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Discussion in 'Lifesize Mammals' started by cstallard, Mar 9, 2021.
How to assembly a cut form
Stout ruff both side and put a coating of bondo on both sides forcing it into the foam cells and line it up, hold or screw in place till it kicks and cools off . If you leave the outside wax on form any bondo that squeezes out won’t stick and can be knocked off . If it is a weight barring form get a few pcs of all thread cut one end on angle , put other end in drill and run it into form making sure it goes thru both sides of cut for support.
Good advice 13 pt. I use 2 part foam rather than bondo on large lifesize forms. I take a 1" spade bit and drill several holes about an inch deep in both pieces. Pour foam, attach screws to secure until the foam sets. For added reinforcement, drill holes, usually 1" in diameter and 1 foot to 16" deep, pour in a little foam and drop a 1/2" rebar or threaded rod in the hole. When the foam sets, it's never coming apart.
Bondo and 2 part foam work, but Gorilla Glue is the best I've used. Just my two cents worth
Be aware, that if you choose the foam for bonding, unless it rises without pressure to compress the foam as it rises, there is a great chance of it to collapse and shrivel after it sets.
I've never had a foam bond fail. Drilling holes in each component gives the foam the ability to expand and bond. It will always squeeze out the edges too.
The only time I have foam collapse is:
Improper mix; Old foam that has taken on moisture, such as from humidity; improper A to B amounts.
treaded rods and foam, wrap jt with cardboard, no prob...bondo not good unless evey speck of dust removed then hard to sand or shape
The original post is how to put a cut form back together, not an altered or expanding a form. 2 half’s that match back up perfect. Just as in the back of most catalogs will show you . Take a hammer and dimple both sides , You don’t have to sand anything. You can put a elk form back together with a skim coat of bondo on both sides and after it dries hang it on the wall and put a 100lbs of salt on its head and it won’t break. As we all know foam will work great but it expands , and as it expands it pushes and will push the 2 half’s apart unless you have a release cut or as Joe said holes drilled in the form. To me doing all of that makes no sense when you have a perfect match just going back together. For smaller stuff that I cut apart to mount like a fox or squirrel just to get the form inside the hide or such I glue them back with 5min epoxy, again I’m just putting to perfect cuts back together not trying to do extra work.
Here's a visual aid for you Bondo believers.
That’s an oops shit!
Here’s another visual aid .
Bondo on metal a non pores material I will agree , on foam with nooks and crannies it will and does hold .
What 13 point said,also use a marker to make " line-up marks" to be sure it is lined up properly and start screws in form so that when you are ready you just have to drive them in.
Once that shoulder mount is assembled and stapled in the back, and cured...it ain't going anywhere...regardless of method of attachment.
George, as a once certified auto body tech, that picture proves nothing. That panel was not properly etched or cleaned and the bondo was put on too heavy and later exposed to outside forces, IE moisture and likely impact or both. Regardless of what you use, foam or bondo to re-attach cut form sections together, that seam is an area of weakness but once the skin is properly glued over the form, barring any major impact, that seam ain't moving. In fact on many of my smaller mammal mounts I remove limbs and such and carve them separate and just use the same hide paste to glue them back on as I am assembling the critter.
Keith, it is a known fact that adding a small amount of water to two part foam helps it's rise, so moisture is not the issue. In fact, Gorilla Glue is a modified foam and calls for water for it to work. Without the proper compression that forms the skin, foam can collapse and distort.
Like I said before a thousand times, there are ADHESIVES that work muck better. As Joey states, once that elk cape cures, it would stand pretty well with no form inside. I used foam AND REINFORCEMENT 2X2s after I had a Bighorn head ounce across the floor once. Didn't bother the horns but sure screwed up the nose. Then I started using foam AND a 3 foot piece of 5/8 threadstock.
Regarding moisture, this is straight from a distributors website, so yes humidity is an issue.
Everything (foam, tools, containers and ambient temperature) must be at 72F before you start using the foam.
If your workspace is colder than 72F, please keep the foam containers off the floor.
Heat closed containers in hot tap water if air temperature is lower than 65F.
Pour foam is very sensitive to humidity.
Humidity causes air bubble which result in a poor quality cured foam.
Do everything possible to avoid getting moisture into the foam.
This includes replacing the lids on containers immediately after use as well as not using pour foam on rainy and/or high humidity days.
Shake Part “B” well for 30 seconds before pouring.
Only mix small quantities of Part “A” and Part “B” at one time.
Do not vary the mix ratio with pour foam.
Do not use a drill to mix pour foam as it will result in premature curing and air bubbles.
Heat the cavity the foam is to be poured into, if it is cold to the touch.
Always wear a respirator or self –contained breathing apparatus and gloves when working with pour foam (A paper painter’s mask is not sufficient!)
Do NOT spray! This is NOT a sprayable foam.
Do NOT use with inflatables and/or canvas
Never mix less than 3 ounces of pour foam, as this quantity is difficult to achieve the correct ratio and will not generate enough heat to cure the pour foam properly.
Keith, I understand your post and reply. However the link you provided is a specialty foam unlike the majority of foams used in the taxidermy industry. If this is the foam you use I stand corrected in my previous reply. There are many variations of foam for different applications, and your link is one of them. Gorilla Glue is a foam that requires water to work and bond. The majority of foams used in the taxidermy industry are basic foams without so many DON'T DO warnings. You are correct for this particular foam, however the typical foam used for taxidermy is far less temperamental and can be enhanced with the addition of a small amount of water
A little experiment today. We currently get our foam from Old Barn Taxidermy in Iowa. This is the same as Ohio Taxidermy uses for their mannikins. I do a whole lot of altering forms and free pouring bases, and go through maybe 30 to 40 gallons of foam a year. So a newbie, I am not.
So today I was working on altering a lifesize ibex, and decided to experiment and do a few ounce pour, with a several drops of water. I hand mixed as usual, and man did it rise fast and expanded more that usual. Maybe there is something to this adding water to the foam.
I poured it out on a plastic sheet and let it rise. (This is what we do just before flipping it over on to a diorama or adding girth to a belly or butt) Once it reached maximum rise, it gave a puff and fell just like a soufflé.
After a few minutes of curing, if you can call it that, the surface did not set up and was spongy. It didn't have the "skin" it normally has. I picked up the cured foam from the plastic, and it broke apart. It lost much of the density a normal mix would have had. It actually crumbled apart.
As to how gorilla glue works, I've never used it.
Did I use too much water... I don't know.
Maybe, just maybe, if you are adding water and you need to compress to get a skin and not have it collapse, the problem is you are adding water.