It is the messy factor that kept me from trying it!

[@jeromesurffoil7033]

Just the info I needed! Thanks for the detailed review!

[@poepflater]

Gorilla glue expands, the fancier version of it expands more... the ordincary one probably calls for 2kg clamping force and the fancy stuff for 4

[@josephcardelle5844]

I’ve had very good luck with gorilla superglue gel

[@susanvaughn741]

The foam actually has a plastic sheet coating that can be pealed off. But I would rasp the section or wire brush the area to be glued to get a true bond into the foam. Then try pvc pipe glue or something that is not too hot.

[@thelwood]

Great information! Yes, we sanded off the plastic for the actual teardrop. And the side by side joint in this test did not have any of the coating. I was impressed that the foam fusion bondef deep into the foam even with the coating on it.