New Scratch built fibreglass/carbon mono build

[minigazz]

Hey, I have finally got round to starting this project off. I have been planning this build for a few months now, doing little bits of research whenever I could fit it in. I have decided that I want to build a mono as I thought it would be easier for a first time working with composites as there are fewer tight radius curves to wet the fibreglass cloth around and the joining of the two hull sections should also be easier. I also want the boat to be around 40 cm long so that it is still portable and can use ~400 motors and controllers.

I have sketched up some drawings and from them made some CAD plans of sorts on solidworks (still a work in progress and am trying to pick up the ropes as i go along!). From here I have made some renders which I figured you guys could look at and tell me where I have gone horribly wrong!

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Enjoy!

[minigazz]

Sorted a few more bits out on the inside of the hull as well as mocking up some hardware.

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[minigazz]

The wood arrived today, Yay! I also finally worked out how to get the rib sections from solidworks printed out as templates which allowed me to attach them to the 3mm birch ply and begin to cut them out. I am now waiting on the post for some saw blades with more and smaller teeth to allow me to cut the ply more cleanly. Hopefully then the build will become more interesting then.

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Comments on the hull would be greatly appreciated! The CAD renders represent what the final hull will look like almost exactly!

[minigazz]

Blades arrived this morning so I could crack on and get this thing built! After sticking the templates to the 3mm birch ply yesterday I carefully cut around each rib with an electric scroll saw (I used 24tpi blades for a clean cut) and then sanded where necessary. I found that I could get pretty near to the line with some good concentration, so little sanding was required in the end. After cutting them all out a found a flat piece of board and measured all the key points at which the ribs will be attached. From here I epoxied the ribs in place on the board using a set square to make sure that they were positioned as correctly as possible. I decided to use this construction method as I have found in the past that while building this type of wooden frame design that slight warps and bends can occur. I am hoping that bonding the ribs to a flat board and then attaching each rib to each other with bridging pieces, longitudinal strips and then the lower skin of the hull before freeing it from the board should prevent it from said warping issues.

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[minigazz]

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[swagger22]

looking good man congrats...keep it coming ... i respect the work put in cant wait to see it run

[minigazz]

Thanks! Been at it again today, although I felt myself get a bit fed up of it so I gave it a break after a few hours. I added bracing between each of the ribs to prevent twisting and warping once the ply skin is added. In my original plans I only had one brace, however I felt it would be better to have two to keep all the ribs parallel. I used rubber bands to trap each of the braces in between each other while the glue dried which seemed to work pretty well. Once the glue had begun setting I attached one of the strips along the side of the hull.

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Tomorrow I hope to get the strip on the other side attached and begin planking the hull. I am not yet sure whether I will break the frame away from the board before planking the bottom of the hull or plank it then break it away.

[CornelP]

Keep it on the board until the glue has set on the hull planks. I know from a painful experience that it still flexes, even with a lot of bracing. Once the hull is covered, you're 80% safe.

[kookie_guy]

Awesome. Great job with the solid works. Wanna share the part and assembly files?

[siberianhusky]

Why pull it off the board at all? I assume it is the plug for a mould? In the first post you said moulded composite.
I'd leave it attached until you have the mould built from the plug. Then pop it off the board and hopefully separate the two.
I usually leave my scratch builds on the board until I have a layer of light glass cloth on the outside.
I really like the lines of your boat, also interested in the whole moulding process. Very nice so far!
Cheers

[minigazz]

The last two days I have got the other strip attached, shaped and then joined the strips together at the bow, reinforced the braces and then begun planking the frame. When joining the bow together I found it was quite weak so I added a gusset to strengthen it. I also thought the frame could maybe do with a little more strength so I used the remainder of the 6x3mm strip to triangulate it all.

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Thanks for all the input guys! I took your advise siberian/cornelP and begun the planking while the frame was still attached to the board - it also helped with the clamping. I used a pretty 'alternative' method in the end to plack the hull - I used electrical tape wrapped tightly over the frame with wooden blocks in strategic places to apply pressure. It may not be the most elegant solution, but it seems to be working. I don't know the best way to send the SW files, but I could share them if you know a good way! I will have to remove it from the board in order to plank the top and make a canopy as I want to make the two moulds with a seamless join. Fibreglassing the hull could be a good idea though! Does anyone have any ideas of which cloth weights I should be using? In metric preferably!

[martno1fan]

Hi if you want to make a seamless join id build your plug into a complete boat first .Then you can build a frame arround it and make a parting dam,this way you know each part will match perfectly.When moulding id suggest doing the top first then bottom,make each mould at least 1/8" thick prefably 1/4",use csm for this and let the first layer cure before adding the rest two layers at a time of 450g-600 mat.Hemi did a great writeup on the process over on RCU that will explain in detail how its done,hope it helps.Please dont glass your plug just prime and paint preferably with durabuild primer,this sands to a smooth hard shiny finnish that can be moulded off once waxed.You can also use gelcoat but durabuilds easier to work with.Youve got lots of work ahead,many dont realise how much good luck with it i like your design.
Mart
heres the thread

http://www.rcuniverse.com/forum/m_8761328/mpage_1/key_/tm.htm

http://www.ecfibreglasssupplies.co.uk/p-867-durabuild-surface-primer-grey-inc-catalyst.aspx

[minigazz]

Today I unclamped the plank i stuck on yesterday and cleaned it all up at first with a knife and then with some sand paper. The taping method worked pretty well for the most part, but a little at the bow needed redoing. After this I roughly cut and then glued the other half of the hull bottom on. Tomorrow I will be cleaning this up and attaching the sides

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Thanks for the advice martno, I will be sure to read that thread. I have been trying to find that kind of thing to no avail so thanks a lot for that! I was thinking of using gel coat as it is a lot cheaper than that durabuild stuff, although I continue to hear good things about it so maybe its worth the money!

[minigazz]

Today I managed to make a fair amount of progress. I cleaned up the bottom hull panel which I attached yesterday and then detached the assembly from the board I have been building on. I did this because I was going to plank the top next leaving the sides until last, however I went against this in the end and planked the sides. Before doing this though I had to trim and then clean up the stalks I had used to attach the ribs to the build board with. The plug is coming along quite nicely now, I just need to sort out the hatch area and then start planking the top.

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I have been reading Hemi's forum pages - that guy really seems to know his stuff! He also has a lot of nice kit which my budget definitely can't stretch to, for example he has spray guns to apply his pva coat. With this in mind I am wondering if it would be possible to just use wax as I would worry about getting a poor finish brushing on the pva. The same is also true for the gel coat, however I may be able to get good result with just a brush.

[kookie_guy]

The PVA is very runny, and you can use a foam brush to apply it, it will come out just fine. Or you can just jump on e-bay and pick up a small spray gun for next to nothing (assuming you have a compressor, lol). For the gel coat, it is easier to use a dump gun, however, brushing it on is fine as well. Remember, you are brushing it onto your plug which should be perfectly smooth. Then you are applying your fiberglass mat to the gel coat, so even if you leave brush strokes, the resin from the fiberglass will fill them in. The perfect gel coat finish is on the other side. Just apply a nice coat of it. And for longer mold life, use tooling gel coat. It's more durable.