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reeljob
09-12-2006, 06:45 PM
I've now got 10 3/8" spanish cedar strips to laminate the stem for my Simmons. Bending 10 strips into a mold is considerably more difficult than I anticipated. WHat should I do? Would it be a good idea to steam bend them and then glue them into the shape of the stem? I don;t know a thing about steam bending. Any other suggestions? I really don't want to make this out of a solid piece.

THanks

South Shore Boatworks
09-12-2006, 09:17 PM
If you want to laminate the stem with the 3/8" thick strips that you mention, you will have to set up a bending/laminating jig. I would start by making a template of the full size stem in the drawings. Next.lay it on a piece of plywood atleast 1/2" thick and attach blocks along the forward or leading edge of the stem template. These are the blocks that the laminations will be clamped against giving the correct shape of the stem. As far as bending, I would not steam the strips. I believe that your lumber is kiln dry and wouldn't steam well. Steaming can cause warpage and cupping. The moisture also interferes with the epoxies ability to bond the laminates. I commonly bend and glue laminates with good success. Before mixing any glue, cover the bending table with a piece of polyethelene plastic sheeting. This eliminates the risk of the laminated stem sticking to the jig. Next,cut out an additional strip of approximately the same length and width of the other strips but only 1/4" thick. This will be used to clamp against instead of clamping directly on the laminates, which can cause uneven pressure and break the laminates. Glueing, apply a coat of un-thickened epoxy to the strips. This will seal the grain then coat the strips with thickened epoxy. Now place the entire stack of laminations on the bending jig. Position the 1/4" strip on the outside of the pile. Slowly clamp the pile of laminations against the blocks on the jig . This should be left clamped for atleast a couple of days. Once it's cured, remove the clamps and trim to size.

GregH
09-12-2006, 09:33 PM
Pardon what may seem like second guessing, but gotta ask- How did you arrive at 10 strips 3/8" thick for the stem? Was this called out in the plans? While I'm completely unfamiliar with Spanish cedar, it's hard for me imagine bending any wood that thick around a radius of less than several feet without steaming it first.

pipefitter
09-12-2006, 09:39 PM
My stem in my Simmons is laminated from 3 layers of 1x LL pine with the grain alternated. Alot less work than layering.The stem will never get wet regularly if ever.Simply stack the 1x's and glue with epoxy and cut your stem shape from that. Much more stable than a solid member without the fuss of molding and gluing.

reeljob
09-12-2006, 09:42 PM
I'm using the 3/8" strips after reading Ellis Rowe's article about his Simmons 18. I think the 18 only needs 9 strips, but the 20 needs 10.

South Shore- i've got a 1/2" ply panel with the stem drawn out and blocks attatched- i'm worried that it won;t be able to take the seemingly immense pressure. I'm going to get some more large clamps. THanks for the 1/4" strip idea- that makes a lot of sense.

As far as steam bending, the spanish cedar is kiln dried. SOmeone I was talking to suggested soaking it in water overnight then steaming it. If I steam it just to get it to take a curve somewhat similar to the stem, wouldn't that make it easier to laminate? I would think that the strips should dry for a period of time after steaming before gluing? I really don;t know much about steam bending, so anything helps.

paladin
09-13-2006, 05:11 AM
as above...do not steam the strips....once the jig is made you start laminating.....for instance, you could laminate 4 strips, then the next day add three or four more and so on....the bending will be easier but will dake a couple of days longer. Tighten the clamps progressively. System Three T-88 makes a good epoxy for this.

Peter Page
09-13-2006, 05:24 AM
Run the strips through the thicknesser and make them 1/4. Just use a few more.

mcdenny
09-13-2006, 07:44 AM
Maybe obvious but nobody said it- clamp everything together WITHOUT glue first. You can make sure everything works and correct problems at your leisure.

dmede
09-13-2006, 10:53 AM
Soaking overnight will help when steaming. There shoudl be no problem steaming them into the mold then letting them set and dry before glueing. However, if I were doing this I would (as already suggested) plane the strips down a bit and just add more of them so I could bend them in with out steaming. Much easier.

Just out of curiosity, why are you so opposed to using a solid piece of wood? That would be the simplest method IMOP.

Bob Smalser
09-13-2006, 12:31 PM
http://pic20.picturetrail.com/VOL12/1104763/8408305/113221960.jpg

While for your stem I'd make a form, the fastest technique for small lams is to steam fairly thick strips and clamp them in place on the boat.

After they take a set and dry out to the moisture content required by the glue (usually in a day, when starting with wood under 10% EMC), they are glued in place using waxed paper as a slip sheet, then removed and shaped:

http://pic20.picturetrail.com/VOL12/1104763/8408305/113344748.jpg

I can knee the whole boat in less time that it would take to make the forms...and with better accuracy and economy, if you consider all the twist that doesn't have to be planed out, weakening most conventionally-lammed knee. Laminations are wonderful things to take the place of hard-to-find crooks with even better strength-to-weight ratios.

pcford
09-13-2006, 12:59 PM
Laminations are wonderful things to take the place of hard-to-find crooks with even better strength-to-weight ratios.

If one is not troubled by moisture cycling delamination.

Bob Smalser
09-13-2006, 01:32 PM
If one is not troubled by moisture cycling delamination.

I agree....most glueline failures I've observed occur after deteriorated paint allows unequal moisture migration. When the athleticism of the wood outdoes the flexibility of the glue, the joint cracks, often aided by UV degradation. And UV alone can destroy glue joints beneath inadequate varnish....epoxy is especially sensitive to UV, and so is UF plastic resin glue.

Get the grain of the lams to match....pure flatsawn to pure flatsaw....use a wood that glues well like DF....and keep the paint maintained. The oldest lamination I currently have in use is over 30 years old and still perfect. Many don't pay enough attention to perfect grain matching.

Moreover, if the part ever does delam, if the boat was constructed properly, it can be removed and repaired. In the meantime, if the lam is mounted with, or in the case of a large lam like a stem, reinforced with screws, it can remain functional until it is repaired.

reeljob
09-13-2006, 04:35 PM
Thanks for the help on this. Steaming seems to me to be a viable option (i don;t know much about it)- after the moisture content of the wood retuirns to normal, wouldn;t it be the same as gluing up non-steamed wood? Maybe I don;t know what I'm talking about.

As far as gluing it up in stages, what should I do to ensure a good epoxy bond between stages? My initial plan was to saturate with epoxy, then slather them with thickened epoxy and clamp together. Should I sand w/ coarse grit and wash w/ warm water before gluing another set of strips on to it?

I got these 3/8" strips milled by the place i'm getting my wood. I don;t have access to a thickness planer, and I initially did not expect 3/8" to be so difficult to bend.

Also what is moisture cycling delamination? My guess would be delamination caused by the wood swelling and cointracting? Wouldn't this be eliminated in an epoxy saturated piece that won;t see UV rays?

dmede
09-13-2006, 05:07 PM
Thanks for the help on this. Steaming seems to me to be a viable option (i don;t know much about it)- after the moisture content of the wood retuirns to normal, wouldn;t it be the same as gluing up non-steamed wood? Maybe I don;t know what I'm talking about.

Yes. It's just a normal glue up with pre-bent peices. Apply an unthickned layer of epoxy, let it set up for a few minutes and then follow with a thickened layer of epoxy. Some tooth to the wood will help but it's not necessary to really rough it up. Don't wipe down with water, use mineral spirits and let it evaporate. When clamping make sure you get good squeeze out but don't over clamp and squeeze it all out.

Do you have any boat building books to follow during this process? Greg Rossels "Building Small Boats" and John Brooks "How to Build Glued Lapstrake Wooden Boats" would be big help here and could answer some of your more basic questions. If you don't have them I'd suggest picking them up or borrowing from your library.

John Meachen
09-13-2006, 05:15 PM
Re-reading the first post I noticed the description of bending the strips into a mould.If my understanding is correct,you appear to be trying to form the strips into a concave former.I always find this more fraught than bending them around a convex shape.Regardless of the direction you are trying to pull or push the laminates,the advice to have a dry run first is good as is the recommendation to do the job in several stages.As Southshoreboatworks says,you should take precautions to avoid having the laminate stick to the jig.Polythene works well but do take care that it doesn't wrinkle and get trapped between two layers of your stem.The advice to use an extra strip as a pressure batten will help you to avoid clamp marks and should mean that you ought not to have any additional preparation after each batch of strips has been added.Steaming is really not all that useful as you will have quite a long wait for the moisture to dissipate.I hope you explained to the supplier of the strips just what you were intending to do with them as there is a chance that breakage will occur if the grain direction is not pretty parallel to the faces.

reeljob
09-13-2006, 06:40 PM
Thanks. I worked on my mold a bit and it seems that 4 strips can be bent into place moderately easily. I'm not going to bother steaming them.
I've got that book- it is very helpful.

I will hopefully have a site set up soon to document my progress. Nothing much to take pictures of yet- just a stack of plywood.