Wharram Builders and Friends

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Bonjour,
Plywood is ordered and will arrive soon. Epoxy, I'm still testing. However, I have two questions.
-When you coat plywood with epoxy, is it acceptable to put the second coat before the first is totally cured, without sanding, or is it better to wait that the first coat is totally dry, sand and put the second coat?
-I tried an epoxy yesterday. The seller made the mixture on a scale. I took two pieces of wood, dry. I put some epoxy mixture on both pieces, tied them and made a garrot, that was very strongly tied. The guy told me to wait half an hour before to untied, and I wait one hour. Took of the strings, and with no effort at all separate the two pieces of wood, with the epoxy still «wet». Oh yes! temperature, well it's summer and well over 30C, or 86F. Before to buy, the question is are all epoxy suiable for wood, and why the mixture of the guy didn't cure?
-Last question for today, so that makes three: to coat, it is normal to mix only epoxy and hardener, without anything else, right?
Thanks for your answers,

Le CP va arriver, et je teste l'époxy. J'ai trois questions.
-Pour l'enduit, est-ce possible de passer la seconde couche avant que la permière soit totalement sèche, et donc sans ponçage, ou est-il préférable d'attendre que la première soit sèche et de poncer avant la seconde couche?
-J'ai essayé hier une résine époxy. Le vendeur a mélangé lui même les deux composants avec une balance, et j' ai collé deux morceaux de bois sec. Je les ai attachés et fait un garrot, serré, qui joignait parfaitement les deux pièces. Le vendeur m'a dit d'attendre 1/2 heure, j'ai attendu une heure. Les deux morceaux se sont séparés sans efforts, et la résine n'avait pas polymérisé. Température extérieure: 30 degrés, au moins. Toutes les époxy sont utilisables sur le bois? Pourquoi celle-ci n'a pas polymérisé?
-Enfin, pour l'enduit du CP, on n'utilise que la résine et le durcisseur, aucun autre ingrédient, n' est-ce pas?
Merci de vos réponses,
Éric

Views: 183

Comment by Ian Bamsey on June 30, 2015 at 2:54am

I am not sufficiently experienced to answer your questions, and others here will provide well grounded responses. However, I found this http://www.westsystem.com/ss/assets/HowTo-Publications/GougeonBook%... a very useful resource.

Ian

Comment by Penn D on June 30, 2015 at 5:10am
G'day Eric...
Your "seller" sounds like they know very lityle about epoxy...
To glue you need to add a filler.. You ate better to have a gap, say a matchstick wide than have it clamped tight... you never clamp so tight that there is no epoxy glue left..
Two most common reasons for epoxy not setting is ... bad ratio... not mixed well enough... i have a simple rule with mixing... i mix unyil i think itd done... then mix it that much again... only then do you add your filler. ..
Your other question... for me the less i have to samd the better... its fine to wet cover say a couple of hours betwern coats at the temps you mention..
Cheers
Comment by Budget Boater on June 30, 2015 at 9:45pm

1. Generally, if you are using an epoxy that cures via amine blush (blushing epoxy), then you must sand between coats. If you use a no blush epoxy, then you can apply coats without sanding provided the previous coat has not cured fully.

2. Epoxy can take 6, up to 24 hours to cure depending on brand, temperature, humidity, etc. I have not seen a typical epoxy that can cure in 30 minutes to an hour. We typically leave the clamps on for at least 8 hours in the temps you show. Epoxy starts wet, then moves to varying degrees of "sticky", then to tack free, and ultimately full cure.

3. Fillers are used to change the epoxy into a gap filling glue, filleting blend, fairing compound, or other substance. We only use straight epoxy for coating and fiberglass work, or when gluing two pieces of planed timber; otherwise we always add various fillers to create a specific product for the job at hand.

Comment by Éric Bouvéron on June 30, 2015 at 10:59pm

Thanks a lot to all of you. I continue my test, and follow your advices, I will check again the epoxy that I tried  on a longer period. Now I'm on the wood sourcing, trying to convince the yard to make the sizes I want.

Comment by andy solywoda on July 1, 2015 at 7:46am

I can recommend this ebook by Russell Brown:

http://www.ptwatercraft.com/ptwatercraft/EPOXY_BASICS.html

Comment by Blanc Jean-Paul on July 1, 2015 at 10:09am

Hello,  

y speak in french it'smore easy for me. And for information the blog just below is mine with a page on my experience of epoxy. 

Lorsque je dois passer plusieurs couches, comme par exemple une imprégnation suivit d'une stratification puis d'un enduit, je ne laisse pas la résine reticuler. Elle doit être encore collante pour poursuivre la couche suivante. Sinon, laisser reticuler, poncer, et reprendre la suite des opérations. Il est évident que la liaison sera meilleure si chaque couche est liée au niveau des molécules. J'ai appliqué sur l'ensemble des coques ce principe, et le résultat est excellent. Si le travail doit être interrompu, il faudra bien poncer l'endroit de la reprise pour une bonne accroche.  Et comme toujours, bien veiller à travailler dans de bonnes conditions. Hydrométrie et températures. 

Comment by Blanc Jean-Paul on July 1, 2015 at 10:25am

Pour la dernière question, la résine est souvent additionné par des charges (poudres) qui selon ce qu'on veut est différente. Donc une résine sans charges, ne sert en principe qu'à imprégner le bois. Il est utile par exemple de charger la résine pour effectuer un collage. Chose que n'a pas du faire le vendeur. 

Comment by Éric Bouvéron on July 1, 2015 at 12:11pm
Merci encore, Thanks again.

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