CA2633134C

CA2633134C - Insulated log homes

Info

Publication number: CA2633134C
Application number: CA002633134A
Authority: CA
Inventors: Ronald A. Wrightman
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-06-25
Filing date: 2008-06-25
Publication date: 2010-03-09
Anticipated expiration: 2028-06-25
Also published as: CA2633134A1; GB0910962D0; GB2461176A

Abstract

A log for a log home has a plurality of pockets formed within the body of the log. The pockets are filled with foam to enhance the thermal rating of the log.

Description

3 [0001] The present invention relates to logs for use in log homes.

4 100021 It is well known to utilize logs stacked one above another to form the wall of a house.
The intersection of logs at corners is accommodated through overlapping joints, either a saddle 6 splined joint or a dovetail joint by providing a connection to a post. Such construction provides 7 an aesthetically pleasing finished product and reflects the traditional values of the environment in 8 which such houses are typically built. Such houses are formed from logs that are rough hewn to 9 shape as they are built into a wall and the gap between the logs sealed with "chinking". As an alternative to the hand hewn log homes, machined logs have been utilized in the construction.
11 Machined logs have a uniform cross section and the abutting faces of the logs are machined to 12 form a seal system to inhibit the ingress of air between the logs making up the wall. Such 13 construction offers greater thermal efficiency for the building and assists in meeting the air 14 infiltration standards of the relevant building codes.

[0003] A further aspect of the building code is the minimum thermal rating, commonly 16 referred to as the R value in North America or U-value in Europe, which is the reciprocal of the 17 R value of the wall. U=5.682/R, taking into account the change in units.
The R value for a log is 18 accepted to be R 1.25 per inch and to meet a requirement for a minimum insulation value of R16 19 it would be necessary to provide 12 inch thick logs. Logs of this dimension are expensive and difficult to obtain in volume and as such make it difficult to attain the minimum values required.
21 It is of course possible to increase the thermal efficiency by insulating the internal surface of the 22 wall but this detracts from the inherent aesthetic value of the log wall construction.

23 [0004] A number of attempts have been made to increase the thermal rating of the log wall 24 material by implementing a thermal break in the log. One of those is shown in PCT application WO 96/07802 in which a plurality of longitudinal slots are cut into the body of the log so as to 26 attempt to provide the necessary thermal efficiency. Thin foam strips can then be set into those 27 cuts. However such an arrangement destroys the integrity of the log and requires careful 28 manufacture in order to ensure that the natural movement of the wood does not result in 21766005.2 1 degradation of the log itself. Such an arrangement also makes it difficult for the inter-engaging 2 seal profiles to be manufactured and maintained. Similar deficiencies exist with the 3 arrangements shown in U.S. Patents 4,344,263 and 3,992,838.

4 [0005] It has also been proposed to laminate a log construction to obtain a thermal break by using inner and outer log panels with a plastic foam block between as shown in WO/95/30807.
6 Such a process, however, is very expensive to produce and has the risk of de-lamination between 7 the foam and the exterior panels given the lifecycle of such a building. De-lamination would 8 subject the foam core to crushing due to the weight of the balance of the logs and as such is not 9 an acceptable practice.

[0006] There is therefore the need for a log construction in which the thermal rating of the 11 log may be increased without destroying the structural integrity of the log.

12 [0007] In general terms the present invention provides a log having a plurality of pockets 13 formed at spaced locations along the log. The pockets are separated by lands constituted by the 14 material of the log that extend transversely between oppositely directed faces of the log. The pockets are filled with an insulating material, typically a foam.

16 [0008] By providing discreet pockets along the length of the log, the structural integrity of 17 the log is maintained whilst its thermal rating is increased. Sealing profiles may be machined on 18 each of the sealing faces and the terminal portions of the log may be devoid of pockets to permit 19 normal joint construction for the corners.

[0009] In one embodiment, the pockets are blind bores extending from an upwardly directed 21 surface of the log and terminating prior to the lower surface. In another embodiment, the bores 22 extend through the log and in a further embodiment the pockets are tapered to receive a tapered 23 plug of pre-foamed foam. Generally the bores are perpendicular to the log surfaces but they may 24 be inclined to increase the cross sectional area if preferred.

BRIEF DESCRIPTION OF THE DRAWINGS

26 [0010] Embodiments of the invention will now be describing by way of example only with 27 reference to the accompanying drawings in which, 28 [0011] Figure 1 is a schematic representation of a house having walls formed from logs.
21766005.2 1 [0012] Figure 2 is a view on the line of 11-11 of Figure 1.

2 [0013] Figure 3 is a side view of a log used in the wall of the house of Figure 1.
3 [0014] Figure 4 is an end view of the log of Figure 3.

4 [0015] Figure 5 is a section on the line V-V of Figure 3.
[0016] Figure 6 is a plan view of the log of Figure 3.

6 [0017] Figure 7 is a plan view of an alternative embodiment of log.

7 [0018] Figure 8 is a view similar to Figure 6 showing a further embodiment of log.
8 [0019] Figure 9 is a view similar to Figure 8 showing a further embodiment of log.

9 [0020] Figure 10 is a side view similar to Figure 3 showing an alternative configuration of log.

11 [0021] Figure 11 is a section on the line XI-XI of Figure 10.

12 [0022] Figure 12 is an end view similar to Figure 4 showing the manufacture of the log of 13 Figure 4.

14 [0023] Figure 13 is a side view of an alternative log [0024] Figure 14 is an end view of the log of Figure 10 showing a method of manufacturing 16 the log of Figure 13.

17 [0025] Figure 15 is a plan view of a further alternative embodiment of plug.

[0026] Referring therefore to the drawings, in Figure 1 a house 10 has side walls 12, 14 that 21 support a roof 16. The side walls 12, 14 intersect at a corner 18.

22 [0027] Each of the walls 12, 14 is formed from a plurality of logs 20 that extend horizontally 23 and are stacked one above another in a vertical direction. As can be seen in Figure 2, the logs 20 24 have a pair of oppositely directed surfaces, designated an outer surface 22 and an inner surface 24. The outer surface 22 and inner surface 24 are interconnected by an upwardly directed 21766005.3 1 surface 26 and a downwardly directed surface 28, it being understood that the terms upper and 2 lower refers to the normal orientation of the logs 20 when assembled into a wall 12,14. The 3 upper and lower surfaces 26, 28 are milled to have complimentary profiles 30,32 such that when 4 stacked one above the other, the profile 32 of lower surface 28 is snugly received on the profile 30 of the upper surface 26. Seals may be incorporated between the tongue and groove 6 formations to provide an effective seal during the inevitable movement of the logs, as more fully 7 described in co-pending Canadian application number 2,557,364.

8 [0028] The log 20 is shown in greater detail in Figures 3 to 6 from which it will be seen that 9 it has an elongate body portion 40 with a terminal portion 42. The terminal portion 42 is provided to accommodate a joint that cooperates with a log 20 of an adjacent wall at the corner 11 18 to interlock the two wallsl2,14. As shown in Figure 3, the terminal portion 42 is provided 12 with a tai144 that forms one-half of a dovetail joint. It will be appreciated that other 13 constructions may be utilized, such as a saddle joint.

14 [0029] The body portion 40 is formed with a plurality of pockets each defined by bores 46 that extend from the upper surface 26 toward the lower surface 28. In the embodiment of Figure 16 3, the bore 46 is of constant circular cross section and is formed by drilling from the upper 17 surface 26 toward the lower surface 28. The bores 46 are uniformly distributed along the body 18 40 and have a diameter less than the spacing between the inner and outer walls 22, 24. In a 19 typical embodiment as shown in Figure 6, a log 20 with a nominal spacing of eight inches between the outer face 22 and inner face 24 is provided with bores 46 having a diameter of four 21 inches. The bores 46 are spaced apart on seven inch centres providing a three inch land 48 22 between each of the bores 46. With the bores 46 spaced apart on the centre line of the log 20, a 23 nominal two inch boundary layer 49 is provided between the bore 46 and the surfaces 22, 24 24 respectively. The bore 46 terminates prior to the lower surface 28 and provides a minimum thickness in the order of 1 inch.

26 [0030] The bore 46 is filled with a expanded foam plug 50 that extends up to the upper 27 surface 26 and is formed to have the same profile as the upper surface 26, as will be described 28 below. The foam plug 50 is typically a closed cell foam such as urethane having a high thermal 29 insulation value. Typically such foams have an insulation of R6 per inch and a suitable foam is 21766005.3 1 available from Polyurethane Foam Systems Inc. of Waterloo, Ontario under the trade name 2 Polarfoam PF-6352-0.

3 [0031] The foam plug 50 may be formed in situ using the bore 46 as a mould.
In this case, 4 the lower face of the bore 46 provides a closed vessel to permit pouring of the liquid foam.

[0032] With the configuration of pockets shown in Figure 6, the insulation value of the log is 6 increased from 1.03 per inch, that is R10.4 to an average value of 20.6.
This increased thermal 7 rating is achieved without affecting the structural integrity or the ability of the log to provide an 8 efficient sealing system in the wall. It should be noted that the end portions 42 are maintained to 9 permit the corner joints to be formed out of solid material with the body 40 offering a higher thermal efficiency. The provision of the end face of the bore 46 provides sufficient transverse 11 strength to inhibit splitting of the log 20 when the profiles 30,32 are engaged.

12 [0033] The provision of the bores 46 is also beneficial to the production of the logs 20. By 13 pre-drilling the logs 20 with the bores 46 they may be stored upside down to prevent water 14 collecting in the bores 46. The provision of the bores 46 decreases the drying time of the log 20 significantly from the typical twelve months, allowing the inventory of log 20 to be reduced.
16 Moreover the whole structure also has the effect of stress relieving the log 20 and thereby 17 reducing the surface cracking that is typically present on the surfaces 22, 24. Such surface 18 cracking does not reduce the overall strength of the log 20 but it is aesthetically displeasing. The 19 cracking that does occur will take place on the upper surface 26 between the pockets, thereby enhancing the thermal efficiency of the lands 48 without adversely affecting the structural 21 strength.

22 [0034] The logs 20 as shown in the embodiments of Figures 1 through 6 may be produced by 23 initially machining the log blank and drilling the bores 46. The log 20 is then left to dry until the 24 required moisture content is attained, after which the foam plug 50 is formed in each of the bores 46. The plug material is mixed in a liquid form and placed into bores 46 where it forms in situ.
26 Thereafter, as shown in figure 12, the upper and lower surfaces 26, 28 are machined to the 27 requisite profile and the tails 44 machined to provide the required joint.
The foam plug 50 is 28 supported on all sides by the walls of the bore 46 and therefore milling of the upper face 26 can 21766005.3 1 be accomplished with the foam core in situ. With the upper and lower surfaces 26, 28 formed, 2 the log can then be assembled into a wall having the requisite thermal rating.

3 [0035] It will be appreciated that the extent of the body 40 may vary from log to log to 4 accommodate features of the building 10 such as doorways and windows. It that event, the end portions 42 may be left solid to accommodate joints or other fixtures, but logs extending across 6 such openings can have the foam plugs 50. The configuration of the bores 46 may vary 7 according to different requirements. For example, in Figure 7, the nominal width of the log 20 is 8 8 inches and bores 46 are 4 inch diameter. The bores 46 are arranged on 8 inch centres providing 9 a 4 inch land 48 and a two inch boundary layer 49. With this configuration an average thermal rating of R 19.4 is obtained.

11 [0036] The bores 46 may also be manufactured with varying cross sections as shown in 12 Figures 8 and 9. In the embodiment of Figure 8, the bores 46 are formed with a square cross 13 section provided by a chain mortiser. In the arrangement of Figure 8, a nominal eight inch log is 14 formed with the bores 46 with four inch sides and on a seven inch spacing.
This provides a land 48 of three inches but the volume of foam provided in the bore 46 is increased compared to a 16 circular cross section. As such, an increase in the order of 25% of the cross sectional area of the 17 foam is obtained to increase the average thermal rating to a value of R=23.4.

18 100371 In the embodiment of Figure 9, the bore 46 are formed from a pair of overlapping 19 circular bores 46 to present an oval cross section. The bores 46 have a 5 by a 2 1/2 dimensions and the land 48 between the holes is in the order of 3 inches. This provides an R value in the 21 order of R 30Ø

22 [0038] As shown on Table 1 below, a number of different configurations may be used to 23 obtain the desired increase in R-value with relatively few pockets. In the first configuration 24 shown in row 1, circular bores of 3 inch radius extend through the log and are spaced apart by a land of 21.5 inch. Surprisingly, the R value of the log is increased from 10.4 to 16.3, which is 26 sufficient to meet the Canadian building code requirements. This increase is attained with a 27 relatively small number of pockets which maintains the integrity of the log.
21766005.3 1 [0039] Similar results are shown in row 2 where square pockets are spaced apart 24 inches to 2 get a similar increase in R value. With overlapping circular bores of 3 inch diameter, as shown 3 in row 3, a land of 35 inches may be used and with an elongated oval, as shown in row 4, a 4 spacing of 45 inches is possible whilst maintaining an R-value above 16.

[0040] An array of smaller diameter staggered pockets, as shown in row 5, may also be used 6 to attain the required value.

7 Table 1 'Insulated'Log R-value Calculator Log Width (in) 8 R-log (per in) 1.3 R-value (log only) 10.4 R-foam (per in) 7 % foam % log R-value U-value U-value BTU/hr/s fVdeg F W/sq m/C
Top View of log 1. s (in) = 21.5 13% 87% 16.3 0.061 0.349 000 0_ s ~ r (in) = 3 Top View of log 2. s(in) = 24 13% 87% 16.2 0.062 0.349 ^ ^ ~ x(in) 6.5 y ^ u_ Iu y (in) = 6.5 x Top View of log 3. s (in) = 35 13% 87% 16.3 0.061 0.348 I~-I c (in) = 3 r r (m) 3 c Top View of log 4. S r s (in) = 46 13% 87% 16.2 0.062 0.350 r (in) = 3 c (in) = 5 c 5 Top View of log 5--- ~-- r s(in) = 2.5 13% 87% 16.4 0.061 0.347 O O O O O O O O r (in) = 1 Minimum value for Canada is R= 12 8 Maximum value in the UK is U = 0.35 W/sq m/C

100411 From the above, it will be seen that a variety of configurations may be adopted to 11 obtain the requisite thermal rating, and that where a particular rating is required, the ratio of foam 12 filled pockets to original log may be adjusted to provide this. As shown below in Table 2, 13 reducing the pocket cross section and the spacing enables the same thermal rating to be achieved 14 as the equivalent configuration in table A, thereby illustrating the versatility of the arrangement when meeting particular building requirements, such as interconnecting walls and services.
21766005.3 1 Table 2 'Insulated' Loci R-value Calculator Log Width (in) 6 R-log (per in) 1.3 R-value (log only) 7.8 R-foam (per in) 7 % Toam % log R-value U-value U-value eTUmOs fVde F waq rn~c Top View of lon 1. s (in) = 4.5 25% 75% 16.2 0.062 0.350 O O (D,__7s' ~ r(in) = 2 Top View of loq 2. s s (in) = 3 25% 75% 16.4 0.061 0.347 ED-1-El V x (in) = 3 Y (in) = 3 X
Top View of log 3. s (in) = 9 25% 75% 16.2 0.062 0.350 v~.J u/ `F11~ r r(In) 2 Ir-i c (in) = 4 c Top View of Iop 4 ~ s`I.LS1/r s (in) = 11.25 25 9/6 75 % 16.3 0.062 0.349 It-il r (In) = 2 c (in) = 4 c Top View of lo g r L U s(in) = 0 25p/o 75% 16.2 0.062 0.350 O O 0 O O O O O r(in) = 0.625 Minimum value for Canada Is R = 12 2 Maximum value In the UK is U = 0.35 W/sq m/C

4 [0042] In each of the above embodiments, the bore 46 is of uniform cross section and 5 terminates prior to the lower surface 28. The bores 46 may of course extend through the log, 6 provided provision is made for inserting the foam. It will also be appreciated that the cross 7 sectional area of the bore 46 may be increased by inclining the axis of the bore 46. In the 8 embodiment shown in Figure 10 and 11, the bore 46 is formed with a tapered cross section and 9 extends between the opposite faces of the log 20. The tapered cross section permits pre-formed plugs 50 that are also tapered to be inserted into the bores 46 where a tight fit is ensured by virtue 11 of the taper. This arrangement perrnits the advantages of the increased thermal rating to be 12 obtained without requiring onsite storage of foaming materials and related material handling 13 concerns. With the arrangement shown in Figure 10 and 11, the plug may be inserted, secured 14 within the bore 46 and the upper and lower surfaces 26, 28 machined to provide the finished log 20.

16 [0043] In an alternative arrangement as shown in Figures 13 and 14, the tapered plug 50 is 17 preformed with the profile of the upper and lower surfaces at respective ends of the plug 50. The 18 plugs 50 may then be inserted into the pre-bored log 20 with the profiles at opposite ends of the 21766005.3 1 plug 50 matching those of the surfaces 26,28. Such an arrangement permits the log to be 2 assembled in situ where this is preferable.

3 [0044] It will be appreciated of course that the arrangement shown in Figure 13 and 14 may 4 also be applied to a bore 46 of uniform cross section allowing through bores 46 to be formed in the log and the subsequent installation of cylindrical plugs 50. Such an arrangement would 6 require a sleeved press to insert the plugs but would also permit the use of a cylindrical extrusion 7 cut to length prior to insertion rather than the in situ foaming as described above.

8 [0045] To facilitate insertion of preformed plugs, the arrangement shown in Figure 15 may 9 be used. As shown in Figure 15, the plug 50 is formed as two part cylindrical portions, 50a, 50b.
Each portion 50a, 50b is slightly less than one half the cross section of the bore 46 providing a 11 gap 60 between the portions 50a, 50b when inserted.

12 100461 The portions 50a, 50b are held in situ by a wedging action in the gap 60. In one 13 embodiment, the gap 60 is filled with expandable foam which expands to hold the portions 50a, 14 50b, and the relatively small gap enables the foam to be supplied by pressurised containers if on site installation is required.

16 [0047] It will be seen therefore that the provision of the pockets in the log 20 provides an 17 opportunity to increase the thermal rating without adversely affecting the integrity of the log.
18 The lands between each of the bores ensure that the inner and outer faces are secured at all times 19 to one another and also provides sufficient strength to avoid crushing of the log. The provision of the foam also allows the sealed profiles to be machined in the plug together with the balance 21 of the sealing faces and for the log to maintain the integrity of the end portions for conventional 22 joining techniques.

23 [0048] Although the invention has been described with reference to certain specific 24 embodiments, various modifications thereof will be apparent to those skilled in the art without departing from the spirit and scope of the invention as outlined in the claims appended hereto.
26 The entire disclosures of all references recited above are incorporated herein by reference.
21766005.3

Claims

1) A log having an elongate body with a pair of oppositely directed wall faces extending between a pair of oppositely directed sealing faces, a plurality of pockets extending from one of said sealing faces through said body to the other of said sealing faces, said pockets being uniformly spaced along said body, said pockets being separated from one another by lands extending between said wall faces, said pockets and lands being dimensioned relative to one another to preserve structural integrity of said log and maintain relative spacing of said wall faces.

2) A log according to claim 1 wherein terminal portions of said body are devoid of pockets.

3) A log according to claim 1 or 2 wherein said sealing face has sealing formations formed thereon for engagement with a complimentary formation on an adjacent log.

4) A log according to any one of claims 1 to 3 wherein said land between pockets has a dimension measured along the longitudinal axis less than the corresponding dimension of said pocket but greater than the spacing of said wall faces from a periphery of said pocket.

5) A log according to any one of claims 1 to 4 wherein said pockets are of substantially constant cross section.

6) A log according to any one of claims 1 to 4 wherein said pockets taper.

7) A log according to any one of claims 1 to 6 wherein said pockets are distributed and sized to provide an increased in thermal rating of said log to at least R16 when said pockets are filled with foam.

8) A log according to any one of claims 1 to 7 wherein said pockets are filled with foam.

9) A log according to claim 8 wherein said foam is preformed and inserted in to said pockets as plugs.

10) A log according to claim 9 wherein a pair of plugs is inserted in a pocket and retained by a wedge spreading said plugs.

11) A log according to claim 9 wherein said plug and pocket are tapered and said plug is retained by interference between said pocket and said plug.

12) A log according to any one of claims 1 to 11 wherein said pocket has a dimension between said wall faces of 50% of the spacing between said wall faces.

13) A log according to any one of claims 1 to 12 wherein said pockets are circular.

14) A log according to any one of claims 1 to 12 wherein said pockets are square.

15) A log according to any one of claims 1 to 12 wherein said pockets are oval.

16) A building including at least one log according to any one of claims 1 to 16.

17) A building according to claim 16 wherein intersecting walls of said building are formed with logs according to any one of claims 1 to 16 and wherein terminal portions of said logs are devoid of pockets.

18) A building according to claim 17 wherein said terminal portions are formed as interlocking joints.

19) A method of forming a log having a pair of oppositely directed sealing faces, said method comprising the steps of forming a plurality of pockets in said log at uniformly spaced intervals along said body, said pockets extending from one of said sealing faces through said log to the other of said sealing faces, said pockets being spaced apart greater than the dimension of said pocket along the axis of said long to provide a land extending between said pockets and filling said pockets with insulating foam.

20) A method according to claim 19 including the step of machining formations on said one face after said foam is formed in said pockets.

21) A method according to claim 19 or 20 wherein said foam is preformed and inserted in to said bores.

22) A method according to claim 21 wherein said pocket is tapered and said foam is preformed with a complementary taper.

23) A method according to claim 21 where said foam is inserted in said pocket as a pair of portions and retained in said pocket by a wedge acting between said portions.

24) A method according to claim 23 wherein said wedge is a foam inserted between said portions.

25) A log having an elongate body with a pair of oppositely directed wall faces extending between a pair of oppositely directed sealing faces, a plurality of pockets extending from one of said sealing faces into said body and uniformly spaced along said body, said pockets being separated from one another by lands extending continuously between said wall faces each of said pockets having a dimension measured in a direction transverse of said walls that is not less than 50% of the spacing between said walls, said pockets and lands being dimensioned relative to one another to preserve the structural integrity of said log and to maintain relative spacing of said wall faces.

26) A log according to claim 25 wherein said lands have a dimension measured along the longitudinal axis of said log less than the corresponding dimension of said pocket but greater than the spacing of said wall faces from a periphery of said pocket.

27) A log according to claim 25 or 26 wherein said pockets have a combined volume that is at least 20% of the volume of said log.

28) A log according to any one of claims 25 to 27 wherein said pockets have a transverse dimension at least 50% of the longitudinal dimension.

29) A log according to any one of claims 25 to 28 wherein said sealing face has sealing formations formed thereon for engagement with a complimentary formation on an adjacent log.

30) A log according to any one of claims 25 to 29 wherein said pockets extend between said sealing faces.

31) A log according to any one of claims 25 to 30 wherein said pockets are of substantially constant cross section.

32) A log according to any one of claims 25 to 30 wherein said pockets taper.

33) A log according to any one of claims 25 to 32 wherein said pockets are distributed and sized to provide an increased thermal rating of said log to at least R16 when said pockets are filled with foam.

34) A log according to any one of claims 25 to 33 wherein said pockets are billed with foam.

35) A log according to claim 34 wherein said foam is preformed and inserted in to said pockets as plugs.

36) A log according to claim 35 wherein a pair of plugs is inserted in a pocket and retained by a wedge spreading said plugs.

37) A log according to claim 35 wherein said plug and pocket are tapered and said plug is retained by interference between said pocket and said plug.

38) A log according to any one of claims 25 to 37 wherein terminal portions of said body are devoid of pockets.

39) A log according to any one of claims 25 to 38 wherein said pockets are circular.

40) A log according to any one of claims 25 to 38 wherein said pockets are square.

41) A log according to any one of claims 25 to 38 wherein said pockets are oval.

42) A building including at least one log according to any one of claims 25 to 41.

43) A building according to claim 42 wherein intersecting walls of said building are formed with logs according to any one of claims 25 to 41 and wherein terminal portions of said logs are devoid of pockets.

44) A building according to claim 43 wherein said terminal portions are formed as interlocking joints.

45) A method of forming a log having a pair of oppositely directed sealing faces and a pair of oppositely directed wall faces, said method comprising the steps of forming a plurality of pockets in said log to extend not less than 50% of the distance between said wall faces and extending from one of said sealing faces to the other of said sealing faces with a land extending between said pockets and filling said pockets with insulating foam.

46) A method according to claim 45 said foam is formed in situ.

47) A method according to any one of claims 45 or 46 including the step of machining formations on one of said sealing faces after said foam is formed in said pockets.

48) A method according to claim 45 wherein said foam is preformed and inserted in to said bores.

49) A method according to claim 48 wherein said pocket is tapered and said foam is preformed with a compounding taper.

50) A method according to claim 48 where said foam is inserted in said pocket as a pair of portions and retained in said pocket by a wedge acting between said portions.

51) A method according to claim 50 wherein said wedge is a foam inserted between said portions.