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>> Home > Boat Building Blogs > Vintage Model Works 46" RAF Crash Tender
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mdlbt.com/23951
Vintage Model Works 46" RAF Crash Tender Print Booklet
Author: robbob   Posts: 95   Photos: 574   Subscribers: 19   Views: 23468   Responses: 263   |   Most recent posts shown first   (Show oldest first)

Showing page 8 of 10   |   Jump to page: 1   2   3   4   5   6   7   8   9   10  

mdlbt.com/24442
Fibreglassing the hull side skins & transom. - Posted: 20th Nov 2016
The fibreglassing process is turning out to be a great deal easier than I anticipated, the cloth weave allows it to conform to the hull shape without any creasing, and the resin brushes on very easily and has no unpleasant smell at all.
I had read other build blogs where the resin was described as having an unpleasant smell and was difficult to work with, perhaps that's because this is epoxy rather than polyester?
In retrospect I could have ordered an alternative resin kit from the supplier where two bottles of hardener are supplied, one slow (95 min pot life) and one fast (17min pot life), because as my confidence increased I could probably do an application with the fast hardener in the shorter time and thus curing time would also be correspondingly quicker.
The transom is the last face to do and once that had cured I could then give the complete hull it's first rub down before I shape and fix the gunwhale and the chine rubbing strakes.
Once these are on I can apply the two further resin coats to get the final finish.

Attached Photos - Click To View Large

Response by allenrod on the 22nd Nov 2016
Hi Robbob,
Don't worry about overdoing the postings, pictures and details, the more the merrier as far as I am concerned, I'm learning a lot from you for which I shall be eternally grateful, I recon most other followers of your posts will agree, keep it all coming and thanks
Response by cenbeth on the 22nd Nov 2016
They aren't boring! Keep them coming!
Response by robbob on the 22nd Nov 2016
Thanks all for your kind responses, it's a shame I can only post 4 pics at a time as I would like to show more detail.
I'll try to keep it all interesting and if you think they are worthy please 'like' the postings.
Robbob.

mdlbt.com/24433
Fibreglassing the hull bottom skins. - Posted: 19th Nov 2016
The hull was prepared for fibreglassing, any pins are punched below the surface, filled and rubbed down with a fine grit paper. The wood does not need any sanding sealer applied as this will react with the epoxy resin.
I cut the cloth roughly to size and shape and laid onto the bottom skin, the upper edge was lightly taped with masking tape to hold it in place.
The resin is mixed to the correct 100:30 ratio and stirred well, the pot life is 95 minutes and will allow me to take my time to get this right.
My previous test was very helpful in establishing a working sequence and I know how the materials will react when I start working them and how much time I have before the brush stops brushing and starts dragging the resin.
The cloth is folded over to the other side of the keel and a thin coat of resin applied over the skin and the side of the keel and then the fabric is carefully folded back onto the wet resin.
The resin immediately starts to draw the cloth to the surface and a very light brushing from the centre outwards helps to make it smooth and flat, the remaining resin can then be gently brushed onto the cloth so that there is an even coating. The cloth needed to be pushed up against the keel sides and I used a steel rule edge to get it into the junction of hull and keel.
I decided to trim the cloth just at the bow along the line of the join in the skins whilst the rein was still wet so that I would have a clean butt join in the cloth in this region instead of an overlap, probably not really necessary as an overlap should sand down ok and that join will be covered by the chine stringer, but it seemed like a good idea anyway.
I did a similar thing on the keel below the propshaft and around the skeg.
This was done with a sharp new Stanley knife blade without disturbing the cloth and the excess cloth removed.
Once the cloth is on you must resist the urge to brush on any more resin or smooth it out any more, this first resin coating only needs to be light as subsequent coats will build up and fill the cloth weave.
I let it to cure overnight and the following day is still felt tacky so I erred on the side of caution and left it for a further day until it was entirely dry to the touch.
The excess cloth was then trimmed back with a sharp blade. Caution, be careful because the cut edge of the cloth is itself very sharp, as I found out the hard way!
Feeling quite satisfied with these initial results and a great deal more confident I repeated the process for the other bottom skin.
At this rate of progress, allowing for proper curing of the resin, it will take 8 days just to cover all five faces of the hull with cloth alone, but a wise man said 'a job worth doing is a job worth doing well' 😄

Attached Photos - Click To View Large


mdlbt.com/24419
Fibreglass & resin tests - Posted: 18th Nov 2016
Whilst researching finishing techniques for the hull I sent off for some samples of woven fibreglass material so that I could choose an appropriate gsm weight. I settled on a 100gsm woven glassfibre twill cloth that is particularly good at conforming to compound curves. The same supplier also does carbon fibre and Kevlar cloth and they are prohibitively expensive but a narrow strip could be good to further protect the bow and keel I suppose.
The resin I have chosen has a 'pot life' of 95 minutes so work can be done at a reasonable pace, the alternative is a 'fast' hardener that has a 17 minute pot life which might entail rather frantic application!
I ordered 3 metres of 1m wide cloth, a 1kg pack of resin & 'slow' hardener, some mixing cups and sticks and 10 disposable brushes for £45 including shipping.
When it all arrived I thought it would be good to do a test piece before the real thing.
The resin and hardener are mixed in a 100:30 ratio by weight, hence the electronic scales in the picture.
I found that the easiest way to use this stuff was to apply a thin coat of resin to the surface, lay the cloth onto it and gently stipple the cloth into the resin, a further thin coat is then brushed on then set aside to cure.
I found it best not to overwork the resin into the cloth, it's definitely a case of 'less is more' as you can easily ripple the cloth and having done so it can be made worse by trying to flatten it. No need for plastic cards or such to smooth it out, it self-levels nicely.
I left it to cure for a couple of days and then experimented with sanding, a detail sander with an 120 grit pad achieved a very good flat surface without going through the cloth.
Two further coats of resin with a rub down between, each with finer grade abrasives, resulted in a glass smooth surface that when keyed would be an ideal surface for the paint system.
Encouraged by these results I decided to do the thing for real 😰
The supplier for these materials is www.easycomposites.co.uk if anyone is interested.

Attached Photos - Click To View Large

Response by BOATSHED on the 18th Nov 2016
I have read lots where people do this, but the results I have had on doing fibreglass on my boat I keep on the Norfolk broads and what I have done in the past on older cars, I do not have the nerve to attempt this on a model boat.
On one boat to try to reinforce I done a second ply skin on it. This seemed to me to be a better alternative with my fibreglass skills.
Response by jarvo on the 21st Nov 2016
Easy Composites do some "how to" videos on there web site, i have used their lighter grade glass cloth and got superb results. i do agree that the longer curing resin is better, you dont need to rush with the longer time to adjust and apply.

mdlbt.com/24409
Deck skins - Posted: 17th Nov 2016
The deck support fillet supplied in the kit is a bit too narrow to support the foredeck skins when they are butted together so I made a substitute from some obechi strip laminated together resulting in a larger surface area for the skins to be glued and pinned to.
I fitted the deck skins in a different order to the instructions starting with the side decks, but made sure that the joins butt together over the bulkheads. All are glued with aliphatic and pinned in place, clamps were used to hold the deck skins down where they meet the cabin sides as I didn't want to use pins there. The towing hook deck and transom decks are also fitted.
Finally all the deck skins are trimmed flush with the hull sides, the pins punched just below the surface and a little filler applied and rubbed down.

Attached Photos - Click To View Large

Response by pmdevlin on the 17th Nov 2016
Hi Rob, coming along real nice 👍

You might not want to do this, but a little tip I was given, stand it on its nose and pour some resin into the bow, particularly at deck, it just firm everything up, and provides a good strong seal against those "too fast into the bank" moments

The original aerokits versions suffered from delamination as in picture one above, which rotted the top deck. I have seen quite a few do this over time, the resin trick seems to stop it, just a thought"!

Paul
Response by robbob on the 18th Nov 2016
Hi Paul.
That's a good tip, particularly if you are renovating an old boat.
I'm using 100gsm fibreglass twill on the outside of the hull with three coats of resin, I'm hoping that will be sufficient reinforcement. The same supplier does carbon fibre and Kevlar cloth, both very costly, and that would make the hull almost bullet proof !
I have no doubt that at some time I will inflict some 'pond rash' on my hull but that's all part of the deal I suppose 😫 .
Rob.

mdlbt.com/24338
Sealing & painting the inside. - Posted: 14th Nov 2016
The next stage is to fit the deck skins but before doing so I drilled some holes in the bulkheads to pass the wiring for the lighting circuits and servos through later.
The battery supports are in place and I have cut two larger holes in bulkheads B4 & B5 and bridged them with a bar to act as a support for wiring and water cooling tubes so everything is supported and looks tidy. I then applied 3 coats of sanding sealer to all accessible areas inside the hull, rubbing down between each coat. I forgot to mention previously that before fitting the bottom and side skins the voids at the bow ahead of B1 were sealed with sanding sealer. I used silver Hammerite paint over the sanding sealer as suggested in the building instructions, and when dried and hardened has provided an attractive and durable finish.
The insides of the cabin sides and cabin formers will probably be painted black at a later stage.

Attached Photos - Click To View Large

Response by robbob on the 14th Nov 2016
Hi don6398
Yes I have , the wiring loom and switch panels are all assembled, tested and ready to install.
I have included in-line power meters to log voltage and current, all the lighting is LED switched by the transmitter including an operational searchlight that rotates by radio control.
I planned, designed and built all that weeks ago.
Keep watching the blog and you will see.. 😀
Robbob.
Response by jaffy012 on the 22nd Jul 2017
hi robbob the hammerite paint you used is that the same paint as used on metal, thanks, colin
Response by robbob on the 22nd Jul 2017
Hi Colin.
Yes, the very same 👍
Rob.

mdlbt.com/24307
Water pickup scoop flange. - Posted: 12th Nov 2016
"Hi bro......any chance you could ?....great, I'll come and visit and watch the master at work"

Clever bugger, and so modest too ! 😁



Attached Photos - Click To View Large


mdlbt.com/24304
Water pickup scoop - Posted: 12th Nov 2016
I'm not very happy with the quality of the plastic water scoop that I have purchased, the threaded portion is only just sufficient to pass through the keel and frankly it looks a bit naff.
Equally, the water outlet I have as similarly poor and I can't seem to find a brass equivalent anywhere, so I decided to make my own.
The tube is 6mm brass and needs to be bent and flared as a scoop so to do the bending I made a jig with a fixed circular former that I filed a round groove in around it's circumference and a square block to retain the tube.
The tube was then annealed to soften it and bent around the former, I also put a curtain wire inside the tube to prevent the tube crushing and although it helped the tube did distort slightly.
Perhaps I should have tried the 'dry salt' or 'fine sand' method but overall I am pleased with end result.
Once in place in the hole I drilled through the keel it looks like it will do the job but it definitely needs a flange of sorts to make it look better.
Maybe a bit of turned brass ?...... 💭

Attached Photos - Click To View Large

Response by justintime2001 on the 12th Nov 2016
What motor and speed controller will you be using rob?
Response by robbob on the 12th Nov 2016
Hi.
The motor is a Turnigy SK3-4250-500 from Hobbyking and the ESC is a 90A water cooled boat ESC , also from Hobbyking (item no. 9261000012).
Rob

mdlbt.com/24301
Installing the skeg and oiler system. - Posted: 12th Nov 2016
Here are some pictures of the skeg fitting, and the position of the oiler system on the propshaft.
The latter is supplied with a short silicone tube with a stopper and also a syringe for applying the lubricant, grease or oil?...a controversial subject it seems, so I have yet to decide ❓ .
I wrapped a single turn of gas PTFE tape (slightly thicker than ordinary plumbing PTFE) around the tube before clamping it into place and drilling through into the shaft tube. This should ensure an oil tight seal. It's very important that any swarf that ends up inside the shaft is flushed out as it could damage the bearing within the prop tube. I have added a ply reinforcing plates on either side of the bulkhead for good measure.
The ply strips either side of the keel will form part of the battery supports in that compartment.


Attached Photos - Click To View Large


mdlbt.com/24286
Skeg...take 2 - Posted: 11th Nov 2016
So I called my younger brother, who has........ a lathe !
'No problem' he said, 'send me a drawing of the bit you need turned and I'll post it to you'.
A short while later it arrived in the post, it fits the shaft like a glove and looks the part too.
I carefully cut and filed a flat bottomed groove along it's length and with some new 14swg brass strip and a 'silver soldering kit' I set about putting it together.
Despite my rather heavy silver soldering, (never done that before) it cleaned up very nicely and the solder joint is strong and firm, but best of all it actually looks worthy of fitting to my boat 😊

The skeg was fitted at the same time as the prop shaft, set into a slot cut through the keel and epoxied firmly in place.

Attached Photos - Click To View Large

Response by onetenor on the 11th Nov 2016
22swg is far too flimsy .No wonder it looked crap
Response by Missouri on the 11th Nov 2016
Clearly your younger brother is the real brains behind the project, as the boat is looking so good! 😉
Response by robbob on the 12th Nov 2016
Brains, yes..big ego, yes..but I don't want to upset him as I might need a few more bits turned soon 😛 😉

mdlbt.com/24284
Skeg.....first attempt - Posted: 11th Nov 2016
So the instructions say "make up a brass skeg from 22swg brass strip", OK so how difficult is that !
Bought some 22swg brass, cut some strips, formed one strip around an 8mm drill bit to make a tube, cut another strip and soft soldered it all together.
It looked rubbish and had no strength at all. 😭
Time to think again...hmmm.......need some expert help here.

Attached Photos - Click To View Large

Response by RedRider on the 12th Nov 2016
Nice work mate!

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