Topic: Bending Of Bulwark Cap Planking For Constructo "Gyoa" (Read 9856 times)

Alan Perry · « **on:** August 23, 2015, 11:01:12 am »

I am currently having problems bending planking for the bulwark cap rail. In the model it is a one piece rail, in reality, it would have probably been made up of several sections with vertically scarfed joints.

The cap planking is 7mm x 2mm x 350mm and the bend is in the horizontal plane and not the vertical plane as a hull plank would be. The curvature is fairly tight on the shoulder. The plank (Manzonia) will not bend cold so I have built a steamer out of 28mm copper tube, 450mm long and fully lagged it. The steam generator is one I purchased from Aldi recently, and, by only using the very short teflon discharge nozzle directly into the low side of the steamer (5 deg. incline), I get a good flow of steam for 9.5 minutes every fill (4 minutes downtime for refilling). The high end has an easily removed cap with a 2mm hole to allow for very slight pressure and has a 1mm water drain at the low end.

I have tested my steamer by steaming a 5mm x 2mm plank for 30 mins and I can get the required horizontal plane profile however I do not think that I will be able to get the profile on a 7mm wide plank.

There are two other options, one, make up the cap planking in several longitudinal sections which would require minimal steaming for bending, or, two, slit my 7mm wide plank into two 3.5mm planks, steam and profile them and then join them when fitting to the bulwarks.

I am sure that members of the Forum have wide experience with this problem and I would very much appreciate any advice.

Tug-Kenny RIP · « **Reply #1 on:** August 23, 2015, 11:08:55 am »

Do you have 'spare' 7mm planks to experiment with ? I am not familiar with Manzonia so do not know its properties.

cheers

ken

Alan Perry · « **Reply #2 on:** August 23, 2015, 11:54:47 am »

Hello Ken,

Unfortunately I do not. I think Manzonia is a fairly hard wood - maybe similar to walnut. It is also difficult (impossible) to get hold of in 7mm plank. If I knew for sure that I could get 7mm plank from Constructo, I would experiment with one of those I have. Does anybody have an email address for Constructo "spares" department.

Alan

Alan Perry · « **Reply #3 on:** August 23, 2015, 01:59:19 pm »

Ken,

I have now found a firm in Cornwall that sells 7mm x 2mm Manzonia so I will try steam bending one of the planks I have, although I am not optimistic.
Cheers Alan

Jerry Hill · « **Reply #4 on:** August 23, 2015, 02:32:03 pm »

Contemporary bulwark cappings I see are usually cut to shape and jointed, I guess the question is how was the original made. I can imagine that laminating 2mm veneers in a manner that is sympathetic the curve may give you a fairly consistent looking rail with only shallow end grain cuts after being cut to the required shape. Its a fairly figureless wood so that may work

Alan Perry · « **Reply #5 on:** August 23, 2015, 05:35:47 pm »

Thanks Jerry & Ken,

Many thanks for your responses.

I have this afternoon tried to steam a 7mm x 2mm Manzonia plank for just over an hour. I have made up a pin board following the profile of the bulwark capping. When I initially tested my steamer I did it with 5mm x 2mm Ramin. This material seemed to take steam fairly well and I achieved my profile. This afternoon after steaming the Manzonia it would appear that the wood is fairly impervious to steam. It was not a completely wasted experiment as with steaming I managed to get slight curvature and I would be able to profile my bulwark using three scarfed sections. Before I progress with a sectioned bulwark capping I shall wait a few days to see whether the Forum can come up with any experiences of doing this job.

dreadnought72 · « **Reply #6 on:** August 23, 2015, 05:50:30 pm »

The advice very often given on forums dedicated to full-size boat building when faced with similar issues is to slice, steam and then laminate (in place). Glue lines can be all-but invisible when the cap rail is sanded.

Andy

Alan Perry · « **Reply #7 on:** August 23, 2015, 06:35:30 pm »

Andy, thanks, yes I have often seen this method used on "modern" yachts. I deal from time to time with a very well known traditional wooden boatbuilder/repairer in Svendsborg, Denmark, and they tend to make bulwark capping in vertical longitudinally oblique scarfed sections instead of horizontal laminated sections. I am sure "Gyoa" would have been built in this manner so, despite Constructo instructions, and, unless I receive better advice from any previous builders of this model, this is probably the way I will go.

Keep Well, Alan

dougal99 · « **Reply #8 on:** August 24, 2015, 01:27:31 am »

I used household ammonia to bend a 12mm x 3mm capping rail on a brittany fishing boat. You have to be carefule not ot soak the wood for too long or it turns very soft and loses all rigidity. 5-10 minutes is enough.

tigertiger · « **Reply #9 on:** August 24, 2015, 06:06:32 am »

I have used window cleaner from the supermarket, find one that contains ammonia.
The wood (pine) became supple but went rigid again when it dried out. This suggests that putting into some kind of former while it dries would help. For a perfect fit the former will need a slightly tighter radius than needed to allow for spring back.

If you can get ammonia I have seen articles suggesting a 10% solution.

Another method without using ammonia.
Start from the stem and lay down the plank on the first part of the curve and follow the gunwhale as far as you can without the plank twisting. Glue and pin in place.
After the glue is dry, bend the plank for the next section for the cap rail, pin and glue in place, wait for glue to dry and repeat. I managed to do mine in 3 or 4 stages.
That is the method used for the model in the picture, which shows the amount of curvature. This model hull is about 30 inches and cap rail is similar dimensions to your timber.

Brian60 · « **Reply #10 on:** August 24, 2015, 08:19:37 am »

You say that your timber is hardwood. If you have enough to spare I would try soaking it in boiling water before steaming it. This would help get the heat into the heart of the wood quicker than just steam alone. The problem with this technique is the time it has to be left to dry afterwards.

Steam alone will 'set' its curve in minutes. Soaking the timber first means the wood can be saturated and take days to dry out again, in the meantime it has to be left pinned to its shape while that happens. Also as mentioned, ammonia works better on softwoods than hardwoods.

Alan Perry · « **Reply #11 on:** August 24, 2015, 09:47:04 am »

The curvature of the schooner above is not extreme and I could cope with that with my steamer. "Gyoa" has a fairly severe bend at the shoulder (roughly where the schooner's foremast is). Incidentally, that schooner is a beautiful model.

I had never heard of the ammonia method, one concern I have is whether the ammonia will bleach the colour out of the wood. I have one plank remaining on which I will try the soak in boiling water prior to steaming suggestion. I have ordered more manzonia (unfortunately a 10m pack minimum) so I will be experimenting at length.

Thank you Gents.

Colin Bishop · « **Reply #12 on:** August 24, 2015, 09:52:55 am »

Google the ammonia method. It is apparently effective but although the wood appears to harden when it dries out it has lost its strength which means you could have two bouts of weeping!

Colin

Alan Perry · « **Reply #13 on:** August 24, 2015, 11:22:54 am »

Has anyone tried soaking plank in methylated spirits before bending. I have just found this on Model Ship World forum but no real results are given.

dougal99 · « **Reply #14 on:** August 25, 2015, 01:07:10 am »

Here is a picture of my fishing boat with dark brown capping rail, just varnished (no fading of colour) and the rail has held the brass staples for the rigging catches. The model is well over 10 years old and still going strong. QED

tigertiger · « **Reply #15 on:** August 25, 2015, 01:31:20 am »

My rails are softwood, and then died with wood stain. Only a little fading.
I have seen other models that use hardwood, for original color I suppose, but hardwoods are brittle.

tigertiger · « **Reply #16 on:** August 25, 2015, 01:32:01 am »

Quote from: Colin Bishop on August 24, 2015, 09:52:55 am

Google the ammonia method. It is apparently effective but although the wood appears to harden when it dries out it has lost its strength which means you could have two bouts of weeping!

Colin

Hi Colin,
What do you mean by weeping?

Colin Bishop · « **Reply #17 on:** August 25, 2015, 06:52:24 am »

Once when you use the he ammonia and then again when the wood disintegrates!
Colin

inertia · « **Reply #18 on:** August 25, 2015, 08:29:51 am »

Dougal
What type of wood is your capping rail? I have a Lord Nelson Victory tug nearing that stage.
Dave M

Stavros · « **Reply #19 on:** August 25, 2015, 12:27:31 pm »

What I usually do is to draw the curve on a piece of 6x2 plank knock some nails along the drawn line...soak the wood under the hot tap...straight into shed ...then simply steam it under a kettle spout and clamp it to the nails,obviously if the bend is not enough re steam it till it conforms to the right shape....clamp and use nails to hold it to the others and leave overnight...next day when removed off the wood it will be bent to shape...have done this with wood as wide as 13mm and 6 mm thick with no splitting...hope this helps

Dave

dougal99 · « **Reply #20 on:** August 26, 2015, 01:15:13 am »

Quote from: Inertia on August 25, 2015, 08:29:51 am

Dougal
What type of wood is your capping rail? I have a Lord Nelson Victory tug nearing that stage.
Dave M

sorry Dave can't recall, it was 9-10 years ago and I've slept since then

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Author Topic: Bending Of Bulwark Cap Planking For Constructo "Gyoa" (Read 9856 times)

inertia

Stavros