CS17 #339 Multiple questions and hopefully pictures

[acreew]

Hello everyone,

So far boat has seemed to come together pretty easy.....maybe a little too easy...

Questions:

1) I let the epoxy cure fully before removing wires.....epoxy is 5:1 ratio....all but approximately 8 wires were removed with soldering gun and meditation. The 8 remaining wires are through the front bulkhead/hull and refuse to budge.....I nipped them off at the surface. Can I leave these wires in? Please say yes.

 

2) I am concerned about 'twist' as I did not level, plumb bob, or anything else I probably was supposed to do when putting in the front bulkhead/temporary support. How do I test for this and is it correctable at this point? Are you able to tell anything from the attached pictures?

 

3) The epoxy over approximately 12-15 inches of the centerline seam in the bow apparently kicked off/overreacted....generally behaved badly and resulted in a bubbling up with apparent porous consistency. Do I need to remove this section and if so....how? Picture of delinquent epoxy below.

 

Thank you very much for any suggestions.

Will

[hokeyhydro]

Wow. Looks like the epoxy bow fillet cooked off. I'll let one of our experts advise on removal or whatever there since digging it out will be a PITA. If you used copper wires you can leave the leftover bits in, many folks do that rather than pull them. For the few stubborn ones that refused to let go on one of my builds I used a 3/32" punch and binged the wire down a tad so could sand without ripping up the sandpaper on the wires. If you used steel wires maybe you could punch them out. A few of my wires did that - tap down one end and surprise, the wire vacated the hole out the other side. Steel will rust, but after being buried in epoxy I don't think they will spoil the finish a rust stain down the road.

Twist is checked by "winding." I make marks with tape on the sheer equidistant from the bow/stern. Find center point on bow/stern and use a string line like a compass sweep to make marks on the tape which I place a few feet in from bow/stern. Then place two sticks across the boat at the marks - sticks should be straight, of course, and a few feet wider than the boat. Now you crouch behind the boat, maybe ten feet back, line your eyeballs up with boat centerline, and sight the sticks. If they are level with each other you're good to go. If not = EEK!

I think it was Spindrift thread recently where Graham the Designer checked in with advice on "fixing" a filleted hull that had a twist.

[hokeyhydro]

found it . http://messing-about.com/forums/topic/8581-catspaw-8-a-question-help-needed/

[Howard]

Winding sticks will reveal the twist, if any. With nothing to go on but the pictures, it looks pretty good as is.

 

As for the cooked epoxy, since the bow section is stressed to begin with, and will be stressed and tested even more when you use it, I'd want that out of there. The question would be how to do it. Grinding it out with a small angle head grinder is certainly one option, but not a good one (these grinders are a brute force method of removing material, but run the risk of doing a lot of damage in a hurry, not to mention the mess they make.......its possible that some CERCLA sites have been created by these). Since even cured epoxy will soften with enough heat, I might try to use an infrared heat lamp at point blank range (inside a foot) to soften it enough to dig it out with a putty knife. Same process as heating the wire, only bigger scale.

 

Not sure where you got your 5:1 epoxy, but for building a boat, I'd give up on that in favor of 2:1 mix. Experiment with various speed hardeners, but you will want at least one that offers a slow cure option. You need the really slow cure version to allow you enough time to mix it and disperse it, not to mention the ability to create a large fillet like this without it going off on you like this one did. The rate at which epoxy will cure is a function of the hardener used and ambient temperature it is used in. The curing process also generates it's own heat, so if you were to use a fast cure hardener on a hot day, it might go off in the pot before you can finish mixing it. A slow cure on a cold day might never harden. A big fillet like that will trap heat as it starts to cure and will act just like a large pot of epoxy. Once it starts to get hot, there is no stopping it. Given a choice on doing a large fillet like that one, I go as slow as I can. Not much bad happens when you go slow.

[acreew]

Thank you for the suggestions. The wires are steel. The epoxy is from RAKA.....I used the 5:1 thinking that it would be stronger/stiffer. It worked great on all other areas of the boat....guess it was to quantity of the epoxy in that one place that caused it to cook. I will attempt to determine twist and hope for the best.

 

Thanks again,

Will

[PAR]

5:1 epoxies need to be especially accurate with the mix ratios, as you've found. 2:1's not as critical. A little bit out with the 5:1 and you're off a significant percentage. Also massing epoxy can cause a wild exothermic reaction, that will cause outgassing (bubbles). If the epoxy is solid, then just grind the surface smooth and apply more goo and tape. If the epoxy is soft (hasn't fully cured), it has to come out.

 

As to the wires, there's a lot of ways to remove them. A good way is to expose the ends of the wire and attach a car or garden tractor battery to each end. This "dead short" will quickly cause the wire to get hot and you can pull it right out. I dislike the idea of steel remaining in the goo, but technically it shouldn't hurt anything, if fully encapsulated with goo and tape.

 

Lastly, about the "trueness" of the hull - you'll get the opportunity to square things up as the seat faces, tops and partitions go it. Make the upright building cradle level, so you can check with a level at key locations, like across the seats, the thwart, the transom corners, etc. The plans have a bow and transom height measurement, so getting it level is fairly easy. As the various structural elements go in, sometimes you might have to force the hull into a slight twist, to insure it remains square.

[acreew]

I will say that the 5:1 resin is much thicker making the use of a pump impossible. The measuring was difficult....at least the way I did it....as I first poured a pre measured amount into a cup X 5 and then 1pour of hardner. Getting the thick goo out of the cup each time was difficult and it made exact measurement very difficult. I would like to hear people's opinion about any benefit as far as strength/rigidity goes. This Resin/Hardner was advertised as being particularly strong and excellent for structural bonds etc., etc. Anyway, I am planning to go over current fillets with 2:1, as it goes on and cures much smoother in my experience.

 

Thanks for advice on cooked epoxy....it is definitely cured and was almost immediately after it started to go off. Will grind it down and cover.......cant imagine being able to get it out of the bow without destroying the boat.

 

Unless there is a clear reason to remove the wires, i plan to encapsulate them and forget it.

 

Thanks again,

 

Will

[Hirilonde]

I will say that the 5:1 resin is much thicker making the use of a pump impossible.

Don't know what brand you are using, but West System works fine with pumps.

[PAR]

I've used most of the brands available and haven't found a viscosity issue with 5:1 formulations, which suggests an environmental issue, not a particular brand, mix ratio or formulation problem. You might try warming the resin a little, say to 80 degrees.

[Charlie Jones]

I built a 35 foot trimaran using WEST Sys (5-1 ratio) and two different kinds of pumps- no problems at all. I've also measured it using a STRAIGHT sided container and a stick.Since then I've used MAS, RAKA and the epoxy from Graham, all using pumps. All 2-1 and sometime again, measured with a stick.Had a friend who had a serious problem with SYS 3, but we think it was bad epoxy- of course, that would NEVER be admitted, but it simply would not cure-even measured using a scale.The ONLY reason I stopped using WEST is cost. Others, particularly the 2-1 from B and B, are just so much less costly that it's a no brainer, UNLESS a customer specified WEST. Then I'd use it of course.A note- be very careful of heat - exothermic reactions- I have a friend who lost a boat that way- it reacted in a contaner, caught a roll of paper towels on fire and burned the boat to the trailer- total loss

[Charlie Jones]

I typed the above with paragraphs, and it simply refused to post- Strange things. Had to go top "More reply options" and hit "add reply". Same thing with this reply . What's going on?