Cracked hull on bj

[paDDY]

So I am very new to this fe addiction and loving it! I bought some two part foam and I am not sure if thats how the crack happened even tho it has an escape route up the sponsons. Also it is hard to tell but there is a pimple like form on my deck. Question is on the crack if I should bother doing anything since its foam behind it?

[dasboata]

The foam expanded and caused those problems,, I am thinking it was a hot day when you pored the foam was it 2 part foam or that spray can stuff ?

[tlandauer]

The foam expanded and caused those problems,, I am thinking it was a hot day when you pored the foam was it 2 part foam or that spray can stuff ?

Agreed!
Also, some 2-part foam will suck down the deck when it is exposed to heat, there was just a discussion two days ago.
I have the stuff from Kintec and I did it in my MG---the only boat done with this procedure by myself in my fleet. It has not happened to me, but I pour several times the mixed foam into the front of the boat, allowing each time to expand fully before the next pour.
Here was the discussion that took place the other day:
http://forums.offshoreelectrics.com/...074#post588074

[tlandauer]

It will be a PITA to remove it, if it is set and doesn't expand any more which I doubt it will, the simplest way to repair it is to get some medium CA to seal the front and the side if it is hair line crack, get thin CA. Just apply along the line and let cure. It you can slightly "massage" the hull, do so with great care and see to it that the CA runs into the crack line. I have repaired hulls that way and it is not a bad repair.

[paDDY]

It was the two part foam they sell on here. I first used half the bottle of each because I was not sure how much it would expand. I waited about a 45 min and used the rest. I assumed I waited long enough because my mixing cup was rock hard with the rest that I could not get to in time. What is medium CA?

[tlandauer]

Well, half bottle from each part is a lot more than i did, I did 1FL.OZ total for each pour. In your case it is fully cured between each pour, but if you did it with the amount in this heat that now we have been having, the RATE OF EXPANSION is too quick and it may very well be the culprit.
Medium CA ( Crazy glue in super market) http://www.offshoreelectrics.com/pro...?prod=dh-pt-03
There is also the thin and thiick version.
Where are you in Calif.? Go to your Local Hobby Shop such as Hobby People, they sell them. Buy the smallest bottle because this stuff has a shelf life and you don't want an opened bottle sitting too long in your tool box or work bench.

[paDDY]

Thanks Tlandauer. I actually have some of that glue in my rc tool box. I am not sure if it is due to the foam or it was a little choppy out and I flipped the boat 4 times or so. On a side note I was getting 39 mph consistently on 4s. It went down to 37.8 after the foam and started porpoising. I really want to break 40. Hoping my new batteries get me there running 4s.

[tlandauer]

Once you sealed the cracks, you are good to go.
Do you mean that you had no porpoising before the foam? Re check your COG again, although that stuff should not be that heavy. IS there any other deformation of the hull, I can't imagine it would have affected the hull, check the hull on a flat smooth surface such as counter top or glass table top, both sponsons should have mirror image of each other, especially in the rear two last steps. The stuffing tube and the prop and rudder may be in the way, do the best you you can to check.
it is known that the Miss Geico porppoises badly, for that one usually has to blue print the sponsons, especially the last two steps. There is a tutorial by this member:http://forums.offshoreelectrics.com/...nting-Tutorial
Hope this helps a bit.
good Luck

[paDDY]

Nooo! I just flipped the boat over and one of the sponsons have a indentation the size of a half dollar! It was not there before the foam. I really don't know how that would happen tho since foam expands. It did porpoise when I first got it but I adjusted the batteries and trim and it ran great. After the foam it started to porpoise again and needs to be re-tuned. Now it looks like I have a bigger issue tho.

[olwarbirds]

If you used all of both bottles it equals alot more weight than you think...its around 2lbs if I remember correctly...it should of expanded 20-30 times the amount you put in.. since you mixed alot at one time it didnt get to expand correctly and it might expand more on a really hot day...In pics it looks like you got some more going on thats not real obvious "yet" ....using superglue aka crazyglue or even the better quality hobby grade medium ca is probably not going to be a fix all...the BJ hull halves are not sealed together that strongly and I bet if you look along the side of the hull there is a stress crack forming between the two halves...I dont want to hear about your boat blowing apart in two halves...look at this closely as we have had to seperate our BJ and MG hulls and re-assemble using cf tape along the seam then we did a cf inlay through out the hull ...as TL had mentioned blueprinting this hull is a good Idea.... DJ

[paDDY]

I did put two coats of west systems epoxy on the joints that come together when I first got the boat. The stuff is killer as I use it on my fishing boat for lots of projects. It did look like the foam bothered the glass joining the hull together tho. I took a pic.

[Namba328]

I strickly never use expanding foam for 2 reasons.... 1 it tends to expand and contract and damage what its in and 2 its normally heavy. I use pool noodles. They are fuel and really oil resistant and the will fit anywhere and you can buy them at any local dollar store and they are light and add hardly any weight what so ever.

[montymike]

Right on me tooo..

[paDDY]

I leaned a lesson the hard way...

[iridebikes247]

I suggest buying the syringes from west marine, they are awesome for stuff like this.

Using a thinned epoxy or glue is fine except this is a crack in an area that can't be properly backed because of the foam. The thin syrines at west marine will allow you to inject epoxy into the crack, not just over the outside of it. I believe this will yield the best results for long term strength. You can use a tiny bit of rubbing alcohol to thin the epoxy if you need to, a small amount goes a long way. In my experience it does slightly weaken the epoxy but not horribly.