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RN Hawker Sea Hurricane IIc

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Phil Cooke23/03/2018 12:10:51
2194 forum posts
1508 photos

Look forward to seeing you in a couple of weeks then Dirk! Great that you are flying with us again on the Orme!! thumbs up

With the fuselage joined and shaped front and back it was time to fit the rear formers F8 and F9. With the complications of vertical positioning created by the former notch and fuselage datum mods - I wanted to do all I could to ensure these 'floating' formers were positioned as accurately as possible. On Sheet 1 I drew a straight line representing the building board from the base of F3 to the base of F7 (as the model sits on the bench) and extended that rearwards to F9. Measurements from that datum to the underside of where the formers are drawn on sheet 1 were taken - 16mm for F8 and 35mm for F9.

Balsa blocks were made up to this height, pinned to the plan with a centreline reference added for ease. The fuselage was then positioned over these blocks and chocked/pinned accurately over the centreline.

f8 1.jpg

Via dry fitting I found I had to notch out the pre cut doubler recesses on both formers by ~2mm on the lower edge.  F8 and F9 were glued into position (again glue only applied on the lower half of the former to allow for fuselage curvature later) and the clamps were in use to give the fuselage an equal squeeze just where required.

F8 is seen here sat on its height guiding block. Note the bottom of F8 protrudes lower than the fuselage side at this stage - it looks odd but it's ok as we still have to add the 3/4" triangular and it will all sand up just fine.

f8 4.jpg

F8 and F9 in place - I used gorilla glue sparingly on the joints, giving me plenty of time to fiddle everything into the exact position and orientation before it was left to dry overnight.

f8 3.jpg

f8 2.jpg

Edited By Phil Cooke on 23/03/2018 12:16:10

Phil Cooke25/03/2018 08:47:44
2194 forum posts
1508 photos

I've fitted the 3/4" triangular section to the rear lower fuselage.

In profile, this runs straight from F7 to F9, however in plan it requires some bending and shaping to enable it to fit into the recesses in the formers whilst taking the natural bow of the rear fuselage.

triangular 1.jpg

I performed a number of hacksaw cuts at 1cm spacing to enable the curvature between F7 and F8. At the rear (in plan) it needs thinning down to zero so the two triangular sections meet directly on the centreline.

You can see in the shot below the section sits fully engaged into the recesses in F8 and F9, sits flush with the fuselage side at F7 and overhangs by over 1/4" at the extreme rear.

triangular 2.jpg

Phil Cooke26/03/2018 22:57:04
2194 forum posts
1508 photos

Sanding the 3/4" triangular section to the required 2D profile curve before the rear lower 5/16" balsa sheeting is added.

triangular 3.jpg

Phil Cooke27/03/2018 16:14:09
2194 forum posts
1508 photos

Rear lower sheet added - 5/16" soft balsa. The fus is wider than the 4" stock at the wing saddle, so to maintain the grain running lengthwise (to aid shaping) two lengths of sheet were glued together with the join positioned right on the centreline. Rough sanded to plan view for now - there's quite a lot of material to come off this to form the Hurricane's characteristic hull - quite rounded at F8 yet very angular around the tailplane.

rear lower sheet.jpg

Phil Cooke27/03/2018 18:14:02
2194 forum posts
1508 photos

Time to bend the lower front fuselage around F2.

Ammonia is required here to enable the 1/8" balsa sides to take on the required profile, applied locally with a brush again, trying not to re-wet the key joint (which opened up before!) After 15 mins or so the wood was pliable enough to take the curve...

f2 curve 1.jpg

I used medium cyano and kicker to 'grab' the fuselage side once it was rolled into position by hand, I then reinforced the joint from the rear with a good fillet of epoxy and micro-balloons. My fuselage suffered a little damage due to load at the corner of F3 - this was due to the pin-holes I'd created here locally when pinning the fus to the board - perforating the wood and making it weak - it was re-clamped and glued square against F3

f2 curve 2.jpg

The fuselage overhangs were trimmed straight awaiting final block sanding to allow the bottom sheeting to be fitted between F3 and F2 later.

f2 curve 3.jpg

Edited By Phil Cooke on 27/03/2018 18:27:46

Phil Cooke30/03/2018 22:24:34
2194 forum posts
1508 photos

After a lull due to work I got some time in the workshop again today - although the majority of it was spent checking over and readying existing airframes for next weekends PSSA event on the Orme.

I managed a little more progress by fitting the soft balsa sheeting below F3 to F2 and I made up the radiator 'core' and some soft balsa cheeks which are still to be shaped and hollowed. The radiator pre-cut parts snapped together beautifully - very satisfying!

f2 lower sheet.jpg

radiator 1.jpg

Phil Cooke01/04/2018 00:01:49
2194 forum posts
1508 photos

I've started to pull the fuselage tops in and over the formers... more ammonia, more clamps! Ammonia was applied all along the fuselage join line to the top - outer surface only - it was left 20 mins for everything to become soft.

I began around the central cockpit area, to glue F6 in place the fuselage needed a squeeze around mid height to bring the width in to match the former at the doubler position - same for F7 - two vertical batons were clamped firm around the wing bolt mount and clamped again at the top until the fuselage nipped up against the former.
fus pull 1.jpg

This curve was then matched moving rearward, again batons were used to try and keep things straight - there's just enough purchase (through baton crushing) with the clamps at this angle - the sides came in nicely around F8 and F9.

fus pull 2.jpg

Once in position and with the ammonia dry, wicking cyano was used first to grab the joint - which was then strengthened with a good fillet of epoxy and microballoons before the clamps were released.

fus pull 3.jpg

Phil Cooke01/04/2018 09:16:42
2194 forum posts
1508 photos

Nothing says 'Happy Easter' quite like the toxic whiff of Ammonia before breakfast thumbs upsmile d

The fuselage needed a little squeeze onto F5 at the doubler location - before glue was added there I positioned it centrally, cantilevered off F6 at the required raked angle with a little scrap wood and cyano. Clamping top and bottom again against batons to ensure a smooth squeeze with no damage to the model surface.

f5 fit 1.jpg

I elected to reinforce the F5/Doubler joint with a little triangular stock - conscious of the loading to follow when we bend in the re-entrant fuselage sides...

f5 fit 2.jpg

The cockpit longerons which run from F4 to the rear of F6 need a twist along their length to drop snugly into the formers - again ammonia was used and the two lengths were clamped and left to dry with ~40degree twist... lets see how effective that is?

f5 fit 3.jpg

Phil Cooke01/04/2018 17:11:28
2194 forum posts
1508 photos

Ok, so I'll come clean - the bending of the two lengths of 1/4" x 1/4" as shown in the photo above created 2 cockpit frame doublers for the same side!! In my mind they would naturally be reversible, but they weren't, so I had to re-wet one and twist it the other way...

cockpit frame.jpg

I found I needed to open up the bottom of the slot in F5 for the cockpit frame doubler to pass through (due to the raked angle of F5) but the twisted lengths went in quite nicely as shown. They still need sanding now to the outer profile of the formers so the skins will fully conform once rolled around.

Chris Barlow01/04/2018 17:54:37
1783 forum posts
1208 photos

When I cut the slots in F4 for the cockpit longerons I cut them 1/4 x 1/4 sq so effectively they twist in the opposite direction.

Also in my efforts to control the bulging in the cockpit area I glued the longerons to F6, F5 and F4 before pulling in the cockpit sides and clamping them to the longerons, tacking them with cyano to fix in place which helped to maintain a straighter cockpit opening.

Phil Cooke02/04/2018 10:40:18
2194 forum posts
1508 photos

It was a bit too late in the day to commence the final fuselage side ammonia curving exercise so I spent a little time cutting out and inspecting the fin and tailplane components before gluing some of them together flat on the board.

Note the little make up piece at the base of the fin which Sarik have added! I'm not having a working rudder so all these parts will be glued flat with the addition of the fin post which needs to be selected by the builder. Balsa quality was good and the density was appropriate on these parts.

fin 1.jpg

Not quite so on the elevators - which were cut from a different sheet and were very dense - the stiffness is good but the weight not so, not right at the back, so Ill consider re-cutting mine from a softer stock. You can see they are clearly a different shade in the photo below.

tailplane 1.jpg

I was wanting to recreate the elevators counter balance section anyway, ahead of the hinge line, as per the full size (below), so a bit more material will need to be cut from the tailplane anyway to make these scale in size and shape.

hurricane tail.jpg

Ron Gray02/04/2018 10:58:29
1299 forum posts
343 photos

Lightening holes?

Phil Cooke02/04/2018 12:13:23
2194 forum posts
1508 photos

Hi Ron - would be fine if I wasn't intending to finish the airframe in light glass cloth and resin which works really well for these PSS models - I'll cut from a lighter grade - a lot of it is sanded away of course as we still have to section the tailplane and elevator.

Alan Gorham_02/04/2018 14:51:58
703 forum posts
88 photos

Keep on truckin' Phil!

Phil Cooke02/04/2018 17:57:09
2194 forum posts
1508 photos

More ammonia action... surprise

Having read with interest Chris' adventures when forming the skins over the top and into the re-entrant section running aft of F5, I spent 10 minutes making myself a pair of tailored clamping guides - which proved a god send and have nicely formed the required shape in that region. Cut from 3/4" balsa and lined with lite-ply to spread the clamps load evenly these really gave me an extra hand during this op.

ammonia 1.jpg

In hindsight I'd also make 2 more of these to help solve the 'bulge' you naturally get around the cockpit region once everything is rolled into place - I used batons in the end with lots of binding tape wrapped around the wing saddle.

In shaping the fuselage correctly around F5 and F6 you get a bulge both ahead and behind the clamps - remember I've already glued the sides to F8 so that end had no-where to go - I decided therefore to force 'the bulge' forwards into the cockpit region. I clamped two batons between F6 and F8 to keep the sides straight going rearwards.

ammonia 2.jpg

At the front it all went pretty well - having given the sides a thorough wetting out and plenty of time for the ammonia to take action - I needed to trim the skins to meet nicely on the centreline between F3 and F4 - no doubt there will be a little shrinkage as the ammonia dries and Ill end up with a little infill needed here. Other than that the only issue was again a little evidence of the fuselage 'key section' not wanting to conform and on a couple of occasions the corner of the key 'popped out' - easy to bend back in and cyano home as below.

ammonia 4.jpg

Around the canopy the resultant bulge was easy to straighten out with more batons forcing the sides onto the longerons... Still no glue on any of these former joints of course, but once the ammonia has dried out I should be able to remove the tape and batons and run round all the internal skin joints with a combo of fast grab cyano and PVA.

Edited By Phil Cooke on 02/04/2018 17:58:46

Phil Cooke03/04/2018 17:09:21
2194 forum posts
1508 photos

Given a full night to dry out, this morning the tape and clamps were removed and glue was added to the now 'freely conforming' skin and former joints. I'm glad to say it's all gone pretty well, but there are a few points worthy of mention...

Firstly at the front where the skins wrap around and upto the top of F2, they've fallen short by a couple of mm - this could be down to shrinkage of the fuselage sides - it needs sanding flat to the top of F2 here to allow the top sheet to be added, ill add a little more 1/8" fuselage side first. An easy remedy.

ammonia 5.jpg

More shrinkage on the top deck between F3 and F4 - this was inevitable as the sides were trimmed to meet butt-jointed on the centreline when they were wet - at least they still both sit on the longeron at Top Dead Centre... again easy to fill and sand with a slither of 1/8" balsa.

ammonia 6.jpg

A view inside the fus shows all the former profiles being met nicely by the skins thumbs up

ammonia 7.jpg

One final issue - F5 and F6 both protrude out a little beyond the top of the fuselage sides behind the cockpit, F6 (vertical former) by just a couple of mm - a similar amount to the top of F2, suggesting shrinkage again. However F5 protrudes more than that, my former I think is a little more vertical than intended which doesn't help - again I'll add some more fuselage side material in here before the tops are sanded in readiness for the 10mm top sheeting.

ammonia 8.jpg

I'm glad to say that's all the ammonia working done for another build! Definitely time for a beer

Phil Cooke05/04/2018 16:59:06
2194 forum posts
1508 photos

Before the top sheeting was added front and rear the fuselage side overhangs needed trimming and where (in my case) the sides fell a little short I've extended them with some little infills before sanding back to the required angle. I also trimmed around the cockpit area.

The snake outer needs to be fitted before the rear top sheeting is added too. I've deviated from the plan a little here and gone for an internal actuation arrangement (actually the prototype was built like this too!) with no external horn on show. Its a little thin down the back but it works well. I secured the blue outer at F4,F7, then F8 and F9 (both drilled with CENTRAL holes to suit) - the snake exits through a hole drilled ~18mm below the tailplane.

snake 1.jpg

snake 2.jpg

I'll need to relieve the fuselage and the fin post/rudder to allow the actuator to articulate +/- 40 degrees about the hinge line.

snake 3.jpg

With the snake outer fitted and secured I've added the 10mm top sheeting both front and back. I used batons again to take out the little bit of 'bow' still evident in the fuselage sides between F7 and F8 - once the top sheet was glued and clamped this held the sides in the correct manner and the bow seems to have gone (where the extra material goes to, I don't know?!)

Phil Cooke05/04/2018 22:56:54
2194 forum posts
1508 photos

Top sheeting added and rough planed/sanded...needs blocking in around the nose and I think that's basically the fuselage done bar a good sanding.

fus status 5 april.jpg

Ron Gray09/04/2018 13:17:21
1299 forum posts
343 photos

Just wondering if planking would have been an easier solution to the multi curved fuz?

Phil Cooke09/04/2018 19:39:17
2194 forum posts
1508 photos

Maybe Ron, but it's quite achievable as drawn and supplied with a little applied method and technique.

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