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Building a Thos. Moser Design New Gloucester Rocking Chair #14: Evaluating the Prototype Top Crest

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Blog entry by DustyMark posted 01-03-2013 07:48 PM 1911 reads 0 times favorited 2 comments Add to Favorites Watch
« Part 13: Shaping the Rocker/Leg Joint Part 14 of Building a Thos. Moser Design New Gloucester Rocking Chair series Part 15: Rum's Brilliant Solution for Lining Up 14 Spindles for Glue-Up »

Ready to Cut Final Top Crest?

I finished turning the 14 back spindles on the first rocking chair over the past three days. As I finished each spindle, I inserted it into the seat. Once I had the middle four spindles completed, I began inserting them into the top crest as well. The prototype top crest is only 1 1/2” tall. The final top crest is 2 5/8” tall and will be cut from some scraps of 12/4 cherry that I had saved since completing my pencil post bed almost 20 years ago. I made a ball and claw foot coffee table from the initial scraps. I used some more to make top crests for a pair of bar stools. I only have enough 12/4 remaining to make three top crests. With two rocking chairs in the works, I want to get this right the first time.

Various Views

This is the third prototype top crest and I think that the angles are sound. This picture gives an idea of how the ash spindles are forced to bend, based on the angles of the holes in the seat and the top crest. These forced curves are pleasing to the eye, but more importantly, provide strength and rigidity to the back assembly. The path of least resistance would be to drill holes that corresponded to straight entries from the seat to the top crest. However, this would yield a back assembly ill-equipped to resist the force of an adult leaning against these 25” long spindles. By forcing curves in the spindles, tension is created within the assembly that helps it flex a little and yet finally hold against the forces of an adult’s upper body in the rocking chair.

This view from the top shows the relationship of the spindle holes as they come through the top crest. The outermost spindles are a compound angle and enter the crest at a 15 degree angle from vertical. As seen by the cut line, I must limit the depth of these holes to 3/4” or possibly 1” to avoid the spindle coming out the back of the top crest. The second outermost spindle enters at a 10 degree angle. The third outermost spindle enters at a 5 degree angle and the rest of the spindles are veritcal.

The spindles are all slanted back to acheive a comfortable reclined seating position. They are drilled at 90 degrees in the seat and then at various angles in the crest to form pleasing curves as viewed from the front.

As viewed from a slightly different angle. I’m very happy with the lines of this chair.

This spindle blank shows how much the spindle is forced into position. I’m surprised at how far ash will bend. I’m careful to keep the straight grain portion of the spindle to the inside and outside of the curve. If you oriented the wavy grain portion to the inside or outside, it might break during assembly or use.

How Do I Assemble 14 Spindles Simultaneously???

I’m able to insert one spindle at a time in the prototype by pushing the spindle up through the top crest and then dropping back down to the seat blank. All of the holes in the final top crest are stopped tenons. That means I’ll need to assemble 14 spindles at the same time. I assembled 7 spindles in a similar top crest for my bar stools last summer and my wife and I were able to handle it.

The trick I used on the bar stools was to insert the spindles in the top crest first and then fit the assembly into the seat. I’m thinking that with three people, we might be able to accomplish the same thing. Here are some other steps I’ll take:

1. Drill all of the top crest holes to specific depths and custom cut the mating spindles to the correct length.
2. Predrill some cross dowel holes into the top crest and the seat to hold the assembly together as we finally get things into place.
3. Use Gorilla glue since it allows easy repositioning and give quite a bit of assembly time.
4. Glue spindles into top crest first.
5. Use blue painters tape to minimize Gorilla glue mess. Tape seat blank and cut through spindle holes with Exacto knife. Do same to underside of top crest. Tape spindles outside joint line.
6. Considering drilling a number of the center spindle holes in the top crest deeper so that I can bring them down into the seat after getting more difficult spindles into place. That would leave less spindles to deal with at once. However, it would be a disaster if they stuck high and I couldn’t get them back down to contact the seat.

I welcome any thoughts or suggestions on this…

Next Steps

Next steps are to cut the back spindles to length and make the final top crest…

-- Mark, Minnesota



2 comments so far

View tsangell's profile

tsangell

211 posts in 1382 days


#1 posted 01-04-2013 05:58 AM

Looks fantastic.

If I had to fight a long glue up that had potential for re-work, it would be liquid hide glue, all the way. And the more hands, the merrier.

View DustyMark's profile

DustyMark

271 posts in 759 days


#2 posted 01-04-2013 01:21 PM

Thanks. I’ve been pondering using liquid hide glue for this particular glue-up. That would give me time to insert the wedges on the seat tenons and cross dowels during the one hour open time. I’m close to a Woodcraft store and will pick some up today.

-- Mark, Minnesota

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