Help Help Help

[CookieOldParticipant @cookieold]

Hi All , Please can someone advise me on the best method of gluing the bulk heads in place on my 1/24 GRP Perkasa hull . I have tryed all the common Epoxi glues with bits of GRP and Plywood and found i could break the joint be hand.I prepped the GRP first with sand paper to give a key.Hope to hear from someone soon.

Cookie

[CookieOldParticipant @cookieold]

Fixing Bulk Heads

[Bob Abell 2Participant @bobabell2]

Hello Cookie

I would use narrow strips of fibre glass cloth, applied with FG resin

A messy job at times, but it should work

Bob

[shipwrightParticipant @shipwright]

Make sure that the surfaces to be glued are absolutely free from grease, oil and dirt (I wipe the area with methylated spirits and then let it dry before gluing)

Ian

[CookieOldParticipant @cookieold]

Thanks Lads

[Dave MilbournParticipant @davemilbourn48782]

Isopon P40 is a car-body filler paste but has the advantage of containing short chopped strands of fibre-glass. I use it for fixing prop tubes into GRP hulls but "blobs" of it would be fine to locate bulkheads and secure them (say at keel and gunwale levels) before using strips of glass-cloth and resin to complete the joints. P40 sets up in about ten minutes and you can smooth it before then with a finger dipped in standard thinners (don't tell the HSE).

I wouldn't worry about the shaft angle. If it's good enough for Vosper-Thorneycroft then who are we to argue? It's one of Paul T's 'bonnet bees'.

Dave M

[CookieOldParticipant @cookieold]

Thanks Dave , That sounds like a good shout , were can it be bought.

[Dave MilbournParticipant @davemilbourn48782]

Halfords – or pretty much any car spares/accessories shop. Don't confuse it with P38, which is a smooth body filler without the chopped strands. You can also buy the laminating resin and glass cloth from Halfords – it's all made by "Davids" or "Fastglas".

[CookieOldParticipant @cookieold]

Hi Dave , Went out this morning and got some did a test on some scrap bits , just been in the workshop and it is solid as a rock in 6 hours. I dont think i need anything else just the P40 is fine just a bit of sanding off of the GRP strands needed

Thanks Cookie

[curlyParticipant @curly]

Hi Cookie

It's too late now, if you want any more. Go to family Bargains,they sell the heavy duty filler with glass strands in for £4.55 for 250ml

Curly

[Dave MilbournParticipant @davemilbourn48782]

Cookie

You're welcome. Just watch your fingers while sanding that stuff – it's sharp!

Dave M

[CookieOldParticipant @cookieold]

Hi Dave M, Having decided to use the P40 to hold the bulk heads in place i started to make the templates for them only to find another problem . The GRP hull is in a kit i bought for a 1:24 scale perkasa by Precedent , it had a very bad twist in it , to overcome this a made a jig to pull it true and it remains in the jig till i get the bulk heads bonded in place . The problem i noticed now is that the sides of the hull are not flat , they are curving outwards quite a lot so the insides of the hull are concave , I always intended to make 7mm thick bulkheads on the advise of Paul T . I placed the 4mm ones that came with the kit into the hull just to see how they fit and there is a 6mm gap at the bottom and top of the hull it only touches in the middle . Do you think i should just live with it and make my bulk heads to fit the concave sides or try and pull the sides flat somehow and if so how would i go about this.

Best regards Cookie

[Dave MilbournParticipant @davemilbourn48782]

The conventional wisdom is to use a hair dryer to warm the hull and bend out any twists or deformations in it, then to hold it until it cools. I've also heard that the ply parts in the kit are not a good fit. I had been commissioned by John Rudd of Precedent to redo the whole model and make the parts for the GRP hull a proper fit, but sadly he died before I'd really started the job and no-one else there seemed that keen for me to continue.

All I can suggest is that you use a combination of eyeball and the plan view to get the hull into the right shape, then make 6mm or 7mm ply bulkheads to fit. Paul T is right in that 3mm liteply is just not the right stuff, but they will serve very well as templates from which you can draft the right shapes i.e. "near enough".

DM

[CookieOldParticipant @cookieold]

Thanks Dave , After starting this my first build i sometimes think i am being to precise about things as i come from a high precision engineering back ground in my job , But having said that i cannot be blamed for wanting thing to look correct i will have a go with my heat gun and put the b/heads in while hot .

Best Regards Dave ( cookie )

[CookieOldParticipant @cookieold]

Hi Dave M. I did as you suggested and put a little heat on the hull and while hot pushed in the bulk heads then let cool . All bulk heads are in place now with P40 and its spot on . Do you think P40 alone will be OK or should i go belts and braces with glass cloth as well. P.S you mentioned the Gunwale level in a earlyier post what is this .Thanks again Dave

[Dave MilbournParticipant @davemilbourn48782]

P.S you mentioned the Gunwale level in a earlier post what is this?

Can't find that reference in this thread, m'duck. The gunwale is the top edge of the side of the hull i.e. in this case where the deck fits. Quite whether or not you want to reinforce with glass cloth is up to you. If you've made a decent job of bridging the joins between hull and bulkheads then I would suggest you needn't bother.

DM

[CookieOldParticipant @cookieold]

Hi DM , I put P40 all round the joint on just blobs and it really is solid so i think it will be OK . Just to change the subject i have poster a question on Battery Run time on this forum and Mayhem , A lot of people say i should ditch the idea of running my MFA 850 motor in the center on 1 ESC and 1 speed 600 at each side on another ESC. And use just 1 speed 900 motor in the center , I have not cut the tube slots in the hull yet so it,s no big deal , I could not think of a better man than yourself to ask your opinion.

Thanks Dave

[Dave MilbournParticipant @davemilbourn48782]

Cookie
As I've said, there's no model which cries out for a brushless motor more than this one. I would strongly suggest going onto the Mayhem forum and asking the question. There are several people there who have fitted brushless motors in models of this size and will be able to advise you on the exact type and a suitable speed controller better than I can. Stavros's Perkasa used a version of the Johnson 960 with less armature winds than the one currently offered by Steve Tranter. Consequently it runs faster, especially with 20 cells! Unfortunately there are none of these motors left that I know of anywhere in the trade.
Go brushless with one motor (or perhaps twin motors). Three is just asking for trouble IMHO. I would imagine a reasonable starting place would be a motor like this one **LINK** with a X50 or X55 prop and a 3S or 4S LiPO battery. The motors are reasonably cheap so you can afford to try a couple of different ones, but go for a good size ESC (eg what they happily describe as 100A+). Maybe this one **LINK** ?
These are NOT recommendations – more like half-educated guesses – and they might be dogs, but if I were to have the same job then I might just start here.

Good luck.

[Paul TParticipant @pault84577]

Cookie

One element of this project that hasn't really been mentioned is the fully loaded weight of your model and on a model of this size the weight plays a very important factor in determining the performance parameters.

The model itself has a hefty 'dry' weight but this can easily double when you start adding chunky motors such as the 850 and 600s with all of the associated ESCs / mixers / receivers, and then when the batteries are added you have a very heavy model.

Having built the timber version of this kit I have first hand knowledge of just how much power is required simply to get the thing moving let alone skimming along in true MTB style.

I agree with Dave M that, in this case a pair of brushless motors are the best option as they offer the optimum power to weight ratio.

Paul

[CookieOldParticipant @cookieold]

Thanks DM & Paul T , I have asked the question on Mayhem.

Dave

[Author]

Posts