Model Boat Mayhem - Forum

Please login or register.

Login with username, password and session length.
Pages: [1]   Go Down

Author Topic: BMPRS Rules  (Read 3454 times)

phillnjack

  • Guest
BMPRS Rules
« on: January 02, 2011, 06:27:40 PM »

Ive looked at the rules on the bmprs site and seen about exhaust must not protrude morethan 2.5 inches or be shielded ?

what exactly do they mean by a exhaust shield, ?
what do these shields look like ?
and do you only need to shield the excess amount of said protrusion. ?



phill %%
Logged

scoop

  • Guest
Re: BMPRS Rules
« Reply #1 on: January 02, 2011, 06:45:16 PM »

Ive looked at the rules on the bmprs site and seen about exhaust must not protrude morethan 2.5 inches or be shielded ?

what exactly do they mean by a exhaust shield, ?
what do these shields look like ?
and do you only need to shield the excess amount of said protrusion. ?



phill %%
Hi Phill,  BMPRS recognised that sometimes hull designs do not have a lot of space inside to shield a hot exhaust from rescue crew when they collect a stricken (dead) boat from the water. So with this in mind we will now allow certain designs to have the exhaust protruding more than 2.5 inches as long as it is covered with some form of heat shield, what it is made from is up to the builder but it needs to be solid and of course heat resistant (ally plate would be good)........rescue crew safety is at the top of the list in our society.....if you have ever caught your hand on a hot exhaust you will know what we mean.

Regards
Scoop
Logged

martno1fan

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,506
  • Location: Blackpool
Re: BMPRS Rules
« Reply #2 on: January 02, 2011, 07:42:56 PM »

Het Scoop i wonder if the heat proof exhaust wraps  would work?i think theres also a spray you can spray on to help also.
Logged

triumphjon

  • Guest
Re: BMPRS Rules
« Reply #3 on: January 02, 2011, 09:17:02 PM »

there is a tape style wrap available from MERLIN MOTORSPORT  castle coombe circiut , wiltshire , its applied like taping a wiring loom . ive a mate with some on his triumph pi that helps stop his feul vaporising in the manifold before it gets to the pistons !
Logged

Stavros

  • Guest
Re: BMPRS Rules
« Reply #4 on: January 02, 2011, 09:26:44 PM »

This stuff is so good you can actually put your hand on the exhaust manifold when the engine is running,I doubt it would work on a rc boat as it would get wet when running,just a thought


Stavros
Logged

scoop

  • Guest
Re: BMPRS Rules
« Reply #5 on: January 02, 2011, 09:30:59 PM »

Het Scoop i wonder if the heat proof exhaust wraps  would work?i think theres also a spray you can spray on to help also.
Nah ya can't go bunging a bit of tape round it.....it's gotta look pretty  {-) {-) {-)
Scoop
Logged

phillnjack

  • Guest
Re: BMPRS Rules
« Reply #6 on: January 02, 2011, 09:44:48 PM »

The exhaust on the back of my boat never gets hot.
Inside you can just about hold your hand on it, but it wont burn .
Its water cooled, ive had exhaust beforethat would rip your skin off straight away.

But after investigating i think i can just about shorten the pipe without causing engine problems.
I run a cmb 90 evo 2 and the pipe at the moment is 34cm from plug to middle of the cone.
If i can get 2 cm less it will just be in the rules.

I do understand that safety of the retrieval crew is very important (never know when you need them)  :P ok2



phill
Logged

triumphjon

  • Guest
Re: BMPRS Rules
« Reply #7 on: January 02, 2011, 11:19:59 PM »

its the amount that protrudes the transom thats what needs to be sheilded  , its weather you can cut the tail pipe section with out causing a problem to your performance ?
Logged

phillnjack

  • Guest
Re: BMPRS Rules
« Reply #8 on: January 03, 2011, 01:57:38 AM »

cutting the stinger can make the pipe react totaly different

Ill find a way round it, even if i have to extend the boat transom by making a false end box



phill
Logged

triumphjon

  • Guest
Re: BMPRS Rules
« Reply #9 on: January 03, 2011, 12:12:25 PM »

dont the rules state it must be sheilded , ive seen some models where although a side exhaust is fitted , using a greater curve on the manifold you can get the pipe to exit in the centre of the boat ? the tuned section waas always measured from the centre of the glow plug to the top of the cone on the pipe , i take it this is still the case ? as amore drastic measure its time for a longer hull !
Logged

phillnjack

  • Guest
Re: BMPRS Rules
« Reply #10 on: January 03, 2011, 01:15:03 PM »

CMB 90 engine has exaust manifold straight out towards transom.

so making the manifold having more of a bend is not an option.




.

phill....
Logged

triumphjon

  • Guest
Re: BMPRS Rules
« Reply #11 on: January 03, 2011, 09:36:02 PM »

ok thats front induction / rear exhaust ? i was refering to side exhaust engines . the outer alloy angle on your engine mounts should be the other way around , ie flat angle to the top and facing away fron the crankcase , so that it bolts into the mounting posts glassed into the hull !
Logged

phillnjack

  • Guest
Re: BMPRS Rules
« Reply #12 on: January 03, 2011, 09:57:36 PM »

I asked about this precise way of mounting engines due to a thread posted back in 1998 model boats.

it seems that vertical mounts is just mainly for the old multi class boats.

the majority of offshore boats use horizontal mounting to their rails.

I fitted some wooden rails to my boat and have had no problems at all.

rather than just sitting on 4 posts, the mounting is spread a lot more giving a strong brace after
the rubbers have done their work in reducing vibration also making it a quieter mounting system.
The wooden rails also take a fair bit of shock away.

Years ago we all mounted the solid way,flat plates bolted directly to engine then to a solid mount of fibreglass.
 a few broken crank cases maybe, but i never got one.
I dont think i would ever mount solid again and take the chance.

The majority of spark ignition boats use rail mounting as well.

so maybe both ways is good,  a good point to think about though.


below is 2 other examples, 1 horizontal, and 1 vertical. both very good


.






phill
Logged
Pages: [1]   Go Up