2 Part type foam in boats.

[Ian Inverarity]

I know everyone says not to use the expanding foam from pressure packs in boats due to continuing expansion, water and fuel absorbtion etc, but has anyone successfully used the two part type foams? I am designing a rigger tub and am thinking about using some of this type of foam to fill some compartments. Any thoughts?

Ian.

 

[TimD]

Ian,

Don't do it! you will regret using the stuff!

 

[topfuel443]

Ill second that..... I have some retired wood hanging on the wall because of that crap.

~ James

 

[Zimmerman]

I'll third that. Actually rigger tubs are pretty easy. I insert styrofoam blocks between the rails and hot wire them off before sheeting it out. Depending on where, this can add a lot to reinforce the structure in terms of weight gain. Cover any exposed foam with a thin coat of epoxy.

 

[Ian Inverarity]

The problem is this; Servo linkages and the water line from the rudder need to run thru these compartments. They are way too long to drill (dont have a drill that long) so I would need to cut styrofoam to fit in after all the links etc are in place, and this would mean cutting out a fair bit so that it can be inserted. My thoughts were ideally I would like the compartments to be sealed, but I wanted foam in there to prevent any water building up in there. So an easier solution would be to pour in foam after everything is in place...

Hmm. Tricky.

Ian.

 

[Mike Hughes]

It is very easy to build yourself your own long drill bit. I usually run a long stainless steal water pickup from the back of the boat to the engine tub. This requires a hole all the way through. I cut little notches on the end a scrap tube. I use this as the drill. You need to put a backing block behind the piece you are drilling so that the wood does not blow out. I have done this with stainless and brass tubing. I just use the cutoff wheel in a dremel to make the notches. Works great.

Mike

 

[MarkScott]

Ian,

I've built many Dumas wood Hot Shot (IV and Sprint series) and used the two part foam WITHOUT problems.

Thing is, take your time, mix only a little and watch how it expands. This was all done with only the top decking needing to be glued in place. I allowed the foam to settle by waiting 48 hours after the final mix / pour.. Then it was just sand to shape and cover with the decking.

Mark...

 

[Ian Inverarity]

Mark,

Have you problems with further expansion or water logging?

Ian.

 

[TimD]

Do you want pic's of what happens when the foam expands over time?

I've got some sponsons here somewhere that the foam was left before 48 hours before shaping and then being covered, and they are bowed and buckled from the stuff!

What sized holes do you need thru the foam Ian? Heat some brass tube and just push it thru!

 

[Ron Olson]

If you do need long drill bits in small diameters, Harry Higley sells them and can be gotten through Tower Hobbies.

 

[Ian Inverarity]

I have access to a good number of long series drills, but for the water line run I need 26 inches! I can pre-drill the formers for that one, but getting thru the foam and coming out in the right place will be tricky. But the real difficulty is I will have a compartment between the radio box and the engine bay that is longer than either the radio box or the engine bay. Thus I cant put a drill bit in either the engine bay or radio box that will be long enough to get thru the compartment! These holes would be for the throttle and radio needle cable runs. Now if I pre- drill the formers for the cable runs, I have to drill thru the foam once it is all assembled, drilling from both sides hoping I am going in the right direction.... :-

Hence the poured foam solution..... ???

Ah the problems with trying to do something different....

Nitrocrazed racing: Making trouble for myself.

 

[MarkScott]

Ian,

I still have two boats in my collection that are over 10 years old that never expanded afterwards. Since the foam is in the spoons and center section of a tunnel, water is not a problem. Both these boats had plenty of time sitting in direct sunlight. I'm not going to say it won't happen, it just didn't happen to me.

Here's a pic of my Sprint that was built in 90.. The two part foam was picked up at a LHS.. Can't say if what is in use today is the same..

Mark

OB Nut Racing...

 

[rhomodel]

I use 2 part foam on most of my boats. Everyone says not to as it would absorb water but I can't notice any water getting in the foam. I hthink people mix up the one part foam and the 2 part foam. The 2 part foam is even gasoline resistent. The trick is not to pour too much in it at a time. If you do so your boat will crack. Depending how much of a volume I need I do it in 3 to 15 times. In the cigar rigger I used 3 pourings for the nose and 2 for the rear. But for my crackerbox and roundnose hydro it was about 15 pours. I mix about 15 ml of each component at a time and pour it in. Depending on the expansion ratio this 30 ml will give 800 ml or 1600 ml foam. After about 15 minutes it is cured (contarry to the 1 part foam that still expands in a closed area after 2 days) and I pour the next batch in. The foam is also an excellent bonding medium by the way.

Julius

 

[Mike G]

Ian, my AC Wildthing is #5 from the mold and it has 2 part foam along the sides, it does not seem spongy or water logged at all, can't say how long it expanded though. I think once you cut it you would want to seal the cut again though.

 

[Ian Inverarity]

Julius,

I think you may be right, the two part foam is not the same as the canned foam.

Mike,

I saw some very old stuff in a plastic cup at school many years ago. If it kept expanding the cup would hae exploded, which it didn't.

Dont know what I will do yet. :-

Ian.

 

[TimD]

Agreed - the canned stuff is different to the 2 part stuff.

I was told the canned stuff is really bad for water absorbtion over time.

 

[EatMyShortsRacing]

Ian,

I have used the 2 part foam. Do it in small batches as the heat and expansion can buckle the boat if you try to do it in one pour.

EMS Racing one part vodka, one part orange juice

 

[Ian Inverarity]

Well, it was my intent to pour the foam in without the top in place, then sand it to shape and glue the top on.

Nitrocrazed racing: 1 part Southern, 1 part coke...

 

[EatMyShortsRacing]

still dont do it in one hit....

E M S R a c i n g

 

[rhomodel]

As the others say don't do it in one time, the outside will harden earlier and the not expanded foam will expand and crush your boat and give 2-part foanm a bad name.